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May / June 2009

Issue 1

coronaryheart.com Hot Topic

ECG Challenge Inside

FFR FAME trial results (Part 2) with opinions from 2 leading cardiologists.

Behind the Scenes Clinical Education with St Jude Medical, UK.

EP Education Atrial Tachycardia

Site Visit The Liverpool Heart and Chest Hospital

New Technology A basic introduction to Cardiac MRI.

NT E M

Conferences

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Liverpool Heart and Chest NHS Trust

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BCS Conference Overview

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CONTENTS

Coronary Heart Publishing Ltd 145 - 157 St John Street London, EC1V 4PY United Kingdom Email: admin@coronaryheart.com Phone: +44 (0) 207 788 7967 Web: www.coronaryheart.com

Contents COVER STORY: 18

Site Visit - The Liverpool Heart and Chest NHS Trust

CIRCULATION 3500 Cardiac Professionals Copyright © 2006 -2009 by Coronary Heart Publishing Ltd. All rights reserved. Material may only be reproduced by prior arrangement and with due acknowledgment of Coronary Heart Publishing. The publication of an advertisement or product review does not imply that a product is recommended by Coronary Heart Publishing Ltd.

Disclaimer:

Coronary Heart should never be regarded as an authoritative peer reviewed medical journal. Coronary Heart has been designed as a guide only, to inform readers who work in the cardiology environment about latest news stories and the different techniques used by others around the world. Whilst all care is taken in reviewing articles obtained from various companies and contributors, it is not possible to confirm the accuracy of all statements. Therefore it is the reader’s responsibility that any advice provided in this publication should be carefully checked themselves, by either contacting the companies involved or speaking to those with skills in the specific area. Readers should always re check claims made in this publication before employing them in their own work environment. Opinions expressed by contributors are their own and not necessarily those of their institution, Coronary Heart Publishing Ltd or the editorial staff.

Low Advertising Budget? Coronary Heart is widely regarded as the favourite dedicated UK cardiology publication for the entire cardiac department. Each edition is developed with the reader in mind with interesting articles and innovative designs. We have a variety of advertising options to match your budget, including sponsorships and content matching placements. Our team firmly believe in building strong relationships with all advertisers which is why our director Tim Larner will personally meet with you to answer any questions you have and assist you in achieving your marketing goals. The coffee’s on us!! See our current advertisers on page 29. ADVERTISING Wendy Rose Rose Media Ltd Email: sales@rose-media.co.uk

Liverpool Heart and Chest Hospital Page 18

FEATURES: 04

Latest News

06

Hot Topic

08

Journal Trawl

09

ECG Challenge

10

Behind the Scenes at SJM

12

BCS Conference Preview

Cover Photo: Dr Scott Murray at the Liverpool Heart and Chest NHS Trust

14

Intro to CMRI

17

Drug Focus

22

EP Education - Atrial Tachycardia

28

ECG Challenge Answer

30

Next Issue, Events & Recruitment CORONARY HEART ™ 3


LATEST NEWS

- The Team Mr Tim Larner Director/Chief Editor Central Manchester University Hospitals NHS Foundation Trust

Dr Simon Redwood Chief Clinical Editor Guy’s & St Thomas’ NHS Foundation Trust

Dr Rodney Foale Senior Clinical Editor Imperial College Healthcare NHS Trust

Mr Ian Wright Chief EP Consulting Editor Imperial College Healthcare NHS Trust

Dr Richard Edwards Consulting Editor Newcastle upon Tyne Hospitals NHS Trust

Dr Divaka Perera Consulting Editor Guy’s & St Thomas’ NHS Foundation Trust

Dr John Paisey Journal Editor Royal Bournemouth and Christchurch Hospitals NHS Foundation Trust

Mr Adam Lunghi Echo Editor CVS - CardioVascular Services, Australia

Mr Stuart Allen CRM Editor Monash Medical Centre, Australia

Ms Mojgan Sani Pharmaceutical Editor Royal Berkshire NHS Foundation Trust

4

CORONARY HEART ™

Volcano Integrated IVUS/ FFR Systems

T

hree more centres now have Volcano’s Integrated Multi-Modality platform in the United Kingdom; Birmingham Heartlands, Castle Hill Hospital in Hull and The London Chest Hospital all had their new systems installed during the last three months. These centres then join the extensive and rapidly growing group of hospitals around in Europe enjoying the benefits of fully integrated multi-modality diagnostic systems. The Volcano systems are easy to use and save time because they are always on and always available, no longer does anyone have to leave the Catheter Lab to find the IVUS or FFR system parked in some out of the way corner.

The latest Volcano Systems offer Rotational IVUS, Solid State grayscale IVUS in addition to their novel VH IVUS technology enabling users to discriminate between various types of plaque. Their latest systems now also include FFR to offer complete lesion assessment integrated into the Lab. To support their new systems Volcano offer extensive on site training through their Product Specialists. In addition Volcano also run a European Preceptorship Programme which is available to all their customers. Full information on all Volcano products is available on their website www.volcanocorp.com or via their local representatives.


LATEST NEWS

Latest News The Liverpool Heart and Chest Centre are using the ACIST for interventional cases.

T

he Liverpool Heart and Chest Centre is one of the largest and most prestigious cardiac centres in the UK. They implant 1200 pacemakers and ICDs per year and perform 2500 PCIs annually. The Centre recently installed the ACIST Contrast Management System. The ACIST helps clinicians perform both diagnostic and interventional procedures. Dr Rod Stables, interventional cardiologist, says, ‘the safety systems on the ACIST, coupled to the fact that there is no need to disconnect and reconnect tubing, virtually eliminate any air embolus risk. Additionally the physician can stand further away, thus reducing radiation exposure’. Another of the benefits of the system includes features designed to save contrast. Dr Stables comments ‘Contrast doses are controlled and recorded with great accuracy, resulting in reduced patient dose’.

The ACIST Contrast Delivery System moves angiography into the 21st century. In addition to providing superior images, the ACIST provides extra safety for both patient and physician.

Exclusively from APC Cardiovascular. Please visit www.apc-cardiovascular.co.uk or call 01270 216142 for more details.

Superintendent Radiographer Chris Abell agreed, saying ‘that while contrast doses are kept to an absolute minimum, the improved opacification has resulted in a higher standard of angiography’. Chris also added ‘We have found the ACIST to be versatile, allowing different techniques to be combined efficiently and is particularly successful with rotational angiography where filling of the coronary vessels is prolonged for the duration of the rotation, so anatomy is well demonstrated from start to finish. Chris also noted the potential benefits when performing primary angioplasty, ‘our newly introduced primary service will really benefit from the built-in safety features coupled with reduced contrast dosing’. The Liverpool Heart and Chest Hospital is this issue’s Site Visit. Refer to page 18.

Left: Chris Abell and Dr Rod Stables (right) with the ACIST Contrast Delivery System

CORONARY HEART ™  


HOT TOPIC

Part 2

Cardiologist Hot Topic “The FAME study showed that routine FFR significantly improved outcomes after (DES) stenting in Multi-Vessel Disease. Do you currently routinely use FFR when stenting equivocal lesions and will results from the FAME trial have an effect on your work practices?”

Dr Richard Carroll MB ChB MRCP Consultant Interventional Cardiologist Imperial College Healthcare NHS Trust London, UK

T

he overreaching principle behind the management of coronary artery disease is the reduction in the risk of myocardial infarction, the prolongation of survival and control of symptoms of angina. The body of evidence for improved survival comes from medical therapy with agents such as statins and ACE inhibitors. We perform percutaneous coronary intervention (PCI) for the relief of the symptoms of angina. Depending on local access to catheterisation laboratories, there is a significant variation in the way patients access PCI. In areas with high access, the patient may be offered diagnostic angiography and proceed to PCI relatively early on in the course of their condition. In areas where there is less access, they may reach the catheterisation laboratory only after they have exhausted medical therapy.

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We have been regular users of FFR techniques and FAME serves mainly to justify our current approaches. Beyond FAME I think flow reserve has much to offer in the identification of epicardial vessel flow limitation due to long segment disease rather than focal stenoses.

Dr Rod Stables Consultant Interventional Cardiologist Liverpool Heart and Chest Hospital NHS Trust, Liverpool, UK

The FAME study, although well constructed and compelling, cannot be interpreted in isolation. Current evidence supports that in the vast majority of patients PCI does not improve survival. The most contemporary of these studies is the COURAGE trial, which underscores previous smaller trials indicating no survival benefit for PCI versus best medical therapy. The majority of patients we now see in the lab have multivessel coronary disease, often with one clear critical stenosis and one or more intermediate or tandem stenoses. It is in these very patients that the FAME investigators attempted to evaluate if PCI guided by FFR provided a benefit to PCI guided by angiography only. We have already seen from the DEFER study that in Patients with single vessel disease, PCI of stenoses with FFR>0.75 does not improve symptoms or survival and may indeed result in an adverse MACE for the patient. Moreover, patients with significant stenoses (FFR>0.75) had elevated event rates over 5 years even if stented. This reflects existing data from myocardial SPECT studies: ie if there is inducible ischaemia: stent, if not, don’t. Perhaps what FFR actually gives us is an in-lab tool for the detection of ischaemia in those patients who do not have good non-invasive data before catheterisation. Perhaps it allows us to address the axiom that, at least for now, with PCI, the less the better.

A number of questions remain unanswered: FAME investigators used FFR of 0.8 as the cut of point, most clinicians in Europe use FFR 0.75. It would be logical to assume that if 0.75 had been used, the results may have differed significantly. It would be important to know what proportion of patients fell in that 0.75-0.8 group, to name but one. I have used FFR in the laboratory for evaluation of intermediate lesions for several years. It is an extremely useful adjunct to the clinical decision making process in those 60+ % lesions where the symptoms are convincing but the lesion is not and there is no non-invasive data. If the symptoms are good, I will analyse lesions of lesser angiographic severity and often am surprised with two or more reproducible FFR readings indicating significance. I never use FFR to analyse the clearly significant lesions. In a lab with staff accustomed to FFR measurement it is quick and effective. In conclusion, my practice shall not change as a result of FAME. I see the results as an endorsement of the use of FFR in those lesions which are of intermediate angiographic severity, but will not find myself putting a pressure wire down those lesions which clearly present a severe angiographic stenosis in the near future.

Part One of this Hot Topic can be found in the previous edition with responses from Prof Adam Timmis and Dr Magdi El-Omar.


it’s time

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JOURNALS

Journal Trawl

Dr John Paisey Consultant Cardiologist and Electrophysiologist Royal Bournemouth Hospital

- Dr John Paisey scans the world’s cardiology journals

P

revious research on the polypill has been in the form of modelling. A clinical study has now been performed to assess safety and surrogate endpoints. Middle aged individuals with at least one risk factor were randomised to polypill or its constituents (Simvastatin, aspirin, thiazide, atenolol and ramipril) alone or in combination. The polypill was effective at treating endpoints and well tolerated.

The Indian Polycap Study. The Lancet, 2009, 373; 9672: 1341 –1351 Catheter ablation of atrial fibrillation is a growing area of practice but the procedural endpoints are variable with some advocating ablation of complex fractionated atrial electrograms, certain extremists even without pulmonary venous isolation. In a study of persistent AF patients not cardioverted by PVI randomised to CFAE ablation or no further ablation there was no difference in AF free survival, although both groups were significantly less likely to remain in sinus rhythm than those who cardioverted during PVI.

H Oral and others J Am Coll Cardiol, 2009; 53:782-789 The curse of composite endpoints continues to afflict CABG vs. PCI trials. SYNTAX randomised patients with three vessel or left main stem disease to CABG or PCI. There were significantly more adverse cardiac/cerebrovascular events in the PCI arm largely due to more repeat PCIs. It doesn’t really answer the question though if you frame it” What would you rather have, one CABG or two PCIs?”

P Serruys and others N Engl J Med 2009;360:961-72 Some people have been banging on for years about warfarin rather than aspirin for heart failure patients without another

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anticoagulation indication. The rationale is that aspirin may make heart failure worse by it’s NSAID action and poor LV function is a recognised risk factor for cerebrovascular events. In a study of 1587 patients in sinus rhythm with heart failure randomised to aspirin, clopidogrel or warfarin there was no difference in a cardiovascular composite endpoint despite modest reductions in stroke and heart failure exacerbations in the warfarin group.

Risk stratification of hypertrophic cardiomyopathy lacks the randomised, ICD intervention evidence base of ischaemic heart disease. One of the risk factors used is syncope and a study of over 1500 patients supports this interpretation with recent unexplained syncope associated with a five fold increase in sudden cardiac death. More temporally remote episodes were weaker predictors and neurally mediated (as judged clinically) episodes were not predictive.

B Massie and others Circulation. 2009;119:1616-1624

P Spirito and others Circulation. 2009;119:1703-1710

Catheter radiofrequency ablation of renal sympathetic inputs is effective in reducing mean blood pressure over one years follow up in a proof of concept trial of fifty patients. The technique appears safe and moderately effective.

Arrhythmogenic right ventricular dysplasia (cardiomyopathy) is increasingly investigated by MRI. Results can be difficult to interpret with a matrix of clinical and radiological major and minor criteria applied. A novel radiological finding dubbed the “ accordion sign,” due to the apparent crinkling of the outflow tract and peritricusopid myocardium, appears to have a high specificity for the condition.

H Krum and others The Lancet, 2009 373; 9671:1275–1281 Opening blocked arteries is a satisfying activity but once an infarct has completed does it offer any benefit to the patient? Not according to a study of nearly a thousand patients with completed infarcts, a battery of quality of life measures demonstrated no advantage but a considerable cost disadvantage when opening the artery was compared with medical therapy.

D Mark and others, N Engl J Med 2009 360:774-783 I previously reported on descriptions of the newly recognised sudden deathcausing early repolarisation syndrome. Effective drug treatment for this condition has now been described with Isoprenalin (acutely) and Quinidine (for maintenance). Beta blockers, amiodarone, verapamil and Class 1C agents were all ineffective.

M Haissaguerre and others J Am Coll Cardiol, 2009; 53:612-619

D Dalal and others J Am Coll Cardiol, 2009; 53:1289-1299 What is the point of putting in a device which needs to pace over 90% of the time to benefit the patient and then allowing the patient’s own rhythm to suppress therapy? Not much, but an excellent study of Holters in resynchronisation recipients with atrial fibrillation has clearly demonstrated much higher rates of intrinsic rhythm and fusion than the device counters would suggest. A useful reminder that CRT recipients with AF must have adequate rate control achieved.

G Kamath and others J Am Coll Cardiol, 2009; 53:1050-1055


ECG CHALLENGE

34

ELECTROPHYSIOLOGY

9 r fo at 200 d e lf n Se rse thm s a s u y ip h yo Rh hil ot rt P bo ea he d H t t ar a B

Insert Title Working together, advancing EP, helping people. Learn more about our collaboration. Visit us at Heart Rhythm 2009 in Boston.

www.philips.com www.bardep.com Bard is a registered trademark of C. R. Bard, Inc. or an affiliate. All other trademarks or registered trademarks are the property of their respective owners. ©2009 C. R. Bard, Inc. All rights reserved. LT04Z0387/Rev.0/04-2009

Ian Wright’s ECG Challenge

History: ECG from a patient with a dual chamber permanent pacemaker, 24 hrs post implant. Leads implanted in conventional RA and RVA locations.

Question: What is the explanation for this ECG appearance?

Answer: See page: 28 CORONARY HEART ™ 9


EDUCATION

A Synergistic Approach to Clinical Education

S

- Behind the Scenes at St. Jude Medical UK

t. Jude Medical understands that today’s clinicians are seeking solutions to deal with an increasingly broad spectrum of cardiac rhythm disorders and comorbidities. Because electrophysiologists (EPs) don’t treat patients separately for Atrial Fibrillation (AF) or Cardiac Rhythm Management (CRM) related conditions, St. Jude Medical has focused its energy on providing practitioners with products and training to treat the full range of EP related issues. With this unique synergy of treatments for both AF and CRM, St. Jude Medical has positioned itself apart from its competitors by providing education that targets complex topics on therapy delivery and disease management, which may have otherwise been segregated along business lines. In the United Kingdom, St. Jude Medical will conduct over 40 unique courses and will target 500 delegates in 2009. Course offerings include those for physicians as well as those for allied professionals and focus on topics that range from cardiac pacing to non-contact mapping to IBHRE exam preparation. Highly-trained specialists offer therapy-based courses focusing on complex disease states such as atrial fibrillation and heart failure and on cutting-edge topics such as remote disease management. Flexibility is the hallmark of the St. Jude Medical education program. Not only is the program flexible enough to accommodate a variety of learning styles and experience levels, but locations can be found throughout the UK and Europe. Whether delegates prefer to attend courses at the UK Learning Centre at Stratford-Upon-Avon or the new St Jude Medical Advanced Learning Centre in Brussels, Belgium, course participants gain first-hand experience in the use of advanced medical technology through innovative training tools.

10  CORONARY HEART ™

Above: Lynne Howell, St Jude Medical Low Voltage Educator instructs on advanced algorithms and troubleshooting in the Larsson Training Room.

Above: Karen Zega, AF Education Manager discusses 3D mapping with clinicians, Abigail Butler, Royal Bournemouth Hospital, Jennifer Cole and Angela Griffiths, John Radcliffe Hospital in the Waller Room for Advanced EP.


EDUCATION

The new St. Jude Medical Advanced Learning Center in Brussels is equipped with virtual reality simulators that enable physicians to hone their skills in lead implantation and will soon enable simulation of advanced ablation and transseptal procedures. A cardiac rhythm simulator allows physicians and cardiac physiologists to develop skills in programming pacemakers, ICDs and CRT devices. Specialists and opinion leaders augment St. Jude Medical’s core teaching faculty with real world experience and practicechanging insights. Partnerships with these clinicians are also helping St. Jude Medical to expand course offerings into complex areas like AF ablation in patients

implanted with devices and patients with heart failure. The goal of St. Jude Medical’s education program is to help clinicians develop new skills allowing them to deliver optimal patient outcomes in a way that reduces risk and increases control. Cross-divisional synergies enhance that mission through a diverse course offering promoting best practice therapy for complex cardiac rhythm disorders and co-morbidities, advanced training technologies, and customized learning methodologies.

Interested in attending a course? For more information on the St. Jude Medical educational offerings please contact your St. Jude Medical AF or CRM sales representative.

Below: Karen Zega with clinicians in the Senning Clinical Room and Wet Lab discussing preparation of St Jude Medical’s non-contact mapping balloon.

CORONARY HEART ™  11


CONFERENCES

2009 British Cardiovascular Society Annual Conference And Exhibition Preview

W

e are pleased to invite you to participate in the British Cardiovascular Society’s 87th Annual Conference and Exhibition. The BCS ACE is the UK’s leading and largest cardiovascular event. With over 2,500 healthcare professionals attending across the 3 days and over 100 industry partners, it is the most highly attended and respected cardiovascular event in the UK. 2009 sees the BCS Annual Conference and Exhibition returning to London but to a new venue, the ExCeL Centre in Docklands, with excellent conference and hotel facilities. The Conference has evolved over recent years and although its scientific content remains important, it has become much more of an educational meeting. With seventeen Affiliated Groups within the BCS there is a wealth of expertise from all areas of modern cardiology, reflected in an “action packed” programme this year. Collaboration between Affiliated Groups as well as educating and updating non specialists is one of the strengths of the Conference. There are also key sessions with the European Society of Cardi-

Above: PCI Simulator ology (ESC) and the American College of Cardiology (ACC) with whom the BCS has a new twinning relationship with the Californian Chapter of the ACC, reflected in a superb joint session on heart failure.

BCS ANNUAL CONFERENCE AND EXHIBITION, 1 TO 3 JUNE 2009 TO BOOK YOUR PLACE, GO TO OUR ONLINE REGISTRATION AT WWW.BCS.COM HELD AT EXCEL, LONDON WWW.EXCEL-LONDON.CO.UK HOTEL AND VENUE INFORMATION CAN BE FOUND IN OUR CONFERENCE SECTION OF THE WEBSITE.

12  CORONARY HEART ™

The Exhibition is an important part of the Conference and this year it has been further integrated into the programme with educational activities occurring in the Exhibition area throughout the meeting. The ever popular simulators have been extended to include electrophysiology this year and look out for the new “Meet the Experts” dotted around the Exhibition Hall providing “snapshots” of good clinical advice in interesting or

difficult areas of clinical practice. On the Wednesday of this three day meeting, there will be a focus on Cardiac Rhythm Management to attract delegates interested in this area who might only be able to attend for a day. If it is not your scene, don’t worry, there will be plenty of other subspecialty areas throughout the day. Dr Iain Simpson Vice President Education and Research, BCS

PROGRAMME OVERVIEW As well as a wide variation of How To sessions, case presentations, moderated posters and sub-specialty lectures from Affiliated Groups of the BCS, below are some of this year’s highlight talks. They are included to give you a flavour of the conference content; for a full outline of the programme visit the conference section of the BCS website, www.bcs.com.


CONFERENCES

Monday 1 June •

Trainee Day including a session with the Specialty Advisory Committee in Cardiology.

Revalidation in Cardiology: where are we and where are we going? Chaired by Prof Keith Fox and Dr Nicholas Boon the session will cover the European, UK and GMC perspective on this key topic.

This year’s Paul Wood Lecture will be given by Dr Valentin Fuster and is titled Promotion of Cardiovascular Health: From Risk Factors to Imaging and Genomics.

Tuesday 2 June •

BCS will join the European Society of Cardiology to give a session on Guidelines and guidance. The session will cover implementation of the ESC Guidelines; the new National Database for Endocarditis; Fitness to Fly report; review of the European Endocarditis Guidance. BCS plenary on Audit and Clinical Practice, which will include talks on national data collection and the rollout of PPCI. BCS and the British Heart Foundation (BHF) have jointly commissioned a report on Inequalities in cardiac care

Above: Lecture Audience

in the UK, by the Oxford Health Associates led by Dr Stephen Green. The findings of the report will be given in this session, followed by panel discussion of the implications.

Joint plenary on Heart Failure by BCS and the American College of Cardiology, with key talks from Dr Michael Fowler, Prof John McMurray and Dr Barry Greenberg.

Wednesday 3 June •

The 2009 BCS Lecture will be given by Prof John Deanfield, and will be titled Investing in your arteries! Lifetime management of atherosclerosis.

This years’ Strickland Goodall Lecture will be given by Prof David Newby and will be titled, Intravascular thrombosis: new frontiers in endothelial function

Don’t forget to stop by the Coronary Heart Publishing stand at Booth 286, towards the back near the simulators. Our Director, Tim Larner would love to meet you.

Left: Echo Demonstration

CORONARY HEART ™  13


CARDIAC MRI

A Simplified Introduction to Cardiac MRI - Coming to a Cardiology Department near you Basic Physics:

Mr Tim Larner Director, Coronary Heart Publishing Ltd Senior Cardiac Radiographer Manchester Royal Infirmary

Image courtesy Siemens Medical Systems

14  CORONARY HEART ™

To give you a full understanding of the physics of Magnetic Resonance Imaging (MRI) would require another 100 editions of this publication, so here is a simplified outline on what this complex imaging modality is. The proper name is actually Nuclear Magnetic Resonance Imaging (NMRI), however in the current world that we live in, the word “nuclear” creates a sense of fear, therefore just MRI is used for consumer comfort.

When you first look at a traditional MRI most people think it is just an overly large CT scanner, however the two imaging systems couldn’t be further apart in the function of obtaining diagnostic images. One uses x-rays (CT), whilst the other uses the effect of magnetic fields on the body’s molecules (MRI). Excite and Relax: We all know that the human body is comprised primarily of water (H20) with hydrogen atoms making up 63%, with


CARDIAC MRI

all parts of the body containing some of the element. In a normal state outside of a strong magnetic field, the hydrogen protons spin randomly at a constant rate in various directions, however in different tissues they have different concentrations. It’s the differences in how they are bound in each type of tissue and the relative concentrations in each tissue that we are measuring.

Components: Primary Magnet: Looking at the image right the primary magnet is the largest part of system. It is comprised of a large electrical wire which is coiled, with an electrical current passing through. This results in a strong magnetic field created in the centre of the coil. Left without any extra intervention the electrical current is subject to resistance, reducing the amount of magnetic field strength. Therefore the coiled wire is surrounded by liquid helium at -269 degrees Celsius, becoming a superconducting electromagnet. The magnetic field produced is then 20,000 times the magnetic field of the earth, developing 1.5 to 3 Tesla, the optimum range for medical imaging. Gradient Magnets: Referring again to the image right you can see additional smaller magnets called Gradient magnets located closer in to the centre from the primary magnet. There are usually three of these magnets each with a field strength 1/1000th that of the primary magnet. The purpose of

these magnets is to precisely adjust the magnetic field so that specific areas of the body can be imaged. RF Coil: When the body is placed inside the MRI the magnetic field forces the hydrogen atoms to spin in one of two directions in-line with the field. When all atoms are aligned a radiofrequency is emitted from the inner coil (RF Coil) which causes the hydrogen atoms to change direction and spin in another direction. This transition causes an energy release as the molecules change from their high-energy state to their low-energy state. The absorption of RF energy by the protons, affecting their energy state (not spin direction) is known as resonance. There are different rates of energy loss for different tissues which are displayed as shades of grey.

Above: MRI Images sagittal and axial of the heart (images courtesy St Paul’s Hospital, Vancouver)

Confused yet?? This is obviously a quick overview of the workings, and there is much more to talk about. At university we learnt how to do the full mathematical problem solvings of Fourier Transforms, a 4 –page extremely advanced mathematical algorithm which are used to determine the individual tissue frequencies and amplitudes of the resonance signal. Consider yourself lucky not to go through that pain!!

Dangers: The biggest danger with MRI’s is the presence of metals either inside the patient as part of a medical procedure or brought in accidently. I heard a story once of a doctor walking in with a pen in their pocket. When they were near the patient the magnetic field pulled at very high speed the pen out of the pocket narrowly missing the head of the patient. There was also a case reported in Australia in 2000 whereby a patient with a newly inserted pacemaker was given an MRI. Although the staff had twice asked if they had a pacemaker the patient each time stated “No”. The reason the patient said “No”, was most likely caused by confusion and stress. The patient died as a result of their pacemaker malfunctioning. Systems must be in place to avoid situations like this occurring.

The MRI diagram above can be found at: http://en.wikipedia. org/wiki/File:Mri_scanner_schematic_labelled.svg

CORONARY HEART ™  15


CARDIAC MRI

A Simplified Introduction to Cardiac MRI (cont...) Disadvantages: •

MR images are obtained through a process called “gating”, whereby the an ECG is used to acquire images at each stage of the cardiac cycle over several heart beats. If a patient has an irregular rhythm this can reduce the image quality.

Patients with metallic objects such as pacemakers are unable to be scanned.

Unlike ultrasound, an MRI is not portable to take to the patient’s bedside.

Gadolinium can be toxic to patients with impaired kidney function, with haemodialysis recommended in some cases.

Future: •

As with all technology, faster computer processors are allowing for real-time MR images. Several new scanners have this capability however the image quality is at present reduced compared with gating.

Some medical device companies are developing MRI safe pacemakers. Medtronic is currently trialing the EnRhythm® MRI SureScan™ pacing system, for this purpose.

Improvements in the development of MRI contrast media agents are occurring all the time, such as what has occurred with cardiac angiography.

Above: MRI Images of the heart (images courtesy GE Healthcare, USA)

Contrast Enhancements: Different tissue densities and their proton relaxation times produce the image contrast differences of an MRI image. However sometimes it is difficult to accurately visualise the differentiation such as in the case of demonstrating an infarction. Gadolinium - DTPA is a paramagnetic compound (attracted to a magnetic field) and is commonly used in cardiac MRI as a contrast agent where it appears very bright in certain tissues. Advantages: •

Visualise structure and function of heart.

Detect and evaluate coronary heart disease

Determine extent of tissue damage and viability post MI / chronic heart disease.

16  CORONARY HEART ™

Can create moving images of the pumping function of the heart demonstrating contraction problems and blood flow abnormalities.

Images can be obtained at any angle allowing physicians to easily obtain images of complex anatomy.

Uses: • • • • • • • • •

ischemic heart disease, myocardial disease, right ventricular abnormalities, pericardial disease, cardiac tumors, valvular disease, thoracic aortic disease, pulmonary artery disease, congenital heart disease before and after surgical repair.

Bibliography 1.

Cluett, J. M.D. 2006, About.com, MRI – What is MRI? Retrieved 1st August 2008, http://orthopedics.about. com/cs/sportsmedicine/a/mri.htm

2.

http://en.wikipedia. org/wiki/Cardiovascular_magnetic_resonance

3.

http://www.radiologyinfo.org/en/info. cfm?pg=cardiacmr&bhcp=1

4.

http://my.clevelandclinic.org/heart/history/future/ mri.aspx

5.

Calvert, J. & Taylor, T., Death Link to Hospital Scan, Retrieved 1st August 2008. http://www.users. on.net/~vision/misc/pacemaker-death.html

6.

http://en.wikipedia.org/wiki/Mri


PHARMACY

Drug Focus

Dr Mojgan H Sani, DPharm, MBA, MRPharmS Head of Clinical Pharmacy Royal Berkshire NHS Foundation Trust

- Ranolazine for Chronic Angina Pectoris

R

anolazine is a new and unique antianginal drug licensed for the management of chronic stable angina pectoris. It acts as selective inhibitor of late sodium influx, thereby attenuating the abnormalities of ventricular repolarisation and contractility associated with ischaemia. Randomised clinical trials have shown the efficacy of the agent in increasing exercise testing and reducing anginal episodes and the use of GTN sprays.

potential for prolongation of the QT interval.

MARISA (Monotherapy Assessment of Ranolazine In Stable Angina) trial was a double blind crossover in 191 patients who had angina-limited treadmill tests. They were randomised to ranolazine or placebo. Total exercise duration at trough (at 12 hour) was significantly improved in the ranolazine group (1).

References:

CARISA (Combination Assessment of Ranolazine In Stable Angina) was a double blind trial of 823 patients with chronic stable angina, already on atenolol, amlodipine or diltiazem. Patients were assigned to either ranolazone or placebo for 12 weeks. Ranolazine showed a significant increase in exercise capacity, time to angina and ECG ischaemia compared to placebo (2). The ERICA (Efficacy of Ranolazine In Chronic Angina) trial investigated the efficacy in patients with persistent symptoms despite optimised therapy with amlodipine. Angina episodes were self-reported during the 6 week double blind phase in 565 patients randomised to either placebo or ranolazine. The trial showed that on average, there was one fewer angina episode per week in the ranolazine group (3). MERLIN – TIMI 36 trial investigated the efficacy of ranolazine in 6,560 patients with Acute Coronary Syndrome. Ranolazine was not associated with a statistically significant decrease in the primary end points of cardiovascular death, myocardial infarction or recurrent ischaemia, compared to placebo. Ranolazine’s side effect profile includes dizziness, constipation, nausea and the

Ranolazine may be a useful therapy in patients with chronic angina pectoris who cannot tolerate the initiation or upward titration of anti0anginal drugs. Further clinical trials are needed in order to confirm its long term safety, its optimal dosing, and efficacy in combination with full doses of other anti-anginal therapies

1.

2.

3.

4.

Chaitman BR, Skettino SL, Parker JO, et a, for the MARISA investigators. Anti-ischaemic effects and long term survival during ranolazine monotherapy in patients with chronic severe angina. J Am Coll Cardiol 2004; 43: 1375-82. Chaiman BR, Pepine CJ, Parker JO et al, for the CARISA (Combination Assessment of Ranolazine in Stable Angina) investigators. Effects of ranolazine with atenolol, amlodipine, or diltiazem on exercise tolerance and angina frequesncy in patients with severe chronic angina. A randomised controlled trial. JAMA 2004; 291: 309-16. Stone PH, Gratsiansky NA, Blokhin A et al, for the ERICA investigators. Anti-anginal effects or ranolazine when added to treatment with amlodipine: The ERICA (efficacy of Ranolazine in Chronic Angina) trial. J Am Coll Cardiol 2006; 48: 566-75. Morrow DA, Scirica BM, Karwatowska-Prokopczuk E et al for the MERLIN-TIMI 36 trial investigators. Effects of ranolazine on recurrent cardiovascular events in patients with non ST elevation acute coronary syndromes. The MERLIN-TIMI 36 randomised trial. JAMA 2007; 297: 1775-83.

CCO National Conference Cardiovascular Therapeutic Update 2009 26th & 27th November 2009, Central London Further information and enquiries via e mail cco@onetel.com or clinical.education@talktalk.net Provisional Programme: • • •

• •

• The two-day event presents an excellent educational opportunity to update and extend knowledge, focusing on the major elements of cardiovascular disease management. The conference will also provide an excellent arena to discuss the latest developments and practical managements of cardiovascular disease. Early registration will attract a discount.

• •

• •

Hypertension and stroke prevention. Cholesterol lowering and Cardiovascular Disease. New evidence in cardiovascular medicine: Hot Topics from International Cardiology Conferences. Acute Coronary Syndrome Update: Prepare for NICE Guidelines. Heart Failure management: An Update Preventive Cardiology: Delivering evidence based cardiovascular prevention Diabetes as a cardiovascular risk factor: new therapeutic targets. Focus sessions on Guidelines from NICE, ESC, ACC & AHA Vascular Risk Assessments: Where are we now? Update from Heart Improvement Programme and Cardiovascular Networks. Thrombosis: Evolving therapies Other clinical networking sessions and guidelines TBC

CORONARY HEART ™  17


SITE VISIT

Liverpool Heart & Chest Hospital NHS Trust The Liverpool Heart and Chest Hospital NHS Trust Thomas Drive Liverpool L14 3PE Fast Facts • Largest single cardiac specialist centre in the UK. • Perform cardiac, thoracic, and abdominal procedures.

From Left: patient, EP consultant Dr Mark Hall and Radiographer Randhir Sadankar

Departmental questions have been answered by Teresa Darmody, Acting Cath Lab Manager.

What is size of your Cath Lab facility / Hospital? Liverpool Heart and Chest is the largest single centre specialist cardiac centre in the UK. The Trust services a population of 2.8 million covering Merseyside, Cheshire, West Lancashire, North Wales and the Isle of Man. The centre also serves as a national referral unit for a range of specialised cardiac and thoracic procedures. The EP service is also one of the largest in the UK. We have 6 cardiac catheterisation labs – 4 of which are used for PCI (3 x bi plane) and 2 are dedicated

1

CORONARY HEART ™

EP labs with in-build EP systems. We also have two pacing facilities including a hybrid theatre where Percutaneous aortic valve and aortic stent procedures are performed. Aortic stenting is performed electively in the treatment of aortic aneurysm and coarctation. Our procedures involve the thorax, however abdominal/ iliac stenting is also performed combined with CABG. Stenting may be performed as an emergency, following acute aortic dissection or leaking aneurysms, patients have come from as far away as Birmingham.

How many staff? Roles? The team compromises of the usual

disciplines of cardiac physiologists, radiographers, registered nurses, health care assistants, transfer staff, a stock team and medics. The nursing team is comprised of 3 teams – 22 nursing staff, 3 stock members and 5 transfer staff. The cardiac physiologists have a team of 20. They also cover 2 pacing theatres, one pacing and one ICD clinic daily, epicardial implants and PAVI cases in theatres, echo and a wide range of other non invasive services. The radiographers have a team of 13 full and part time staff, also covering the hybrid theatre where pacing, aortic


SITE VISIT

stenting and percutaneous aortic valve replacements are undertaken. Their rotation to the main department also involves general radiography or CT scanning. We stick to fairly traditional roles although we have a member who recently finished the assistant practitioner course and we are looking at a role being one involving cross training to some degree.

Types of procedures: We essentially divide into EP and interventional coronary procedures. These include Angiograms, PCI, Alcohol Septal Ablation, PFO/ASD closures and valvuloplasty. We perform ablation for AVRT, AVNRT, A. Flutter, A. Tach, PVI and ablation for Ischemic and idiopathic VT. In the hybrid theatre, Percutaneous Aortic Valve Replacements have recently been introduced for patients not suitable for surgery, with calcific aortic valve disease

From Left: patient and registrar Dr Scott Murray

Equipment: •

Xray equipment is all Philips. 2 bi-plane Allura 10-10 flat plate systems with rotational angiography capability and stent boost.

2 single plane Allura flat plate detector systems set up for EP procedures with low dose and low frame rate fluoroscopy capabilities.

1 Integris biplane conventional lab for PCI and a single plane Integris situated adjacent to the day ward suitable for diagnostic lists.

The hybrid theatre is an Allura FD 20 with rotational capabilities, subtracted angiography and smart mask.

We have two mobile Pulsara image intensifiers with cardiac capabilities and low dose fluoroscopy designed for long screening times often required for BiVentricular pacing.

Standard assessment and diagnostic tools of IVUS (Volcano) and RADI and Volcano pressure wire. We utilise the rotablator and laser also.

EP has 2 integrated EP labs each fitted with a Bard EP system, Carto system and Navix system.

From Left: behind screen Cardiac Technician Tony Fern, Registered Nurse Zia Ur-Rehman, Cardiology Consultant Dr Nick Palmer ( behind screen), HCA Sylvia Shaw and Registrar Scott Murray. CORONARY HEART ™  19


SITE VISIT

Liverpool Heart and Chest Hospital (cont...) Procedures performed per year: In 2008 we did roughly • 1584 angiograms • 2335 PCI • 870 EP studies with predication of 1000 this year. • 1200 Pacing and ICD procedures • 55 PFO/ASD closures.

Cross-training of staff: The “generic” cath lab worker is something we have put a lot of thought into but not yet realised. A suitable course with accreditation in the local area is required.

New procedures implemented: On the 26th of Jan 2009 we commenced phase one of our PPCI service. We are still refining our delivery and to date it is going well thanks to such thorough planning involving people such as the cardiac network, the North West Ambulance Service, all participating hospitals, CCU and all supporting departments, the Cath Lab Manager Karen Wafer, and the consultants Dr Perry and Dr Mills who put in a lot of time doing face to face education. It also involved a dedication for this to work from all the cath lab staff as the target times put a lot of additional pressure on the team as some live more than 30 mins drive away. We currently work on an ONCALL basis for PPCI out of hours and not shifts. The second new procedures we are involved in are the Percutaneous AO valve replacements, from the trans apical and femoral approach as considered appropriate.

Inventory Management: Our stock comprises mostly of stock that we own and some consignment. We Re-order using the Oracle Stock Management System and NHS logistics for stock items. We are looking to move to a fully computerised stock management

20  CORONARY HEART ™

From Left: Cardiac Technician Tony Fern, RN Zia Ur-Rehman, patient, Cardiology Consultant Nick Palmer, Registrar Scott Murray and head of Sylvia Shaw HCA system that records every item used in the near future.

Haemostasis Management: The majority of our interventional procedures are done radially with only 2 of our 7 PCI consultants preferring to take the femoral approach. EP by its nature predominantly requires only venous punctures, be that femorally and /or via the subclavian approach. Therefore we use a range of techniques for haemostasis depending on approach, patient attributes and operator preference which may take in factors such as the need to keep the approach free from complication for future use such as a planned IABP insertion. The main devices used are the Terumo TR Band available in 2 sizes and the angioseal. We also use compression devices such as the Radistop and the Femstop.

Measures implemented to cut costs: We always look at competitive prices when buying. Bulk items go out to

tender. We aim to minimise stock held in each lab to promote stock rotation and efficient use of resources. Recently we purchased the ACIST device in order to minimise contrast use and reduce the amount of wasted and disposed of contrast.

Training for new employees: For the nursing staff in an ideal world they would get 6 weeks supernumerary where they work with a dedicated mentor and complete competencies. In this time they aim to learn roughly how the department functions and the circulating role. This will be built on later by learning the scrub role competencies and eventually Oncall. For the cardiac Physiologists the training is very similar. They will have a period of time spent in the lab with a mentor (varies depending on their length of experience and type of work the individual performed at their previous centre). At the end of this period they will then complete in-house competencies.


SITE VISIT

For Radiographers, Induction training for new staff, additional training for new equipment eg the ACIST New techniques PAVI, aortic stenting, rotational angiography and Radiation protection refreshers. In house audit days, quality groups, cardiology lunch time meetings, chest imaging talks. Also external cardiac courses

Continuing education programs available to staff: There are opportunities for conferences and study days. Also programs to maintain proficiencies such as ILS/ALS.

Kinds of competency checks staff have to undergo once employed: Not all nursing staff scrub or goes oncall. We are currently working on competencies where each nurse will learn in 3 parts – first the circulating, then scrub and oncall simultaneously depending on the staff members individual progress and Banding. It is not a requirement for ONCALL to scrub as there is routinely a SpR to assist the consultant. There is the standard yearly mandatory training and we have monthly audit pm’s where training is scheduled involving outside speakers from companies.

Department Management structure: The department is headed by the Cath Lab Manager who works alongside the technical lead for Cath lab / EPEP and Head of Radiography. Below each discipline is the standard Banding structure. On the medical side the department has a clinical lead for the Labs which is Dr Rod Stables.

Dealing with late finishing of cases: This is a problem that arises no matter where you work. Wherever rules are put in place they are always tested to the limit as you want to get the most out of the service and sometimes you just can’t foresee the length of time a procedure may take. There are set session times for the labs and the nursing staff are

EP cardiac technician Neil Ness and EP Consultant Mark Hall. rostered to start prior to and after the completion of these sessions. The cardiac physiologists and Radiographers differ in there hours so at times when multiple labs overrun this presents an issue. We can run one on after hours as that becomes the ONCALL team.

Policy for company reps within the labs: All visitors must sign in and out. They book in advance with a consultant and on their lab visits they are not to introduce

new products as they are required to book separate appointments to introduce these thereby relieving some pressure on the consultant when they are working in the lab.

What is the best part of working at your facility? With the large volume of acute work we do you get to see a wide spectrum of cases including more unusual presentations that in a smaller department you may never witness.

CORONARY HEART ™  21


Sponsored by:

EP EDUCATION

Atrial Tachycardia Ian Wright, Technical Head EP, St Mary’s Hospital, Imperial College Healthcare NHS Trust, London, UK

F

irstly there is disagreement about how the term atrial tachycardia should be used. A strict definition would be all fast rhythms which originate in the atria and that not require other tissue to sustain. This would of course include typical atrial flutter and atrial fibrillation (AF). We can exclude AF however as atrial tachycardias must be (fairly) regular.

– an analogy is a Mexican wave. The time taken for one revolution of the circuit (the cycle length) determines the rate of tachycardia. Focal tachycardias are ablated by identifying the site of earliest activation - in atrial tachycardias this occurs before the onset of the p wave on the surface ECG. Re-entrant tachycardias are ablated by defining the tachycardia circuit and ablating a critical isthmus (narrow region) of slow conduction without which the circuit cannot sustain. In focal tachycardias there is often (but not always) an iso-electric baseline between p waves, as is seen in sinus tachycardia. If this is evident in all 12 leads the rhythm is likely to be focal. Unfortunately the preceding T wave can interfere with this determination during one to one conduction. An iso-electric interval occurs because atrial activation occurs in a shorter period of time than the tachycardia cycle

length, leaving an interlude between the latest atrial activation and the next depolarisation of the focus. However, where there is slow atrial conduction away from the focus and/or the tachycardia is particularly rapid the iso-electric line can be absent. In macro re-entrant atrial tachycardia (atrial flutters) there must be continuous activation in the re-entrant circuit from one cycle to the next (see fig 4). This manifests as “flutter” or “f” waves on the surface ECG rather than distinct p waves. Re-entrant atrial rhythms occur in patients with atrial pathology, previous atrial surgery or extensive ablation for AF. At EP study mode of initiation and termination, reliance on isoprenaline for induction, warm-up/cool down and responses to entrainment contribute to an understanding of the mechanism, which is critical for the adoption of an appropriate ablation strategy.

Focal verses re-entrant mechanisms In practice electrophysiologists tend to use this term to refer to focal atrial tachycardias. Re-entrant tachycardias are referred to as macro re-entrant atrial tachycardia or atrial flutters. Sometimes distinction between focal and re-entrant cannot be made on the basis of the surface ECG, particularly if there is atrial disease or previous surgery/ablation. For example both focal and re-entrant atrial tachycardias are reported as a complication after AF ablation and in these patients a diagnosis of the underlying mechanism may only be possible at an EP study. A focal tachycardia originates from a point source with activation spreading concentrically to activate surrounding tissue. The rate of firing of the focus drives the tachycardia rate – sinus tachycardia for example is a focal atrial tachycardia. In contrast re-entrant rhythms occur due to the existence of an “endless loop” of activation with an impulse travelling in a circuit formed by obstacles to conduction

22

CORONARY HEART ™

Fig 1: Atrial tachycardia with 2 to 1 A-V conduction (p waves are indicated in lead one). This could easily be mistaken for sinus rhythm. There are discrete p waves with an iso-electric interval. The p wave axis is very similar to sinus rhythm as this is a high crista tachycardia – i.e. from a region close to the sino atrial node.


EP EDUCATION

Fig 2: Focal crista tachycardia. Shaded areas contain no atrial signals corresponding to the iso-electric interval on the surface ECG, suggesting a focal mechanism. Care must be taken to ensure that signals spanning this interval have not been missed.

Fig 3: Macro re-entrant (incisional) right atrial tachycardia – no clear iso-electric period

CORONARY HEART ™  23


Sponsored by:

EP EDUCATION

Atrial Tachycardia (cont...)

Fig 4: Intra-cardiac signals in macro re-entrant atrial tachycardia. There is continuous activity from cycle to cycle (between vertical lines). A long fractionated signal on the ablation catheter (Mapd) spans the time between two groupings of atrial electrograms. Such signals characterise a slowly conducting critical isthmus in a reentrant circuit – ablation at this site terminated tachycardia.

3D mapping technology

Fig 5: 3D left atrial (LA) map (Ensite NavX, St. Jude Medical).

Patients with multiple tachycardias or complex re-entry present challenges for conventional mapping techniques. This map shows electrical voltage and ablation points superimposed on a CT scan of the left atrium in a patient with mitral valve replacement and previous epicardial surgical Maze procedure. The ability to view the anatomy in three dimensions, record ablation points, identify regions of scar tissue and follow wave-front propagation facilitated ablation of five atrial tachycardias in this patient. In this view there is a cluster of pink ablation points which terminated one tachycardia. Green dots show PV encirclement.


EP EDUCATION

Diagnosis In the absence of bundle branch block or an accessory pathway atrial tachycardias present as a regular narrow complex tachycardia. The differential diagnosis is AV nodal re-entrant tachycardia (AVNRT), A-V re-entrant tachycardia (AVRT) atrial tachycardia or atrial flutter. Atrial tachycardia can sustain without the participation of the ventricles or the AV node. The diagnosis is therefore self evident where there is a high degree of A-V block (see fig 4). When atrial tachycardias are conducted to the ventricle in a one to one relationship the diagnosis may be more difficult. Adenosine can be used to induce transient high grade AV block – if the tachycardia can sustain despite loss of AV conduction it is atrial tachycardia. Unfortunately some atrial tachycardias are terminated by adenosine (adenosine sensitive) and so termination, though suggesting AV nodal involvement in a circuit (i.e. AVNRT, AVRT) cannot rule out atrial tachycardia.

Fig. 6. Focal left atrial tachycardia with one to one conduction

In some cases the p wave morphology can be seen to be inconsistent with retrograde atrial activation. In AVNRT and AVRT the atrial activation must be retrograde –it must begin somewhere on the A-V ring. A p wave axis or intra-cardiac signal sequence not consistent with retrograde atrial activation strongly supports a diagnosis of atrial tachycardia. This is seen in figures 1 and 2 showing tachycardia from the superior crista terminalis. The p wave is similar to a sinus p wave with activation from superior to inferior (“high to low”). On the intracardiac signals the high right atrial (HRA) signal is much earlier than the annular signals (CS and His catheter) – inconsistent with retrograde activation. When the atrial sequence is consistent with retrograde activation, particularly when compatible with atypical AVNRT, the diagnosis is more difficult. Pacing manoeuvres can be used to facilitate a diagnosis. One technique involves entraining the tachycardia from the ventricle and observing the A-V relationship on cessation of pacing (see fig 7) An A-A-V response (in contrast to an A-V response) upon cessation of ventricular pacing as-

Fig. 7. Simulated A-A-V response during sinus rhythm. Sinus rhythm is a focal atrial rhythm. By pacing the ventricle faster than the sinus rate the ventricular pacing has entrained the sinus node. When pacing is stopped there is a retrogradely conducted atrial event (A). In AVRT or AVNRT the next event would be ventricular (V) – an A-V response. In atrial tachycardia the next event is atrial (the next depolarisation of the focus – in this case the SA node) which is then conducted to the ventricle – giving an A-A-V response.

CORONARY HEART ™  25


Sponsored by:

EP EDUCATION

Atrial Tachycardia (cont...) sociated with 1:1 ventriculo-atrial conduction is highly sensitive and specific for distinguishing atrial tachycardia.

Right atrial focus

Left Atrial Focus

Crista terminalis

Pulmonary veins

Focal atrial tachycardia

Tricuspid annulus

Superior mitral annulus

Focal atrial tachycardia (AT) is a relatively uncommon form of supra-ventricular tachycardia (10%) often in the absence of structural heart disease. It is usually located to one of a number of specific anatomical “hot spots”. The pulmonary veins have received an enormous amount of publicity in recent years due to their importance in atrial fibrillation. However, 75% of patients presenting for ablation of regular focal atrial tachycardias (in patients who have not had previous AF ablation) have a right atrial source. The crista terminalis accounts for some 60% of right atrial tachycardias whilst the pulmonary veins are the site of origin of half of all left atrial tachycardias. The cellular mechanism underlying focal atrial tachycardias is abnormal automaticity or triggered activity. Automatic tachycardias may exhibit “warm up” and “cool down” behaviour on initiation and termination.

Coronary sinus (CS) ostium

Left atrial appendage

Perinodal tissue (Triangle of Koch)

CS body

Right side of inter-atrial septum

Left side of septum

Right atrial appendage Table 1. Common sites for focal atrial tachycardias (in order of frequency of occurrence).

Ablation of focal atrial tachycardia Ablation is achieved by targeting sites of earliest atrial activation that precede the p wave during tachycardia (see fig 8). Potential complications are related to the anatomical location of the focus. The crista terminalis is close to the sinus node and the phrenic nerve, so there is a potential for damage to these structures. Sinus node damage is rare but its location can be mapped used 3D mapping systems and the timing of the ablation electrogram should not be the earliest recordable signal in sinus rhythm. Proximity to the phrenic nerve can be checked phrenic nerve stimulation by high output pacing from the ablation catheter. There is a risk AV block complicating ablation of Triangle of Koch foci due to their proximity to the AV node. Cryoablation may be used to maximise safety. Left atrial locations necessitate transeptal puncture with its associated risks.

26  CORONARY HEART ™

Fig 8. Signal at successful ablation site for mid crista tachycardia. There are two components on the ablation catheter (Mapd) as it is sitting on the crista which forms a line of conduction delay or block. The small first component is much earlier than the atrial signal on the other catheters and was the earliest that could be found during extensive mapping. Timing with respect to p wave onset is problematic due to masking by the T wave. The site was confirmed as the focal origin as application of radio frequency energy terminated tachycardia (fig 9).


EP EDUCATION

References/further reading Kistler PM, Roberts-Thomson KC, Haqqani HM, Fynn SP, Singarayar S, Vohra JK, Morton JB, Sparks PB, Kalman JM P-Wave Morphology in Focal Atrial Tachycardia: Development of an Algorithm to Predict the Anatomic Site of Origin Journal of the American College of Cardiology Vol. 48, No. 5, 2006 Knight BP, Adam Zivin A, Souza J, Flemming M, Pelosi F, Goyal R, Ching Man K, Strickberger A, Morady F A Technique for the Rapid Diagnosis of Atrial Tachycardia in the Electrophysiology Laboratory Journal of the American College of Cardiology Vol. 33, No. 3, 1999

Fig. 9. Termination with ablation

More control. Less risk. St. Jude Medical is focused on reducing risk by continuously finding ways to put more control into the hands of those who save and enhance lives.

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ST. JUDE MEDICAL, the nine-squares symbol and MORE CONTROL. LESS RISK. are trademarks and service marks of St. Jude Medical, Inc. and its related companies. ©2009 St. Jude Medical. All Rights Reserved.

CORONARY HEART ™ 27


Refer to Question on Page 9

ECG ANSWER

ECG Challenge Answer Ian Wright, Technical Head EP, St Mary’s Hospital, Imperial College Healthcare NHS Trust, London, UK

Answer: The atrial lead had migrated into the ventricle.

T

he ECG shows a board complex rhythm at around 60 bpm. Beats 1,2,3,5,6,7 and 9 have a consistent morphology and the QRS is immediately preceded by a pacing spike. There appears to be a second pacing spike in the middle of these QRS complexes which have a left bundle branch block (LBBB) morphology. They are markedly positive in the inferior leads, all consistent with an origin near the right ventricle outflow tract (RVOT). Beats 4 and 8 are quite different with a more normal dual chamber pacing appearance. We see what appears to be an atrial pacing spike followed by an AV delay and then a ventricular pacing spike that evokes a response. The initial pacing spike does not capture the ventricle on

2

CORONARY HEART ™

these beats. The QRS morphology here is more consistent with conventional right ventricular apex pacing (negative in II and aVF). On inspection of the ECG baseline between atrial spike and QRS on these two beats there does not appear to be a stimulated p wave – it appears that the atrial stimulus has not captured the atrium. The ventricular output now captures as the ventricle is available for excitation. This appearance is consistent with a system where the right atrial lead has prolapsed into the ventricle and is intermittently capturing the ventricular myocardium (in this case probably near the RVOT). What is interesting is the difference in interval between the two sets of pacing spikes. On beats 1,2,3,5,6,7 and 9 (RVOT morphology) the interval between the two pacing spikes is about 3 small squares, or around 120ms. On beats 2 and 4 the interval is considerably longer – perhaps 4.5 small squares or 180ms. Why should the paced AV delay change like this?

Cross-talk inhibition In some early pacemakers a potentially catastrophic interaction between atrial pacing and ventricular pacing occurred – the ventricular channel sensed the “tail end” of the atrial pacing pulse (beyond the cross chamber blanking period). Hence the atrial output inhibited ventricular pacing – a condition known as cross talk inhi-

bition. This leads to persistent inhibition of ventricular pacing resulting in patients with no AV conduction having only paced p waves! To prevent this from happening device manufacturers introduced a timing window during the first part of the AV delay immediately after atrial blanking. During this interval ventricular sensing does not inhibit the impending pacing pulse, which is delivered to the ventricle regardless, at the end of the AV delay (this is known as committed pacing). A drawback of committed pacing is the possibility of stimulation during the ventricular vulnerable period if the sensed R wave is in fact real rather than artefact (see below). Induction of VT facilitated by R on T pacing in a patient with an ICD without safety pacing. A ventricular ectopic occurs during the AV delay but does not inhibit the subsequent ventricular impulse. Because the programmed AV delay is long the pacing impulse falls outside the refractory period and captures the ventricle. Unfortunately this short coupled beat induces VT.

Safety pacing One neat solution is to deliver committed pacing but to force a short AV delay so that the paced beat falls too soon to capture the ventricle - in case the signal is not artefact. This is safety pacing. A commonly used safety pacing AV delay is 110ms – the precise AV delay in this example. Where the atrial stimulus has captured the ventricle the resulting signal has been sensed during the ventricular safety pacing window, resulting in a contraction of the AV delay. The programmed AV delay (around 180ms) can be seen in the beats where the atrial stimulus fails to capture the ventricle (beats 2 and 4).


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Heart Rhythm Congress 2009

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CORONARY HEART ™  29


RECRUITMENT + EVENTS

Events Diary: May 19-22

Next Issue Guide:

Barcelona, Spain

Edition 19 (July/August)

EuroPCR 2009 Visit: www.europcr.com

June 1-3

BCS Annual Conference and Exhibition 2009 London, ExCeL

Visit: www.bcs.com

Echocardiography •

Invasive Cardiology •

treating bifurcations with comments from Prof Adam Timmis and Dr Rod Stables.

5th Sheffield Practical Cath Lab Course

Visit: www.angioed.com

October 18-21

Heart Rhythm Congress 2009

26-27 November

CCO National Conference Central London

Can Cardiac CT improve your practice?

- A Case study from the BMI London Independent Hospital. •

Cardiology Underworld:

- Opening up your doors to after hours animal cases.

Hilton Birmingham Metropole, Birmingham

Visit: www.heartrhythmcongress.com

Hot Topic: - Complex strategies for

October 5-6

Medical Education Centre, Northern General Hospital, Herries Road, Sheffield S5 7AU

Interesting Case Studies

Management •

The evolution of Cardiac MRI

Your experience with hybrid labs for PCI.

Email: cco@onetel.com Like to advertise or submit articles? See page 3 30

CORONARY HEART ™


RECRUITMENT

Your World Medical Recruitment News

Y

our World brings a fresh approach to Medical Recruitment. We want to be the agency that you come to for your temporary and permanent staffing by supplying you with the best service. We have brought together a host of experienced consultants that all have genuine knowledge in their specialist medical field and will supply you with an honest and reliable service just when you need it. We have over 15 years experience in Cardiology and Radiography recruitment and have developed many long term working relationships with clients and candidates built on trust, understanding, reliability and delivery. If you are a professional looking to join a professional agency that’s doing all the right things then please register online at www.yourworldmedical.com or browse our current positions available in the UK and Southern Hemisphere.

if you are considering using our services for temporary or permanent staff in the future. Your World invest time and energy in the correct way and stick rigidly to a thorough vetting procedure ensuring the highest quality standards. We offer the very best support to our candidates by ensuring they have the tools required to assist them to do the job they are employed to do. We also make a big effort to listen to our candidates thus ensuring their requirements match your needs. For further information on working with us please call the team on 020 7426 6999 or visit our website www.yourworldmedical.com. We look forward to hearing from you!

If you are looking for staff you can submit a vacancy online at www.yourworldmedical.com and your consultant will contact you upon receipt of this to discuss your requirements. Alternatively you can request a call back simply request information

Medical Recruitment Specialists in Cardiology and Radiography Call now to register your interest if you are seeking work or staff

Call the our specialist team direct

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Locum and permanent positions, domestically and internationally for Cardiac Physiologists, Cath Lab staff and Sonographers. Trainee roles are also available.

For clients and candidates in Australia and New Zealand please contact Australia freephone 1300 36 23 37 tel +612 9994 8074 info@yourworldmedical.com.au New Zealand Freephone 0800 508 018 info@yourworldmedical.co.nz

CORONARY HEART ™  31


From Basic Science to Bedside

BCS Annual Conference and Exhibition 2009 Venue: London, ExCeL Date: 1 to 3 June 2009 3 Day meeting of educational and scientific interest in Cardiovascular Medicine International Keynote Lectures including Dr Valentin Fuster Educational content based on the new European Curriculum

Members of the British Cardiovascular Society can register for free before 31 March 2009. For registration or details on how you can become a member of the Society please go to www.bcs.com.


Coronary Heart #18