Identification technique for cardiac arrhythmias in dogs and cats

PRESENTATION

BROCHURE Identification technique for cardiac arrhythmias in dogs and cats

Identification technique for CARDIAC

ARRHYTHMIAS in dogs and cats Enrique Ynaraja Ramírez

cardiac arrhythmias in dogs and cats

Identification technique for cardiac arrhythmias in dogs and cats

Identification technique for

Identification technique for CARDIAC

ARRHYTHMIAS in dogs and cats Enrique Ynaraja Ramírez

AUTHOR: Enrique Ynaraja Ramírez.

FORMAT: 17 × 24 cm.

NUMBER OF PAGES: 160.

NUMBER OF IMAGES: 230.

BINDING: hardcover.

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This handbook will help its readers develop their skills and experience in the diagnosis of cardiac arrhythmias in dogs and cats. It is intended for veterinary clinicians and final-year students of veterinary medicine who wish to improve their knowledge of this simple, safe, non-invasive, repetitive and economical diagnostic technique. A wide variety of graphic resources –diagrams, graphs, tables and pictures– complement the text to facilitate the learning process and make it more enjoyable. In addition, the content is enriched with QR codes including audio files and videos concerning the main arrhythmias.

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Identification technique for cardiac arrhythmias in dogs and cats

Presentation of the book Electrocardiography is a simple, non-invasive, safe and useful diagnostic technique, which should be included within any study protocol for cardiac function. No matter how much special tests are made: ultrasounds, cardiac markers, complex blood analysis, X-rays or any other diagnostic technique, only an electrocardiogram informs us about the presence of cardiac arrhythmias allowing, in this case, their quantification and identification.

This handbook, which provides a direct, simple and practical approach for the identification of arrhythmias, is aimed at veterinary clinicians. It includes a large number of figures that complement the text and shows the concepts described in each chapter using electrocardiogram traces. A series of QR codes linked with videos and sound have also been included to complete the explanations given in the book.

The final chapter regarding medical treatments intends to help veterinarians to take decisions when handling these drugs, that are used sporadically on many occasions. Basic instructions about dosage, intervals, indications and contraindications for each antiarrhythmic drug have been included.

Undoubtedly, veterinarians concerned about electrocardiographic interpretation will find this handbook useful, entertaining and straightforward. No major electrophysiological explanations or biochemical and cellular concepts, that are not usually of interest when dealing with a patient with a cardiac arrhythmia, are given.

JoaquĂ­n Bernal de Pablo-Blanco Cardiovet Veterinary Electrocardiographic Telediagnostic Service

Identification technique for cardiac arrhythmias in dogs and cats

The author Enrique Ynaraja Ramírez He graduated and obtained his PhD in Veterinary Medicine from the Complutense University of Madrid. He is accredited Specialist in cardiology of small animals from AVEPA (Spanish Veterinary Association of Specialists in Small Animals). He has been Professor of the Faculty of Veterinary Medicine of the Complutense University of Madrid, as well as of the Cardinal Herrera-CEU University of Valencia.

He is a founding partner of Cardiovet, a company providing telediagnosis services in veterinary cardiology to more than 1,000 practices in Spain, Portugal and Latin America, and he also currently works in Servicios Veterinarios Albeytar in La Vall d’Uixó, Castellón (Spain).

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He has published 140 articles in journals from 18 countries, participated in more than 500 courses and congresses held in 22 countries and written 8 books as well as numerous online courses. He has also collaborated actively with the main companies of the small animal veterinary industry in Spain to offer courses and programmes in order to present, promote or launch both pharmacological and nutritional products as well as pet food.

Communication services Website Online visualisation of the sample chapter.

Presentation brochure in PDF format.

Author´s CV. Sample chapter compatible with iPad.

www.grupoasis.com/promo/cardiac_arrhythmias

Identification technique for cardiac arrhythmias in dogs and cats

Identification technique for CARDIAC

ARRHYTHMIAS in dogs and cats Enrique Ynaraja RamĂ­rez

Table of contents 1. Introduction to electrocardiography: use of the diagnostic technique and calculation of basic parameters Introduction Frequency ECG measurement Measurement time: ECG log lenght Measurement fragment on the paper ECG log speeds

3. Supraventricular arrhythmias Introduction Aetiopathogenesis Primary and secondary heart diseases Extracardiac causes with cardiac impact Other causes Pathophysiological mechanisms

Electrocardiographic identification Atrial extrasystole

Devices to calculate the frequency

Possible confusions or errors

Regularity of the heart rhythm

Auscultation of extrasystoles

2. Sinus rhythms Introduction Identification of the sinus rhythms Electrocardiographic characteristics of the sinus rhythm Regular sinus rhythm Wandering atrial pacemaker

Sinus tachycardia Treatment

Sinus bradycardia Treatment

Sinus arrhythmia Respiratory sinus arrhythmia Non respiratory sinus arrhythmia

Atrial extrasystoles: multiple, combined and in rhythms

Atrial tachycardia Auscultation of paroxysmal tachycardias

Atrioventricular extrasystole Auscultation of atrioventricular extrasystoles

Atrioventricular tachycardia Auscultation of atrioventricular tachycardia

Atrial flutter Atrial fibrillation Auscultation of atrial fibrillation

4. Ventricular arrhythmias Introduction Causes of ventricular tachyarrhythmias Cardiac or cardiovascular origin Non-cardiac origin Iatrogenic

Ventricular extrasystole or premature ventricular complex Definition and concepts Electrocardiographic identification Multifocal ventricular extrasystoles R-on-T phenomenon Association of ventricular extrasystoles: repetition and rhythms

Ventricular tachycardia Ventricular flutter Twisting of the points Measures against a ventricular flutter

Ventricular fibrillation Treatment Ventricular pre-excitation Wolff-Parkinson-White Syndrome

5. Sinus bradycardia and bradyarrhythmias

Cardiac protection mechanisms Escapes and atrioventricular escape rhythms Escapes and ventricular or idioventricular escape rhythms

Treatment

Annex. Cardiac autonomic response tests Atropine test Procedure Result

Isoprenaline test Procedure Result

6. Antiarrhythmics Introduction Classification of antiarrhythmics Amiodarone Beta blockers Digitalics: digoxin y digitoxin Diltiazem Flecainide Lidocaine

Introduction

Mexiletine

Aetiology

Procainamide

Sinus bradycardia

Sotalol

Blocks Sinus pause or sinus arrest Atrial arrest Atrioventricular blocks

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TECHNIQUE TO IDENTIFY CARDIAC ARRHYTHMIAS IN DOGS AND CATS

Causes of ventricular tachyarrhythmias Cardiac or cardiovascular These are often a result of primary cardiac processes such as canine and feline dilated cardiomyopathy (this is much less common), feline hypertrophic cardiomyopathy, canine hypertrophic cardiomyopathy secondary to birth defects, hypertension, etc.

They occur in cases of myocarditis, which may be traumatic, infectious or idiopathic; and in cases of endocarditis and serious heart valve diseases (especially in those with acute symptoms such chordae tendineae rupture).

They may also appear in cases of pericarditis; idiopathic, neoplastic, haemorrhagic or inflammatory pericardial effusion; cardiac tamponade; and thoracic trauma. In addition, they result from cases of hypoxia and myocardial ischaemia, which may be acute or chronic (myocardial fibrosis).

Non-cardiac Non-cardiac ventricular tachyarrhythmias occur in cases of primary or secondary autonomic nervous system abnormalities; symptoms of various electrolyte imbalances, which may occur separately or in combination (hypopotassaemia/hypokalaemia, hypocalcaemia or hypomagnesaemia); states of hypoxia, anoxia and hypothermia; and hypertension and serious symptoms of hypotension. They also occur in serious systemic processes such as anaemia, pyometra and infections (pyelonephritis, septicaemia, peritonitis, etc.); and serious renal, hepatic and gastrointestinal diseases.

They may also appear due to electrocution, as a result of sudden immersion in cold water or during induction of anaesthesia.

Iatrogenic Ventricular tachyarrhythmias may occur in cases of overdose; poisoning; and, occasionally, treatments with correct doses of digitalis drugs, quinidine, mexiletine, procainamide and some general anaesthetics (e.g. barbiturates). They may develop with the use of sympathomimetic drugs — terbutaline, salbutamol, bambuterol or orciprenaline — and also the use of adrenaline, etilefrine or noradrenaline. In addition, they may appear with the use of methylxanthines (theophylline and derivatives: diprophylline, aminophylline, etc.), although in these cases they tend to be due to an overdose of the medicine.

75 Ventricular arrhythmias

The pathophysiological mechanisms by which these arrhythmias appear vary and usually occur in combination: ventricular tachyarrhythmias occur due to an increase in the automaticity of the ventricular myocardial fibres and as a result of re-entry phenomena.

Ventricular extrasystole or ventricular premature complex Definition and concepts

Audio of common ventricular extrasystoles

Video of a single right ventricular extrasystole

Video of a single left ventricular extrasystole

Ventricular extrasystoles, much like supraventricular extrasystoles, may be called ventricular premature complexes, as in many articles and books. Its initialisms are IVPC (idioventricular premature complex) or VPC (ventricular premature complex). Although texts refer to ventricular extrasystoles, initialisms always allude to premature complexes. Neither name is more or less correct than the other, and the two names may be used interchangeably. Ventricular extrasystoles consist of ventricular contractions that occur “too soon�, or prematurely, and develop due to a non-sinus (ectopic) electrical impulse located in the bundle of His or ventricular myocardium.

Electrocardiographic identification In ventricular extrasystoles, the ectopic focus, which is responsible for causing an electrical discharge, is located in the ventricular myocardium, in the bundle of His (ventricular portion of the intrinsic conduction system) or below it (branches of the bundle of His or Purkinje fibres). Ventricular depolarisation follows an abnormal direction of conduction through the ventricular myocardium and the impulse is transmitted by extension from one cardiac muscle cell to another, not necessarily through the specific conduction system.

This abnormal conduction of electrical stimulation is reflected in the electrocardiographic tracing and causes ventricular premature electrical cycles with distorted (abnormally wide) QRS complexes consisting exclusively of two waves: ventricular depolarisation (R wave) and ventricular repolarisation (T wave).

Ventricular extrasystoles may or may not be followed by a pause. The RR interval, i.e. the interval between two consecutive R waves when they have a sinus origin, must be measured. Next, the interval between the R wave of the extrasystole and the R wave thereafter, i.e. the RR interval subsequent to the extrasystole, must be measured. It can then be checked whether or not it is similar to the sinus interval.

76

TECHNIQUE TO IDENTIFY CARDIAC ARRHYTHMIAS IN DOGS AND CATS

Most often, the RR interval prior to the extrasystole is shortened (hence, premature complexes, true to their name, occur prematurely) and the subsequent RR interval is lengthened: there is a pause after a contraction made too soon (Fig. 3).

Figure 3. Isolated or single left ventricular extrasystoles or premature complexes.

Figure 4. Paired left ventricular extrasystoles: the same diagnostic criteria as in Figures 2 and 3 are met but, in this case, the two VPCs occur one right after the other with no sinus complex between them.

Figure 5. Paired left VPCs. This tracing is similar to the previous one, but the VPCs have a lower voltage in both their R wave and their T wave.

Figure 6. Left VPC; it has a lower voltage in both its depolarisation and its repolarisation (R wave and T wave). It meets all other diagnostic criteria: absence of a P wave, prior RR interval shorter than the sinus intervals, subsequent RR interval longer than the sinus intervals (not twice as long and therefore not a compensatory pause), R wave too wide and T wave inverse to the R wave.

77 Ventricular arrhythmias

Extrasystoles are often followed by a pause that is considered to be compensatory (RR interval after the extrasystole at least twice as long as a normal sinus RR interval). However, in other cases, extrasystoles are followed by a pause that is not considered to be compensatory; in this case, the subsequent RR interval is longer than the sinus RR interval but not twice as long.

Sometimes there is no subsequent pause, whether compensatory or non-compensatory, and the subsequent RR interval is as long as or even shorter than the RR interval in sinus cycles.

It has already been seen that the P wave may have normal morphology or may not be present. In all cases, the P wave is not associated with ventricular activity; the P wave and the ventricular RT complex are independent. What is observed is that in some cases the P wave does not even appear on the ECG and sometimes a P wave appears with no relationship to the ventricular RT interval.

In these cases of a P wave present in ventricular extrasystoles, when sinus depolarisation reaches the atrioventricular node (AVN), the ventricles are producing an autonomous impulse and this is what prevails. The P wave appears on the ECG far from, close to or fused with the VPC itself. This relative position is due entirely to chance and the different VPCs of that same ECG do not follow any particular pattern.

The P wave is generated normally in the sinoatrial node (SAN) and conducted towards the AVN, but before it arrives at the bundle of His and is distributed by the ventricles, the ventricular extrasystole appears and there is a combination of a non-conducted sinus P wave plus a ventricular RT complex.

These may seem to have a certain relationship to each other, but, as indicated, if multiple extrasystoles are analysed the PR interval may be seen to be irregular and in some extrasystoles it may be that not even one P wave appears close to ventricular activity.

In other cases there are no P waves and there are only cardiac cycles generated and conducted by the ventricles without involving the atria or SAN (Figs. 4 and 5).

The T wave in ventricular extrasystoles has a high polarity (is very positive or very negative); it is usually peaked and its polarity is always opposite to that of the ventricular R wave. If there is a positive R wave, then there is a large negative T wave, and if there is a negative R wave, then there is a large positive T wave (Fig. 6).

In ventricular extrasystoles there is atrioventricular dissociation in which atrial electrical activity is independent of ventricular electrical activity.

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TECHNIQUE TO IDENTIFY CARDIAC ARRHYTHMIAS IN DOGS AND CATS

To study the origin of ventricular extrasystole it is necessary to look at ECG lead II. On this lead, if the depolarisation deflection of the ventricular extrasystole (R wave) is positive, the ectopic focus is located in the right ventricle; if it is negative, it is located in the left ventricle.

Sometimes, it is not so easy to check whether the R wave is positive or negative, and it may even really have two components (negative/positive biphasic wave or positive/negative biphasic wave). In these cases, it is sufficient to look at the corresponding T wave, which is always of inverse polarity and aids in identifying the origin in the right or left ventricle: a positive T wave indicates that the difficult-to-visualise R wave must be negative (left ventricle), and a negative T wave indicates that the corresponding R wave must be positive (right ventricle), even if it is not possible to analyse it properly.

Multifocal ventricular extrasystoles Ventricular extrasystoles may be unifocal or monofocal, originating in the right ventricle (these are positive on lead II and have a negative T wave) or the left ventricle (these are negative on lead II and have a positive T wave); or may be multifocal, with more than one ventricular focus generating extrasystoles, in which case extrasystoles of different shapes and sizes and even some that are positive (right) and some that are negative (left) may be seen on the same ECG (Fig. 7).

Although the haemodynamic consequences depend more on overall heart rate and the frequency of their presentation than on their origin, multifocal ventricular extrasystoles are believed to have a worse prognosis and be potentially more dangerous and more serious than unifocal ventricular extrasystoles.

Video of multifocal ventricular extrasystoles

Video of left ventricular extrasystole with the R-on-T phenomenon

Figure 7. Multifocal VPCs; a VPC originating in the right ventricle (positive on lead II) and one originating in the left ventricle (negative on lead II) may be seen. In both cases the subsequent pause is not compensatory, since the subsequent RR interval, while longer than the sinus RR interval, is not at least twice as long.

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