NON-INVASIVE CARDIOVASCULAR CARTOGRAPHY
What is Realistic Geometry Cartographic Imaging? The new field of Realistic Geometry Cartographic Imaging (RGCI) finds application in the field of Science, Technology, Oil Exploration, Nuclear Science, Medical Imaging etc. RGCI is a patent pending imaging technique, where, in simple terms, the structure of an object is imaged based on the behavior of the object. How is RGCI applied in Imaging Coronary Artery Stenosis? The parameters needed for RGCI are first acquired. The acquired parameters are then mapped against a mathematical model and a cartogram is obtained, which is the collective behavioral pattern of the Heart and its Circulation status. The deviation difference of these behavioral patterns are then calculated and a three dimensional array of image units are created which is embedded into a realistic geometry model of the structure of the coronaries. The image thus obtained are called Realistic Geometry Cartographic Image (RGCI) of the Coronaries.
What are the parameters needed for RGC Imaging of Coronary Artery Disease? Since the Human Cardiovascular System is a closed loop fluid mechanics system, we will need all the parameters relating to Pressure, Volume and Time to obtain the true behavior of the system. How such complex parameters are obtained non – invasively? All these complex parameters are obtained using high precision data acquisition system. Pressure, volume, time are collectively obtained by simultaneously recorded Electrocardiography, Phonocardiography, non-invasive continues blood pressure and trans-thoracic bio-impedance. How are the measurement made on the patients? The patient is first wired to a “RGC Imaging Machine” using 12 disposable electrodes (4 for ECG and 8 for trans-thoracic bio-impedance) and a special high sensitive narrow band-width phono-transducer. The recording is made for 6 minutes at rest in the supine position. A high-speed computer with parallel processing architecture computes the algorithms and prints out the results. How long does the whole procedure take? The whole procedure takes about 20 minutes, from start to finish.
CARDIAC MRI These techniques take detailed anatomic pictures of the body. The pictures are acquired by exposing the body to magnetic fields. This causes energy to be released by hydrogen atoms in the body. This emitted energy is detected and a picture of the interior of the body is constructed. Side effects are rare and mild. Sometimes, an intravenous injection of something called gadolinium is also given. Traditional magnetic resonance imaging (MRI) scanners require that the patient be placed in a small cylindrical tube. This can be somewhat unsetting for claustrophobic patients. Newer scanners are more open but do not produce the high quality pictures that the closed scanners do. Patients can expect to hear loud knocking noises from the scanner as the images are acquired. Because of the powerful magnets used, patients with pacemakers or certain other metallic substances in their body cannot undergo this procedure. Note that patients with some types of metal, such as artificial heart valves and artificial hips, can undergo this procedure safely. It is important to let the staff of the MRI unit know the patient’s complete medical history so that they can determine if the procedure can be safely performed. In cardiology, MRI scans are primarily used to evaluate the aorta (the main blood vessel that supplies blood to the rest of the body). The chambers of the heart and the strength of the heart muscle can be visualized. Leaky and narrowed heart valves can be evaluated. Tumors in the heart can be detected. MRI is an excellent test to assess congenital heart disease. Stress tests can be performed with MRI also. Much of the same information can be obtained more conveniently and at lower cost by standard echo-
cardiography or transesophageal echocardiography. However, there are rare situations when MRI scanning is required. Magnetic Resonance Angiography (MRA) is an MRI scan that essentially produces an angiogram, i.e., pictures of blood vessels. It is quite useful for larger blood vessels such as the aorta and the arteries that go to the brain. It is getting better as time goes on for picturing the small, curving coronary arteries that lie on the surface of the beating heart. It holds promise for the future.
HOLTER MONITORS AND EVENT RECORDERS (AMBULATORY MONITORING IN EVALUATING HEART RHYTHM PROBLEMS) Ambulatory monitoring (Holter monitoring and event recorders) is done to record a patient’s ECG for a prolonged period of time, on an outpatient basis. The purpose of ambulatory monitoring is to look for evidence of transient cardiac problems-that is, problems that come and go, and that are not apparent when a standard ECG is performed. Ambulatory monitoring is particularly useful in diagnosing transient heart arrhythmias, and transient cardiac ischemia. How ambulatory monitoring is performed? There are two general types of ambulatory monitoring – the Holter monitor, and the event recorder. With the Holter monitor, electrode leads are applied to the skin (similar to the leads used in recording a standard ECG), and attached to a tape recorder. The patient is sent home and resumes normal activities while the tape recorder records a continuous ECG tracing for 24 or 48 hours. The holter equipment is then removed, and then the tape is analyzed. In contrast, event recorders do not record every heart beat on a tape. Instead, event recorders use a circular tape that stores only approximately 30 seconds of a patient’s heart rhythm. That is, at any given time while a patient is wearing them, event recorders will have the most recent 30 seconds of the patient’s ECG. When the patient experiences the symptom of interest, he/she presses a button that freezes the recording, which is the transmitted by telephone to an interpreting center. A major advantage of event recorders is that they can be used for up to 30-60 days, until the transient symptom being looked for occurs. Another advantage is that, as long as the symptom of interest typically lasts for more than a minute or two, the ECG electrodes do not actually need to be attached all the time. Since attaching the electrodes takes less than a minute, they can simply be attached as needed. What information can be gained from ambulatory monitors? The Holter monitor will show the doctor every one of the patient’s heart beat for a continuous 24-48 hour period. If any abnormal beats or heart arrhythmias occur during that time, they will be identified. In addition, the Holter monitor can give information about changes in the ST segment of the ECG during the monitoring period. Some patients who have cardiac ischemia will not actually experience symptoms
during their ischemia episodes. (This condition is called “silent ischemia”) By analyzing changes in the ST segment, silent ischemia can often be diagnosed by Holter monitoring. Event monitors are excellent at correlating a patient’s heart rhythm with a patient’s symptoms. If a patient’s symptoms are caused by a transient cardiac arrhythmia, event monitors are often the best way to make the diagnosis. Hope you liked this article! This article is written by Dr. Bimal Chhajer (Non-Invasive Heart Treatment Specialist)