Central Cardiology Medical Clinic

Supraventricular Tachycardia

Peter Nalos, MD, FACC and FACP

CAUTION: The information presented here is for educational purposes only and is not a substitute for advice or individual medical care which should be provided by your personal physician. If you have questions regarding your health or symptoms described here, please contact your doctor for appropriate care.

These are tachycardias where the abnormal rhythms affect the racing of the upper chamber. The most common type is AV node reentry where there exists two different electrical pathways within the region of the AV node which allow impulses to go in an uncontrolled, rapid, regular heart rate and this is amenable to radiofrequency ablation, as well as drug therapy. Patients may have the Wolff-Parkinson-White syndrome where there is an extra pathway not associated with the AV node, which may be in a number of different places including the left side of the heart, between the left ventricle and the left atrium, as well as between the free wall of the right atrium and right ventricle, or even in the septal region. These often can be diagnosed on the surface electrocardiogram showing an abnormal conduction pattern called a delta wave where the ventricle is activated early through this "short circuit." These pathways may be amenable to radiofrequency ablation as well. Another common form of supraventricular tachycardia is atrial flutter and atrial fibrillation. In atrial flutter there may be a regular motion of electricity around the tricuspid annulus, the valve between the right atrium and the right ventricle, and this may be regular and cause rapid heart rates and may be amenable to both drug therapy, as well as to radiofrequency ablation in the posterior septal region. Atrial fibrillation is a chaotic upper chamber rhythm where the atrium may be at rates of more than 300-400 beats/minute and the impulses are filtered through the AV node and go at variable rates to the main pumping chamber. Ventricular tachycardias are more serious types of arrhythmias which may lead to cardiac arrest and death, especially in the setting of a poor left ventricular function and coronary artery disease. For both the atrial and ventricular arrhythmias, the catheters are connected to a stimulator which allows programmed impulses to be delivered by the electrophysiologist performing the study, and he can introduce extra beats that are timed critically to start up tachycardias. In most cases the tachycardias can be terminated with pacing from either the upward or lower chambers but occasional cardioversion is necessary if the ventricular fibrillation occurs. Slow heartbeats (bradycardias) also occur and these may occur due to a sick sinus node where the impulses do not fire at appropriate rates and the heart rate may drop. Electrical heart block occurs when impulses are interrupted between the upper and lower chambers, either the AV node or the His Purkinje system as it goes into the ventricle, and the electrophysiology study can bring out these in certain cases so that appropriate therapy, such as a permanent pacemaker, may be diagnosed as the best treatment. In preparation for the electrophysiology study, the patients will have EKG's and routine blood tests performed, and they will go into the electrophysiology laboratory at the hospital where an intravenous line will be placed. They will be sedated mildly with a sedative and catheters will be introduced under sterile preparation into the veins in the groin area and sometimes the neck or the upper chest area. The study is not usually painful once the catheters are introduced, and this is done with local anesthetic. The study may take anywhere from 40 minutes to several hours, depending on whether other procedures are being done with it, such as drug studies or radiofrequency ablation.

* Risks of the Study
Any invasive procedure that requires catheters to be inserted in the body covers some risk; however, the risk is quite small and the electrophysiology study is considered to be relatively very safe. Some patients may develop bleeding at the site of the insertion of the catheter; very rarely are blood clots formed inside the chambers of the heart or perforation of the vessels of the heart or heart valves. Death during or related to the electrophysiology study is extremely rare, less than 1 in 3,000. Following the electrophysiology study, one has to lay flat between four to six hours, and patients either will be admitted for further therapy with medications, or ablation, or may be discharged at that time, depending upon the results of the test.

Peter Nalos, MD, FACC and FACP - is Board Certified in Internal Medicine, Subspecialty Board of Cardiolovascular Diseases. Doctor Nalos is a Fellow of the American College of Cardiology. Dr. Nalos is certified by and a member of NASPE (North American Society of Physician Electrophysiologists).