Arrhythmias - Tachycardia (PSVT)

 

Paroxysmal Supraventricular Tachycardia (PSVT)
© Alan B. Schwartz, M.D. January1999/version 1.1

INTRODUCTION

Paroxysmal supraventricular tachycardia (PSVT) is the medical term for rapid heart beating that begins and ends suddenly. While most people feel badly when they have these episodes, they are relieved to learn that they do not represent a serious or life threatening condition.

Hopefully, this information sheet will provide you with the understanding of the diverse causes of these symptoms, methods of evaluation and treatment options. For the overwhelming majority, treatment will allow them to live a normal life.

DEFINITION

Paroxysmal supraventricular tachycardia is a fast heart rhythm that starts and stops suddenly. It may occur in young as well as older patients. It is very common, particularly in people whom are otherwise healthy.

This rhythm involves the upper chambers of your heart called the atria. Generally rhythm problems that originate from this region are not dangerous (as opposed to those that originate from the lower chambers, the ventricles).

The normal heart rate at rest is 50 to 100 beats per minute. During PSVT, the heart rate may range from 120 to 240 beats per minute. The symptoms from PSVT stem from the rapidness of the heart rate.

CAUSE

In the majority of cases, the rapid heart beating which you have is due to a small "extra piece" of heart tissue you were born with. This condition is not "genetic". It is unlikely that you will pass this condition to your children. However, since tachycardias are relatively common, it would not be unusual for several members of a family to have the same symptoms.

This "troublemaker" tissue responsible for this problem is usually located around border of the mitral or tricuspid heart valves or in the right or left atrial chambers.

If the site is in the atrium, we call the rhythm atrial tachycardia or atrial flutter. If the abnormal tissue connects the atrium to the ventricle, we call it a bypass tract (because it short-circuits the normal electrical connection between the atrium and the ventricle, the atrio-ventricular (AV) node). Bypass tracts are further divided into those that can be recognized on an EKG (called the WPW syndrome) and those that can not. The WPW syndrome differs from other types of PSVT’s because this form can be dangerous in rare circumstances.

In the WPW syndrome, the bypass tract which connects the atrium to the ventricle is fast and therefore any fast heart rhythms which originate in the atria will be transmitted to the ventricles at the same rapid rate. This is potentially dangerous because the heart does not work well at very fast rates. In normal persons, the only connection between the atrium and the ventricle is the AV node which has a built-in safety mechanism (like speed bumps) to slow the rate of any transmitted atrial rapid rhythm

More commonly, others have bypass tracts that are not identifiable by EKG but are still responsible for tachycardias. These are not potentially life threatening. The type of tachycardia they produce is called AV reciprocating tachycardia.

In distinction to the fast pathway bypass tracts mentioned above, there are also slow pathways that cause problems. These slow pathways are located near the AV node and are the source of yet another tachycardia called an AV nodal re-entry tachycardia.

PROGNOSIS

The prognosis of people with PSVT is related to whether or not they have any underlying cardiovascular disease. If there is none, the prognosis is excellent and there is a very small risk of any life threatening consequence.

SYMPTOMS

The symptoms are related to the rate of the rapid heart rhythm. Some people are oblivious to the fact that their heart is racing and only feel vaguely tired. Others may have severe symptoms of lightheadedness, blackouts, chest pain or shortness of breath. Any exertion may be quite tiring and simple activities like climbing stairs may be difficult.

Why do these symptoms occur? When the heart beats fast, it does not have time to fill fully with blood. Therefore, the heart pumps less blood than it ordinarily would. This results in a low blood pressure and subsequent lightheadedness. If the blood pressure is very low, one may experience a blackout. Shortness of breath occurs because of increased pressure in the blood vessels which lead from the lungs to the heart. This increased pressure causes fluid to leak into the lung tissue impairing oxygen exchange. The increased pressure results from a back up of blood into the lungs because of the weakening of the heart pump due to the tachycardia.

A frequent trigger for PSVT is bending over.

WORK UP

A test frequently employed to determine exactly what kind of tachycardia is causing the symptoms is the event monitor. This is a very light weight tape recorder which has a 5-minute memory loop and is worn on the belt with thin wires attached to electrodes on the body. The person pushes a button on the device when he or she feels symptoms. As long as no more than 5 minutes has elapsed, the recorder will show the rhythm associated with the symptoms. The recorder is can be played by telephone to a center which will provide a recording of your heart rhythm (EKG) so that your doctor will be able to "see" what has happened.

• You can help your doctor by taking your pulse and measuring your heart rate during episodes. Keep track of the date they occur and how long they last. Note down also what symptoms you have. If the episodes last long enough and the tachycardia has not been captured on an EKG in the past, go to our office or to the Emergency Department and have an EKG done. This will be very helpful to your doctor in deciding what treatment would be the best for you.

TREATMENT

• a) General Measures

Certain circumstances make tachycardias more likely to occur.

• The consumption of alcohol, nicotine and caffeine could make your tachycardia episodes more frequent. If you are not getting enough sleep, correct this if you can. If you can not, discuss this with your doctor.
• Avoid a low potassium level. This may occur with excessive sweating, diarrhea or vomiting. Eat foods that are high in potassium. This includes not only bananas and dried fruits such as raisins but also leafy green vegetables, brussel sprouts, citrus fruits and dates.
• Try to decrease emotional stress in your life (I know this is easier said than done).
• Avoid exercise, bending over, etc. and other activities that you notice reliably triggers your heart to race.

• b) Medical Therapy

If these measures do not help, there are medicines that can reduce or eliminate PSVT as long as they are taken. The dilemma is that while these medicines are very effective they may have side effects. Some of these side effects may include fatigue, cold hands or feet, inability to exercise completely, bad dreams, constipation and dizziness, low heart rate and low blood pressure. Rare side effects include sexual problems and depression. All of these side effects go away when the drug is stopped. None of these medicines have long term irreversible problems.

Remember the drugs only work when you take them so that you must take the medicines for life. Also, the drugs are not perfect so you may have some breakthroughs. However, for most people, the medicines work very well.

An alternative to medical therapy is a procedure called Catheter Ablation. For the majority, catheter ablation is an equal alternative to medical therapy. Catheter Ablation is preferred when medicines are not doing the job, when they can not be tolerated, or when the prospect of taking medicines life is not desired by the individual. Some doctors feel that ablation is the first line treatment over medicines for most PSVT.

• c) Electrophysiology Study and Catheter Ablation

The Electrophysiology study combined with Catheter Ablation is another miracle of modern medicine. Using a catheter (a long thin flexible tube), “surgery” to cure a heart rhythm disorder can now be performed under mild sedation through a pinhole in the vein or artery in the leg! In this procedure, the catheter is positioned near the tissue that is supporting the rapid rhythm and cautery (heat) is delivered to destroy that tissue. The amount of tissue eliminated is very small, about the size of the tip of a pencil, so that the area of damage is small. Frequently many such cauteries need to be performed during the ablation procedure until the rhythm problem is cured. The catheter ablation procedure is done after your doctor performs an Electrophysiology study. The purpose of the Electrophysiology study is to determine where the little extra piece of tissue is located and whether it can be successfully ablated or cauterized.. The procedure is performed in the hospital under intravenous sedation and requires a 18 to 24 hour hospital stay.

About 85% of PSVT’s can be cured using this technique. The success rate is about 95%, the recurrence rate after a successful procedure is about 5% and the complication rate is 2 to 3 %. Serious complications, if they occur, usually require several more days in the hospital. The kind of serious complications which can occur include fluid around the heart, collapse of the lung requiring a tube to re-inflate the lung, damage to a heart valve, blood clot to the lungs or damage to the normal conduction system requiring a pacemaker (this risk only applies if the area being ablated is near the normal conducting system, the AV node). All of these complications can be successfully treated. We have performed many of these procedures on teenagers and on persons in their 80’s without any major problems.

If you have any questions, please call or write Alan Schwartz, M.D. by telephone, e-mail or fax.

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