A B C D E F G H I J K L M N O P R S T U V W

ABNORMAL HEART RHYTHMS (VENTRICULAR)

What are Abnormal Heart Rhythms (Ventricular)?

The heart has an electrical system which makes sure that the chambers of the heart beat in a regular manner. Each heartbeat starts with a spark in a tiny area of the heart called the sinus node. The impulse passes through the receiving chambers (the atria) to the pumping chambers (the ventricles) through a conduction system. Although the heart's pumping function may be normal, it will not work properly if there are electrical defects. There may be defects in the sparking or the conduction, and this can cause short circuits with too many electrical impulses. The heart may then beat too fast, or irregularly. What effect this has depends on the speed of the heart, the age of the patient, and whether there is other heart disease. An awareness of a rapid rhythm is often called "palpitation" and the rapid rhythm itself is called a tachycardia.

Young people can tolerate rapid heart rates (up to 200 beats per minute) if their hearts are otherwise normal. Some may not even be aware of it. Older people feel dizzy and may even faint with a much smaller change in the speed of the heart. In addition, the patient may feel breathless, get chest discomfort or pain, and feel sick or sweaty. The type of heart rhythm also is important. If the rapid rhythm comes from the pumping chambers (ventricular tachycardia) it is usually more important than if it starts in the receiving chambers (atrial tachycardia).

The symptoms of ventricular tachycardia are usually worse and it can become chaotic (ventricular fibrillation). This may be life threatening, because the blood pumping also becomes chaotic. A slow type of palpitation is caused by extra beats called ectopics or extrasystoles. These beats are weak but are often followed by a pause which some people feel as "my heart missed a beat". The next beat is normal but is strong and can also sometimes be felt as "my heart gave a thump". Unless there is other heart disease present, ectopic beats are unimportant. They do not need treatment. Many people have them without knowing it.

Why do Abnormal Heart Rhythms (Ventricular) occur ?

Some patients have only an electrical defect without other heart disease, but when tachycardias arise in the ventricles there is usually additional heart trouble. This may be coronary disease, including heart attacks (myocardial infarction), heart muscle disease (cardiomyopathy), or infection. Changes in heart rhythm may occur now and then, the heart switching back and forth from normal to abnormal. These switches may happen very frequently (several times a day) or very seldom (once or twice a year). The attacks themselves may last a few seconds, or several hours.

Treatment Involved for Abnormal Heart Rhythms (Ventricular)

DIAGNOSIS

Any possible underlying abnormalities are investigated by blood and other tests.. Electrocardiograms (ECGs) are used to record the rhythm and to distinguish an atrial tachycardia from a ventricular tachycardia. As the abnormal rhythm may not be present all the time the ordinary ECG may not help. If the attacks are brought on by exercise, an exercise test may be useful. The ECG is recorded whilst you walk on a treadmill at a gradually increasing speed and incline. A portable 24-hour Walkman-sized ECG (Holter) recorder can be used to record ECG faults which come and go. ECG wires are stuck to the skin of the chest and are connected to the recorder, which is carried on a belt. If this recording is also normal, pocket sized recorders may be carried for several weeks. These are placed on the skin when you have an attack (event ECG) and are switched on by pressing a button. The recording can then be relayed over the telephone.

A similar recorder, called a loop ECG can record for several days (as long as the batteries last). It only retains the last 10-20 minutes recording in the memory. After an episode of palpitation this can be ‘frozen’ in the memory by pressing a button. ECGs from inside the heart can be recorded if all the other methods fail to allow a diagnosis. Thin wires (electrodes) which are passed inside the heart from the veins in the groin or neck. This type of investigation is called an electrophysiological study. A special pacemaker can be used to start and stop a ‘tachycardia’ This can be especially useful when trying to assess exactly where in the heart it starts and how it responds to treatment.

TREATMENT

Any underlying condition revealed by investigation is treated. For example, treatment is required for a heart attack (myocardial infarction) and for the other diseases mentioned above. Various medicines are used to put the rhythm back to normal. There is a group of medications derived from, or similar to, lignocaine which is a local anaesthetic. Another particularly effective drug is called amiodarone. If ventricular tachycardia threatens life, a short general anaesthetic is given, followed by an electric shock from a machine called a defibrillator. This is called DC cardioversion and is a safe method of treatment. This allows the heart rhythm to return to normal although it does not necessarily prevent the tachycardia occurring again.

Defibrillators have now been miniaturised and are occasionally implanted in the body, like pacemakers. An electrophysiology study can be extended to provide treatment of ventricular tachycardia, as well as diagnosis. Short bursts of radio-frequency electrical energy can be passed through special electrodes. These heat the tip to 50 – 60º centigrade. This burns out tiny sections of the electrical pathways which are responsible for the short circuits which in turn cause the rapid rhythm. This is called ablation therapy. It has the advantage that it usually leads to a permanent cure. Because ablation therapy is so successful, other techniques such as permanent pacemakers are used less often. They are used mainly for treating slow heart rhythms, but can occasionally be used for treating fast rhythms. The above treatments are usually successful in controlling or curing ventricular tachycardia. However, there is sometimes the risk that it may degenerate into the chaotic rhythm, ventricular fibrillation. DC cardioversion then becomes an emergency. This is normally administered using an external defibrillator. They have now be miniaturised and can be implanted in the body like pacemakers. This is becoming increasing useful for patients in whom there is risk of ventricular tachycardia recurring in spite of other treatments.

After Treatment for Abnormal Heart Rhythms (Ventricular)

Medications are more successful in some people than others. If the abnormal rhythm (palpitation) recurs, the doctor must be told. If the drug is not working, another one may be tried. All treatments have side effects, mostly minor ones. On the whole, with medication, abnormal heart rhythms are controlled rather than cured: once any drug is started, it must be continued and taken regularly to be effective. Any medication can occasionally make the tachycardia worse and others may have to be tried. After successful ablation, minor palpitations may still be present. However, they are not usually troublesome or important. Implanted defibrillators require regular check ups in the same manner as pacemakers, in a special clinic.

If Abnormal Heart Rhythms (Ventricular) are Left Untreated …

Ventricular tachycardia should always be treated, as the function of the heart usually deteriorates. Furthermore, this rhythm may degenerate into ventricular fibrillation. This rhythm does not lead to effective pumping of the blood and the patient is therefore in a critical condition.

Effects on Family of Abnormal Heart Rhythms (Ventricular)

The presence of a tachycardia in itself should not cause concern. If there is an underlying heart condition, this may need separate treatment. This condition may affect lifestyle, in which case some support from the family is always helpful.