What is ventricular tachycardia?

What is ventricular tachycardia?

Ventricular tachycardia (VT) is an abnormal fast rhythm originating from the ventricles, the lower chambers of the heart. Normally heart rhythm originates from the sinus node, the natural pacemaker of the heart, situated in the right upper chamber, right atrium. Ventricular tachycardia is serious abnormality of heart rhythm which can lead to fall in blood pressure and occasionally progress to cardiac arrest or sudden stoppage of the heart. Ventricular tachycardia needs urgent treatment.

Ventricular tachycardia can occur with and without other structural heart disease. Any heart disease which can cause a scar in the heart muscle like a heart attack can cause ventricular tachycardia. Ventricular tachycardia is usually riskier when it is associated with a structural heart disease as both problems contribute to the risk of the illness.

Those without structural heart disease are primary electrical disorders of the heart. There are certain genetic disorders which have high risk of recurrent episodes of ventricular tachycardia. Two important conditions in this category are the long QT syndromes and Brugada syndrome. Long QT syndrome is an electrical disorder of the heart present at birth. But it may not manifest immediately and can come with symptoms later on.

Another genetically mediated electrical disorder of the heart is catecholaminergic polymorphic ventricular tachycardia (CPVT). In CPVT, the ventricular tachycardia occurs with emotional stress and exercise. It can occur in children, causes a lot of distress and is a dangerous disease.

Abnormalities in the blood levels of electrolytes like potassium and magnesium can also cause ventricular tachycardia. It usually occurs when blood potassium or magnesium levels are low. Both are related in a way that when blood magnesium levels are low, potassium levels also come down. This is because magnesium has a role of regulating potassium movements in the kidney.

Ventricular tachycardia can also occur as an adverse effect of some medications. These are medications which prolong the QT interval on the ECG. They produce acquired long QT interval and have manifestations like the congenital variety. Those with congenital long QT syndromes can have worsening if they are given these medications. In fact, QT interval testing is routinely done when any new medication is considered for regulatory approval.

Ventricular tachycardia can be sustained or non-sustained, lasting less than 30 seconds. Obviously, sustained ventricular tachycardia is more dangerous. Some varieties of ventricular tachycardia can be brought on by exercise and relieved by rest.

Person having ventricular tachycardia usually feels the fast heart beats (palpitation) and sometimes may feel dizzy. Rarely unconsciousness and fall can occur if the ventricular tachycardia is very fast. Such fast VT may need immediate correction with a regulated direct current shock given by a special equipment known as defibrillator. Other cases can be treated by medications given as injections. After treatment, tests are needed to find out what was the cause and to know the chance of recurrence.

Ventricular tachycardia is documented by an ECG (electrical recording of the heart), taken during the episode. If that opportunity was missed, it can be documented by longer term ECG monitoring like a 24 hour Holter monitoring. Infrequent episodes need external loop recorders which can monitor about a week or an implantable loop recorder which can monitor for 3 years or even more.

When there is an associated structural heart disease, that has to be treated appropriately. Those with recurrent episodes need continuous preventive medications. A special device known as an implantable cardioverter defibrillator (ICD) which can monitor the heart rhythm regularly and give electrical treatment when needed is another life saving option.

Any abnormality in blood electrolytes have to be corrected and cause for the abnormality identified and treated. Any potential medications which had produced the ventricular tachycardia as an adverse effect has to be discontinued and substituted with another suitable one.