Ventricular tachycardia (VT)
Fast rhythm originating from the lower chambers of the heart. Ventricular tachycardia is a potentially life threatening disorder of the heart rhythm. It can progress to ventricular fibrillation (cardiac arrest) where the heart stops pumping.
What causes ventricular tachycardia?
Very often it is a scar of a previous heart attack which causes recurrent VT. It is also common during an acute heart attack. It is one of the important risks of an acute heart attack in the early hours due to electrical instability of the damaged heart.
VT can occur due to abnormalities in the levels of electrolytes in the blood like low potassium and magnesium levels. These levels are routinely tested in those with VT and corrected if abnormal.
Several medications can produce VT as adverse effect. Hence it is mandatory to test any new drug for ECG abnormalities before market launch.
There are few inherited primary electrical disorders of the heart which can cause VT. Though rare, they are prone for recurrent episodes of this life threatening disorder of heart rhythm.
What are the important symptoms of ventricular tachycardia?
Most common symptom is undue awareness of heart beats known as palpitation. Occasionally some slow varieties of VT may be asymptomatic and well tolerated. But most often VT produces significant symptoms including dizziness and sometimes breathlessness when there is a worsening of underlying heart disease due to the fast rate.
What treatment modalities are available for treatment of ventricular tachycardia?
VT with lower rates and without other symptoms can be treated with medication under cardiac monitoring in the intensive care unit. Fast VT with fall in blood pressure or breathlessness needs urgent conversion with an electrical countershock using a defibrillator in the intensive care unit, with proper sedation.
Recurrence of VT can be prevented by continuous use of medications. Those which have a high chance of recurrence need protection with an implantable cardioverter defibrillator which automatically detects and electrically treats the VT. Slower VT will be overdriven by rapid electrical pulses given to the heart known as overdrive pacing. Faster VT or those which do not respond to overdrive pacing are treated by internal electric shocks given directly within the chamber of the heart. Though the person may feel a jolt with the internal shock, it is life saving.
Recurrence can also be prevented by a procedure known as catheter ablation. In this procedure, small electrodes are introduced into the heart and electrical signals are mapped to find out the origin of the VT. Once the origin is located, radiofrequency currents are delivered using an ablation catheter to destroy the tiny irritable focus which is triggering the VT.