Ventricular tachycardia

Ventricular tachycardia (V-tach or VT) is a cardiovascular disorder in which fast heart rate occurs in the ventricles of the heart. Although a few seconds of VT may not result in permanent problems, longer periods are dangerous; and multiple episodes over a short period of time are referred to as an electrical storm, which also occurs when one has a seizure (although this is referred to as an electrical storm in the brain). Short periods may occur without symptoms, or present with lightheadedness, palpitations, shortness of breath, chest pain, and decreased level of consciousness. Ventricular tachycardia may lead to coma and persistent vegetative state due to lack of blood and oxygen to the brain. Ventricular tachycardia may result in ventricular fibrillation (VF) and turn into cardiac arrest. This conversion of the VT into VF is called the degeneration of the VT. It is found initially in about 7% of people in cardiac arrest.

Ventricular tachycardia can occur due to coronary heart disease, aortic stenosis, cardiomyopathy, electrolyte imbalance, or a heart attack. Diagnosis is by an electrocardiogram (ECG) showing a rate of greater than 120 beats per minute and at least three wide QRS complexes in a row. It is classified as non-sustained versus sustained based on whether it lasts less than or more than 30 seconds. The term ventricular arrhythmia refers to the group of abnormal cardiac rhythms originating from the ventricle, which includes ventricular tachycardia, ventricular fibrillation, and torsades de pointes.

In those who have normal blood pressure and strong pulse, the antiarrhythmic medication procainamide may be used. Otherwise, immediate cardioversion is recommended, preferably with a biphasic DC shock of 200 joules. In those in cardiac arrest due to ventricular tachycardia, (CPR) and defibrillation is recommended. Biphasic defibrillation may be better than monophasic. While waiting for a defibrillator, a precordial thump may be attempted (by those who have experience) in those on a heart monitor who are seen going into an unstable ventricular tachycardia. In those with cardiac arrest due to ventricular tachycardia, survival is about 75%. An implantable cardiac defibrillator and medications such as beta-blockers or amiodarone may be used to prevent recurrence. Non-dihydropyridinecalcium channel blockers such as verapamil have a limited role and may be of benefit in idiopathic interfascicular reentrant LVT, but should be avoided in the vast majority of cases per AHA guidelines, especially in patients with structural abnormalities such as heart failure with reduced ejection fraction or necrotic damage due to prolonged acute coronary syndrome, in which beta-blockers remain first-line whereas non-dihydropyridines may precipitate the onset of hemodynamic collapse.