Ventricular tachycardia: arrhythmia

2021-05-31 03:44 PM

Irregular tachycardia is caused by ischemic damage, and ventricular tachycardia is also a common cause of ventricular fibrillation, because of the rapid and continuous repetition of myocardial excitation.

The figure shows a short paroxysmal ventricular tachycardia. The electrocardiogram of paroxysmal ventricular tachycardia takes the form of a series of continuously repeating extrasystoles without a normal rhythm in between.

Irregular tachycardia is caused by two causes. First, this form of tachycardia usually does not occur unless there is significant ischemic damage to the ventricles. Second, ventricular tachycardia is also a common cause of ventricular fibrillation because the excitatory rhythms of the myocardium repeat rapidly and continuously, which we will discuss in the next section.

Figure. Ventricular tachycardia (lead III).

Occasionally, cardiotoxicity by digitalis causing local excitation also causes ventricular tachycardia. Antiarrhythmic drugs such as amiodarone or lidocaine can also be used to treat ventricular tachycardia. Lidocaine inhibits the increase in membrane sodium permeability during action potentials, thereby inhibiting the onset of the abnormal pacing point that causes tachycardia. Amiodarone has many actions such as prolonging the action potential and phase of myocardial repolarization and slowing the conduction of the atrioventricular node. In some cases, an electric shock may be needed to restore a normal heart rhythm.