Mechanisms of Initiation of Ventricular Tachyarrhythmias

The mechanisms responsible for ventricular tachyarrhythmia (VT) initiation have been studied extensively since the beginning of the last century. Multiple approaches including clinical observations; experiments in vivo, in vitro, and at cellular and genetic levels; theoretical analysis; and numeric simulations have been used. Most VTs are initiated by spontaneous discharge(s) at one or several sites in the ventricle, which can contribute to, or precipitate, reentry that then maintains the VT. Although most VTs occur in abnormal hearts such as in patients with coronary artery diseases, cardiomyopathy, abnormal ionic currents, or other problems, VT can also be functional, occurring in seemingly normal hearts when the conditions for its initiation are met. Because of the possible outcome of sudden cardiac death and the increasingly aging population in the industrialized countries, managing VT is a significant and important clinical task. Understanding the mechanisms of its initiation is one of the key steps in developing clinical strategies to prevent and treat VT. However, the mechanisms of VT initiation are still not fully understood and are the topic for a brief overview in this chapter.