Heart failure due to right ventricular apical pacing: the importance of flow patterns

In patients receiving permanent cardiac electrical stimulation, a high burden of apical right ventricular pacing is associated with an increased incidence of heart failure. Despite the large body of electrocardiographic, echocardiographic, and pathological data, mechanisms underlying this serious complication are not fully understood. Moreover, the empirical use of alternative right ventricular pacing sites, both in the experimental and in the clinical setting, has not provided better results in terms of clinical outcome. Recent data derived by echocardiographic particle image velocimetry of intracardiac flows have shown abnormal flow patterns in patients with dyssynchrony of left ventricular wall contraction, and the reversion to normal flow dynamics after successful electrical cardiac resynchronization therapy. This suggests that a normal intraventricular flow pattern is strongly dependent on the highly coordinated contraction of the ventricular wall segments and that an abnormal sequence of wall contraction may trigger the development of overt heart failure. This review summarizes the state of the art on this topic, highlighting postulated underlying basic mechanisms linking abnormal flow with the development of pacing-induced heart failure. This research line suggests the importance of studying intraventricular fluid dynamics as a new powerful tool for a more complete understanding of mechanisms involved, and ultimately to prevent pacing-related heart failure.