Echocardiographic aspects of multisite pacing in patients undergoing cardiac resynchronization therapy.

Echocardiography has emerged as an accepted approach to define dyssynchrony in patients with advanced stage of heart failure (HF). Unfortunately no single echocardiographic parameter has been established to predict positive response after cardiac resynchronization therapy (CRT) and the nonresponder rate of 20-30% is still a matter of discussion and research. One of the most promising techniques in this regard is two-dimensional strain echocardiography based on speckle tracking with the potential to disclose residual dyssynchrony after primary CRT. An important reason for weak response to CRT is suboptimal position of the coronary sinus (CS) lead. Initial clinical benefit after CRT may mask partial residual dyssynchrony, which may cause worsening and recurrence of HF symptoms over time. Echocardiography helps to define the location of residual dyssynchrony and may identify patients who would benefit from implantation of a second CS-lead and triple-site pacing. If primary CRT fails due to imperfect placement of the CS-lead or due to coronary vein abnormalities and an epicardial approach is not appropriate, dual site pacing of the right ventricle may be an alternative procedure.