Optimal stimulation of the left ventricle.

Cardiac resynchronization therapy has been proposed to alleviate heart failure symptoms refractory to classic drug treatment. Potential benefits hinge on a number of key components, including judicious selection of patients likely to respond to the therapy and appropriate placement of the leads, particularly the lead responsible for left ventricular pacing. Evidence of ventricular asynchrony is an individual prerequisite for consideration of cardiac resynchronization therapy. Ventricular asynchrony can be diagnosed by recording a QRS duration >150 msec or during echocardiography, with the goal of investigating the mechanical aspect of asynchrony. The optimal left ventricular pacing site can be defined by the latest segmental contraction, which is mainly the mid-lateral wall. The first-choice technique to initiate left ventricular pacing consists of a transvenous approach via the coronary sinus tributaries. In practice, the final left ventricular pacing location also depends on highly variant coronary sinus anatomy, acceptable electrical parameters, and lead stability. Procedure-related complications, which consist mainly of coronary sinus perforation and phrenic nerve stimulation, remain low (<1%) and should decrease further with the use of new features specific to the procedure.