Left ventricular lead placement in cardiac resynchronization therapy: where and how?

Cardiac resynchronization therapy (CRT) offers proven benefit to patients with refractory symptomatic chronic heart failure (New York Heart Association Class III or IV), severe left ventricular (LV) systolic dysfunction (LV ejection fraction <35%), and LV dyssynchrony (QRS width >120 ms). Cardiac resynchronization therapy has the potential to improve survival and functional capacity, reduce hospital admissions, and promote LV reverse remodelling. Although difficult to truly evaluate, up to 30% of patients do not attain symptomatic benefit. Factors associated with a poor outcome include inappropriate patient selection, inadequate device programming, presence of myocardial scar, and suboptimal LV lead placement. Left ventricular dyssynchrony is an important determinant of CRT response, although at present no reliable single measure to identify patients beyond QRS width has been identified. In this review, we discuss the effect of LV lead placement to pace the region of maximal dyssynchrony, the impact of total scar burden on response, and the relationship between LV lead position and localized scar. Consideration is also given to prospectively defining placement of the LV lead including surgical epicardial lead positioning.