Cardiac resynchronization therapy for chronic heart failure: why does it not always work?

Since coronary angiography and ventriculography are performed in all of these patients with LV dysfunction and symptoms of heart failure, it seems silly to waste the opportunity to study this technique and its value in identifying patients who will respond to CRT, at least in the immediate post-CRT state. The critical factors that may result in a successful long-term positive result of CRT in patients with optimal device programming and optimized medical therapy for heart failure are these: (1) Venous anatomy suitable for electrical stimulation of the LV free wall. (2) Viable myocardium in the septum and the LV free wall. (3) Adequate perfusion of the microcirculation in the distribution where the leads are being placed.