Non responders to biventricular pacing may respond to left ventricular pacing

Biventricular pacing (cardiac resynchronization therapy or CRT) is an established mode of therapy for heart failure in those with QRS duration of 120 milliseconds or more, indicating cardiac dyssynchrony. Some reports have indicated that left ventricular pacing alone may avoid the downside of right ventricular pacing. Thibault B et al {for the Evaluation of Resynchronization Therapy for Heart Failure (GREATER-EARTH) Investigators} conducted a multicentric, double-blind, crossover trial comparing left ventricular vs biventricular pacing regarding exercise tolerance and left ventricular remodeling in symptomatic patients with left ventricular ejection fraction of 35 percent or less and QRS duration of 120 milliseconds or more [Left Ventricular Versus Simultaneous Biventricular Pacing in Patients With Heart Failure and a QRS Complex ?120 Milliseconds. CIRCULATIONAHA.111.032904
Published online before print November 21, 2011, doi: 10.1161/?CIRCULATIONAHA.111.032904]. They could recruit over two hundred patients from eleven centers. Though there was no significant difference between the groups regarding the outcome, about one third of the non responders to left ventricular pacing responded to biventricular pacing and about one fifth of the biventricular pacing non responders responded to left ventricular pacing. This could suggest an additional option for non responders to CRT. It is interesting to note that the greatest improvement in NYHA (New York Heart Association) symptom class and response to six minute walk test occurred during the run in period of two to eight weeks before randomization.