BackgroundBiventricular (BiV) pacing is the most common mode of delivering cardiac resynchronization therapy (CRT). However, initial clinical studies have indicated that left ventricular (LV) pacing is not inferior to BiV pacing. This study was conducted to address whether LV only pacing can provide the same hemodynamic response as BiV pacing.MethodsThis before–after clinical trial was conducted at Ekbatan Hospital, from July 2012 to November 2014. Patients with a LV ejection fraction ≤35% and a QRS duration ≥0.12 s who had a standard indication for ventricular pacing were enrolled. The CRT devices of all patients had already been set for BiV pacing. Therefore, their CRT devices were set for LV only pacing for 3 months. The hemodynamic status of the patients was assessed by echocardiography before setting the CRT device to LV only pacing (as a control) and 3 months after (as an intervention).ResultsThere was no statistically significant difference between the effect of BiV pacing and LV only pacing on the hemodynamic responses including LV ejection fraction, LV end diastolic and systolic volume, and velocity time integral of the aortic valve. Moreover, no significant difference was seen between men and women either.ConclusionsLV only pacing is not inferior to BiV pacing, and the hemodynamic response was similar in the two groups. However, the LV mode has a number of advantages over the BiV mode. More evidence, based on large clinical trials, is needed to confirm our results.