Left ventricular versus biventricular pacing: a randomized comparative study evaluating mid-term electromechanical and clinical effects.

Background: Although left ventricular (LV) pacing has been proposed as an alternative to biventricular (BIV) pacing for heart failure (HF) patients, few comparative data are available on the electromechanical effects of these pacing modalities at mid-term follow-up. Aim: To investigate the clinical and echocardiographic effects of LV versus BIV pacing in a mid-term randomized study. Methods: After implantation of a device with LV/BIV pacing capabilities, 22 patients with chronic HF and left bundle branch block were randomized to LV or BIV pacing. Patients were assessed both preimplantation and after 3 months by clinical examination, ECG and echocardiography with pulsed tissue Doppler imaging. Results: At 3 months LV pacing improved clinical parameters, LV ejection fraction (+5%, range 5-8%, P = 0.007) and intraventricular dyssynchrony (-40 ms, range -50 to -15 ms, in septal to lateral delay, P = 0.008) to a similar extent to BIV pacing. A decrease in interventricular mechanical delay (-25 ms, range -40 to -5 ms, P = 0.008) and QRS duration (-28 ms, range -40 to -5 ms, P = 0.008) was observed in BIV, but not in LV patients. Conclusion: In this pilot evaluation, LV pacing appeared to be associated with clinical benefits similar to BIV pacing at mid-term follow-up, and this was combined with an improvement in intraventricular dyssynchrony, regardless of variations in interventricular dyssynchrony and QRS duration. Echocardiographic evaluation of intraventricular dyssynchrony seems to be an appropriate method for assessing the chronic response to LV pacing.