The effect of left ventricular pacing site on cardiac resynchronization therapy outcome and mortality: the results of a PROSPECT substudy

AIMS: Left ventricular pacing site (LV-PS) was prospectively collected to test the influence of the anatomical LV-PS on the outcome of cardiac resynchronization therapy (CRT) and mortality. METHODS AND RESULTS: Four hundred and twenty-six patients with standard indications for CRT underwent echocardiographic and clinical evaluation before and after CRT implantation. The LV-PS was determined from fluoroscopy using the clockwise principle (CP). The LV-PS was categorized into three prospectively defined groups: between 3 and 5 o'clock and longitudinal basal/mid-position (Group A, 'optimal'); between 12 and 2 o'clock and longitudinal mid-apical anterior position (Group B, 'non-optimal'); and all other (Group C, 'other'). Of 333 patients, followed for 0.9 years (mean), adequate images were available to define the LV-PS. Left ventricular pacing site was Group A for 118 patients, Group B for 56, and Group C for 159. The three groups were comparable regarding gender, aetiology, and NYHA class; however, patients in Group A were younger. No relation was found between the LV-PS groups and CRT outcome or all-cause mortality. However, further exploratory subanalyses suggest that LV-PS may impact outcomes in non-ischaemic patients, those with left bundle branch block, and when LV-PS is apical in location. CONCLUSION: Using the CP to define anatomical LV-PS, no relation was found between the LV-PS groups and CRT outcome and mortality. Exploratory analyses warrant further studies.