Impact of interventricular lead distance and the decrease in septal-to-lateral delay on response to cardiac resynchronization therapy.

AIMS To investigate the influence of interlead distance and lead positioning on success of cardiac resynchronization therapy (CRT) in patients with advanced chronic heart failure and electrical dyssynchrony. Despite application of established selection criteria, 20-40% of the patients do not respond to CRT. METHODS AND RESULTS We examined consecutive patients in whom CRT was implanted. Response to CRT was defined as a decrease in the left ventricular end-systolic volume >or=10% after 6 months. A comparison was made between patients who were responders to CRT and those who were non-responders. A univariate and stepwise multivariate logistic regression was performed with regard to predictors for response. Between January 2004 and January 2008, 174 patients who were treated with CRT were classified as responders [n = 95 (55%)] or non-responders [n = 79 (45%)]. Responders had a significantly larger horizontal interlead distance on the lateral thoracic X-ray [odds ratio (OR) 2.8 (1.2-6.6), P = 0.01], a septal-to-lateral delay >60 ms [OR 4.9 (2.0-11.4), P < 0.0001], non-ischaemic cardiomyopathy [OR 3.0 (1.3-6.9), P = 0.009], a left ventricular end-diastolic diameter <67 mm [OR 4.2 (1.8-9.9), P = 0.001], angiotensin-converting enzyme inhibitor use [OR 8.1 (1.7-38.2), P = 0.008], and no tricuspid valve insufficiency [OR 6.9 (1.3-35.5), P = 0.02]. Post-implantation responders had a significantly greater decrease in the intraventricular delay (septal-to-lateral delay 62 +/- 62 vs. 26 +/- 65 ms, P = 0.001), but not in the interventricular mechanical delay. CONCLUSION Larger interlead distance on the lateral thoracic X-ray, associated with positioning of the left ventricular lead in the posterior position, is associated with response after 6 months of follow-up. Furthermore, diminishing the septal-to-lateral delay is predictive for response.