RESUMEN
BACKGROUND: Effective cardiac resynchronization therapy (CRT) is more likely with widely separated left ventricular (LV) and right ventricular (RV) pacing leads tips. We hypothesized that lead separation is an important factor in determining the clinical response to CRT. METHODS: A retrospective study of 86 consecutive patients age 71 ± 10 years, male (74%), coronary disease (71%), atrial fibrillation (23%), LV ejection fraction (22 ± 9%), QRS duration (160 ± 27 ms), New York Heart Association (NYHA) class III (81%), NYHA class IV (19%) undergoing CRT from January 2006 to September 2008. The median follow-up was 12 months and clinical response to CRT was defined as reduction of NYHA class by one or more. The three-dimensional separation between RV and LV pacing lead tips was calculated using measurements obtained from orthogonal posteroanterior and lateral chest radiographs performed the day after implantation. RESULTS: Fifty-nine patients (69%) responded to CRT. There was a statistically significant association between increased three-dimensional lead separation and clinical response to CRT (P= 0.005). Stronger association was obtained when lead separation was corrected for cardiac size (P= 0.001). A significantly higher response rate of 88% was achieved in patients with QRS duration of 160 ms or more, and lead separation of 100 mm or more compared with 60% when lead separation was less than 100 mm and QRS duration remained the same (P = 0.027). CONCLUSIONS: Greater three-dimensional separation of LV-to-RV leads is associated with improved response to CRT. A prospective multicenter trial is needed to assess lead separation as a predictor for response.