Prominent R wave in ECG lead V1 predicts improvement of left ventricular ejection fraction after cardiac resynchronization therapy in patients with or without left bundle branch block

BACKGROUND QRS morphology on postprocedural ECG indicating posterolateral left ventricular pacing may be predictive of response to cardiac resynchronization therapy (CRT). OBJECTIVE The purpose of this study was to assess whether a positive vector in V-1 and/or negative vector in lead I on the first postprocedural ECG, suggesting posterolateral capture from CRT, correlates with improvement in left ventricular ejection fraction (LVEF). METHODS A retrospective chart review was conducted on all patients who underwent CRT implantation at our institution between April 2008 and December 2011. Biventricular (BiV) paced QRS morphology was defined as R/S >= 1 in V1 and/or R/S <= 1 in lead I. The primary outcome was improvement of LVEF >= 7.5%. The chi(2) and t tests were used for analysis. RESULTS Of 68 patients, 49 (72%) met our BiV paced QRS morphology criteria. Thirty-four of these 49 patients (69%) had improvement in LVEF. Of the 19 patients who did not meet our criteria, 17 (89%) did not have an improvement in LVEF (sensitivity 94%, specificity 53%, chi(2) = 19.04, P < .0001). The average LVEF improvement in patients who met our BiV paced QRS morphology criteria was significantly greater than in those who did not (14.27% vs 2.63%, P = .0001). Preprocedural left bundle branch block was not a predictor of echocardiographic response. CONCLUSION Our results highlight the importance of periprocedurat ECG analysis to optimize response to CRT. Moreover, patients without left bundle branch block still benefited from CRT if they met our BiV paced morphology criteria. This suggests that postprocedural left ventricular activation as reflected on the ECG may supersede the baseline conduction delay.