A novel electrocardiographic predictor of clinical response to cardiac resynchronization therapy.

Aims: A wide QRS with left bundle branch block pattern is usually required for cardiac resynchronization therapy (CRT) in patients with dilated cardiomyopathy. However, ∼30% of patients do not benefit from CRT. We evaluated whether a detailed analysis of QRS complex can improve prediction of CRT success.

Methods And Results: We studied 51 patients (67.3 + 9.5 years, 36 males) with classical indication to CRT. Twelve-lead electrocardiogram (ECG) (50 mm/s, 0.05 mV/mm) was obtained before and 3 months after CRT. The following ECG intervals were measured in leads V1 and V6: (i) total QRS duration; (ii) QRS onset-R wave peak; (iii) R wave peak-S wave peak (RS-V1 and RS-V6); (iv) S wave peak-QRS end; and (v) difference between QR in V6 and in V1. Patients were considered as responder when left ventricular ejection fraction (LVEF) increased by ≥5% and New York Heart Association class by ≥1 after 3 months of CRT. Of ECG intervals, only basal RS-V1 was longer in responders (n = 36) compared with non-responders (52.9 ± 11.8 vs. 44.0 ± 12.6 ms, P = 0.021). Among patients with RS-V1 ≥45 ms 83% responded to CRT vs. 33% of those with RS-V1 < 45 ms (P < 0.001). RS-V1 ≥ 45 ms was independently associated with response to CRT in multivariable analysis (odds ratio 9.8; P = 0.002). A reduction of RS-V1 ≥ 10 ms by CRT also significantly predicted clinical response. RS-V1 shortening correlated with improvement in LVEF (r = -0.45; P < 0.001) and in MS (r = 0.46; P < 0.001).

Conclusion: Our data point out that RS-V1 interval and its changes with CRT may help to identify patients who are most likely to benefit from CRT.