[Role of electrocardiogram in predicting cardiac resynchronization therapy response]

To explore the role of electrocardiogram(ECG)in predicting cardiac resynchronization therapy (CRT) response.

This study retrospectively analyzed ECG of 92 CRT patients, who received CRT therapy from 2001 to 2013 in our center and were followed up for 6 months. The patients were divided into responder group (n=64) and non-responder group (n=28). The baseline and 6-month data including QRS width, heart rhythm and axis variation were analyzed. The definition of responder is left ventricular end systolic volume (LVESV) reduction ≥15% within 6 months after CRT. After CRT therapy, the ventricular activation was changed as left to right (frontal plane), posterior to anterior and axis changed in a clockwise direction. The change in more than two directions was defined as prominent axis change. Logistic analysis was performed to analyze the role of ECG in predicting CRT response.

(1) Baseline parameter comparison between the two groups: the proportion of female and LBBB is significantly higher (P<0.01; P=0.04), while the proportion of atrial fibrillation/flutter (Af/AF) is significantly lower (P<0.01) in responder group than in non-responder group. The pre-CRT average QRS duration is much wider in responder group than in non-responder group (P=0.01). (2) Comparison of follow-up with baseline results in two groups: NYHA heart function level, 6 minutes walking distance, QRS duration, LVEF, LVESV improved significantly (P<0.01) post-CRT in responder group. In non-responder group, the QRS duration and LVESV deteriorated significantly (P=0.02, P<0.01), while post-CRT NYHA heart function level improved significantly. In responder group, pre-CRT ECG axis of 53 patients (82.8%) pointed to left and 58 patients (90.6%) pointed to posterior; post-CRT ECG axis of 49 patients (76.6%) pointed to right and 30 patients (40.6%) pointed to anterior. In non-responder group, pre-CRT ECG axis of 25 patients (89.3%) pointed to left and 24 patients (85.7%) pointed to posterior; post-CRT ECG axis of 17 patients (60.7%) pointed to right and 12 patients (42.9%) pointed to anterior. Post-CRT, the proportion of ECG axis prominent change was significantly higher in responder than in non-responder group (62.5%(40/64) vs. 32.1%(9/28), P=0.007). (3)Predicting value: pre-CRT QRS width ≥140 ms (OR=4.97, 95% CI 1.53 to 16.13, P=0.008)and post-CRT prominent axis change (OR=5.1, 95% CI 1.67 to 15.5, P=0.004)were found to be independent predictors of CRT responders. Af/AF pre-CRT was associated with reduced CRT response (OR=0.25, 95% CI 0.08 to 0.80, P=0.02).

ECG may play a role in predicting CRT response. QRS width and Af/AF before CRT and ECG axis change post-CRT could be used to predict CRT response.