Electrocardiographic predictors of clinical response to cardiac resynchronization therapy in patients with heart failure

Cardiac resynchronization therapy (CRT) is one of the established treatment modalities for systolic heart failure with wide QRS morphology on electrocardiogram (ECG). It acts by synchronized pacing of left and right ventricles in order to coordinate systolic contraction of the left ventricular septum and the free wall. Predicting proper responders to the CRT still remains elusive. Post-implantation 12-lead ECG showing a tall R wave in lead V1 of ≥4 mm and predominant negative deflection (S wave) in lead I (RV1SI pattern) has been postulated as a marker of optimal resynchronization after CRT. We investigated whether presence of this ECG pattern predicts better response and improvement in heart failure outcomes at 6 months after CRT device implantation and found to be very much helpful. Method: Post-implant 12-lead ECG of 75 patients were reviewed and divided into two groups based on the positive RV1SI (Group I) or negative RV1SI (Group II) pattern on ECG. At six months, follow-up response rate was assessed on the basis of echocardiographic parameters of Left Ventricular End Systolic Volume (LVESV) & Left Ventricular Ejection Fraction (LVEF), and functional assessments {(Packer’s Clinical Composite Score, 6-minutes walk test (6MWT) and Minnesota living with heart failure questionnaire (MLWHF)} compared to baseline (pre-implant) values. Result: Evaluation of the post-CRT ECG of 75 patients revealed 29 (38.66%) in Group I and 46 (61.33%) in Group II. It was found that patients in Group I showed better response to CRT in comparison to Group II with respect to improvement in echocardiographic parameters (LVESV reduction of 25.69% vs. 21.81% and EF improvement of 40.29% vs. 33.44%) and functional assessment parameters (6MWT improvement 374.6 meters vs. 218.06 meters, MLWHF improvement 3.85 vs. 1.22 and clinical composite score (New York Heart Association functional class improvement from class IV to II 75% vs. 50% and heart failure related hospitalization after CRT implantation of 3.45% vs. 21.74%). Conclusion: Patients with a positive RV1SI pattern in post-implant 12-lead ECG showed better response with CRT at six months. This simple tool can be used to predict clinical improvement after therapy and accordingly proper positioning of the LV lead or programming the lead-vectors to get such ECG pattern may yield proper CRT response.