Electrocardiographic predictors of response to cardiac resynchronization therapy in patients with intraventricular conduction delay

Background: Little is known about predictors of response to cardiac resynchronization therapy (CRT) in patients with intraventricular conduction delay (IVCD). The purpose of this study was to investigate the benefits of CRT and significant variables on surface electrocardiogram (ECG) to predict response to CRT in those patients. Methods and Results: Among the cohort of 152 CRT patients, 40 patients with IVCD were evaluated. Sixteen patients (40%) were responders. At baseline, responders had a wider QRS duration (158±18 vs. 144±18 ms, P=0.02) and a higher frequency of left axis deviation (LADEV; 75% vs. 29%, P=0.004) compared with non-responders. After CRT, greater shortening of QRS duration (ΔQRS; 26±24 vs. 7±24 ms, P=0.02), axis shift from LADEV to right axis deviation (RADEV; 69% vs. 13%, P<0.001), and both rightward forces in lead I and anterior forces in V1 (56% vs. 13%, P=0.003) were found more frequently in responders. Multivariable logistic regression analysis showed that LADEV at baseline, or ΔQRS and axis shift from LADEV to RADEV after CRT were independent predictors of response to CRT. Conclusions: Patients with IVCD may not respond to CRT, but LADEV at baseline and reversal of ventricular activation after CRT on surface ECG could be important to predict response to CRT.