Abstract 3246: Characterization of Super-Response to Cardiac Resynchronization Therapy
Background: In select patients with heart failure, cardiac resynchronization therapy (CRT) has been shown to improve ejection fraction (EF) by an average of 5%. Certain patients experience a more robust improvement in EF with CRT sometimes to normalization. Little is known about the baseline characteristics of this population and if there are any factors associated with such response.
Methods: We extracted demographic, clinical, ECG, and echocardiographic data on 518 consecutive patients presenting to the Cleveland Clinic, Cleveland Ohio between 02/2005 and 08/2007 of which 325 patients had pre- and post-implant echocardiograms. Patients whose EF improved by ≥20% were termed “super- responders.” Differences between the groups in univariate analysis were then entered into a Cox logistic regression model to determine factors associated with super-response.
Results: From this cohort 44 patients met criteria for super-response. Baseline variables including age, pre-implant QRS duration, BMI, type of cardiomyopathy, common comorbidities, and cardiac medications were similar between the two groups. Super-responders were more likely to be female (53.8% vs. 30.9%, p=0.0064) with a native left bundle branch block pattern (LBBB) (63.6% vs. 36.3%, p=0.008), and to have a narrower post-CRT paced QRS complex (ms) (147.7±18.6 vs. 154.9±24.3, p=0.02). The baseline ejection fraction was similar between super and non-super responders (21.72±6.57% vs. 22.76±8.01%, p=0.52); however, super-responders had considerably lower pre-implant left ventricular end-diastolic and systolic diameters (cm) (5.626±0.78 vs. 6.141±1.07, p=0.0036 and 4.571±1.047 vs. 5.154±1.156, p=0.0060), respectively. On multivariate analysis, female gender (p=0.03) and LBBB (p=0.002) remained significantly associated with super-response.
Conclusion: Super-responders to cardiac resynchronization tend to be female patients with a native LBBB pattern on pre-implant ECG.