Background: Response to cardiac resynchronization therapy is most favorable in patients with heart failure with QRS duration ≥150 ms and left bundle branch block and less predictable in those with QRS width 120 to 149 ms or non-left bundle branch block.
Methods and results: We studied 205 patients with heart failure referred for cardiac resynchronization therapy with QRS ≥120 ms and ejection fraction ≤35%. We tested the hypothesis that contractile function using speckle-tracking echocardiographic global circumferential strain (GCS) from 2 short-axis views and global longitudinal strain (GLS) from 3 apical views add prognostic value to electrocardiographic criteria. There were 112 patients (55%) with GLS >-9% and 136 patients (66%) with GCS >-9%. During 4 years, 81 patients reached the combined primary end point (death, circulatory support, or transplant) and 120 reached the secondary end point (heart failure hospitalization or death). Both GLS >-9% and GCS >-9% were associated with increased risk of unfavorable events as follows: for the primary end point (hazard ratio=2.91; 95% confidence interval, 1.88-4.49; P<0.001) and (hazard ratio=3.73; 95% confidence interval, 2.39-5.82; P<0.001) for the secondary end point (hazard ratio=2.10; 95% confidence interval, 1.45-3.05; P<0.001) and (hazard ratio=3.25; 95% confidence interval, 2.23-4.75; P<0.001). In a prespecified subgroup of 120 patients with QRS 120 to 149 ms or non-left bundle branch block, significant associations of baseline GLS and GCS and outcomes remained: P=0.014 and P=0.002 for the primary end point and P=0.049 and P=0.001 for the secondary end point. Global strain measures had additive prognostic value to routine clinical or electrocardiographic parameters (P<0.001).
Conclusions: Baseline GCS and GLS were significantly associated with long-term outcome after cardiac resynchronization therapy and had additive prognostic value to routine clinical and electrocardiographic selection criteria for cardiac resynchronization therapy.
Keywords: cardiac resynchronization therapy; cardiomyopathy; echocardiography; heart failure; hospitalization; prognosis.
© 2016 American Heart Association, Inc.