Characteristics of Responders to Cardiac Resynchronization Therapy: The Impact of Echocardiographic Left Ventricular Volume

Background: One-third of patients who receive cardiac resynchronization therapy (CRT) are classified as nonresponders. Characteristics of responders to CRT have been studied in multiple clinical trials. Hypothesis: Independent predictors of CRT response may be identified by studying a series of patients in routine clinical practice. Method: One hundred twenty-five patients were examined retrospectively from a multidisciplinary CRT clinic program. Echocardiographic CRT response was defined as a decrease in left ventricular (LV) end-systolic volume of =15% and/or absolute increase of 5% in LV ejection fraction at the 6-month visit. Results: There were 81 responders and 44 nonresponders. By univariate analyses, female sex, nonischemic cardiomyopathy etiology, baseline QRS duration, the presence of left bundle branch block (LBBB), and left ventricular end-diastolic volume (LVEDV) index predicted CRT response. However, multivariate analysis demonstrated that only QRS duration, LBBB, and LVEDV index were independent predictors (QRS width, odds ratio [OR]: 1.027, 95% confidence interval [CI]: 1.0041.050, P = 0.023; LBBB, OR: 3.568, 95% CI: 1.2849.910, P = 0.015; LVEDV index, OR: 0.970, 95% CI: 0.9530.987, P = 0.001). Although female sex and nonischemic etiology were associated with an improved CRT response on univariate analyses, after adjusting for LV volumes they were not independent predictors. Conclusions: QRS width, LBBB, and LVEDV index are independent predictors for echocardiographic CRT response. Previously reported differences in CRT response for sex and cardiomyopathy etiology are associated with differences in baseline LV volumes in our clinical practice. Dr. Heist has received research grants (modest) from Biotronik, Boston Scientific, and St. Jude Medical; honoraria (modest) from Biotronik, Boston Scientific, Medtronic, Sorin, and St. Jude Medical; and consultant/advisory board positions (modest) from Boston Scientific, Sorin and St. Jude Medical. Dr. Singh has received research grants (significant) from Biotronik, Boston Scientific, Medtronic, and St. Jude Medical; and consultant/advisory board positions (modest) from Biosense Webster, Biotronik, Boston Scientific, CardioInsight, Medtronic, Sorin, St. Jude Medical, and Thoratec Inc. The statistical analysis was conducted with support from Harvard Catalyst. The Harvard Clinical and Translational Science Center (National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health Award UL1 RR 025758, and financial contributions from Harvard University and its affiliated academic healthcare centers). The authors have no other funding, financial relationships, or conflicts of interest to disclose.