Does presence of left ventricular contractile reserve improve response to cardiac resynchronization therapy? An updated meta-analysis.

Abstract

Up to a third of patients undergoing cardiac resynchronization therapy (CRT) do not have a clinical or echocardiographic response. It is also unclear, whether contractile reserve (CR) could predict CRT response. This meta-analysis examines whether the presence of CR improves response to CRT and whether this is modulated by other clinical factors. Search of PubMed/EMBASE/Cochrane databases for articles examining response to CRT stratified by the presence or not of CR. End-point classified as clinical or echocardiographic response. The analysis compared response to CRT (echocardiographic or clinical) between patients with or without CR. 824 patients in 12 studies were included. The presence of left ventricular CR was associated with a significant reduction in echocardiographic non-responders to CRT compared to patients without CR (OR: 0.16, 95% CI 0.08-0.33, p<0.00001). The presence of left ventricular CR was associated with a significant reduction in clinical non-responders to CRT compared to patients without CR (OR: 0.23, 95% CI 0.14-0.37, p<0.00001). Sensitivity analysis showed no difference in response when pooling studies using left ventricular ejection fraction (LVEF) or non-LVEF markers of CR. Meta-regression showed that CR was associated with lower rates of non-responders and this was more pronounced in patients with a narrower mean QRS complex. Identification of CR is associated with improved response to CRT. Importantly, QRS width is a potential moderator variable which can explain part of the heterogeneity in echo response. The combination of CR and QRS width may modulate the response to CRT.