Patients with LV dyssynchrony >/=65 ms respond to CRT and have an excellent prognosis after CRT.

Background-Currently, one third of patients treated with cardiac resynchronization therapy (CRT) do not respond.Nonresponse to CRT may be explained by the presence of scar tissue in the posterolateral left ventricular (LV) segments, which may result in ineffective LV pacing and inadequate LV resynchronization. In the present study, the relationship between transmural posterolateral scar tissue and response to CRT was evaluated. Methods and Results-Forty consecutive patients with end-stage heart failure (NYHA class III/IV), LV ejection fraction Յ35%, QRS duration Ͼ120 ms, left bundle-branch block, and chronic coronary artery disease were included. The localization and transmurality of scar tissue were evaluated with contrast-enhanced MRI. Next, LV dyssynchrony was assessed at baseline and immediately after implantation with tissue Doppler imaging. Clinical parameters, LV volumes, and LV ejection fraction were assessed at baseline and at a 6-month follow-up. Fourteen patients (35%) had a transmural (Ͼ50% of LV wall thickness) posterolateral scar. In contrast to patients without posterolateral scar tissue, these patients showed a low response rate (14% versus 81%; PϽ0.05) and did not show improvement in clinical or echocardiographic parameters. In addition, LV dyssynchrony remained unchanged after CRT implantation (84Ϯ46 versus 78Ϯ41 ms; PϭNS). Patients without posterolateral scar tissue and severe baseline dyssynchrony (Ն65 ms) showed an excellent response rate of 95% compared with patients with a posterolateral scar and/or absent LV dyssynchrony (11%). Conclusions-CRT

Background-In patients with severe heart failure and dilated cardiomyopathy, cardiac resynchronization therapy (CRT) improves left ventricular (LV) systolic function associated with LV reverse remodeling and favorable 1-year survival. However, it is unknown whether LV reverse remodeling translates into a better long-term prognosis and what extent of reverse remodeling is clinically relevant, which were investigated in this study. Methods and Results-Patients (nϭ141) with advanced heart failure (meanϮSD age, 64Ϯ11 years; 73% men) who received CRT were followed up for a mean (ϮSD) of 695Ϯ491 days. The extent of reduction in LV end-systolic volume (LVESV) at 3 to 6 months relative to baseline was examined for its predictive value on long-term clinical outcome. The cutoff value for LV reverse remodeling in predicting mortality was derived from the receiver operating characteristic curve. Then the relation between potential predictors of mortality and heart failure hospitalizations were compared by Kaplan-Meier survival analysis, followed by Cox regression analysis. There were 22 (15.6%) deaths, mostly due to heart failure or sudden cardiac death. The receiver operating characteristic curve found that a reduction in LVESV of Ն9.5% had a sensitivity of 70% and specificity of 70% in predicting all-cause mortality and of 87% and 69%, respectively, for cardiovascular mortality. With this cutoff value, there were 87 (61.7%) responders to reverse remodeling. In Kaplan-Meier survival analysis, responders had significantly lower all-cause morality (6.9% versus 30.6%, log-rank 2 ϭ13.26, Pϭ0.0003), cardiovascular mortality (2.3% versus 24.1%, log-rank 2 ϭ17.1, PϽ0.0001), and heart failure events (11.5% versus 33.3%, log-rank 2 ϭ8.71, Pϭ0.0032) than nonresponders. In the Cox regression analysis model, the change in LVESV was the single most important predictor of all-cause (␤ϭ1.048, 95% confidence intervalϭ1.019 to 1.078, Pϭ0.001) and cardiovascular (␤ϭ1.072, 95% confidence intervalϭ1.033 to 1.112, PϽ0.001) mortality. Clinical parameters were unable to predict any outcome event. Conclusions-A reduction in LVESV of 10% signifies clinically relevant reverse remodeling, which is a strong predictor of lower long-term mortality and heart failure events. This study suggests that assessing volumetric changes after an intervention in patients with heart failure provides information predictive of natural history outcomes. (Circulation. 2005;112:1580-1586.)

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The extent of LV reverse remodeling at midterm follow-up is predictive for long-term outcome in CRT patients.

From 30% to 40% of heart failure patients with QRS duration >120 ms do not exhibit left ventricular dyssynchrony, which may explain the nonresponse to CRT. Alternatively, 27% of patients with heart failure and a narrow QRS complex show significant left ventricular dyssynchrony and may be candidates for CRT.

Pacing at the site of latest mechanical activation, as determined by speckle tracking radial strain analysis, resulted in superior echocardiographic response after 6 months of CRT and better prognosis during long-term follow-up.

The extent of scar tissue and viable myocardium were directly related to the response to CRT. Furthermore, scar tissue in the LV pacing lead region may prohibit response to CRT. Evaluation for viability and scar tissue may be considered in the selection process for CRT.