Extent of myocardial viability predicts response to biventricular pacing in ischemic cardiomyopathy

Background: The clinical response to biventricular pacing is unpredictable, especially in patients with ischemic cardiomyopathy. Objectives: The purpose of this study was to prospectively examine the relationship between the extent of myocardial viability and the response to cardiac resynchronization therapy. Methods: Twenty-one patients with ischemic left ventricular (LV) dysfunction (left ventricular ejection fraction [LVEF] 21 ± 5%), New York Heart Association (NYHA) functional class III-IV, and QRS > 120 ms received biventricular devices. Myocardial viability was assessed by myocardial contrast echocardiography, and a perfusion score index (PSI) was calculated from summed segmental perfusion scores. LV performance was assessed by echocardiography on the day after implantation and at 6 months. Results: PSI was closely correlated with acute improvement in LVEF (P = .003, r = 0.65), stroke volume (P = .02, r = 0.54), and end-systolic volume (P = .05, r = -0.49). PSI also correlated with early diastolic LV relaxation (E′, P < .05, r = 0.50) and global myocardial performance or Tei index (P = .003, r = 0.63). By multiple linear regression analysis, PSI provided incremental predictive value to the degree of dyssynchrony, measured by tissue Doppler imaging, for predicting improvement in LVEF. At 6 months, PSI remained positively correlated with improvement in ventricular performance and with reduction in LV end-diastolic dimension (P = .003, r = -0.68). PSI also influenced the clinical variables of NYHA class, 6-minute walk distance, quality-of-life score, and number of hospitalizations for heart failure. Conclusion: In patients with ischemic cardiomyopathy, the extent of myocardial viability predicts acute and long-term improvement in LV performance, exercise tolerance, and reduction in LV end-diastolic dimension with biventricular pacing.