P4985Blunted heart rate reserve as an imaging-independent predictor of abnormal left ventricular contractile reserve

Abstract

Abstract Background Stress echocardiography (SE) relies on regional wall motion and left ventricular contractile reserve (LVCR) based on force (systolic blood pressure/end-systolic volume). An additional non-imaging parameter based on EKG is the blunted heart rate reserve (HRR) which is a simple marker of altered autonomic balance and is associated with worse prognosis independently of ischemia. Aim To assess the relationship between HRR and LVCR in patients undergoing SE. Methods We enrolled 4707 patients (age 63.6±11.3 yrs, 2800 males) referred to SE for known or suspected coronary artery disease (CAD) and/or heart failure (HF) in 21 SE laboratories in 8 countries. The employed stress was exercise (n=2062), dipyridamole (n=2007) or dobutamine (n=638). We assessed LVCR (stress/rest ratio of force=systolic blood pressure/end-systolic volume, ESV). Stress-specific abnormal cutoff value of LVCR were <2.0 for exercise and dobutamine and <1.1 for dipyridamole. All readers had passed the upstream quality control reading for wall motion abnormalities and ESV. HR (with 12-lead ECG) was obtained each minute and recorded at rest and peak stress. HR reserve (HRR) was calculated as the peak/rest HR ratio. Results HRR was related to LVCR at cumulative (n=4707; r=0.351; p<0.001: see figure) and stress-specific analysis for exercise (r=0.351; p<0.001), dipyridamole (r=0.241; p<0.001) and dobutamine (r=0.214; p<0.001). At multivariate logistic regression analysis, blunted HRR (optimal cutoff: 1.73 for exercise, 1.306 for dipyridamole, 1.932 for dobutamine) was a significant predictor of abnormal LVCR at stress-specific analysis for exercise (Odds ratio = 0.285, 95% Confidence Intervals: 0.149–0.546, p=0.0001), dobutamine (Odds ratio = 0.187, 95% Confidence Intervals: 0.057–0.617, p=0.0001) and dipyridamole (Odds ratio = 0.263, 95% Confidence Intervals: 0.115–0.602, p=0.002). Conclusion A blunted HRR is a useful non-imaging predictor of abnormal LVCR response during exercise or pharmacological SE. HRR is a simple biomarker of autonomic unbalance of physiologic and potentially prognostic meaning. A “slow heart” during stress (with blunted HRR) is more often a “weak heart”, with blunted increase in force.