The Prognostic Value of Coronary Flow Velocity Reserve in Two Coronary Arteries During Vasodilator Stress Echocardiography

Abstract

Vasodilator stress echocardiography (SE) allows combined evaluation of regional wall motion and Doppler coronary flow velocity reserve (CFVR) of both the left anterior descending coronary artery (LAD) and the right coronary artery (RCA). The aim of this study was to prospectively assess the prognostic correlates of LAD and RCA CFVR on SE. A total of 1,365 patients with known or suspected coronary artery disease underwent dipyridamole SE with combined evaluation of CFVR in both the LAD and the RCA. Ischemia was present on SE in 263 patients (19%). CFVR was abnormal (≤2.0) in 545 patients (40%): 172 in the LAD only, 149 in the RCA only, and 224 in both the LAD and the RCA. During a median follow-up period of 20months, 44 deaths and 98 myocardial infarctions occurred. In the overall population, LAD CFVR ≤ 2.0 (hazard ratio [HR], 3.93) and inducible ischemia (HR, 2.74) were multivariate prognostic predictors. In the subset with ischemia on SE, CFVR did not add to peak wall motion score index (HR, 2.23). In patients without ischemia on SE, age (HR, 1.04), anti-ischemic therapy at the time of testing (HR, 1.6) and LAD CFVR≤2.0 (HR, 10.8) were independent prognostic indicators. In patients without ischemia on SE and LAD CFVR >2.0, the 4-year event rate was 4% in those with RCA CFVR > 2.0 and 18% in those with RCA CFVR ≤ 2.0 (P<.0001). Ischemia on SE with high peak wall motion score index identifies a high-risk subset regardless of the underlying CFVR response. Absence of ischemia on SE is associated with intermediate risk, and LAD CFVR is essential to identify a truly low-risk subset. RCA CFVR is less useful than LAD CFVR but may have a role for further risk stratification in patients without ischemia and normal LAD CFVR.