978-118 Exercise Capacity and Coronary Flow Reserve in Patients with Intermediate Coronary Stenoses

In patients with coronary disease, exercise time is a predictor of disease severity. More severe disease is associated with shorter exercise time due to greater ischemia. In patients with intermediate coronary stenoses, however, it is unclear whether stenosis severity predicts functional effects. Thus, we examined the relationship between exercise time and the angiographic and physiologic significance of 25 intermediate coronary stenoses (40–70%). Using an intracororary Doppler flow wire we measured coronary flow reserve (CFR) as the ratio of adenosine-induced hyperemic coronary flow velocity to resting velocity. Stenosis severity was determined by quantitative angiography. Patients subsequently underwent maximal exercise testing on a Bruce protocol. No patient had left ventricular dysfunction, ischemia in other vascular distributions or other diseases known to limit exercise capacity. Exercise time was normalized for age and gender according to the method of Bruce. Total exercise time ranged from 3.9 to 12.8min while normalized time ranged from 37 to 152% of predicted. CFR ranged from 1.0 to 3.5 (normal≥2.0) and was directly related to exercise time (r=0.7, p<0.0001, SEE=2.1) and normalized exercise time (r=0.7 p<0.0001, SEE=25), Normalized exercise time was 72±21% of predicted in patients with an abnormal CFR vs 125±23% of predicted in those with normal CFR (p<0.0001). There was no relationship between angiographic percent stenosis and exercise time (r=-0.01) or normalized exercise time (r=-0.01). Normalized exercise time was ≥100% of predicted in 9 of 11 patients with a normal CFR, and <100% in 13 of 14 patients with abnormal CFR. The sensitivity, specificity and predictive accuracy of normalized exercise time for CFR were 93%, 82% and 88%, respectively. Thus, in patients with intermediate coronary stenoses and no other exercise limitations, treadmill exercise time is a useful marker of the physiologic severity of disease