Aims
Despite revascularization and optimal medical treatment, patients with coronary artery disease (CAD) have reduced exercise capacity. In the absence of coronary artery stenosis, coronary flow reserve (CFR) is a measure of coronary microvascular function, and a marker of future poor outcome in CAD patients. The aim of this study was to examine the relationship among CFR, systolic and diastolic function, peripheral vascular function, and cardiopulmonary fitness in CAD patients.
Methods and Results
Forty patients with median left ventricular ejection fraction (LVEF) 49 (interquartile 46–55) with documented CAD without significant left anterior descending artery (LAD) stenosis underwent cardiorespiratory exercise test with measurement of VO2peak, digital measurement of endothelial function and arterial stiffness, and an echocardiography with measurement of LVEF using the biplane Simpson model, mitral early (E) and late (A) inflow velocities, and tissue Doppler diastolic (e′) and systolic (s′) velocities. Peak coronary flow velocity (CFV) was measured in the LAD using pulse-wave Doppler. CFR was calculated as the ratio between peak CFV at rest and during vasodilator stress. Median CFR was 2.22 (1.90–2.62) and VO2peak was 21.8 (17.6–25.5). VO2peak correlated significantly with CFR (r = 0.57, P < 0.001), E/e′ (r = −0.35, P = 0.04), and s′ (r = 0.41, P = 0.01) and with LVEF (r = 0.35, P = 0.03). CFR remained independently associated with VO2peak after adjustment for systolic and diastolic function.
Conclusions
Coronary flow reserve measured noninvasively predicts cardiopulmonary fitness independently of resting systolic and diastolic function in CAD patients, indicating that cardiac output during maximal exercise is dependent on the ability of the coronary circulation to adapt to the higher metabolic demands of the myocardium.