Pathophysiological and clinical implications of high intramural coronary blood flow velocity in aortic stenosis

We sought to recognize the blood flow velocity (BFV) through the left anterior descending (LAD) coronary artery and its small intramyocardial (IM) branches by transthoracic Doppler-echocardiography in patients with aortic stenosis (AS). Sixty-two patients, aged 74.0 ± 9.6 years, 37 women, with preserved left ventricular (LV) function, apparently free of active ischemic disease, were enrolled and classified into 3 groups according to the mean gradient (MG) across the aortic valve: 13 patients (21%) entered the group A (MG ≤ 20 mmHg), 29 (48%) group B (MG 21-40 mmHg) and 20 (31%) group C (MG > 40 mmHg). Peak and mean coronary BFVs were demonstrated to gradually increase according to AV gradient, especially through the IM arteries. Peak IM-BFV was 58.9 cm/s (95% CI 46.4-71.4) in group A, 73.2 cm/s (95% CI 64.8-81.6) in group B, and 96.4 cm/s (95% CI 86.3-106.5) in group C (p < 0.001), whereas peak LAD-BFV was 38.1 cm/s (95% CI 32.8-43.3), 44.4 cm/s (95% CI 40.9-47.9) and 47.3 cm/s (95% CI 43.1-52.5), respectively (p = 0.03). Also, 34 patients complaining with unspecific symptoms showed much higher IM-BFV than those who were not. High values were also recognized in patients with LV ejection fraction/velocity ratio (EFVR) ≤ 0.90 (IM-BFV 91 ± 26 cm/s vs. 72 ± 24 cm/s in those with EFVR > 0.90, p = 0.001). In conclusion, AS patients in the present study showed gradually higher coronary BFVs according to AS gradient, especially through the IM vessels, and both peak and mean velocities were discriminating specific patient subsets. Pathophysiological mechanisms and potential clinical implications are discussed.