Increased heterogeneity of coronary perfusion in patients with early coronary atherosclerosis

Background in patients with typical angina but angiographically normal coro nary arteries, abnormal vasomotor function is assumed to be a major underly ing cause. However, data on this issue are conflicting, and recent studies suggest that fluid dynamic abnormalities exist in these patients. The aim o f the study was to evaluate whether early stages of atherosclerosis are cha racterized by alterations of baseline coronary hemodynamics and endothelium -independent vasomotion. Besides established intracoronary Doppler paramete rs, heterogeneity of perfusion was assessed and related to early signs of a therosclerosis as determined by electron-beam computed tomography (EBCT). Methods In 59 patients with typical angina and angiographically normal or n ear-normal coronary arteries, intracoronary Doppler measurements were perfo rmed in all 3 major coronary arteries. Baseline average peak velocity (bAPV ) and hyperemic average peak velocity (hAPV) in response to intracoronary i njection of adenosine were measured, and coronary flow velocity reserve (CF VR) was calculated. Heterogeneity was assessed as variability of bAPV, hAPV , and CFVR and was calculated as (STD/MEAN) - 100. Doppler data were analyz ed according to tertiles of the EBCT-derived Agatston calcium ;core (ie, sc ore 0-1 [lowest tertile], 2-28 [medium tertile], and > 28 [highest tertile] ). Results The mean EBCT-derived Agatston calcium score was 49 +/- 107. No cor onary calcium was observed in 17 (29%) patients. The mean values of bAPV, h APV, and CFVR were not different between the calcium score tertiles. Howeve r, patients in the highest tertile had a significantly increased variabilit y index of bAPV (29.6%+/- 11.6%) compared with patients in the lowest terti le (13.4%+/-7.3%, P < .0001). Variability of CFVR was also increased in the se patients (15.5%+/- 11.7% vs 10.5%+/-4.0%, P =.03). Conclusion These results indicate that early stages of atherosclerosis are characterized by microvascular abnormalities that do not uniformly affect t he myocardium but are heterogeneous. The high variability of baseline coron ary flow velocity with increasing coronary calcium suggests that in patient s with early stages of atherosclerosis fluid dynamic effects may play a cru cial role even in the absence of angiographically appreciable epicardial st enoses.