Slow Coronary Flow May be a Sign of Diffuse Atherosclerosis: Contribution of FFR and IVUS

Slow coronary flow (SCF) is a phenomenon characterized by delayed opacification of coronary arteries in the absence of epicardial occlusive disease, in which many etiological factors such as microvascular and endothelial dysfunction, and small vessel disease have been implicated. We aimed to investigate the epicardial resistance in relation to SCF by using fractional flow reserve (FFR) and intravascular ultrasound (IVUS). Both have been combined to disclose the related epicardial flow resistance and the arterial anatomy. The study population consisted of 19 [8 (42.1%) male, 11 (57.9%) female; age=55.9±9.4 years] patients with SCF. As compared to expected normal values (1.0), FFR values (0.83±0.13) were significantly lower (p=0.0001). In patients with SCF, a strong negative correlation was seen between TIMI frame count and FFR (r=0.551, p<0.05). On IVUS investigation, the common finding was longitudinally extended massive calcification throughout the epicardial arteries and increased intimal thickness (0.59±0.18mm). A negative correlation between intimal thickness and FFR was determined (r=0.467, p<0.05). In conclusion, we demonstrated decreased FFR in patients with SCF. Decreased FFR levels have been attributed to increased resistance in epicardial coronary arteries due to diffuse atherosclerotic disease which has been demonstrated by IVUS.