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 aetiological factors such as microvascular and endothelial dysfunction, and small vessel disease have been implicated. We aimed to investigate the epicardial resistance in relation with 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.

Coronary pressure and FFR measurement were performed in 19 (8 (42.1%) men, 11 (57.9%) women; age = 55.9 +/- 9.4 years) patients with SCF. All patients underwent subsequent IVUS investigation at the same setting. As compared with expected normal values, FFR values were significantly lower (1.0 vs. 0.83 +/- 0.13, 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). Upon IVUS investigation, the common finding was longitudinally extended massive calcification throughout the epicardial arteries and increased intimal thickness (0.59 +/- 0.18 mm). A negative correlation between intimal thickness and FFR was determined (r = -467, p < 0.05).

We have demonstrated the decreased FFR in the patients with SCF. Decreased FFR levels have been attributed to increased resistance in the epicardial coronary arteries due to diffuse atherosclerotic disease which has been demonstrated by IVUS.