Pathophysiological Significance of Velocity-Based Microvascular Resistance at Maximal Hyperemia in Peripheral Artery Disease

Aim: Maximal hyperemic response, leading to examination of microvascular resistance in lower-limb lesions is not well understood. This study aimed to investigate the infrainguinal arterial physiological response through a hyperemic condition and the pathophysiological significance of microvascular resistance in peripheral artery disease. Methods: Sixteen limbs with focal stenosis of the superficial femoral artery (SFA) and 16 control limbs were analyzed. We assessed the fractional flow reserve (FFR), vascular flow reserve (VFR), and hyperemic microvascular resistance (h-MR) of the SFA with a pressure/Doppler flow sensor-tipped combination guidewire before and after endovascular therapy (EVT). Skin perfusion pressure (SPP) on both the dorsal and the plantar sides of the foot was measured at baseline before and after the endovascular procedures. Results: FFR (p < 0.05) and VFR (p < 0.05), but not h-MR, improved after EVT. There was no association between h-MR and FFR or VFR before EVT. h-MR was negatively correlated with the dorsal SPP before EVT (r = −0.589, p < 0.05). h-MR in patients with high h-MR before EVT significantly decreased after EVT (p < 0.05). Patients with high, but not those with low, h-MR before EVT exhibited a significant increase in dorsal and plantar SPP after EVT (p < 0.05, each). Conclusion: EVT for SFA stenosis improved FFR and VFR comprehensively, with no apparent change in h-MR. However, high h-MR before EVT may play a predictive role for limb perfusion improvement associated with h-MR reduction after EVT.