Abnormal coronary flow velocity reserve after coronary artery stenting in patients - Role of relative coronary reserve to assess potential mechanisms

Background-Absolute coronary flow velocity reserve (CVR) after stenting may remain abnormal as a result of several different mechanisms. Relative CVR (rCVR= CVRtarget/CVRreference) theoretically normalizes for global microcir culatory disturbances and facilitates interpretation of abnormal CVR. Methods and Results-To characterize potential mechanisms of poststent physi ology, CVR was measured using a Doppler-tipped angioplasty guidewire in 55 patients before and after angioplasty, after stenting, and in an angiograph ically normal reference vessel. For the group, the percent diameter stenosi s decreased from 75+/-13% to 40+/-18% after angioplasty and to 10+/-9% (all P<0.05) after stent placement. After angioplasty, CVR increased from 1.63/-0.71 to 1.89+/-0.55 (P<0.05) and after stent placement, to 2.48+/-0.75 (P <0.05 versus pre- and postangioplasty). After angioplasty, rCVR increased f rom 0.64+/-0.26 to 0.75+/-0.23 and after stent placement to 1.00+/-0.34. In 17 patients with CVRstent less than or equal to 2.0, increased basal coron ary flow, rather than attenuated hyperemia, was responsible in large part f or the lower CVRstent compared with patients having CVRstent >2.0. In 8 pat ients with CVRstent <2.0, a normal rCVR supported global microvascular dise ase, The subgroup of 9 patients with CVRstent <2.0 and abnormal rCVR (16% o f the studied patients) may require a pressure-derived fractional flow rese rve to differentiate persistent obstruction from diffuse atherosclerotic di sease or microvascular stunning. Conclusions-Although a majority of patients after stenting normalize CVR fo r the individual circulation (ie, normal CVR or normal rCVR), in those with impaired CVRstent the analysis of coronary flow dynamics suggests several different physiological mechanisms. Additional assessment may be required t o fully characterize the physiological result for such patients to exclude remediable luminal abnormalities.