Immediate and long-term effect of balloon angioplasty or stent implantation on the absolute and relative coronary blood flow velocity reserve.

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Abstract
Background —There is controversy regarding the immediate and long-term effects of PTCA on the coronary flow reserve. Methods and Results —A total of 54 patients with 1-vessel disease and normal left ventricular function were studied after balloon angioplasty (n=34) or stent implantation (n=20). Distal coronary blood flow velocity reserve (CFR) was defined as the ratio of adenosine-induced hyperemic versus baseline blood flow velocity with a 0.014-in Doppler guidewire. The relative CFR was defined as the ratio of the distal CFR and the reference CFR measured in the normal adjacent coronary artery. Hemodynamic and angiographic measurements were performed before and directly after balloon angioplasty or stent implantation and at 6-month follow-up. CFR after PTCA ≤2.5 was defined as an impaired CFR. Immediately after PTCA, CFR improved toward the range of the reference artery CFR. In both the balloon-treated and the stent-treated groups, initial high CFR values decreased and impaired CFR values increased at follow-up toward the values of the reference CFR in patients without restenosis. Impaired CFR after balloon angioplasty (33%) or stent implantation (58%) in patients without restenosis was related to an increased baseline flow velocity that normalized at follow-up. Patients with an increase of CFR after stenting were characterized by an unaltered baseline flow velocity and an increased adenosine-induced hyperemic flow velocity. Conclusions —An impaired CFR (≤2.5) is a frequent finding after balloon angioplasty or stent implantation as a result of a high baseline flow velocity. Normalization of impaired CFR at follow-up in patients without restenosis was associated with a decline of the baseline flow velocity after both balloon angioplasty and stent implantation, supporting the contention that this phenomenon relates to a slow recovery of autoregulation of the microvascular bed.

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