Postocclusion hyperemia provides a better estimate of coronary reserve than intracoronary adenosine in patients with coronary artery stenosis.

OBJECTIVE: The aim of this study was to compare the ability of intracoronary adenosine (ADE) and postocclusion hyperemia (PH) to cause maximal hyperemia in humans. BACKGROUND: The current clinical standard for induction of maximal coronary hyperemia is intracoronary ADE. However, animal studies have shown that maximal hyperemia was not achieved by ADE and that PH yielded a higher hyperemic response. METHODS: In 10 stable patients with coronary artery stenosis > or = 80%, basal and peak coronary blood flow velocity (intracoronary Doppler) were measured before and after coronary angioplasty (PTCA), both after an intracoronary bolus of 60 mcg ADE, and after 30-second occlusion of the coronary artery by a balloon angioplasty catheter. Coronary reserve was estimated through coronary flow reserve (CFR = peak-to-resting coronary blood flow velocity), and coronary resistance reserve (CRR = [resting aortic pressure/resting coronary flow velocity]/[aortic pressure at peak velocity/peak coronary flow velocity]). RESULTS: Before PTCA, ADE and PH result in comparable CFR (1.79 +/- 0.65 vs. 1.95 +/- 0.52, respectively; p = 0.0846), but CRR was higher with PH (1.75 +/- 0.52 vs. 2.14 +/- 0.81, respectively; p = 0.0125). After PTCA, CFR and CRR were significantly lower with ADE than with PH (CFR = 2.53 +/- 0.58 vs. 3.31 +/- 0.67, respectively; p = 0.0001, and CRR = 2.58 +/- 0.49 vs. 3.46 +/- 0.79; p = 0.0004, respectively). Lastly, the higher the coronary reserve, the greater the differences between ADE and PH values. CONCLUSIONS: Because intracoronary 60 mcg ADE elicits a lower hyperemic response than PH, intracoronary ADE represents a potential source of error in coronary reserve measurements, and may result in an underestimation of the physiological significance of a coronary artery stenosis.