An ideal coronary vasodilator for studying coronary flow reserve should rapidly produce a maximal hyperemic response, be short acting to permit repeated measurements, and not alter systemic hemodynamics. We measured with a Doppler tip balloon catheter, in 12 patients before and/or after percutaneous transluminal coronary angioplasty the hyperemic response following 12.5 mg intracoronary papaverine and following gradually incremental bolus injections of intracoronary adenosine, starting from 0.05 mg until a maximal hyperemic response or side effects. The mean dose (±SD) of adenosine needed to produce maximal hyperemia was 0.23 (±0.20 mg). Coronary blood flow velocity after adenosine increased to 1.6 ± 0.3 times resting coronary blood flow velocity, comparable in magnitude to the hyperemia following intracoronary papaverine. The time from injection to peak effect after adenosine was 7.4 (SD ± 2.2) sec and after papaverine 26 (SD ± 7) sec. Adenosine resulted in a bradyarrythmia in three patients. Intracoronary adenosine is a potent and very short acting vasodilator for studying coronary flow reserve, but the side effects and unpredictability of the dosage needed to produce maximal hyperemia may limit its applicability.
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