The concept of coronary flow reserve.

Coronary reserve has been defined as the ratio of coronary resistance under control (rest) conditions and of coronary resistance after maximal coronary vasodilation. The latter can be achieved by various interventions, the most important and clinically relevant example being intravenous administration of dipyridamole at 0.5 mg/kg of body weight. For patients without coronary artery disease, the coronary reserve is about 400 to 500%, i.e., the normal heart is capable of reducing its coronary resistance to minimal values of 0.18 to 0.2 mm Hg/ml/min/100 g or to increase coronary flow by approximately four- to fivefold. The determination of coronary reserve in humans implies the availability of adequate methods. Systematic analyses of different coronary blood flow measurements have proved the gas chromatographic argon method to be the most appropriate and accurate method for clinical conditions, as previously described in detail. In this report, our findings on the coronary reserve analysis in various clinical conditions are described as follows: (a) coronary artery disease, (b) inflammatory disturbances of the microcirculation, (c) hypertensive microangiopathy, (d) rheologic abnormalities of the heart, and (e) pressure and volume overload due to hypertension and heart valve lesions (metabolic overload).