Measurements of Normal and Collateral Coronary Blood Flow by Close‐arterial and Intramyocardial Injection of Krypton85 and Xenon133

ABSTRACT A recent method for measuring collateral blood flow in the myocardium of dogs was based on an analysis of the composite clearance of Krypton 85 administered close‐arterially (J ohansson , L inder and S eeman 1964, 1966). This method has been critically analysed and various sources of possible errors in the estimations are discussed. Comparisons between paired measurements by this technique and results obtained by recordings of the wash‐out rate of intramuscularly injected Xenon 133 depots, in the well‐perfused and ischemic myocardial areas respectively, strongly suggest that the method is fairly accurate and reliable, despite the fact that it has obvious theoretical limitations. The results also reveal that the collateral flow to the ischemic area is not entirely uniform. Within a narrow border zone there is a steep reduction of blood flow, with a more gradual diminution towards central parts of the ischemic zone. This regional heterogeneity in collateral flow could not for several reasons, be analysed in exact detail from the composite curve alone, but was revealed by recordings of clearance of strictly localized, intramuscular tracer injections. Peak flow during reactive hyperemia could also be fairly satisfactorily measured, provided certain precautions were taken. The results suggest that it is, in addition, possible to make a fair estimation of the mass of the ischemic tissue from the composite curve. The method may prove to be useful in experimental studies designed to investigate different means for improving collateral blood supply to an ischemic myocardial area.