Objective: Absolute myocardial blood flow (MBF) is not well-defined in large normal populations, and appears to be heterogeneous in both humans and animals. These factors contribute to the difficulties in defining resting MBF to hibernating myocardium. We therefore assessed absolute baseline and hyperemic MBF in a large population of normal humans.
Methods: MBF was quantified by positron emission tomography with oxygen-15-labeled water at baseline and during hyperemia induced by either adenosine or dipyridamole in 131 men and 38 women, aged 21-86 (mean 46+/-12) years. MBF was corrected for workload using the rate-pressure product (RPP).
Results: Uncorrected baseline MBF ranged from 0.590 to 2.050 (mean 0.985+/-0.230) ml/min/g (coefficient of variation=27%), and corrected MBF from 0.736 to 2.428 (mean 1.330+/-0.316) ml/min/g (coefficient of variation=24%). MBF in the inferior region was significantly (P<0.0001) lower than either the anterior or lateral regions. Baseline MBF in females was significantly (P<0.001) higher than in males.
Conclusions: These results confirm the heterogeneity of MBF in normals and highlight the difficulty in establishing the lower limit of normal MBF.