Abnormal longitudinal, base-to-apex myocardial perfusion gradient by quantitative blood flow measurements in patients with coronary risk factors

Background-A longitudinal, base-to-apex myocardial perfusion gradient has been described in patients with coronary artery disease (CAD) and was attributed to diffuse coronary luminal narrowing. We asked whether an abnormal perfusion gradient also existed in patients without CAD but with coronary risk factors. We measured myocardial blood flow (MBF) with N-13-ammonia and PET at rest and during hyperemia in patients with coronary risk factors but without CAD. Methods and Results-Regional MBF was measured in absolute units with N-13-ammonia and PET at rest and during dipyridamole hyperemia in 36 patients with coronary risk factors (age, 55 +/- 10 years) and in 36 age-matched (age, 53 +/- 10 years) and in 28 young (age, 25 +/- 5 years) normal subjects. MBF was determined globally, for each of the 3 coronary territories, and in the mid and mid-to-apical sections of the left ventricle (LV). Myocardial perfusion on qualitative analysis was normal at rest and during hyperemia, and no flow defects were present. MBF in absolute units was similar in the 3 coronary territories. However, hyperemic MBFs in the mid-to-apical LV section were lower than in the mid LV section in the "at-risk" group (2.04 +/- 0.61 versus 1.71 +/- 0.40 mL . min(-1) . g(-1); P<0.004) but not in the age-matched or in the young normal subjects. Conclusions-The abnormal longitudinal, base-to-apex perfusion gradient observed during dipyridamole MBF suggests the presence of a functional and/or structural alteration of the coronary circulation associated with coronary risk factors, possibly reflecting developing coronary atherosclerosis or preclinical CAD.