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 b een described in patients with coronary artery disease (CAD) and was attrib uted to diffuse coronary luminal narrowing. We asked whether an abnormal pe rfusion gradient also existed in patients without CAD but with coronary ris k factors. We measured myocardial blood flow (MBF) with N-13-ammonia and PE T at rest and during hyperemia in patients with coronary risk factors but w ithout CAD. Methods and Results-Regional MBF was measured in absolute units with N-13-a mmonia and PET at rest and during dipyridamole hyperemia in 36 patients wit h 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 th e mid and mid-to-apical sections of the left ventricle (LV). Myocardial per fusion 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 c oronary territories. However, hyperemic MBFs in the mid-to-apical LV sectio n 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-m atched or in the young normal subjects. Conclusions-The abnormal longitudinal, base-to-apex perfusion gradient obse rved during dipyridamole MBF suggests the presence of a functional and/or s tructural alteration of the coronary circulation associated with coronary r isk factors, possibly reflecting developing coronary atherosclerosis or pre clinical CAD.