Abstract
Background Myocardial perfusion reserve (MPR) reflects endothelial function of the coronary artery and can be altered by various atherosclerotic risk factors. We previously reported that hypertension is associated with impairment of MPR, especially subendocardial MPR. However, information is limited regarding the impact of normal-high blood pressure (systolic blood pressure (SBP) of 130-139mmHg, diastolic blood pressure (DBP) of 85-89mmHg, or both) on MPR. Purpose To determine if MPR was already altered in patients with normal-high blood pressure by using a quantitative analysis of stress-rest myocardial perfusion MRI. Method We studied 73 subjects without hypertension (SBP<140mmHg and DBP<90mmHg) who did not exhibit regional myocardial ischemia and myocardial scar on stress CMR study. Subjects were divided into two groups (Normal-high group: n=19, 68±9 year-old, 17 men; Normal-optimal group (SBP<130mmHg and DBP<85mmHg): n=54, 68±10 year-old, 33 men) according to blood pressure. Stress-rest myocardial perfusion MRI was acquired with blood signal saturation correction, and absolute subendocardial and epicardial myocardial blood flow (MBF) and MPR were quantified. MPR were calculated as stress MBF divided by rest MBF. Result The averaged transmural MPR in subjects with normal-high blood pressure was significantly lower than that in normal-optimal group.(2.74±1.61 vs. 3.80±2.03, p=0.043). When subepicardial MBF and subendocardial MBF were analyzed separately, MPR in subepicardial myocardium did not demonstrate significant difference between two groups (3.09±1.66 vs. 4.29±2.49, p=ns). In contrast, MPR in subendocardial myocardium was significantly reduced in the high-normal group than in the normal-optimal group. (2.57±1.51 vs. 3.65±1.66, p=0.015) Conclusion In the current study evaluating subjects without regional myocardial ischemia or significant coronary artery disease, subendocardial MPR was significantly decreased in the group with normal-high blood pressure. The result of this study suggests that endothelial function of the coronary artery is already altered in patients with normal-high blood pressure.
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