Effects of normal blood pressure, prehypertension, and hypertension on coronary microvascular function

Background - The assessment of coronary flow reserve (CFR) by transthoracic Doppler echocardiography has recently been introduced into clinical practice, and reduced CFR has been suggested to be a sensitive indicator of hypertensive end-organ damage; however, to date, this methodology has not been used to evaluate CFR in subjects with prehypertension. Accordingly, the present study was designed to evaluate CFR in subjects with prehypertension. Methods and Results - We measured CFR of 40 subjects with prehypertension, 60 patients with hypertension, and 50 normotensive healthy volunteers using transthoracic Doppler echocardiography. None of the subjects had any systemic disease. Age, gender, body mass index, heart rate, lipid profiles, fasting glucose levels, and hemoglobin were similar among the 3 groups. CFR was significantly lower in the hypertension group than in the prehypertension and control groups; in addition, it was significantly lower in subjects with prehypertension than in control subjects (2.23 +/- 0.47, 2.54 +/- 0.48, and 2.91 +/- 0.53, respectively). Furthermore, we found that prehypertension (beta=-0.31, P < 0.01) and hypertension (beta=-0.57, P < 0.01) were significant predictors of lower CFR in a multivariable model that adjusted for other variables. CFR was significantly and inversely correlated with age (r=-0.20, P=0.01), systolic blood pressure (r=-0.51, P < 0.01), diastolic blood pressure (r=-0.47, P < 0.01), high-sensitivity C-reactive protein levels (r=-0.21, P=0.01), left atrium diameter (r=-0.22, P < 0.01), mitral E deceleration time (r=-0.19, P=0.02), and mitral A velocity (r=-0.27, P < 0.01), whereas mitral E/A ratio was significantly and positively correlated with CFR (r=0.26, P < 0.01). Conclusions - CFR is impaired in subjects with prehypertension, but this impairment is not as severe as that in hypertension.