Coronary vasodilator reserve and Framingham risk scores in subjects at risk for coronary artery disease

Background  The relationship between coronary vasodilator reserve and risk of coronary heart disease (CHD) in subjects without coronary artery disease (CAD) is not well known. Methods and Results  We studied 289 subjects (mean age, 58 ± 10 years) without overt CAD and at low (<10%) to intermediate risk (10%–20%) for CHD based on Framingham risk scores (RAMPART [Relative and Absolute Myocardial Perfusion changes as measured by Positron Emission Tomography to Assess the Effects of ACAT Inhibition: A Double-Blind, Randomized, Controlled, Multicenter Trial]). Coronary flow reserve (CFR) and coronary vascular resistance (CVR) were calculated from rest and adenosine nitrogen 13 ammonia positron emission tomography studies. Framingham-estimated CHD risk was used to as a surrogate for outcomes. Compared with subjects with low-risk scores (n = 150), those with intermediate-risk scores (n = 139) had a higher minimal CVR (49.3 ± 17.41 mm Hg · mL^-1 · min^-1 · g^-1 vs 52.4 ± 16.4 mm Hg · mL^-1 · min^-1 · g^-1, P = .05) and lower CFR (2.8 ± 1.0 vs 2.5 ± 0.8, P = .02). CFR was inversely related to CHD risk (R=-0.2, P = .006), and CVR was directly related to CHD risk (R = 0.2, P < .001). The mean CFR was significantly lower in patients in the first quartile of CHD risk compared with those in the fourth quartile (2.3 ± 0.7 vs 2.8 ± 1.0, P = .02), and the minimal CVR was significantly higher (44 ± 15 mm Hg · mL^-1 · min^-1 · g^-1 vs 53 ± 14 mm Hg · mL^-1 · min^-1 · g^-1, P < .05). Conclusions  In subjects without clinical CAD and at low to intermediate risk, CFR assessed by positron emission tomography is inversely related to estimated 10-year CHD risk.