Impaired coronary flow reserve evaluated by echocardiography is associated with increased aortic stiffness in patients with metabolic syndrome: an observational study.

Objective: Metabolic syndrome (MetS) is a strong predictor of cardiovascular events and coronary flow reserve (CFR), an indicator of microvascular function, has been found to be impaired in MetS. Aortic stiffness (AS) is a simple and effective method for assessing arterial elasticity. The aim of this study was to evaluate whether there is an independent association of impaired coronary flow and aortic elasticity in patients with MetS.

Methods: Forty-six patients (mean age 47.3 ± 6.6 years) with the diagnosis of MetS according to the ATP III update criteria and 44 age and gender matched controls (mean age 46.0 ± 6.1 years) were included into the cross-sectional observational study. Peak diastolic coronary flow velocities were measured in left anterior descending artery by pulsed wave Doppler at baseline and after adenosine infusion, and CFR was calculated as the ratio of hyperemic to baseline velocities. Aortic strain, distensibility and stiffness were calculated by M-mode echocardiography. Statistical analysis was performed by using Student t-test, Chi-square test, Pearson correlation and linear regression analyses.

Results: CFR was significantly lower in patients with MetS than in controls (2.3 ± 0.2 vs 2.7 ± 0.2, p<0.001). In the MetS group, aortic distensibility (10.4 ± 3.5 cm².dyn⁻¹.10⁻⁶ vs. 12.7 ± 3.4 cm2.dyn⁻¹.10⁻⁶, p=0.002) was decreased and AS was significantly increased (6.5 ± 2.0 vs. 3.2 ± 0.8, p<0.001). In multivariate linear regression analysis, AS (β=-0.217, p=0.047), systolic blood pressure (β=-0.215, p=0.050) and waist circumference (β=-0.272, p=0.012) had an independent relationship with impaired CFR.

Conclusion: This study demonstrated that coronary flow reserve is impaired in patients with MetS and there is an independent relationship between impaired CFR and increased aortic stiffness, systolic blood pressure or waist circumference.