Aortic distensibility independently affects exercise tolerance in patients with dilated cardiomyopathy

Background - Peak exercise oxygen consumption (V̇o₂) is crucial for the prognostic stratification of patients with congestive heart failure, but its hemodynamic determinants are still not completely understood. Aortic wall elasticity modulates left ventricular function and coronary blood flow. Whether an increased aortic pulse-wave velocity (PWV), a known marker of arterial stiffness, may predict peak V̇o₂ in patients with dilated cardiomyopathy (DCM) has to be clarified. Methods and Results - A total of 78 patients with clinical diagnosis of DCM (aged 62 ± 11 years; female 29%; mean ejection fraction 34 ± 9%) were selected. All patients underwent a complete echocardiographic-Doppler evaluation. Aortic PWV was measured by Doppler ultrasonography immediately before the exercise. A bicycle exercise test with expiratory gas exchange monitoring was performed to determine V̇o₂. Plasma concentration of the amino-terminal propeptide of type III procollagen (PIIINP), a marker of extracellular matrix turnover, was determined. Mean PWV was 5.7 ± 2.2 m/s, and V̇o₂ was 16.5 ± 4.5 mL · kg^-1 · min^-1. The hemodynamic variables correlated with Vo₂ were PWV (r = -0.39, P = 0.0007) and stroke volume (r = 0.38, P = 0.002). In a multivariate analysis, PWV (P = 0.04) and stroke volume (P = 0.05) were independently correlated with V̇o₂ accounting for 34% of its variance. PIIINP levels correlated with PWV (r = 0.35, P = 0.002) and a more restrictive diastolic filling pattern (r = 0.40, P = 0.02). Conclusions - Increased aortic stiffness measured by PWV is an independent predictor of peak V̇o₂ and could partially explain exercise intolerance in patients with DCM.