Aortic augmentation index is inversely associated with cardiorespiratory fitness in men without known coronary heart disease

Background: We investigated whether the aortic augmentation index (AIx), a measure of arterial wave reflection and stiffness, is associated with cardiorespiratory fitness in men without known coronary heart disease (CHD). Methods: Asymptomatic men (n = 201, mean age 51 +/- 9.2 years) referred for a screening exercise electrocardiogram (ECG) underwent applanation tonometry to obtain radial artery pulse waveforms, and an ascending aortic pressure waveform was derived by a transfer function. The AIx is the difference between the first and second systolic peak of the ascending aortic pressure waveform, expressed as a percentage of the pulse pressure. Cardiorespiratory fitness was assessed by maximal oxygen consumption (VO2 max mL/min/kg) during a symptom-limited graded exercise test. Multivariable regression analyses were used to identify significant independent determinants of AIx and of VO2 max. Results: Diabetes was present in 2.5% of subjects, 34.8% had history of smoking, and 29% were hypertensive. Mean (+/- SD) AIx was 19.9% +/- 9.0% and mean VO2 max was 33.9 +/- 6.4 mL/min/kg. In a multivariable linear regression model, AIx was positively associated with age, hypertension, and history of smoking and inversely with heart rate, height, and body mass index (BMI). The VO2 max was significantly inversely related to AIx after adjustment for age, heart rate, height, and BMI (r = -0.22, P = .002), after further adjustment for CHD risk factors (total cholesterol, HDL-cholesterol, history of smoking, diabetes, hypertension) (P = .006), and after additional adjustment for behavioral factors (physical activity score, alcohol intake, and percent body fat) (P = .022). Conclusions: These findings indicate that AIx, a measure of arterial wave reflection and stiffness, is inversely associated with cardiorespiratory fitness in men without CHD.