We investigated whether aortic characteristic impedance (Zc), that is, the ratio between the pulsatile change in pressure and flow in the proximal aorta, is related to left ventricular hypertrophy and geometry independently of blood pressure (BP). A total of 438 never-treated hypertensive individuals (men 62%, age 48 ± 11 years, BP 147/90 ± 16/10 mmHg) underwent echocardiography and 24 h BP monitoring. Aortic pressure waveform was obtained from radial tonometry with a generalized transfer function (SphygmoCor). Using a validated aortic blood flow model based on higher order Windkessel theory (ARCSolver), aortic Zc, forward (Pf) and backward (Pb) wave amplitudes and their ratio (Pb/Pf = reflection magnitude) were calculated from central waveform.Results:
After adjusting for age, BMI, and 24-h SBP, aortic Zc was higher in individuals with left ventricular hypertrophy (0.230 ± 0.09 vs. 0.205 ± 0.07 arbitrary units, P = 0.04 in women; 0.232 ± 0.07 vs. 0.214 ± 0.06 arbitrary units, P < 0.05 in men). Women with left ventricular concentric remodeling had higher adjusted Zc (0.225 ± 0.08 vs. 0.203 ± 0.07 arbitrary units, P = 0.04), whereas men did not differ (0.218 ± 0.07 vs. 0.218 ± 0.07 arbitrary units, P = 0.64). After controlling for age, BMI, 24 h SBP, and other relevant variables, aortic Zc independently predicted left ventricular mass (β = 0.14, P < 0.05) and relative wall thickness (β = 0.21, P < 0.01) in women, and left ventricular mass in men (β = 0.11, P < 0.05), whereas other arterial function parameters had no independent relation with left ventricular mass or geometry.Conclusion:
Aortic Zc has a significant association with left ventricular mass and a sex-specific one with left ventricular concentric geometry in hypertension. These effects are independent from, and additional to, those of 24 h SBP.