1.5 BLOOD PRESSURE-INDEPENDENT ASSOCIATION BETWEEN AORTIC CHARACTERISTIC IMPEDANCE AND LEFT VENTRICULAR MASS IN HYPERTENSION

Abstract

Background: It is uncertain whether pressure/flow ratio in the proximal aorta, namely aortic characteristic impedance (Z c ), is related to left ventric- ular (LV) mass independently of blood pressure (BP) level. Methods: 435 never-treated subjects with uncomplicated essential hyperten- sion free from overt cardiovascular disease (men 62%, age 48 11 years, BP 148/92 16/10 mmHg) underwent M-mode echocardiography and 24-hour BP monitoring. Aortic waveform was obtained from tonometric radial waveform with a validated generalized transfer function (SphygmoCor). Aortic Z c and forward (P f ) and backward (P b ) wave amplitudes were calculated from central waveform using an aortic blood flow model based on higher-order Windkessel theory (ArcSolver), [Weber T et al, Hypertension EPub May 14, 2012]. Results: Patients with LV hypertrophy (LV mass > 51 g/m 2.7 ) had a higher brachial systolic BP (SBP 153 18 vs 146 15 mmHg, p < 0.001), central systolic BP (142 18 vs 133 16 mmHg, p < 0.001), aortic Z c (0.235 0.08 vs 0.211 0.06 AU, p < 0.001), P f (31.7 9 vs 28.6 7 mmHg, p < 0.001), and P b (19.8 7 vs 18.1 5 mmHg, p Z 0.02), while reflection magnitude (P b /P f ) did not differ (0.62 0.10 vs 0.63 0.10, p > 0.3). After controlling for age, sex, and mean arterial pressure as a measure of distending pressure, LV mass index maintained an independent association with Z c (partial r Z 0.14,p Z 0.002), while the association of either Pb or Pf with LV mass became no longer significant. In a multiple linear regression model, Z c independently predicted LV mass index (b Z 0.116, p Z 0.005) along with age, mean arterial pressure, and body mass index. Conclusion: Aortic characteristic impedance has a significant, pressure- independent relationship with LV mass in human hypertension