P166 EXPLORING AGE-ASSOCIATED CHANGES IN HEMODYNAMICS: INSIGHTS FROM 24-HOUR BLOOD PRESSURE MONITORING

Background and Objective: Aging is associated with progressive alterations in the structure and function of the heart and arteries, which can occur independently. This study aims to investigate the hemodynamic changes occurring in aging normotensive subjects concerning heart and arterial function. We employed a novel method based on blood pressure values obtained during 24-hour ambulatory blood pressure monitoring (24-h ABPM). Methods: A cross-sectional study was conducted involving 3,220 non-obese patients referred for 24-h ABPM, who did not have hypertension and were not taking any medications. 24-hour mean hemodynamics was obtained using a non-invasive method based on Ct. Ct was estimated as: Ct/BSA= 38/PPth+ 4/5 × Td/T - 3/7, where BSA: body surface area, Td: diastolic time, T: cardiac period, and PPth: theoretical pulse pressure. The stroke volume (SV) was estimation as: SV= Ct (PP+MSP ×Ts/τ), where PP: pulse pressure, MSP: mean systolic pressure, Ts: systolic time, τ: diastolic pressure decay time constant. Cardiac output (CO) and SVR were obtained using conventional formulas. Results: Among the participants, 64.6% were female, with an average age of 51.0±15.3 years, Ct of 0.96±0.21 mL/mmHg, CO of 5.2±0.68 L/min, and SRV of 1394±178 dyn.s/cm 5 . An age-related reduction in stroke index and cardiac index are noteworthy, stabilizing from the sixth decade of life onward (41.1±2.0 mL/m 2 and 3.0±0.23 L/min/m 2 , respectively). Conversely, Ct exhibits an early increase from the third to fifth decades of life (1.04±0.18 mL/mmHg), followed by a continuous and gradual decline until the ninth decade (0.71±0.16 mL/mmHg). Meanwhile, SVR demonstrates an upward trend until reaching and maintaining high values from the sixth decade of life (1426±167 dyn.s/cm 5 ) onward with a clear shift in arterial hemodynamics (Analysis of variance [ANOVA]; P value <0.001) (Figure). Conclusions: The current method based on 24-hour ABPM effectively portrays the cardiac and arterial hemodynamics that mirror age-related circulatory alterations. This method offers a valuable pathophysiological basis for understanding the aging blood pressure profile.