Abstract 16655: Impact of Age, Race, and Arterial Stiffness on Ambulatory Heart Rate-Stroke Volume Counter-Regulation

• Published in: Circulation (New York, N.Y.) Vol. 138; no. Suppl_1 Suppl 1; p. A16655
• Main Authors: Elsayed, Sherif M, Elango, Kalaimani, Ahmed, Rahil, Bhura, Sajeer, Osmond, Peter J, Izzo, Joseph L
• Format: Journal Article
• Language: English
• Published: by the American College of Cardiology Foundation and the American Heart Association, Inc 06.11.2018
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/circ.138.suppl_1.16655

BackgroundWe have previously reported a strong negative correlation between stroke volume index (SVI) and heart rate (HR) within and between normal and hypertensive individuals and have defined the slope of the SVI-HR relationship as an index of the efficiency of rate-volume counter-regulation. SVI-HR slope may also reflect the efficiency of diastolic filling (Starling forces).ObjectiveTo investigate whether SVI-HR slope is influenced by demographic or hemodynamic variables.Design and method24 hr. ambulatory pulse wave analysis (PWA, Mobil-O-Graph, IEM, Stolberg, DE) with a 20-minute sampling interval was performed in a convenience sample of 94 normal and hypertensive subjects. Systolic (S) and diastolic (D) blood pressure (BP), pulse pressure (PP), HR, cardiac index (CI), SVI (= CI/HR) and the slope of the SVI-HR regression line were calculated in each subject. Group data were analyzed using IBM SPSS software with Pearson linear regression and stepwise multiple linear regression methods.ResultsCharacteristics of the cohort were (mean ± SD)age 57±17 years, weight 82.5±19 kg, 59% women, 62% Caucasians, BP 135±20/80±14 mm Hg, and HR 69±12 beats/min). There was a strong negative correlation between individual SVI and HR values (r = -0.53; p < 0.001). Slope correlated with age (r=0.268), race (greater in Blacks), and PP (r=0.222) (all p<0.05). Stepwise multiple linear regression modeling yielded the following relationshipSVI-HR Slope = - 0.31 race + 0.227 PP - 0.535 (multiple r = 0.381, p<0.001); excluded variables wereage, gender, height, weight, 24 hr. SBP, MAP and DBP.ConclusionsThere is a strong negative correlation between HR and SVI; the slope of this relationship is affected by age and PP (lower slope in older people or with wide PP) and race (greater slope in Blacks). In a multiple regression model, age was replaced by PP but age and PP are closely related to arterial stiffness. Lower SVI/HR slope with age may signify a parallel increase in “cardiac stiffness” or diastolic dysfunction. Why blacks exhibit more effective rate-volume counter-regulation is unknown.