Abstract 9242: Tight Regulation of Left Ventricular Transmural Filling Pressure in Healthy Individuals

Abstract

Background: Healthy aging impairs left ventricular (LV) compliance and relaxation, which results in a decreased stroke volume in elderly individuals. By contrast, lifelong exercise training can preserve LV compliance and increase stroke volume in the elderly. However, it is unclear whether LV transmural distending pressure (LVTMP), which is thought to be the true preload for the LV, is influenced by healthy aging or lifelong exercise training. Methods: Healthy subjects (n=159; 99 male, 60 female) with no cardiovascular diseases were enrolled. Sedentary subjects were recruited from Dallas Heart Study, a multiethnic probability-based sample of Dallas County residents. Lifelong exercisers were recruited from Aerobics Center Longitudinal Study, a cohort which has documented lifelong exercise training patterns for 25 years. Subjects were stratified into 3 ‘sedentary’ age groups and 3 ‘lifelong training’ groups: Sedentary Age < 40 (n=30), Age 40-64 (n=43), and Age 65+ (n=21); Lifelong Training Age 65+ 2-3sessions/wk (n=23), Age 65+ 4-5 sessions/wk (n=20), and Age 65+ 6-7sessions/wk and competitive (n=22). All subjects underwent invasive right heart catheterization to determine stroke volume by thermodilution, pulmonary capillary wedge pressure (PCWP), and right atrial pressure (RAP). To eliminate the effect of external constraint on the LV, LVTMP was defined as PCWP - RAP. Results: Stroke volume decreased with increasing age and this age-related decline of stroke volume was prevented by lifelong exercise training. No effects of lifelong training on PCWP or RAP were observed in subjects > 65 years (p ≥ 0.76). In sedentary subjects, PCWP and RAP appeared to be slightly higher in Age <40 and Age 40-64 than Age 65+. However, LVTMP was identical among 6 groups (3.1±1.4 ∼ 3.6±1.5 mmHg, p = 0.74) and tightly controlled within a remarkably narrow range. Conclusion: True LV preload was tightly regulated in healthy subjects irrespective of age or lifelong exercise training. Therefore, changes in stroke volume associated with healthy aging or lifelong exercise training are not related to changes in LVTMP, but rather to changes in LV compliance.