Attenuated cardiovascular reserve during prolonged submaximal cycle exercise in healthy older subjects
Luis C. L. Correia, MD*,
Edward G. Lakatta, MD*,
Frances C. O’Connor, MPH*,
Lewis C. Becker, MD, FACC ,
Jon Clulow, ARRT, CNMT,
Susan Townsend, RN,
Gary Gerstenblith, MD, FACC and
Jerome L. Fleg, MD, FACC*,*
* Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, USA
Division of Cardiology, Johns Hopkins Hospital, Baltimore, Maryland, USA
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Figure 1 Oxygen consumption (VO2), cardiac output, and its components. On this and subsequent figures, mean values ± SEM of individual cardiac parameters are shown before exercise, every 10 min during exercise through 40 min, and at end-exercise for subjects younger versus those older than the median age of 50 years. The p value shown is derived from repeated measures analysis of variance comparing all time points between 10 min and 40 min of exercise, achieved by 19 of 20 younger subjects and 17 of 20 from the older group. Oxygen consumption remained constant in both age groups across time but was higher in younger subjects (A). An increase in cardiac index (CI) (B) occurred in each group, with a trend toward a larger increase in younger subjects. Stroke volume index (SVI) (C) increased modestly and to a similar extent in both groups between 10 and 40 min; heart rate (HR) (D) was consistently higher in the young.
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Figure 2 Left ventricular volumes and pump function. End-diastolic volume index (EDVI) (A) remained relatively constant throughout exercise in both groups but was consistently higher in older subjects. End-systolic volume index (ESVI) (B) declined between 10 and 40 min in both groups, though to a greater extent in younger subjects. Conversely, ejection fraction (EF) (C) increased in both groups but to a lesser extent in the older group. Contractility index, defined as systolic blood pressure/ESVI (D), increased in the young but did not change significantly in the older group.
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Figure 3 Left ventricular afterload. There were similar significant declines in systolic blood pressure (SBP) (A) and total systemic vascular resistance (TSVR) (B), as well as in diastolic blood pressure and arterial elastance index (not shown), in both age groups between 10 and 40 min of exercise.
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