Changes in Cardiac Output with Age

Abstract

In the first of two papers, the details and results of a systematic, carefully standardized application of dye dilution technic to the measurement of cardiac output are reporte(l. A substantially reduced output was a consistent finding in older subjects. Fa(tors responsible for this are analyzed in this article, and further interpretations are made in the succeedinig a1rticle. One result of the analysis of time-concentration curves of dye provides an interesting relationship to (linical estimates of circulation time.INVESTIGATIONS of cardiac output ill older, but presumably "normal," adults were made by Starr and his coworkers,1 by Lewis2 and by Aperia3 16 to 20 years ago, using the indirect gas methods then available. Although the insensitivity of these methods could mask a sizeable change, Starr and his associates noted that in the "period before 20 years the average cardiac index is higher than at any time later, after 50 it slowly declines. The number of cases was too small to demonstrate the significance of the difference." Their series included only nine cases over 50 years of age; the oldest was 76. Lewis, in a systematic agewise study, found a small decrease in cardiac index in 100 male subjects between 40 and 89 years of age. He considered that the observed changes represented neither statistically nor physiologically a significant decline and that they were predominantly the result of a decrease in oxygen consumption. A decrease of about the same order may be calculated from the data reported by Aperia,3 utilizing the acetylene technic of Grollman. These indirect Fick gas methods are now recognized as yielding values which are approximately 25 per cent too low, but even allowing for this, a sizeable decrease in cardiac output cannot be said to have been demonstrated by these studies, despite a consistent suggestion in this direction.Age comparisons, using the Fick principle with right heart catheterization, were sought in the studies of Stead and his colleagues,4

The effect of ageing on the hepatic clearance of propranolol.

“…Where cardiac output was decreased, the cerebral coronary and skeletal blood flow tended to be maintained at the expense of supply to other organs including the liver. Brandfonbrener, Landowne & Shock (1955) Sherlock et al (1950) estimated hepatic blood flow from the extraction of bromsulphthalein and concluded that it was reduced by 40-50% at the age of 60 when compared to that in individuals averaging 25 years. As the average age of elderly subjects was 78 years, the longer half-life after i.v.…”

What really declines with age?

“…Early studies by the group of Dr. Nathan Shock in Baltimore strongly supported this thesis. In so-called healthy human volunteers, the cardiac output (Brandfonbrener et al 1955), renal creatinine clearance (Rowe et al 1976) and all other physiological parameters examined were demonstrated to steadily decline with age. However, later by the same group in Baltimore, in a longitudinal study, neither the cardiac output (Rodeheffer et al 1984) nor renal creatinine clearance (Lindeman et al 1985) was shown to decline with age.…”

Improving aerobic capacity in healthy older adults does not necessarily lead to improved cognitive performance.

“…Performance on reaction-time tests of attention and memory retrieval was slower for the older adults than for a comparison group of 24 young adults, and there was no improvement in the older adults' performance on these tests as a function of aerobic exercise training. Results suggest that exercise-related changes in older adults' cognitive performance are due either to extended periods of training or to cohort differences between physically active and sedentary individuals.Several parameters of cardiovascular functioning (e.g., maximal heart rate, cardiac output, and left ventricular ejection fraction during exercise) typically exhibit a decline during later adulthood, even in the absence of overt coronary disease (Brandfonbrener, Landowne, & Shock, 1955;Gerstenblith, Lakatta, & Weisfeldt, 1976;Port, Cobb, Coleman, & Jones, 1980;Strandell, 1976). There is, in addition, a significant agerelated decline in cardiorespiratory fitness (i.e., aerobic capacity), the ability to sustain maximal expenditures of energy.…”