Exercise training enhances cardiac function in response to an
afterload stress in older men .
Spina, Robert J., Michael J. Turner, Ali A. Ehsani.
Section of Applied Physiology, Division of Geriatrics and
Gerontology, and Cardiovascular Division, Department of Medicine,
Washington University School of Medicine, St. Louis, MO
APStracts 3:0398H, 1996.
This study was designed to characterize cardiac adaptations to
endurance exercise training (EET) in older healthy men by evaluation
of changes in left ventricular (LV) function in response to an
afterload stress in the presence of cardiac muscarinic receptor
blockade. Eight men 65 +/- 2 yrs old (mean +/- SE) underwent 9 months
of EET. O2max was determined during treadmill exercise. LV function
was assessed with 2D-echocardiography and pulsed Doppler transmitral
flow velocity profile at baseline, after an i.v. bolus of atropine
and during infusion of graded doses of phenylephrine. O2max was
increased by 29% in response to training (28.9 +/- 1 to 37.3 +/- 1
ml/kg/min). Baseline end-diastolic diameter (EDD) was increased, with
no change in LV wall thickness-to-radius ratio, after training
suggestive of eccentric left ventricular hypertrophy. EDD, end
-systolic dimension and end-systolic wall stress ([sigma]es) increased
similarly in response to phenylephrine before and after training.
Fractional shortening (FS) decreased in response to phenylephrine
before but not after training. When the changes in FS (_FS) during
phenylephrine infusion were plotted as a function of changes in
[sigma]es, _FS was significantly higher after than before training (p
= 0.003) at comparable increases in [sigma]es, indicative of improved
contractile function. This adaptive response was preload-independent,
as EDD did not differ between the trained and untrained states during
phenylephrine infusion. Heart rate responses to phenylephrine were
similar before and after training. Exercise training resulted in a
higher (p = 0.028) early-to-late transmitral diastolic flow velocity
ratio at virtually identical heart rates, suggestive of improved
diastolic filling. The results suggest that EET induces an
enhancement of LVsystolic function in response to an afterload stress
in older healthy men.
Received 27 December 1995; accepted in final form 26 August 1996.
APS Manuscript Number H1211-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996