AJP - Heart and Circulatory Physiology, Vol 243, Issue 6 876-H883, Copyright © 1982 by American Physiological Society
Persistence of myocardial failure following removal of chronic volume overload
W. H. Newman, J. G. Webb and P. J. Privitera
Length-contractile force curves and dose-response curves of heart rate,
blood pressure, and contractile force were recorded from the left ventricle
of six anesthetized dogs in a control state. These measurements were
repeated at an average of 56 days following creation of an atrioventricular
fistula when signs of heart failure were present. The fistula was then
closed and the dogs restudied after an additional 57 days. Heart failure
was associated with a shift up the ascending limb of a depressed
length-contractile force curve and a depressed contractile response to
isoproterenol. For instance, 0.1 micrograms/kg of isoproterenol produced a
173 +/- 8% increase in contractile force in control and 42 +/- 7% in
failure. The contractile response to ouabain (30 micrograms/kg) was
unchanged in heart failure, i.e., 36 +/- 5% in control vs. 39 +/- 4% in
heart failure. When the dogs were restudied following fistula closure, the
length-contractile force curve was still depressed as was the contractile
response to isoproterenol, whereas the response to ouabain was again
unchanged from control. Plasma norepinephrine and renin levels increased 5-
and 10-fold, respectively, during heart failure and then returned to
control following closure of the fistula. The data support the view that
myocardial dysfunction associated with volume-overload heart failure is not
reversible within the same time frame as its onset.
