Left ventricular adaptation to sustained pressure overload in the conscious dog.

Abstract

SUMMARY. The early adaptation to aortic stenosis was studied in eight conscious dogs previously instrumented with a left ventricular micromanometer and ultrasonic crystals measuring left ventricular minor equator, left ventricular major axis, and ventricular wall thickness. Data were compared during control, acute inflation of a supravalvular aortic cuff ocduder and 24 hours after aortic stenosis with and without jS-blockade. Acute aortic stenosis increased peak systolic pressure and end-systolic pressure with a decrease of percent systolic shortening of minor diameter (%AL). Twenty-four hours after aortic constriction for heart rates, end-diastolic dimensions, and systolic pressures similar to those measured during acute aortic stenosis, %AL was significantly increased, compared with acute aortic constriction, and was close to control values. End-systolic diameter was not significantly different from control during sustained pressure overload, although end-systolic stress was increased by 26.7 ± 6.1% (P < 0.01 with control), representing a leftward shift of the end-systolic stress-diameter relation. Similar results were obtained under /J-blockade. We conclude that there is, in this model of moderate pressure overload, a nonsympathetic increased inotropic state very early after aortic constriction. (Circ Res 54: 21-29, 1984)

The effect of sustained stellate ganglion stimulation on left ventricular contractility in the dog.

“…Kanazawa et al reported that close positive correlation between left ventricular diameter and left ventricular segment length obtained as the same manner exists, and that the end-systolic P-L relationship is thus acceptable for estimating ventricular contractility (Suga and Sagawa 1974; Kanazawa et al 1983;Crozatier et al 1984). Aortic constriction has also been used as an experimental procedure for evaluating left ventricular contractility (Monroe et al 1968;Crozatier et al 1984). In the present study, as shown in Figs.…”

“…We used the pressure-segment length rather than the pressure-volume relationship in the present study because Suga and Sagawa have shown a close positive correlation between ventricular diameter and volume at the end-systolic phase and end-diastolic phase in both isovolumic and ejection beats. Kanazawa et al reported that close positive correlation between left ventricular diameter and left ventricular segment length obtained as the same manner exists, and that the end-systolic P-L relationship is thus acceptable for estimating ventricular contractility (Suga and Sagawa 1974; Kanazawa et al 1983;Crozatier et al 1984). Aortic constriction has also been used as an experimental procedure for evaluating left ventricular contractility (Monroe et al 1968;Crozatier et al 1984).…”

Improved myocardial efficiency in the working perfused heart of the spontaneously hypertensive rat.

“…overload is a common finding in the clinical setting. 1 " 5 Experimental studies using papillary muscles from hypertrophied rat hearts have demonstrated improved economy of myocardial contraction. 6 ' 7 In contrast, the majority of studies performed in vivo in several animal species and in humans have failed to confirm these findings.…”

Inhibition of Hypertrophy, Per Se, May Not Be a Good Therapeutic Strategy in Ventricular Pressure Overload: Other Approaches Could Be More Beneficial

“…Thus, the increased wall thickness induced by hypertrophy allows for obtaining a normal ejection without an increase in inotropic state through a normalized wall stress. C, In contrast, when these relations were studied early (24 hours) after cuff inflation, 45 an increased inotropic state was demonstrated, because normal shortening was obtained for a larger wall stress. This produced a leftward shift of the end-systolic stress-strain relation compared with the immediate cuff inflation.…”

“…Basis of the stress hypothesis of ventricular adaptation to pressure overload. The general shape of the pressure-volume and stress-strain lines was freely drawn using the calculated loops that we generated in dogs, 45 with the mean values of diameter, pressure, and stress given in the references quoted below. A, Schematic representation of the pressure-diameter relations obtained in vivo in chronically instrumented closed-chest dogs.…”