REGULATION OF EXTERNAL WORK OF CONCENTRIC HYPERTROPHIED LEFT VENTRICLES IN UNANESTHETIZED HYPERTENSIVE DOGS

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This study aimed to evaluate the change in external work and its control mechanism in the concentric hypertrophied heart induced by systemic hypertension. The calculated stroke work, myocardial contractility, afterload, and preload were examined in the baseline period (Control Stage, CS) and in the eighth week after the induction of perinephritic hypertension (Hypertensive Stage, HS) in unanesthetized dogs. These variables were examined with echocardiograms and high-fidelity left ventricular (LV) and ascending aortic pressures. Mean aortic pressure was significantly (p<0.05) elevated from 95±10 to 134±27 mmHg in HS. The ratio of end-diastolic wall thickness to radius significantly (p<0.05) increased in the HS. The calculated stroke work of the LV chamber was significantly (p<0.05) increased from 7022±1203 to 8860±1548×10^3 erg in HS while the stroke work normalized for wall thickness by calculating the wall stress was not altered (3069±1086 v.s. 2989±866 erg; CS v.s. HS) with no significant change in heart rate in HS. In the HS, the end-systolic wall stress (afterload) and the slope of end-systolic wall stress-dimension relationship (myocardial contractility) were unchanged while the end-diastolic wall stress (preload) slightly reduced. These results suggest that, in the concentric hypertrophied left ventricle induced by systemic hypertension, the LV myocardial external work is normal, whereas the LV chamber external work increases. Furthermore, the major role for allowing the LV myocardial external work to remain normal seems to be not the compensatory changes in preload, myocardial contractility, or heart rate, but rather myocardial hypertrophy; an adaptation to preserve normal ejecting wall stress to chronic pressure overload.
社団法人日本循環器学会の論文
1990-11-20

REGULATION OF EXTERNAL WORK OF CONCENTRIC HYPERTROPHIED LEFT VENTRICLES IN UNANESTHETIZED HYPERTENSIVE DOGS

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