Modification of force-interval relations during early adaptation to pressure overload in dogs.
Ventricular function was analyzed in the end-systolic and end-ejection pressure-volume diagrams in seven conscious dogs during acute aortic stenosis (AS) and sustained stenosis (SS) 24 h later. Dogs were previously instrumented with a left ventricular micromanometer and ultrasonic crystals measuring left ventricular major and minor axes and parietal wall thickness. The end-ejection pressure-calculated volume points were significantly shifted to the left during SS as compared with those obtained during AS both during a regular atrial pacing (150 beats/min) and during spontaneous heart rate. Postpacing beats were not different during AS and SS. During AS, end-systolic volume was larger after short intervals (SI) between beats (22.5 +/- 1.6 ml) than after long intervals (LI; 20.8 +/- 1.7 ml) for a smaller end-systolic pressure (P less than 0.001). This difference was minimal during SS. When SS was compared with AS, the end-systolic and end-ejection pressure-volume points were significantly shifted to the left after SI but not after LI. This suggests an acceleration of the restitution process during SS that modifies ventricular force-frequency relations and increases ventricular function as compared with AS, particularly for high heart rates.
INSERM U2, Hôpital Léon Bernard, Limeil-Brévannes, France.
B
B
Crozatier
L
L
Hittinger
M
M
Chavance
D000222:Adaptation, Physiological; D000818:Animals; D001024:Aortic Valve Stenosis / Q000503:physiopathology; D004285:Dogs; D006321:Heart / Q000502:physiology*; D006439:Hemodynamics; D009200:Myocardial Contraction; D012016:Reference Values; D013997:Time Factors