Steady-state effects of preload and afterload on isovolumic indices of contractility in autonomically blocked dogs

The steady-state effects of independently altering left atrial pressure (LAP), aortic pressure (AP), and heart rate (HR) on left ventricular isovolumic indices were studied in autonomically blocked open-chested dogs. With mean AP and HR constant (dP/dt)max and (dP/dt)DP40 (that is dP/dt at a develop...

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Bibliographic Details
Published in:Cardiovascular research 1980-05, Vol.14 (5), p.245-253
Main Authors: BROUGHTON, ARCHER, KORNER, PAUL I
Format: Article
Language:English
Subjects:
Animals
Aorta - physiopathology
Autonomic Nerve Block
Blood Pressure
Dogs
Heart - physiopathology
Heart Atria - physiopathology
Heart Rate
Heart Ventricles - physiopathology
Myocardial Contraction
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Summary:The steady-state effects of independently altering left atrial pressure (LAP), aortic pressure (AP), and heart rate (HR) on left ventricular isovolumic indices were studied in autonomically blocked open-chested dogs. With mean AP and HR constant (dP/dt)max and (dP/dt)DP40 (that is dP/dt at a developed LVP of 5.3 kPa [40 mmHg]) rose to an approximate plateau above LAP 1.6 kPa (12 mmHg) implying optimum diastolic LV fibre length above this LAP. However, the index (dP/dt/TP)max (TP = total LVP above atmospheric) fell progressively at LAP > 1.6 kPa (12 mmHg). Increasing HR (LAP constant) increased (dP/dt)max by 5.6 ± 0.7% of basal value for every 10 beats.min−1 over HR range 120 to 200 beats·min−1. With LAP and HR constant changing AP in the aortic diastolic pressures (ADP) range 6.7 to 20 kPa (50 to 150 mmHg) had no effect on (dP/dt)DP40 and (dP/dt/TP)max, which occur early in systole. (dP/dt)max was afterload independent at ADP > 12 kPa (90 mmHg), but fell by about 5% (P
ISSN:0008-6363
1755-3245
DOI:10.1093/cvr/14.5.245