Evaluation of left ventricular contractile performance utilizing end-systolic pressure-volume relationships in conscious dogs.
The relationship between left ventricular end-systolic pressure and volume has been proposed as a model of left ventricular contraction which may be useful for quantifying inotropic state independent of preload and afterload. Although the model has been well-validated in isolated hearts, systematic evaluation in conscious animals with an intact peripheral circulation has been limited. Accordingly, we derived end-systolic pressure-volume relationships in twelve conscious dogs, chronically instrumented to measure left ventricular pressure and dimensions from endocardial ultrasonic crystals in three orthogonal axes. We examined the linearity of the end-systolic pressure-volume relationship, its response to alterations of inotropic state and the peripheral circulation, and the influence of beta-adrenergic reflexes. End-systolic pressure-volume relationships were constructed by linear regression of end-systolic pressure-volume coordinates produced by transient inferior vena caval occlusions during atrial pacing. The relations were highly linear; of 127 inferior vena caval occlusions, the correlation coefficient was 0.96 +/- 0.05 (mean +/- SD). The slope of the end-systolic pressure-volume relationship was not significantly altered either by a moderate resistive afterload induced by angiotensin II infusion, or by a moderate increase in preload produced by dextran, but was increased from 4.7 +/- 2.3 to 6.5 +/- 2.2 mm Hg/ml (P less than 0.05) in response to the positive inotropic stimulus of dobutamine. The volume intercept at zero end-systolic pressure was unaffected by dextran or dobutamine, but was decreased from 12 +/- 8 to 5 +/- 11 ml (P less than 0.01) by angiotensin II infusion, indicating a leftward shift of the end-systolic pressure-volume relationship.(ABSTRACT TRUNCATED AT 250 WORDS)
D000319:Adrenergic beta-Antagonists; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001775:Blood Circulation / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002306:Cardiac Volume / Q000187:drug effects; D004280:Dobutamine / Q000494:pharmacology; D004285:Dogs; D006352:Heart Ventricles / Q000503:physiopathology; D009200:Myocardial Contraction / Q000187:drug effects; D011433:Propranolol / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000502:physiology; D013599:Systole; D016276:Ventricular Function
D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta; D000804:Angiotensin II; D004280:Dobutamine; D011433:Propranolol