title: Influence of acute hemodynamic changes on the negative peak of the first derivative of apex cardiogram during ventricular relaxation in dogs.
abstract: The effect of various alterations in the preload, the afterload and the inotropic state of the left ventricle on the first derivative of apex cardiogram (dA/dt) was studied in 9 anesthetized dogs to clarify some of the determinants of the negative peak of dA/dt and isovolumic relaxation time. The first derivative of the apex cardiogram was recorded simultaneously with the left (ventricular pressure, conventional left apex cardiogram, first derivative of left ventricular pressure (dP/dt), electrocardiogram and phonocardiogram. Both dA/dt and dP/dt curves were similar in contour and occurred nearly simultaneously. This close relationship was preserved during various acute haemodynamic changes. The maximum negative dA/dt and the isovolumic relaxation period was closely related to the level of afterload. Large rapid augmentation of mean aortic pressure resulted in a significant increase in the negative dA/dt and shortening of the isovolumetric relaxation time, where reduction of afterload had an opposite effect. Isoprenaline acutely augmented minimum dA/dt. It is concluded that measurement of negative peak dA/dt under some conditions is a reliable noninvasive technique for assessing myocardial relaxation.
mesh_terms: D000818:Animals; D004285:Dogs; D005260:Female; D006352:Heart Ventricles / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology; D007702:Kinetocardiography; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects*; D009599:Nitroprusside / Q000494:pharmacology; D011433:Propranolol; D013328:Strophanthins / Q000494:pharmacology; D014684:Venae Cavae / Q000502:physiology
chemical_list: D013328:Strophanthins; D009599:Nitroprusside; D008464:Mecamylamine; D011433:Propranolol; D007545:Isoproterenol