The effect of contractility and preload on matching between the canine left ventricle and afterload

• Published in: Circulation (New York, N.Y.) Vol. 73; no. 1; pp. 161 - 171
• Main Authors: MYHRE, E. S. P, JOHANSEN, A, BJØRNSTAD, J, PIENE, H
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD Lippincott Williams & Wilkins 1986
• Subjects: Animals; Aorta - physiology; Biological and medical sciences; Blood Pressure; Cardiac Output; Cardiology. Vascular system; Coronary Vessels; Dogs; Embolism - physiopathology; Female; Heart; Heart - physiology; Heart - physiopathology; Heart failure, cardiogenic pulmonary edema, cardiac enlargement; Heart Rate; Heart Ventricles; Male; Medical sciences; Microspheres; Models, Biological; Myocardial Contraction; Pulse; Research Design; Software; Stroke Volume; Heart; Fissipedia; Carnivora; Cardiac performance; Cardiovascular disease; Left ventricular failure; Left ventricle; Vertebrata; Experimental disease; Mammalia; Heart disease; Hemodynamics; Dog; Hypertrophy
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/01.CIR.73.1.161

We define matching between ventricle and afterload to imply that the ventricle is adapted to its afterload to yield maximum external work output. For the ventricle, this optimal adaption will depend on end-diastolic dimension, heart rate, and contractility. Because contractility is impaired during ventricular failure, we propose that the adaption between ventricle and load is not as good during failure as during normal conditions. According to our definition, this implies that during failure external work output is less than maximum. Ventricle-load matching is then not present, i.e., a mismatch exists between ventricle and load. This hypothesis was tested in a canine preparation in which arterial load of the left ventricle was varied from one beat to the next. Left ventricular depression was induced by injections of 50 micron microspheres into the left coronary bed. We observed left ventricular stroke volume and external work during afterload variations at three different preload levels before and after microembolization. Before embolization the control observations of work and stroke volume were positioned at the apex of parabolas relating work to stroke volume. After embolization, however, control observations fell down along the left limb of the parabolas. These observations were independent of preload. Thus this study, carried out in a preparation with the heart in situ, supports the idea that the normal left ventricle is matched to its load and demonstrates ventricle-load mismatch when the left ventricle is failing.