The pressure-volume and stiffness-pressure relations in the isolated rabbit left ventricle.

Abstract

SummaryA balloon was introduced into the isolated rabbit left ven- Many studies have been done on cardiac muscle mechanics and on the ventricular performance, but few attempts have been made to elucidate the interrelation between both frameworks. One of the reasons has been the difficulty in controlling the intraventricular volume. Recently, SUGA and SAGAWA (1974) overcame this difficulty by adopting the intraventricular balloon method to the isolated dog heart. OKUYAMA (1983) has determined the hyperbolic relation between pressure and ejection velocity in the rabbit ventricle and has successfully shown the quantitative interrelation of force-velocity with ventricular wall muscle. This study was aimed at determining the pressure-volume and stiffness-pressure relations in the rabbit ventricle to compare them with the tension-length and stiffness-tension relations of wall muscle.Thirteen adult female rabbits, weighing 2.5-4.4 kg, were anesthetized with intravenous urethane (1.3-2.5 g/kg) administration, and under artificial ventilation the heart was exposed through midsternal thoracotomy. Preparation procedures and the experimental setup were described in detail by OKUYAMA (1983). In brief, after the establishment of retrograde coronary perfusion, the heart was isolated and a thin latex balloon was inserted into the left ventricular cavity. The balloon was connected to a volume control system, which consisted of a cylindrical chamber, a magnet shaker and an electrical feedback amplifier. The intraventricular volume could be changed at various velocities at any instant. The retrograde