The volume in the left ventricle and that in the right ventricle were measured statically starting from zero transmural pressure, when the ventricle is in the state of elastic equilibrium, to a negative transmural pressure of 30 mm Hg. Freshly excised dog hearts were submerged in Ringer's solution at 10°C to establish zero transmural pressure, to offset the contribution of the weight of the ventricular walls on the shape of the ventricle, and to retard the onset of postmortem changes. The volume was approximated by an equation which included a power function of the body weight and another of the ventricular weight. For male dogs, the left ventricle when in the state of elastic equilibrium contained a mean volume of 14.5 ml for a body weight of 10 kg and a ventricular weight of 58 g; the corresponding figure for the right ventricle was 12.2 ml. In a quiescent heart below a certain ventricular volume, potential energy will be stored in structural elements of the ventricle wall that will facilitate the filling of the ventricle. This work was supported in part by the Life Insurance Medical Research Fund, by Grant H-3796 from the National Institutes of Health, U. S. Public Health Service, and by the Georgia Heart Association. ADDITIONAL KEY WORDSPreliminary results were presented as "Form Elasticity of the Heart," at the Fall Meeting of the American Physiological Society, Stanford, California, 1960. Accepted for publication October 17, 1986. the ventricular volume in the state of elastic equilibrium, could store potential energy in the strained elastic elements. Diastolic recoil would then tend to produce a negative transmural pressure of the ventricle, increase the atrioventricular pressure difference, and facilitate the filling of the ventricle through a "vis a fronte," i.e. suction. A graphic representation of the concept was previously published by Kolder et al. (3). The purpose of the present study is to measure under controlled conditions the left and right ventricular volume in the state of elastic equilibrium and to relate the measured volumes to body weight, weight of both ventricles, and sex. This statistical information will be of value in assessing the ventricular volume at which elastic forces in the ventricular wall start contributing to diastolic filling. MethodThe technique used for the present experiments is similar to that previously described (3). Dogs were anesthetized with pentobarbital (30 mg/kg body weight, iv) and rapidly exsanguinated. The chest was opened and the heart removed
The effects of temperature on the development of rigor mortis in cardiac muscle have never been investigated systematically. Brecher and Kissen 1 found that pressure-volume characteristics of non-beating, submerged dog ventricles remained constant for at least 30 minutes following circulatory arrest at 35°C. Using similar methods, Griggs et al. 2 found this period to be approximately 80 minutes at 36°C and 300 minutes at 5°C. These and other related studies of rigor mortis 3 " 9 were not primarily directed at the effects of varying temperature under controlled conditions. We have therefore adapted the technique of Brecher and Kissen 1 to permit systematic investigation of tlie effects of temperature on the onset and development of rigor mortis in dog hearts. This study provides a background for future investigations in which the time limits for development of rigor mortis must be known.Methods The principle of the method is to establish an "elastic equilibrium" of the ventricles b}7 submerging the heart in Ringer's solution. The state of elastic equilibrium of a ventricle is characterized by zero transmural pressure. Under this condition there is always a certain volume of fluid in the freshly excised ventricle. Upon reducing the intraventricular volume, the transmural pressure becomes negative and upon fluid addition it becomes positive. This method lends itself to pressurevolume studies in which any stretch of the ventricular walls can be avoided. Since such stretch might affect the development of rigor mortis, half of the experiments were done with negative transmural pressures only and compared with the others From the in which both negative and positive transmural pressures were produced.Fifty-five mongrel dogs of various ages were used, 37 for studies on left ventricles, 18 for studies on right ventricles. Preceding these experiments, most of the animals had been employed in other studies which did not involve the cardiovascular system. The animals were anesthetized intravenously with sodium pentobarbital (30 mg/kg of body weight). Six minutes after the injection they were rapidly exsanguinated from a femoral artery. Four minutes after the beginning of exsanguination the removal of the heart from the pericardial sac was completed. The aorta and pulmonary artery were severed 5 cm from their origin and the systemic and pulmonary veins were divided at their entrance into the atria. The hearts were then rinsed in Ringer's solution and the aorta and pulmonary artery stumps were ligated. The experimental arrangement is shown in figure 1.A Tygon cannula (inner diameter 10 mm) was placed in the atrioventrieular orifice and secured by a ligature around the atrioventrieular groove. The hearts were submerged in Ringer's solution in a constant temperature bath. The bath could be adjusted to temperatures between 1°C and 50°C (± 0.25). The composition of the buffered Ringer's solution used was NaCl 0.9 g, KC1 0.03 g, CaCl 2 anhyd. 0.026 g, 3\ T aHCO 3 0.055 g, water to 100 ml 2 The ventricular cannula was connected via...
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