1983 Volume 29 Issue 2 Pages 191-203
The contractile performance of the rabbit left ventricle during chronic pressure-overloaded hypertrophy without failure was studied. About four weeks after constriction procedure of the descending aorta, the heart was isolated and retrograde coronary perfusion was established with modified Krebs solution. A latex balloon was inserted into the left ventricular cavity, and the intraventricular volume could be changed with a constant velocity by a magnetic shaker connected to the balloon. The pressure-volume relation and the relation between pressure and volume-velocity of the left ventricle were determined and compared with those of normal controls. The isovolumic developed pressures at any ventricular volume were larger in the hypertrophied heart than in the normal. However, the calculated wall stress plotted against the relative volume (the volume relative to the volume at which the maximum pressure was developed) was smaller in the hypertrophied heart. The pressurevelocity relation of the left ventricle was measured by the isovelocity method. The relationship in the hypertrophied as well as the normal heart could be adequately approximated with a hyperbolic equation. The maximum pressure was larger, but the maximum velocity was smaller, in the hypertrophied heart than in the normal. It is concluded that the left ventricular stress and the maximum velocity decreased in connection with pressure-overloaded hypertrophy in spite of an increase in the maximum pressure. These results indicate that the contractile performance decreases in the chronic pressure-overloaded hypertrophied heart.
