Inotropic drugs alter the physical properties of the ventricular wall that contribute to mechanical impedance during the filling period in an isolated dog heart model.
Should not inform inotrope use from isolated-heart data alone; leaves open whether wall impedance affects clinical diastolic filling.
Selected inotropic drugs were studied in an isolated right ventricle preparation in which the work load and heart rate could be controlled. Records of ventricular pressure and volume were made. Rate of ventricular relaxation was estimated, and mechanical impedance to inflow was calculated as the ratio of intraventricular pressure to inflow. The negatively inotropic drugs slowed relaxation and increased impedance. Strophanthin-K reversed these effects. Adrenalin decreased impedance. It is concluded that, during the filling period, inotropic drugs alter those physical properties of ventricle wall which contribute to mechanical impedance.
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Buckley et al. (1955) studied this question.
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