Solomon Garb

Inotropic Action of Epinephrine, Nor-epinephrine, and N-Isopropyl-Norepinephrine on Heart Muscle.∗†

Summary and Conclusions d-1 Nor-epinephrine (Arterenol) and the N-isopropylnorepinephrine (Isuprel) exert a powerful inotropic action on mammalian heart muscle.

The T Deflection of Isolated Mammalian Heart Muscle Electrogram

Both bipolar and unipolar electrograms recorded from well-oxygenated isolated papillary muscle preparations consist of R and T deflections in the same direction. The T is inverted by anoxia, rapid late, and injury. When cut linear strips of ventricular muscle are observed for many hours, during which time they presumably recover from the initial injury, the T deflection becomes upright in most cases, and then can be depressed and inverted by anoxia or rapid rates of stimulation. Since, in the absence of modifying factors, the T is in the same direction as the R deflection in a simple linear strip, it probably cannot be adequately explained on the basis of membrane repolarization. Since the nerve after-potentials are believed to represent processes involving oxidative metabolism, the T deflection may also be produced by metabolic processes, although the possibility cannot be excluded that it represents a combination of membrane repolarization and other processes.

Effects of rhythm and rate changes on inotropic action of ouabain.

Summary In failing cardiac muscle, postextrasystolic potentiation decreases at a slower rate than response in a series at a regular frequency. Postextrasystolic contraction is not improved by ouabain. The latent period of ouabain action is related to elapsed time, not the total number of contractions.

The relationship of blood viscosity to the intensity of heart murmurs

Abstract 1. 1. A method of producing and recording a murmur is described. 2. 2. The murmur produced was found to decrease precipitously with increased blood hemoglobin levels. 3. 3. The results show that lowering of viscosity is, in itself, enough to produce a definite murmur where none was heard before. This may indicate the origin of the hemic murmur. 4. 4. With high blood viscosities, the absence of a murmur does not rule out gross structural cardiac abnormalities.