Heart Force Effects of Sympathomimetic Amines as a Basis for Their Use in Shock Accompanying Myocardial Infarction

The treatment of 14 patients in severe shock accompanying myocardial infarction with l -norepinephrine (Levophed) in some cases and phenylephrine (Neo-Synephrine) in others demonstrated a significantly higher recovery rate with l -norepinephrine. Twelve of the patients were in congestive heart failure. Using strain-gage technics in fully conscious, trained dogs, l -norepinephrine was shown to produce substantial increments in heart contractile force in addition to its recognized pressor effects. Approximately equipressor doses of Neo-Synephrine under the same conditions had little effect on contractile force. These pronounced differences in heart force effects are presented as a basis for the difference in clinical results.