Left ventricular performance in endotoxin shock in dogs

Abstract

Endotoxin shock, with maximal velocity of contraction (Vmax) as the index of contractility, showed no myocardial depression in an earlier 4 h study. Because of reports of late deterioration, 6 dogs were studied until spontaneous death (9-18 h). Heart rate nearly doubled and left ventricular filling pressure and aortic mean pressure fell, but Vmax did not change significantly. Because of concern that the marked increase in heart rate may have contributed to an artifactual maintenance of Vmax (due to its frequency dependence), a final group of 5 dogs with 3 additional indicators of contractility were studied. End-systolic pressure-diameter ratio (Emax), ejection fraction (sonar-determined from the minor axis of the left ventricle) and frequency-normalized average rate of generation of power density (FARPD) all fell early and remained low until death. Thus, myocardial contractility is evidently significantly reduced in endotoxin shock, early and sustained. Its presence is masked somewhat in the untreated subject by the reduced work load, secondary to hypovolemia.