Endotoxin impairs cardiac hemodynamics by affecting loading conditions but not by reducing cardiac inotropism.
Acute myocardial dysfunction is a typical manifestation of septic shock. Experimentally, the administration of endotoxin [lipopolysacharride (LPS)] to laboratory animals is frequently used to study such dysfunction. However, a majority of studies used load-dependent indexes of cardiac function [including ejection fraction (EF) and maximal systolic pressure increment (dP/dt(max))], which do not directly explore cardiac inotropism. Therefore, we evaluated the direct effects of LPS on myocardial contractility, using left ventricular (LV) pressure-volume catheters in mice. Male BALB/c mice received an intraperitoneal injection of E. coli LPS (1, 5, 10, or 20 mg/kg). After 2, 6, or 20 h, cardiac function was analyzed in anesthetized, mechanically ventilated mice. All doses of LPS induced a significant drop in LV stroke volume and a trend toward reduced cardiac output after 6 h. Concomitantly, there was a significant decrease of LV preload (LV end-diastolic volume), with no apparent change in LV afterload (evaluated by effective arterial elastance and systemic vascular resistance). Load-dependent indexes of LV function were markedly reduced at 6 h, including EF, stroke work, and dP/dt(max). In contrast, there was no reduction of load-independent indexes of LV contractility, including end-systolic elastance (ejection phase measure of contractility) and the ratio dP/dt(max)/end-diastolic volume (isovolumic phase measure of contractility), the latter showing instead a significant increase after 6 h. All changes were transient, returning to baseline values after 20 h. Therefore, the alterations of cardiac function induced by LPS are entirely due to altered loading conditions, but not to reduced contractility, which may instead be slightly increased.
Dept. of Intensive Care Medicine, Univ. Hospital Center and Faculty of Biology and Medicine, CHUV-BH 08-621, 1011 Lausanne, Switzerland.
Li
L
Jianhui
Nathalie
N
Rosenblatt-Velin
Noureddine
N
Loukili
Pal
P
Pacher
François
F
Feihl
Bernard
B
Waeber
Lucas
L
Liaudet
D000818:Animals; D001158:Arteries / Q000503:physiopathology; D006328:Cardiac Catheterization; D009202:Cardiomyopathies / Q000209:etiology* / Q000503:physiopathology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004548:Elasticity; D019446:Endotoxemia / Q000139:chemically induced / Q000150:complications* / Q000503:physiopathology; D004731:Endotoxins / Q000008:administration & dosage; D006339:Heart Rate; D007274:Injections, Intraperitoneal; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D013318:Stroke Volume; D013997:Time Factors; D014655:Vascular Resistance; D016277:Ventricular Function, Left; D017725:Ventricular Pressure
D004731:Endotoxins; C044101:endotoxin, Escherichia coli