Myocardial dysfunction associated with low-dose endotoxin administration in adult horses.

BACKGROUND: Horses with endotoxemia have variable myocardial function, but little is known about the severity or persistence of myocardial dysfunction (MD). HYPOTHESIS/OBJECTIVES: Horses with experimentally induced endotoxemia have systolic and diastolic MD. ANIMALS: Twelve systemically healthy horses. METHODS: Horses were given Escherichia coli lipopolysaccharide 30 ng/kg over 60 min. Echocardiography and cardiac troponin I (cTnI) measurements were performed at baseline, 1, 3, and 5 h post-endotoxin. Fluid therapy (10 L), polymyxin B (6000 IU/kg), and flunixin meglumine (1.1 mg/kg) were administered intravenously, and then echocardiogram and cTnI measurements were performed (post-treatment). Results were compared using linear mixed models and adjusted for multiple comparisons. Significance was set at P < .05. RESULTS: All horses showed signs of MD. A significant increase in heart rate from baseline was noted at all timepoints (P < .001). No significant increase in cTnI occurred at any timepoint. Ejection fraction decreased from baseline at 3 and 5 h (mean, 72%, 62%, and 65%, respectively; P < .001 at both timepoints). Using tissue Doppler imaging (TDI), the index of myocardial performance increased at 1, 3, and 5 h (mean, 0.40, 0.55, 0.66, 0.55; P < .01 at all timepoints). Using two-dimensional speckle tracking (2DST), the magnitude of global longitudinal strain was decreased from baseline at 3, 5 h, and post-treatment (mean, -21%, -16%, -17%, and -19%; P < .0001, .0001, and .04, respectively). CONCLUSIONS AND CLINICAL IMPORTANCE: Systolic and diastolic MD are evident in the absence of increased cTnI. Advanced echocardiographic modalities such as TDI and 2DST improve diagnostic capability for identifying regional abnormalities.