Myocardial depression as a component of endotoxic shock in horses: preliminary results of an echocardiographic study

Cardiovascular consequences of septic shock are well described in humans but these hemodynamic disturbances have not yet been studied in endotoxic horses. The endotoxins act directly and indirectly to cause a myocardial depression associated with a systemic hypotension responsible for a fall of both the cardiac output and the systemic vascular resistance in end-stage endotoxic shock. The hypothesis was that myocardial depression was a component of endotoxic shock in horses. In this way, fifty horses admitted in clinic with signs of endotoxic shock and 17 healthy control horses were submitted to a doppler echocardiographic exam to assess the impact of endotoxic shock on equine cardiac function. A shock score from 1 to 4, based on clinical evaluation, non invasive systolic blood pressure, and blood tests was attributed to each endotoxic horse. Echocardiographic and Doppler parameters were compared between the 5 groups using a multivariable ANOVA analysis. Score 1, 2, 3 and 4 groups included 11, 17, 12 and 10 horses, respectively. Some markers of systolic function included the ejection time (ET), ET corrected for HR and mean velocity of circumferential fibre shortening corrected for HR, the aortic velocity time integral and deceleration time, and the stroke volume were significantly lower, whereas the HR and the peak velocity of the late diastolic filling of the mitral Doppler flow and its velocity time integral were significantly higher in endotoxemic horses than in controls. Thanks to an increase in HR, the cardiac output was not significantly different between groups. Even if the tachycardia, the fall in preload and a probable decrease in afterload doubtless influence the observed changes, the results of this study suggest that a myocardial depression with both an impaired systolic and diastolic left ventricular function could be a component of endotoxic shock in horses.