Feasibility of transoesophageal echocardiography for evaluation of left ventricular performance in anaesthetised horses.

This research investigates the ability to successfully use transoesophageal Doppler echocardiography as a method to examine heart function in sedated horses, suggesting it as a minimally invasive and feasible approach for monitoring a horse’s ventricular performance during anesthesia.

Study Methodology and Measurements

• The researchers conducted the experiment on seven Thoroughbred horses with halothane-induced anaesthesia. The investigation involved performing echocardiography four times under uniform conditions.
• In one instance, they infused dobutamine hydrochloride at a rate of 4 micrograms/kg/min for 20 minutes, to alter the heart’s behaviour.
• The team used high pulsed repetition frequency Doppler echocardiography (HPRF) to obtain aortic blood velocity recordings. These recordings allowed the calculation of values such as maximum acceleration (dv/dtmax), maximum velocity (Vmax), left ventricular ejection time (ET), pre-ejection period (PEP), velocity time integral (VTI), and cardiac output (CO).

Outcome Observations and Conclusion

• The variation and confidence intervals in the results obtained from Doppler echocardiography were more consistent than the results collected from cardiac catheterisation.
• Doppler indices showed better repeatability between anaesthetic sessions when compared to the maximum rate of the left ventricular pressure rise (LVdp/dtmax).
• There was significant variability between horses for heart rates Vmax, dv/dtmax, and VTI, indicating individual differences in cardiac function.
• Following the dobutamine infusion, all measured variables, except the heart rate, VTI, and CO, showed significant changes. These changes exceeded the predicted 95% confidence intervals for single measurements in all significantly affected variables, hinting that these Doppler indices can be used to assess changes in a horse’s haemodynamic function.
• The procedure’s safety was confirmed by the absence of serious adverse effects associated with the probe’s insertion into the oesophagus. There was only evidence of mild issues, such as serous nasal discharge (lasting up to 24 hours post-anaesthesia) and minor nasal bleeding during probe insertion, observed in a total of 5 instances.
• Ultimately, the study concludes that transoesophageal Doppler echocardiography offers a viable, minimally invasive procedure to continuously monitor the systolic performance of a horse’s left ventricle during anaesthesia.