The effect of insulin infusion on heart rate and systemic blood pressure in horses with equine metabolic syndrome

Background There is little evidence that horses with equine metabolic syndrome (EMS) have higher resting blood pressures than horses with normal insulin sensitivity. However, there are indications that EMS horses have an altered dynamic response to the cardiovascular effects of insulin. Objectives To examine heart rate and the systemic blood pressure response in EMS and control horses during insulin infusion. Study design Cross-sectional study. Methods Horses were examined with an oral sugar test (OST) and a euglycaemic hyperinsulinaemic clamp (EHC). Based on the results from the OST, the horses were classified as either EMS or control. Blood pressure was measured before the start of the EHC and at 60, 120 and 180 min of the EHC. Results There were 16 EMS and 12 control horses. Mean resting heart rate was higher for EMS horses compared with control (35.6 +/- 5.1 vs. 30.3 +/- 3.5 beats/min). Systolic, diastolic and mean arterial blood pressure did not differ between groups at the start of the EHC. Blood pressure decreased gradually during the EHC in the control group, whereas the EMS group showed no decline in systolic, diastolic or mean arterial pressure. Main limitations Limited number of horses. Conclusions Horses with EMS have cardiovascular changes that affect resting heart rate and systemic blood pressure during insulin infusion.