Cardiac output, left ventricular ejection rate, plasma volume, and heart rate changes in equine laminitis-hypertension.

This research article explores the changes in heart function and plasma volume in horses suffering from acute laminitis-hypertension, a condition caused by overconsumption of carbohydrates. The researchers observed significant increases in cardiac output, heart rate, and arterial pressure that seemed to correspond with non-significant changes in peripheral resistance and a delayed decrease in plasma volume.

Investigating Acute Laminitis-Hypertension

• The researchers induced acute laminitis-hypertension in eight horses through carbohydrate overloading. This abnormal load on the GI tract prompted this severe condition.
• By monitoring the resulting hemodynamic changes – shifts in blood flow and blood pressure – the researchers aimed to understand how this condition affects the cardiovascular system of the horse.

Key Findings

• They recorded a significant (p < 0.01) surge in cardiac output, left ventricular ejection rate, heart rate, and arterial pressure. This indicates that the horses' hearts were working harder and faster, possibly in response to the disease.
• They also noted a delay in a decrease in plasma volume and changes in peripheral resistance. However, the statistical significance of these changes was not apparent, suggesting they might not be directly influenced by the disease, or their fluctuation could be due to other factors.
• Interestingly, the substantially increased cardiac output and left ventricular ejection rate, coupled with little to no change in either peripheral resistance or plasma volume occurring 16 hours after the onset of severe lameness (Obel grade 3), hinted at an increase in myocardial contractility or the heart’s ability to contract.

Implications

• The research provides valuable insights about the correlation between the onset of Obel grade 3 lameness in acute laminitis and these particular pathophysiological changes.
• Understanding this relationship could be instrumental in providing better treatment and management strategies for horses with acute laminitis-hypertension.
• In discussing the results, the researchers considered their findings in relation to clinical signs, serum electrolyte changes, plasma L-lactate alterations, and the histologic deterioration of the digit, to draw a comprehensive picture of how acute laminitis-hypertension impacts the equine body.