Effects of diltiazem on hemodynamic variables and ventricular function in healthy horses.

The research is discussing a study on the effects of the drug diltiazem on the heart rate, rhythm, ventricular function, hemodynamics, and blood flow in healthy horses.

Research Methodology

In framing the investigative structure, a dose-finding methodology was employed. Eight healthy horses were treated intravenously with diltiazem every 30 minutes. These were treated to achieve cumulative dosages of 0,1,1.5, and 2 mg/kg. Thereafter, various measurements were taken during each treatment period. It included estimating:

• Plasma diltiazem concentration
• Heart rate and rhythm through electrocardiography
• Left ventricular (LV) function and central hemodynamics via cardiac catheterization
• LV dimensions through echocardiography
• Forelimb blood flow using Doppler sonography

Findings

The administration of diltiazem resulted in plasma concentrations between 390 and 910 ng/mL, but this varied among horses. Observations from the cardiac treatment showed occasional depression of the sinus and atrioventricular (AV) nodes. Moreover, there was a slight impairment of systolic and diastolic LV function.

Vascular Effects

Diltiazem’s vascular impact included arterial vasodilation, increased limb blood flow, and decreased systemic vascular resistance. The baroreceptor reflex-mediated sympathetic activation resulted in an increased sinus node rate. This likely muted the depressive effects of diltiazem on myocardial and nodal tissues.

Side Effects

Issues arose in two horses, they developed transient high-grade sinus arrest with severe systemic hypotension. These outcomes suggest that dosage may be limited due to hypotension, a side effect resulting from vasodilation and the direct suppression of sinus node discharge.

Potential Applications

Despite the observed side effects, diltiazem appears to be relatively safe for use in healthy horses. Given its inhibitory effects on AV nodal conduction, the drug might be beneficial for controlling heart rates in horses with atrial fibrillation.