Abstract | BACKGROUND: Although atrial arrhythmias are clinically important in horses, atrial electrophysiology has been incompletely studied. HYPOTHESES: Standard electrophysiologic methods can be used to study drug effects in horses. Specifically, the effects of diltiazem on atrioventricular (AV) nodal conduction are rate-dependent and allow control of ventricular response rate during rapid atrial pacing in horses undergoing quinidine treatment. ANIMALS: Fourteen healthy horses. METHODS: Arterial blood pressure, surface electrocardiogram, and right atrial electrogram were recorded during sinus rhythm and during programmed electrical stimulation at baseline, after administration of quinidine gluconate (10 mg/kg IV over 30 minutes, n = 7; and 12 mg/kg IV over 5 minutes followed by 5 mg/kg/h constant rate infusion for the remaining duration of the study, n = 7), and after coadministration of diltiazem (0.125 mg/kg IV over 2 minutes repeated every 12 minutes to effect). RESULTS:
Quinidine significantly prolonged the atrial effective refractory period, shortened the functional refractory period (FRP) of the AV node, and increased the ventricular response rate during atrial pacing. Diltiazem increased the FRP, controlled ventricular rate in a rate-dependent manner, caused dose-dependent suppression of the sinoatrial node and produced a significant, but well tolerated decrease in blood pressure. Effective doses of diltiazem ranged from 0.125 to 1.125 mg/kg. CONCLUSIONS AND CLINICAL IMPORTANCE:
|
Authors | Colin C Schwarzwald, Robert L Hamlin, John D Bonagura, Yoshinori Nishijima, Cheyney Meadows, Cynthia A Carnes |
Journal | Journal of veterinary internal medicine
(J Vet Intern Med)
2007 Jan-Feb
Vol. 21
Issue 1
Pg. 166-75
ISSN: 0891-6640 [Print] United States |
PMID | 17338165
(Publication Type: Clinical Trial, Journal Article, Research Support, Non-U.S. Gov't)
|
Chemical References |
- Cardiovascular Agents
- Diltiazem
- Quinidine
|
Topics |
- Animals
- Atrial Function
(drug effects, physiology)
- Atrioventricular Node
(drug effects, physiology)
- Cardiovascular Agents
(pharmacology)
- Diltiazem
(administration & dosage, pharmacology)
- Dose-Response Relationship, Drug
- Electrophysiologic Techniques, Cardiac
- Female
- Heart Atria
(drug effects)
- Horses
(physiology)
- Male
- Quinidine
(administration & dosage, pharmacology)
- Sinoatrial Node
(drug effects, physiology)
|