Effects of dofetilide and ranolazine on atrial fibrillatory rate in a horse model of acutely induced atrial fibrillation.

This study is examining the effects of two antiarrhythmic drugs, dofetilide and ranolazine, on the atrial fibrillatory rate, a potential heart disease biomarker, in horses. This is achieved by monitoring changes following treatment on surface electrocardiography in an acute model of atrial fibrillation.

Study Design and Methodology

• The research was conducted on eight horses each subjected to pacing-induced atrial fibrillation (AF) on four separate days.
• The horses were treated with dofetilide, ranolazine, a combination of the two, or a saline control for comparison. These treatments were administered in four incremental doses.
• To understand the effects of the treatments, atrial fibrillatory activity was extracted from surface electrocardiographs (ECGs) using a process called spatiotemporal QRST cancellation.

Findings of the Study

• The mean atrial fibrillatory rate before drug infusion was 297 ± 27 fpm.
• Dofetilide was found to reduce the atrial fibrillatory rate following the infusion of low doses and within 5 minutes preceding cardioversion. This result was statistically significant (P < 0.05).
• Ranolazine was seen to cause a reduction in the atrial fibrillatory rate in the last minute before cardiac conversion, another statistically significant result (P < 0.05).
• The combination of dofetilide and ranolazine reduced the atrial fibrillatory rate in a manner similar to dofetilide used alone.
• There was a trend towards a lower atrial fibrillatory rate before drug infusion among horses cardioverting on low doses of the drugs.%+}

Conclusions

• The atrial fibrillatory rate gathered from surface ECGs showed a difference in the mode of action on AF between dofetilide and ranolazine.
• Ranolazine and dofetilide had notably different effects, with dofetilide causing a reduction in the atrial fibrillatory rate and ranolazine demonstrating a cardioverting mechanism distinctly different from a slowing of the fibrillatory process.