Hemodynamics before and after conversion of atrial fibrillation to normal sinus rhythm in horses.

This research evaluates how the conversion of atrial fibrillation to normal sinus rhythm impacts hemodynamics, the dynamics of blood flow, in horses. The primary findings indicate that the onset of atrial fibrillation in conscious, resting horses doesn’t invariably correlate with a decline in the hemodynamics, especially in absence of other cardiac diseases. Moreover, the use of intravenous quinidine proves to be safe and effective in managing acute atrial fibrillation in anesthetized horses.

Study Design and Participants

• The study involved 17 horses that presented with atrial fibrillation or flutter, an irregular heartbeat condition.
• Of these, eight suffered from atrial fibrillation of unknown duration while seven developed atrial fibrillation during anesthesia. Meanwhile, atrial flutter arose during recovery from anesthesia in two horses.

Hemodynamic Measurements and Findings

• The researchers found that hemodynamic measurements were normal in seven out of eight conscious horses with atrial fibrillation.
• Distinct observations were made in one conscious horse presenting with signs of congestive heart failure – a decrease in cardiac output and an increase in pulmonary arterial and right atrial pressures.
• In horses where atrial fibrillation occurred during anesthesia, arterial blood pressure lowered in five out of seven.
• Conversely, in the two horses which developed atrial flutter during recovery from anesthesia, both heart rate and arterial blood pressure increased.

Atrial Fibrillation Conversion and Its Effects

• The conversion of atrial fibrillation to normal sinus rhythm, facilitated through oral quinidine, largely reduced pulmonary arterial and right atrial blood pressures.
• In one horse, the restoration of normal sinus rhythm led to a decreased heart rate and an elevated cardiac output.

Conclusions

• The occurrence of atrial fibrillation in conscious, resting horses does not always result in a degradation of hemodynamics, particularly when unaccompanied by other cardiac conditions.
• Intravenous quinidine therapy emerged as a safe and efficient way to turn the acute onset of atrial fibrillation back to normal sinus rhythm in anesthetized horses.