Arrhythmias in newborn thoroughbred foals.

This study investigates the occurrence of arrhythmias in newborn thoroughbred foals and determines the types of arrhythmias most commonly present. The researchers also assess if foetal electrocardiograms can predict neonatal arrhythmias and conclude that these arrhythmias are likely a normal physiological process during adaptation to extra-uterine life, caused mainly by high vagal tone and hypoxaemia at birth.

Study Design and Methodology

• The researchers gathered foetal electrocardiograms (ECGs) from 39 of 50 Thoroughbred foaling mares shortly before delivery.
• Following birth, electrocardiographic studies were conducted on the 50 newborn foals during their adaptive period. This helped understand the electrical activity of the heart immediately after birth.

Findings and Results

• In 48 out of the 50 foals, paroxysmal arrhythmias or mixed arrhythmias were observed. The most common arrhythmias found were sinus arrhythmias and atrial premature contraction.
• Other observed arrhythmias included atrial fibrillation, ventricular premature contraction, partial atrioventricular block, ventricular tachycardia, atrial tachycardia and idioventricular rhythm.
• The duration of the arrhythmias recorded was approximately 5 minutes. There were no cases where the arrhythmia lasted more than 15 minutes post birth.

Interpretation and Conclusion

• No indication of the likelihood of neonatal arrhythmias could be detected from analysing the foetal ECG recordings.
• Two foals displayed irregularities in growth and development, but all others developed normally, indicating these arrhythmias did not have significant long-term impacts.
• The researchers concluded that the arrhythmias observed are likely a normal physiological process that occurs in newborn Thoroughbred foals as they adapt to extrauterine life. High vagal tone and hypoxaemia at birth were proposed as probable contributing factors to the arrhythmias.