Occurrence of cardiac arrhythmias in Standardbred racehorses.

This research studied the occurrence of heart rhythm disorders, known as cardiac arrhythmias, in a specific breed of racehorses called Standardbreds. The research team used handheld devices to record the heart rhythms before and after races over a 12-week period. They found that older age was a significant risk factor for these heart conditions. The findings may be useful in monitoring trends and developing screening programmes for this issue.

Methodology

• The researchers conducted a prospective, observational study implementing convenience sampling—a non-random sample based on easy availability and accessibility.
• The team collected non-continuous electrocardiographic (ECGs) recordings over a 12-week period from Standardbred horses participating at a single racetrack. ECGs measure the electrical signals in the heart, thus showing any irregularities in the heart’s rhythm.
• ECGs were taken before and between 6 and 29 minutes after each race using a handheld recording device.
• Using this data, the team calculated the prevalence (how common it is) and frequency (how often it happened) of cardiac arrhythmias for all horses.
• Univariate logistic regression analysis was employed to identify risk factors for heart rhythm disorders. This method looks at the connection between a single variable, for example, the age of the horse, and the likelihood of heart rhythm disorders occurring.

Results

• A total of 8,657 ECGs were recorded from 1,816 horses.
• Some instances of cardiac arrhythmias were identified. Six horses experienced atrial fibrillation (heart quivering instead of beating properly) after racing, one horse presented supraventricular tachycardia (fast heart beat that begins above the heart’s lower chambers) before the race, and two horses had ventricular tachyarrhythmias (fast, irregular heartbeats) after racing.
• An important finding was that older age was a significant risk factor for atrial premature contractions (extra, abnormal heartbeat) before racing and for atrial fibrillation and ventricular ectopy (irregular heartbeats) after racing.

Conclusions

• The researchers found that both physiological (related to the normal function of the body) and pathological (related to disease) cardiac arrhythmias can appear in seemingly healthy Standardbred racehorses both before and after racing.
• The recommendation was made for future studies to examine the influence of cumulative hours spent in training and racing as a potential risk factor for cardiac arrhythmia.
• The data on prevalence and frequency could be valuable for veterinarians and regulatory personnel in tracking trends in heart rhythm disorders among Standardbred racehorses and in developing screening programs for these disorders.