Prevalence and clinical importance of heart murmurs in racehorses.

This research studied the commonality of heart murmurs in Thoroughbred racehorses and their association with the horses’ racing performance. The study found that heart murmurs are quite common in racehorses, but there was no significant connection between the presence of a heart murmur and the horses’ performance in races.

Methods

• The study involved a clinical and retrospective analysis on 846 Thoroughbred racehorses.
• The horses went through cardiac auscultations performed by three individuals. This is a procedure where the horses’ hearts were listened to in order to detect any abnormal sounds that could indicate heart diseases.
• For a subset of 30 horses, Doppler echocardiographic examinations were also conducted. This is an imaging technique that uses ultrasound waves to visualize the structure and function of the heart, and can precisely identify and assess heart murmur characteristics.
• The researchers analyzed race records for 753 horses from the past two years to find an association of heart murmurs with performance.

Results

• The study found that heart murmurs were detected in 686 out of the 846 horses (81.1%) through cardiac auscultation.
• Systolic murmurs, that occur when the heart muscle contracts, were most common. Specifically, 43.1% of horses had systolic murmurs loudest over the pulmonary valve area and 27.4% had systolic murmurs that were loudest over the aortic valve area.
• Tricuspid and mitral valve areas were also areas where systolic murmurs were found in 28.5% and 3.8% of the horses, respectively.
• Diastolic murmurs, that typically happen when the heart muscle relaxes and fills with blood, were much less common than systolic murmurs.
• Analyses of race records did not reveal any significant association between the presence of heart murmurs and the horses’ racing performance.

Conclusions

• The findings suggested that heart murmurs are common in racehorses.
• Despite their prevalence, most heart murmurs had no apparent clinical importance, as they showed no significant connection to the horses’ racing performance.