Heart sounds and murmurs of the normal horse.

The research article discusses the unique characteristics of heart sounds in horses, noting that four sounds are often heard during routine cardiac auscultation, compared with the two or three typical in most animal species. This article investigates these unique sounds, along with associated murmurs, and attempts to better understand their production and significance in overall cardiovascular health.

Unique Heart Sounds in Horses

• The researchers note that, unlike most animals, horses frequently have four heart sounds detectable during a routine cardiac auscultation. These sounds differ because they manifest during the period of atrial systole and rapid ventricular filling. The additional components in these phases are not usually observable in other species.
• Moreover, when the horse’s heart rate accelerates, there’s a “summation” of the third and fourth heart sounds, creating a distinct triple rhythm sound.

Prevalent Heart Murmurs in Horses

• Another interesting revelation from this study is the frequent detection of heart murmurs in horses; specifically, presystolic, early diastolic, and early systolic murmurs, even when there were no clinical or post-mortem indications of cardiovascular disease.
• Interestingly, these murmurs became particularly noticeable under conditions associated with an increased sympathetic tone, which is the body’s fight-or-flight response.

Investigative Study and Approach

• The peculiar occurrence of these sounds and murmurs, linked with hemodynamic events that typically do not produce audible sounds in humans and other animals, provided an intriguing topic for the researchers to investigate.
• By studying these unique circumstances in horses, they hoped to gain a better understanding of sound production mechanisms in the cardiovascular systems across all species.
• The findings presented are based on the characteristics of phonocardiograms recorded from normal horses, in combination with experimental and clinical observations made over several years in the researchers’ laboratory.