Phonocardiography in the horse: 2. The relationship of the external phonocardiogram to intracardiac pressure and sound.

This research focuses on understanding the connection between external phonocardiograms, sounds and pressures in various heart chambers, and aortic systems in horses. The findings reveal that most of the first sound seems to originate from the left side of the heart after the AV valves are closed, while the second sound is the aftermath of sudden slowdown of blood against already shut semilunar valves.

Objective of the Research

• The research aimed at observing the correlation between the phonocardiograms obtained from an external microphone placed on the cardiac area, and the varying pressures and sounds from the diverse chambers of the heart and aorta, during separate cardiac cycles.

Findings of the Research

• According to the data collected and analyzed, much of the initial heart sound seems to come from the left side of the heart. The occurrence of this sound comes after the closure of the AV (AtrioVentricular) valves, which are integral in controlling the blood flow between the heart’s upper chambers (atria) and the lower ones (ventricles).
• The second sound is a result of the sudden stopping of blood against the semilunar valves that are already closed. Semilunar valves are the heart’s exit valves and they halt backflow of blood into the heart after it is pumped out from the ventricles.

Further Observations

• The research also observed systolic murmurs at the aortic root, which were found to be harmless and a result of enhanced flow and turbulence at the peak of ejection.
• However, it was found that these systolic murmurs might not be externally recorded. This indicates that the externally recorded data might not provide a comprehensive picture of the cardiac activity.