The presence of mitral valve prolapse (MVP) and any secondary myocardial changes (e.g., papillary muscle fibrosis) that could create pro-arrhythmic myocardial substrate are currently uninvestigated in the horse. In humans, MVP has been associated with sudden cardiac death (SCD) due to the formation of pro-arrhythmic myocardial substrates that lead to cardiac arrhythmias. Further investigation into the role that MVP plays in equine SCD is needed.

This study aims to use 3D electro-anatomical mapping technology to identify and describe the myocardial electrophysiologic changes associated with MVP to improve our understanding of the contribution of MVP in the creation of pro-arrhythmic myocardial substrates that could cause cardiac arrhythmias leading to equine SCD. First, horses will undergo cardiac phenotyping, specifically documenting the presence or absence of MVP, in addition to other echocardiographic and electrocardiographic features.

The horses will then undergo 3D electro-anatomical mapping of cardiac chambers under general anesthesia. Electrical activation patterns and myocardial voltage signals will be investigated to identify areas of potential fibrosis and abnormal conduction in the myocardium, both during normal sinus rhythm and any spontaneous arrhythmias that occur. The inducibility of ventricular arrhythmias will be assessed. Horses will be euthanized, and histopathology will be performed, aiming to link the findings of the 3D mapping studies and histological abnormalities together to describe the presence and function of pro-arrhythmic myocardial substrates.

Results between horses with and without MVP will be compared phenotypically, electrophysiologically and histologically with an overarching goal of improving our understanding of pathophysiology and diagnosis of MVP in horses and identifying arrhythmogenic substrates to further investigate as causes for equine SCD. We have a strong team with experience in 3D electro-anatomical mapping, equine cardiology and cardiac pathology. This study is the first to investigate ventricular myocardial substrates in horses and will develop 3D electro-anatomical mapping as a diagnostic tool for ventricular arrhythmias in horses.