Cardiopathological observation on a case of persistent ventricular tachycardia in a pony mare.

This research investigates the cardiopathological conditions associated with persistent ventricular tachycardia (rapid heart rate) in an aged pony mare, with significant signs of myocardial fibrosis (heart tissue scarring) located near the left bundle branch of the heart.

Introduction

The research begins with the study of a 20-year-old pony mare diagnosed with persistent ventricular tachycardia. Ventricular tachycardia is a heart arythmia characterized by a rapid heart rate originated from heart’s ventricles. It is generally life-threatening and requires quick medical attention. The persistent form of this disorder continues for more than 30 seconds or requires medical intervention to cease.

• The pony in the study was chosen due to the persistent nature of its ventricular tachycardia. The aim was to explore the internal cardiological conditions related to this disorder in equine subjects.

Cardiopathological Examination

The pony mare underwent a cardiopathological examination post-mortem, primarily to understand the physical abnormalities present in her heart associated with the persistent ventricular tachycardia.

• The heart of the pony was found to be abnormally enlarged and rounded, with dilated ventricles. This is indicative of a medical condition typically associated with heart disease, wherein the heart fails to effectively pump blood.
• A large white patchy lesion was observed in the longitudinal section of the ventricular septum, specifically in the relatively higher portions. The size of this lesion was approximately 5×25 mm, making it a significant and unusual discovery.

Microscopic Examination: Myocardial Fibrosis

The white lesion was studied microscopically to understand its nature and potential role in the persistent ventricular tachycardia.

• The examination revealed an extensive section of myocardial fibrosis – a scarring of heart tissue – located close to the proximal part of the left bundle branch of the heart. This bundle branch plays an essential role in the heart’s electrical conduction system, dictating the rhythm of heartbeats.
• In parts, the fibrotic lesion was found to be in contact with the bundle branch, suggesting a possible mechanical or electrical disruption in the heart’s usual operations.

Discussion

The myocardial fibrosis found in the ventricular septum could significantly correlate with the persistent ventricular tachycardia in the pony mare.

• The presence of such a lesion can contribute to an irregular heart rhythm (or arrhythmia) by disrupting the regular conductive pathways, leading to the heart’s automatic or re-entry mechanism. Automaticity refers to the heart’s ability to generate electrical impulses automatically, while a re-entry mechanism refers to abnormal electrical signals circulating within the heart’s chambers.
• Both these scenarios exaggerate the heart’s rhythmic activity, leading to a rapid and irregular heartbeat – a characteristic of ventricular tachycardia.

In conclusion, this research presents valuable insights into the cardiopathological findings in a horse with persistent ventricular tachycardia and suggests the significance of myocardial fibrosis located near the left bundle branch of the heart. More consistent studies are needed for a definitive take on the mechanism of fibrosis-induced ventricular tachycardia.