Regional coronary blood flow in ponies

Area of Science:

• Cardiovascular Physiology
• Myocardial Perfusion
• Coronary Circulation

Background:

• Understanding regional myocardial blood flow is crucial for diagnosing and treating ischemic heart disease.
• Previous studies have established baseline blood flow patterns in the equine heart.
• The effects of coronary artery occlusion on transmural and regional flow distribution require further elucidation.

Purpose of the Study:

• To measure regional coronary blood flow in anesthetized ponies before and during coronary artery occlusion.
• To determine the distribution of blood flow within the myocardium, including transmural gradients.
• To quantify the impact of coronary occlusion on blood flow to ischemic myocardial regions.

Main Methods:

• Radioactive microspheres (15 µm ± 5 µm diameter) were injected into the left atrium of ponies under open-thorax anesthesia.
• Regional myocardial blood flow was assessed both under normal conditions and during occlusion of major coronary arteries.
• Transmural blood flow was analyzed using endocardial/epicardial flow ratios in the left ventricle.

Main Results:

• Normal blood flow was highest in the interventricular septum and left ventricular wall, followed by the right ventricle, interatrial septum, atria, and valves.
• The endocardial to epicardial flow ratio in the normal left ventricle was approximately 1.36 (free wall) and 1.33 (septal wall).
• Coronary artery occlusion reduced blood flow to ischemic areas to 3.8–20.6% of normal, with a disproportionate decrease in endocardial flow (68.89% of normal ratio).

Conclusions:

• The study quantifies regional myocardial perfusion patterns and highlights the vulnerability of endocardial regions during ischemia.
• Findings provide insights into the heterogeneous distribution of coronary blood flow and its response to reduced perfusion.
• This research contributes to understanding the pathophysiology of myocardial ischemia and informs potential therapeutic strategies.