Equine coronary hemodynamics during brief coronary occlusions at three levels of collateral function

Electrocardiographic Changes in a Horse with Induced Myocardial Infarction

Simple Summary

During acute myocardial infarction (AMI), the electrophysiological changes are clearly visible on the 12-lead electrocardiogram (ECG), and are as such, an important diagnostic tool in human cardiology. Similar to humans, changes are seen on the ECG in both pigs and dogs, but so far, this has not been studied in horses, despite equine cardiology being a growing field. This study aimed to investigate the ECG changes seen with a 12-lead ECG in a horse with induced myocardial infarction. The ECG changes observed in this case report were comparable to other species with AMI and showed similar patterns throughout the different phases of occlusion. The results could, therefore, indicate that a 12-lead ECG can be used to detect signs of ischemic heart disease, such as AMI, in horses, while they also potentially elucidate certain translational connections between human and veterinary medicine.

Abstract

During acute myocardial infarction (AMI), the ischemia and necrosis of the infarcted tissue result in local electrophysiological changes, which bring about deviations of the ST segment and T wave. In this case report, the aim was to investigate whether these changes could be detected with a 12-lead electrocardiogram (ECG) during acute occlusion of the coronary artery in a 15-year-old Standardbred mare (scheduled for euthanasia due to non-cardiac health problems). The left anterior descending (LAD) coronary artery was occluded using an angioplasty balloon catheter guided through the carotid artery. Two coronary occlusions of 30 min were induced, separated by a 10-min reperfusion phase. AMI led to ST deviations and T-wave amplitude changes (maximum ST deviation was 1.98 mV; T-wave amplitude increased from 6.58 to 9.25 mV). The ST segment almost returned to the baseline during the reperfusion phase. The ECG changes seen after the infarction were comparable to those reported in other species with AMI, suggesting that the 12-lead-ECG can potentially be used to detect signs of myocardial infarction in horses.

Coronary collateral growth and its therapeutic application to coronary artery disease

There is a tremendous body of data concerning the coronary collateral circulation in both experimental animals and humans. The functional importance of a well-developed coronary collateral circulation has now been documented. The paradigm regarding the principal stimulus for coronary collateral growth has shifted from myocardial ischemia to increased shear stress at the site of pre-existing collateral arterioles. Numerous experimental and clinical studies have contributed to elucidation of the mechanisms of coronary collateral growth. Stimulation of coronary collateral growth is an alternative therapeutic approach to patients with intractable angina pectoris who are not indicated for percutaneous coronary intervention and/or coronary artery bypass grafting. Pharmacological and mechanical modulations accelerating coronary collateral growth have been challenged. Because it is conceivable that a well-developed coronary collateral circulation attenuates myocardial ischemia upon exercise, further research addressing coronary collateral growth is needed in both experimental models of myocardial ischemia and human coronary artery disease.