Ligation of Left Anterior Descending Coronary Artery in Rats for Developing Occlusive Myocardial Infarction Model

Summary

The protocol shows the development of a myocardial infarction (MI) model by permanently ligating the left anterior descending coronary artery in rats. Animal survival post-MI is essential to salvage cardiomyocytes in the ischemic zone, prevent infarct expansion, and reduce post-myocardial inflammation and fibrosis.

Abstract

Cardiovascular disease (CVD), including ischemic heart disease and stroke, is a major cause of mortality and morbidity throughout the world. Myocardial infarction is a clinical syndrome of ischemic heart disease that occurs due to prolonged ischemia. Ischemic myocardium undergoes functional, metabolic, and structural alterations, leading to irreversible damage to a portion of the myocardium due to necrosis. Experimental models of myocardial infarction are crucial for understanding the acute and chronic cellular, molecular, and morphological changes occurring during and post-MI and for developing and optimizing novel targets or strategies for treatment. The surgical model of MI in small animals employing permanent closure of the left anterior descending coronary artery (LAD) nearly resembles human MI. The goal of this study is to establish a surgically induced MI model involving the closure of the LAD coronary artery indelibly in rats. The experimental protocol includes an initial induction of anesthesia with ketamine 80 mg/kg and xylazine 12 mg/kg i.p., intubation of an endotracheal cannula using an otoscope without performing tracheotomy under ventilator-assisted ventilation with the use of extrinsic positive end-expiratory pressure (PEEP) to prevent the collapse of alveoli. A thoracotomy procedure was adopted that limits the lesions caused to skeletal muscles during surgery. This approach is minimally invasive, repeatable, and lowers mortality post-surgery. In this model, animals survived 4 days post-MI to understand the short-term pathobiological changes, mainly post-MI inflammation, angiogenesis as a natural process of infarct healing, and ultimately, fibrosis in infarcted myocardium.

Introduction

Cardiovascular disease (CVD), mainly comprising ischemic heart disease (IHD) and stroke, is a major cause of mortality and morbidity across the world. According to the World Heart Federation, 20.5 million people died from cardiovascular disease in 2021^1,2. Myocardial infarction (MI), also known as a heart attack, is an acute clinical syndrome of IHD. During MI, myocardial tissue suffers irreversible damage as a result of prolonged ischemia, which is usually caused by an occlusive thrombus formed over a ruptured atherosclerotic plaque in a coronary artery³.

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Protocol

The experimental procedures were performed as per protocol after approval from Institutional Animal Ethics Committee (IAEC) [Protocol No. (IAEC/KCP/2023/009)]. The guidelines of the Committee for the purpose of control and supervision (CCSEA) and the Ministry of Environment, Forest and Climate Change, Government of India, were followed in handling and taking care of experimental animals.

1. Anesthesia and intubation of endotracheal cannula (Duration: 10-15 min)

1. Use Wistar rats of either sex, weighing 200 - 240 g, aged more than 6 months. Record the weight of the rats. Anesthetize the rat by administering Ketamin....

Results

Endotracheal intubation is necessary to assist ventilation during the LAD ligation procedure involving open-chest thoracic procedures in rats. Successful intubation is confirmed by basal respiratory parameters before surgery and the maintenance of stable respiration, tidal volume, and minute volume during the surgical procedure (Figure 5).

The success of the LAD ligation procedure was confirmed by evaluating cardiac Troponin T and Troponin I as biochemical markers.......

Discussion

Our present study represents the induction of Myocardial Infarction through permanent closure of the left anterior descending coronary artery (LAD) in rats. In this surgical protocol, anesthetic Ketamine 80 mg/kg administered by intraperitoneal route induced quick anesthesia, along with intraperitoneal administration of Xylazine 12 mg/kg, produced sufficient muscle relaxation, thereby facilitating the whole surgical procedure effectively as well as smooth post-surgery recovery after a short duration with minimal side eff.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
18-Gauge intravenous cannula	Kent scientific, US
20-Gauge intravenous cannula	Kent scientific, US
4-0 Polypropylene suture	Khanna Surgical
6-0 silk suture	Nanak Surgical
8-0 silk suture	Nanak Surgical
Adson forceps	Nanak Surgical
Anaesthesia apparatus	Orchid Scientific
Anaesthesia induction chamber	Orchid Scientific
Curved scissors	Nanak Surgical
Endotracheal intubation tube	Kent Scientific, US
Hair removal cream	Nanak Surgical
Heating pad	Kent scientific, US
Hooked forceps	Nanak Surgical
Ketamine			Gift sample from KVAS, Amritsar
Micro needle holder	Nanak Surgical
Nitrile gloves	Nanak Surgical
Operation table
Otoscope	Nanak Surgical
Pean forceps	Nanak Surgical
Rib retractor	Nanak Surgical
Straight tweezer	Nanak Surgical
Strait nipper	Nanak Surgical
Surgical hair cap	Nanak Surgical
Surgical mask	Nanak Surgical
Surgical Stereomicroscope	Olympus Magnus	24B1187	Stereo zoom MSZ-TR microscope with arm boom stand, zoom ratio: 1:7 objective zoom: 0.65 - 4.5x Eyepiece 10x/22 mm Magnification : 6.5 - 45x with 10x eye piece LED ring illumination
Toothless forceps	Nanak Surgical
Tramadol			Gift sample from Amandeep hospital, ASR
Tweezers	Nanak Surgical
Ventilator	RoVent (Kent Scientific,  US)	RV-04-220	Automatic Ventilator with volume and pressure control and temprature warming and monitoring
Xylazine			Gift sample from KVAS, Amritsar