Murine Left Anterior Descending (LAD) Coronary Artery Ligation: An Improved and Simplified Model for Myocardial Infarction

Summary

We provide a reliable method for left anterior descending artery (LAD) ligation in a mouse model. This method is comparatively less invasive than other methods, involving endotracheal intubation, a left-sided thoracotomy approach, and thoracentesis. This method can be used as a model for both acute and chronic myocardial infarction (MI).

Abstract

Ischemic heart disease (IHD), or acute coronary syndrome (ACS), is one of the leading causes of death in the United States. IHD is characterized by reduced blood supply to the heart, resulting in the loss of oxygen to and the ensuing necrosis of the heart muscle. The MI model has gained popularity for its use as a short-term ischemia-reperfusion model and a long-term permanent ligation model. Below, we describe a reliable method for the permanent ligation of the LAD. With mouse genetic engineering technology becoming more advanced, and with an increasing availability of quality murine surgical instruments, the mouse has become a popular model for MI surgeries. Our surgical model incorporates the use of an easily reversible anesthetic for the rapid recovery of the mouse; a minimally invasive endotracheal intubation without involving a tracheotomy; and a thoracentesis through the original thoracotomy site without creating an additional incision in the chest, as is done in some other methods, to effectively remove excess blood and air from the chest cavity. This method is comparatively less invasive than other methods, which dramatically reduces surgical and post-surgical complications and mortality and improves reproducibility.

Introduction

Coronary disease, or ACS, is the most prevalent cardiovascular event and will be considered the main cause of morbidity and mortality worldwide in 2020¹. The cause of ACS is the presence of a myocardial thrombosis due to the rupture of a coronary atherosclerotic plaque that blocks or reduces blood flow to the heart tissue². Therefore, there are clinical signs consistent with the presence of acute myocardial ischemia, such as myocardial infarction (MI)^3,4. MI leads to a loss in mass of the cardiomyocytes and a progression to pathological ventricular remodeling, wh....

Protocol

This animal protocol has been reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) at Rhode Island Hospital.

1. Anesthesia and Intubation

1. Weigh the mouse to calculate the dosage of post-operative pain medication.
2. Place the mouse in an induction chamber and deliver 4% isoflurane for 9 - 10 min, monitoring the animal throughout. Turn on a hot bead sterilizer so that the apparatus can preheat to approximately 250 °C. Preheating will take 15 - 20 min.
3. Once the mouse reaches a deep plane of anesthesia, with a breathing rate of approximately 32 breaths/min, place the mouse supine on....

Results

The mice are euthanized twenty-eight days after surgery, and the hearts are harvested and examined. The mice are anesthetized with 50 - 75 mg/kg ketamine and 5 - 10 mg/kg xylazine. When the animal is under adequate anesthesia, the thoracic cavity is opened, and using a 23-gauge needle, cold potassium chloride (KCL, 30 mM) is injected into the posterior basal region of the heart. The heart is arrested in diastole. For further validation of the ligation, the heart is removed from the animal.......

Discussion

With an increasing use of the MI model in laboratories, the described procedure seeks to increase the efficiency and survival rate of the mice while minimizing their post-operative pain and discomfort. This protocol strives to minimize mortality by making numerous improvements to various aspects of the LAD ligation procedure. There are a few distinctions. Some murine intubation studies that utilize ketamine and xylazine along with isoflurane for induction, due to the benefit of their longer duration of a.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
High-Intensity Light Source	Harvard Apparatus	72-0215
SurgiSuite Operating Platform	Kent Scientific Corporation	SurgiSuite	Uses a rechargeable, battery-operated far infrared warming pad. Charge overnight before surgery.
SurgiSuite LED Lighting Kit	Kent Scientific Corporation	SURGI-5003
Hot Bead Sterilizer	Fine Science Tools	18000-45	Preheating takes 15 - 20 min. Instruments take 20 s to sterilize.
Small Rodent Anesthesia System	VetEquip Inc.	901810
Isofluorane	Piramal Enterprises	66794-017-10
Buprenorphine	Rhode Island Hospital Pharmacy	NDC 12496-0757-1, 12496-0757-5
Surgical Loupes	Roboz	RS-6687
Small Rodent Ventilator	Harvard Apparatus	73-0043
Lubricating Drops	Thermo Fisher Scientific	19-898-350
Electric Razor	Kent Scientific Corporation	CL 9990-1201
Hair Removal Cream	Nair
Medical Tape	Thermo Fisher Scientific	18-999-380
Betadine	Thermo Fisher Scientific	19-027136
70% Isopropanol Wipes	Thermo Fisher Scientific	22-363-750
Surgical Drapes	Braintree	SP-TS
Surgical Gloves	Thermo Fisher Scientific	18999102D
5-0 Polypropylene Sutures	Ethicon	8630G
8-0 Nylon Sutures	Fine Science Tools	12051-08
Platinum-Cured Tubing	Harvard Apparatus	72-1042	0.3 mm inside diameter x 0.6 mm outside diameter
0.9% Saline	Thermo Fisher Scientific	19-310-207
4-0 Polypropylene Sutures	Ethicon	8631G
1 CC Syringe with 25-Gauge Needle	Thermo Fisher Scientific	14-826-100
Scissors	Kent Scientific Corporation	INSS600225
Forceps	Kent Scientific Corporation	INS700100
Cotton Swabs	Thermo Fisher Scientific	23-400-118
IV Catheter, 20-Gauge	Thermo Fisher Scientific	NC9892181
Retractor	Kent Scientific Corporation	INS 750369
Forceps	Fine Science Tools	11003-12
Dissecting Forceps, Straight	Kent Scientific Corporation	INS 700101
Dissecting Forceps, Curved	Kent Scientific Corporation	INS 700103
Hemostatic Forceps, Straight	Kent Scientific Corporation	INS 750451
Hemostatic Forceps, Curved	Kent Scientific Corporation	INS 750452
Tissue Forceps	Kent Scientific Corporation	INS 700131
Needle Holder	Kent Scientific Corporation	INS 600109
Scissors	Kent Scientific Corporation	INS 600225