Generating Murine Model of Myocardial Infarction: A Surgical Procedure for Permanent Ligation of Left Anterior Descending Coronary Artery in Mouse Model

Use an electric razor to quickly shave an anesthetized 25 to 30-gram male C57BL/6 mouse on the throat and the left side of the rib cage. Confirm a lack of response to toe pinch. Apply ointment to the animal's eyes. Place the mouse in the supine position on a heating pad and place a small gauze compress under the head to avoid overheating the eyes.

Secure the limbs with adhesive tape. Pass a loop of 5-0 silk suture under the upper incisors and secure the extremity of the loop onto the heating pad to keep the mouth open during the cannulation. Apply depilatory cream to the pre-shaved areas and gently massage with a cotton swab for 1 minute.

Remove the excess fur and cream with gauze and clean the exposed skin with drops of 0.9% saline solution and gauze. Apply pieces of sterile gauze to the shaved throat and thorax and soak the gauze with iodopovidone. Set the ventilator at a tidal volume of 7 milliliters per kilogram and a ventilation rate of 140 strokes per minute.

Move the mouse under a microsurgery stereomicroscope. Holding the skin on the center of the throat, make a 0.5-centimeter incision along the caudal/cephalic line and separate the lobes of the salivary gland. Use curved forceps to gently separate the fascia of the sternohyoid muscle until the larynx and trachea are visible. Then, secure the edges of the opening with retractors attached to elastic bands.

Next, gently pull the tongue sideways and use forceps to insert the blunted inner needle of a 16-gauge cannula into the trachea. Visualize a correct insertion into the trachea through the throat incision and connect the cannula to the ventilator. Place sterile 0.9% saline supplemented with iodopovidone-soaked gauze onto the incision to keep the tissues wet during the operation.

Then, place the exhaust tubing into water. The presence of bubbles indicates a successful intubation. For ligation of the left anterior descending coronary artery or LAD, carefully move the mouse into the right side decubitus position and resecure the left anterior limb in the new position.

Identify the line between the left pectoralis minor and major muscles and make an oblique 1-centimeter skin incision along the line. Using blunt dissecting micro-scissors, separate the fascia of the pectoralis muscles without incising the tissues and use retractors attached to elastic bands to maintain the separation.

Set the ventilator with a positive end-expiratory pressure of 3 centimeters of water. Use blunt forceps to open the chest cavity at the third intercostal space between the third and fourth ribs. Place two retractors into the rib cage, one on each rib, and use a curved fine forceps to carefully remove the pericardium without harming the heart and lungs.

Locate the LAD as a superficial bright-red line running from the edge of the left auricle toward the apex. Use a needle holder to pass a 7-0 silk suture under the LAD, 2 to 3 millimeters below the left atria. Pulling the silk slowly to avoid tearing heart tissue, tie the ligature with three knots. The lower left part of the left ventricle will instantly turn pale upon ligation.

Now, release the rib retractors, and holding the third rib with forceps, make two passes with the 6-0 silk suture under the third and fourth ribs. Place three drops of 37 degrees Celsius, 0.9% saline solution onto the opening and shut the expiration exhaust tube for 2 or 3 respiratory cycles to properly inflate the lungs.

Tighten and secure the suture with two throws, and release the retractors holding the muscles, helping the muscles return to their correct anatomical location. Then, close the thoracic skin with two stitches and two throws of 5-0 suture silk. Close the throat skin with one stitch a 5-0 suture silk and two throws.