Cardiovascular Surgery Instrument Kit

Cardiovascular surgery is mainly performed to treat the complexities of ischemic heart diseases, congenital heart diseases, valvular heart diseases, endocarditis, rheumatic heart diseases, and atherosclerosis. It also includes heart transplantation.

The preferred rodent species for conducting cardiovascular research is shifting from rat to mouse. The main advantage of using the rat is its bigger size. However, the development of more sophisticated micro-dissecting microscopes and imaging devices, high-caliber microsurgical instruments, small catheters for hemodynamic measurements, etc., has made microsurgery in the mouse more feasible than rats. Mouse models mimicking human diseases are essential tools in biomedical research, which aim to understand the underlying mechanisms of many disease states. Mouse models have gained popularity because of their small size, rapid gestation age (21 days), relatively low husbandry costs, and convenience in housing and handling. Moreover, the extensively characterized mouse genome and gene-targeting (i.e., knockout) and transgenic overexpression experiments are widely performed using mice rather rats (Tarnavski, 2009).

Thoroughly clean and sterilize the instruments used for the surgery.  Autoclave and disinfect the equipment. Clear the operating area of any disturbances and ensure asepsis. Before the surgery, record the subject identification details such as strain and gender, most importantly note the weight of the subject. Also, examine the subject physically to assess its health status and activeness. Ensure that the subject has been acclimated to the facility appropriately. Acclimation process can last from a few days to a couple of weeks.

Anesthesia

• Anesthetize the surgical subjects with pentobarbital 70 mg/kg in a solution of 15 mg/ml (Use a face mask or an anesthetic chamber to anesthetize the animals). Do not administer analgesics pre-operatively.
• Shave the chest with a hair clipper or a razor.
• Place the animal on the surgical stage in surgical position for the subsequent intubation, wire 3-0 silk behind the front incisors, pull taut and fix with tape.
• Intubate the animal with a 20-ga catheter, attached to the extender.
• Connect the intubation tube to the ventilator and start ventilating the animal.
• Perform the surgical procedure at the room temperature (except for the ischemia-reperfusion).
• Prepare the surgical field.

Mouse Cardiac Surgery Protocol (Tarnavski et al., 2004)

• Open the chest with a lateral incision at the 4th intercostal space on the left side of the sternum and retract the chest.
• Remove the pericardial sac and pass an 8-0 silk suture in the myocardium at the anterior surface of the heart for one second and then remove it.
• Close the chest wall by approximating the third and fourth ribs with one or two interrupted sutures, return the muscles to their original position, and the skin closed with retract4-0 prolene suture.
• Gently disconnect the animal from the ventilator.

Aortic Banding (Pressure-overload Model) Method (Tarnavski, 2009)

• Locally anesthetize the animal by injecting 0.1 ml of 0.2% lidocaine subcutaneously at the surgical site.
• Transversely incise the skin 5-mm with scissors 1–2 mm higher than the level of the ‘‘armpit’’ (with paw extended at 90^o) 2 mm away from the left sternal border.
• Separate the two layers of thoracic muscles.
• Separate the intercostal muscles in the 2d intercostal space.
• Interpolate the chest retractor to facilitate the view.
• Pull the thymus and surrounding fat behind the left arm of the retractor. Gently pull the pericardial sac and attach it to both arms of the retractor.

The steps mentioned above remain the same for both ascending aortic constriction and transverse aortic constriction.

Ascending Aortic Constriction (AAC)

1. Bluntly dissect the ascending portion of the aorta on its lateral side from the pulmonary trunk with Foerster curved forceps.
2. Place Foerster curved forceps from the medial side under the ascending aorta, hold the 7-0 silk suture on the opposite side and pass it underneath the aorta.
3. Tie a loose double knot to create a loop 7–10mm in diameter.
4. Position a needle of proper size into the circuit.
5. Tie the loop around the aorta and needle, and bind with the second knot; immediately remove the needle to provide a lumen with a stenotic aorta. Make another knot to secure the tie.
6. Remove the chest retractor and re-inflate the lungs.
7. Close the chest wound layer-by-layer.

Transverse Aortic Constriction (TAC)

1. Bluntly depart the thymus, and pericardial sac with slightly curved forceps, then separate the aortic arch from the surrounding tissues and vessels.