To begin, position the anesthetized and intubated animal on its back and cover it with sterile towels. Use monopolar electrocautery to make a 20 centimeter incision, extending from the sternal notch proximally down to the xiphoid process distally, and to incise layers of muscles, subcutaneous fat and connective tissue down to the sternum. Then carry out a medium sternotomy, employing an oscillating saw.
For efficient visualization of the mediastinum, use a specialized chest retractor. Dissect adhesions using monopolar electrocautery or Metzenbaum scissors. Then expose LIMA by dissecting the parasternal muscle and fat.
Next, start the dissection of the LIMA by elevating the left sternal border to ensure optimal visualization. Apply gentle traction to the adventitia and expose the arterial and venous branches of the LIMA. Employ blunt dissection using electrocautery tip to carefully separate it from the chest wall.
Use hemo clips on the branches and cauterize the chest wall side of these branches. Then clip the distal end of the LIMA just before the point of bifurcation and divide the conduit. Secure the distal end with a freely tied 2-O silk suture.
After preparing the proximal end for grafting, evaluate the flow quality manually by allowing the graft to bleed briefly. Now clamp the distal end of the LIMA conduit with an atraumatic bulldog clamp to prevent bleeding. Stabilize the left anterior descending, or LAD artery, using silicone retraction tape and a tissue stabilizer that's secured to the sternal retractor.
Perform an arteriotomy in the LAD artery distal to the stenosis, using an 11 blade, and extend it with iris scissors. Position an appropriately sized coronary shunt in the LAD artery. Conduct the LIMA to LAD anastomosis using a 7-O running, non-absorbable suture in an off-pump bypass technique.
Take a three millimeter exosome suspension and use a five milliliter syringe equipped with an 18 gauge needle to mix it. Then gradually pipette 1.5 milliliters of this suspension onto two absorbable collagen sponges, placed in a medium sized Petri dish. To target the hibernating region of the heart, place the exosome sponge upside down on the epicardium of the anterior septal region in the distribution of the LAD artery.
Carefully arrange two sponges to fully cover the hibernating region. Use a polyglactin mesh on each collagen sponge to ensure proper coverage and sew the mesh onto the epicardium with fine 7-O interrupted sutures. Make a separate stab incision near the inferior aspect of the sternotomy incision and place the chest tube carefully on the anterior aspect of the heart.
Approximate the sternum using non-absorbable sutures, employing a figure eight pattern. Close layers of muscle and skin using 2-O and 3-O absorbable sutures, respectively, following the standard procedure. After evacuating the chest cavity with a chest tube, seal the wound using a purse string suture.
Once the wound is closed, remove the chest tube. At rest, the peak filling rate over end diastolic volume is compared among four animal groups. In low dose dobutamine infusion, the group with hibernating myocardium had a decrease in peak filling rate.
The coronary artery bypass graft surgery group showed improvement, while the coronary artery bypass graft, plus mesenchymal stem cell group, saw a significant increase. MRI analysis revealed that coronary artery bypass graft, plus mesenchymal stem cell group does not alter regional systolic function at rest. However, under stress this group showed significant improvement in regional systolic function compared to coronary artery bypass graft.
