The heart is located at the center of our chest cavity. It is surrounded by the ribs and protected by the sternum. The main function of the heart is to supply oxygen to tissues and organs in our body. Arteries are vessels responsible for the transport of blood from the heart to all parts of our body while veins carry blood from all parts of our body back to the heart.
Just like any organs, the heart receives blood supply from arteries known as the coronary arteries. But sometimes, these arteries may become narrowed over the years as plague gets lodged in the surrounding vessel wall. Eventually, the heart suffers from insufficient blood supply and become functionally impaired.
Coronary artery bypass grafting (CABG) is a common surgical procedure used for the management of such condition. The idea here is that the cardiothoracic surgeon would extract an artery (internal mamillary artery) or a vein (great saphenous vein) from the body, and establish a common pathway from beyond the site of coronary artery occlusion to the upper portion of aorta to restore blood transportation. This common pathway is also known as a graft. Depending on severity, some patients may need up to 2 or 3 grafts for the surgery.
On the day of operation, the patient will be asked to put on a surgical gown. Then, the patient will be given a sedative either by mouth or inhalation mask before being transported to the operation theater. A sterile drape is placed over the patient’s body and an intravenous line is set for necessary drug administration as the surgery proceeds. Then, antiseptic solution is spread on the surface of the chest. The cardiac and respiratory parameter is constantly being monitored throughout the surgery.
A vertical incision is made at the center of the chest using a scalpel. Next, the sternum is revealed and a saw is used to cut it open. A retractor is used to seperate the halved sternum leaving the chest cavity opened. Sawing through the sternum requires an enourmous amount of pressure and strength but it takes only about a minute or so.
On the other end, the surgical assistant(s) should be responsible for the grafting procedure. Similarly, an incision is made at the medio-posterior side of the ankle up to the thigh region. The great saphenous vein is determined. It is extracted slowly but carefully for inspection of quality.
The cardiothoracic surgeon would cauterize the pericardium to have the heart exposed. A tube known as cannulus is attached to the arteries and veins of the heart and connected to the heart-lung machine for blood oxygenation. A clamp is placed at the aorta near the cannulus and a chemical agent (potassium chloride) is infused intravenously to slow the heart before it finally stops beating. Prior to this, IV heparin is administered to prevent clotting of blood. At this point, the heart lung machine is turned on as it takes over the pumping action of the heart.
And the surgery BEGINS. Everything prior to this was just paving road and building up momentum for this stage of operation.
Using a magnifying surgical loupes, the surgeon makes a small incision several millimeters away from the predetermined site of occlusion. The hand-picked graft is carefully stitched over the incision site in a circular manner, using a tiny strand of suture made of polypropylene. Next, a surgical punch is used to create a hole for at the wall of aorta to connect the other end of the graft.
Once the repair is done, the flow of cardioplegic solution is gradually stopped, restoring the heartbeat and the clamp blocking the flow of blood to the heart is removed. So the heart will once again receive normal oxygenated blood. This washes out the cardioplegic solution and the heart starts to beat again. The support from heart-lung machine is gradually slowed as the heart takes over providing blood to the circulation. When this process is completed, the patient is said to be off bypass. After a short wait to ensure heart-lung machine is not required again, the cannulus is then removed.
Approaching towards the end of the surgery, a draining tube is fixated to the chest to prevent fluid from accumulating in the pericardial sac. Lastly, the sternum is put back together using a steel wire to allow healing.
Finally the 6 hours bypass surgery is completed!