Coronary Artery Bypass Grafting - Indications, Procedure, and Complications

Introduction

Coronary artery bypass surgery, also known as coronary artery bypass graft or CABG, is a surgical procedure that is done to restore a normal and smooth flow of blood in an obstructed coronary artery. Normally a coronary artery functions as a transportation channel of blood to the heart and related structures such as cardiac muscle. The coronary artery bypass graft is done for the relief of angina pectoris, which has not been treated by any kind of strongly tolerated anti-ischemic drug, as well as for the prevention and relief of left ventricular dysfunction, and to reduce the risk of fatality. It should be noted that coronary artery bypass grafting or CABG is not done for the prevention and cure of myocardial infarction or heart attack.

How Is Coronary Artery Bypass Grafting Performed?

Coronary artery bypass grafting is generally performed when the heart is stopped, which necessitates the implication of cardiopulmonary bypass. An alternative technique of performing this procedure is available that allows coronary artery bypass graft to be performed while a heart is already beating heart without using the cardiopulmonary bypass or even while using it, this procedure is referred to as an "off-pump" surgery. The other way of performing coronary artery bypass grafting is when the heart is beating, and surgery is done using partial assistance of cardiopulmonary bypass, this procedure is called "on-pump beating". Off-pump graft offers several advantages over the on-pump and off-pump while minimizing their respective side effects.

Coronary artery bypass is generally indicated when the coronary artery has more than 50 or 99 percent obstruction. This obstruction is bypassed because of the thickness of arteriosclerosis and atherosclerosis. Arteriosclerosis is the thickening of the artery, loss of vessel elasticity, as well as calcification of the arterial wall that results in the narrowing of the affected coronary artery. On the other hand, atherosclerosis is the deposition of yellowish plaques that are made of cholesterol, lipids, and several other cellular debris which get lodged in the inner layer of the arterial wall of a large artery or medium-sized artery, which is generally going to end up in an obstruction of the artery. Both of these condition has the potential to limit the flow of blood because of narrowing.

What Are the Complications of Coronary Artery Bypass Grafting?

Every invasive or even non-invasive surgery related to the cardiovascular system is prone to certain kinds of complications. Mentioned below are a few of the complications of coronary artery bypass grafting.

• Postperfusion syndrome or pump head is a transient impairment of the neurocognitive function. There have been several studies that show a relationship between coronary artery bypass grafting and a decline in cognitive behavior. But there is another school of thought that holds a strong belief that the decline in cognitive power and skills is not because of the surgery but is actually the aftermath of the obstruction of the affected coronary artery, which takes over five years to develop and present itself clinically.

• A loss of the normal functioning of the brain is a major complication observed, especially in the senior group of patients. There are several other factors that are related to the physical and psychological growth and healing of older people who have undergone coronary artery bypass grafts that lead to altered or loss of mental norms.

• The circulatory system, especially the flow of blood between the heart and the lung, along with the surgery, is known to release an array of debris, such as bits of blood cells, tubing pieces, and deposition of plaques. This generally occurs when the healthcare provider clamps or connects the aorta, the largest artery, to the tubing, which results in the formation of emboli in the blood and thus results in mini-strokes. Other cardiovascular surgeries and related factors are known to result in some kind of mental damage because of hypoxia, high body temperature or even low body temperature, abnormalities in blood pressure, irregular rhythms of the heart, and fever post-surgery.

• Sternum that becomes nonunion.

• Increase in the risk of sternum devascularization.

• Myocardial infarction due to embolism.

• Hypoperfusion.

• Graft failure.

• Graft stenosis occurs slightly later after the surgery, especially of the saphenous vein, because of the atherosclerosis deposits that cause recurrent angina pectoris and myocardial infarction.

• Acute renal failure because of embolism or hypoperfusion.

• Episodes of stroke after an embolism or even hypoperfusion.

• Vasoplegic syndrome after cardiopulmonary bypass.

• Hypothermia.

• Pneumothorax or the collection of air that lodges around the lung and then compresses the lung.

• Hemothorax or the accumulation of blood in the space near the lungs.

• Pericardial tamponade, or the collection of blood near the heart, compresses the cardiac tissues and leads to poor perfusion between the body and the brain. Chest tubes are fixed between the heart and lungs to avoid this.

• Clogging of the chest tubes in the initial stages of the post-operative stages.

• Pericardial tamponade.

• Pleural effusion or the accumulation of fluid in the spaces around the lungs can eventually lead to a state of hypoxia (absence of sufficient oxygen in tissues) and thus result in a slow recovery.

• Pericarditis or infection of the protective sac of the heart.

• Lower extremities edema.

• Extravasation.

• Inflammation.

• Ecchymoses from vein graft.

• Accumulation of around 4.1 kg of fluid within the extremities can be successfully managed with a tight thigh-length compressive stocking, along with elevation of the limb, as well as early and frequent slow and brisk walking. The avoidance of standing for a long time in the same place, sitting in the same position for a long time, and bending the legs at the knee for more than the prescribed degrees must be kept in mind.

What Are the Types of Graft Used in Coronary Artery Bypass Grafting?

The blood vessel that has been affected is highly dependent on the healthcare provider and team, as well as the institution and facility where the coronary artery bypass grafting is done. Mentioned below are a few of the graft that is used during the procedure of coronary artery bypass grafting.

• The left internal thoracic artery or LITA, previously called the left internal mammary artery or LIMA, is grafted into the left anterior descending artery as well as a combination of several other cardiac arteries and veins is used for other types of coronary arteries.

• The great saphenous vein of the leg is used as a graft in around 80 % of all coronary artery bypass grafting procedures.

• The right internal thoracic mammary artery, or RITA or RIMA, along with the radial artery or RA, is taken from the forearm. It should be noted that the radial artery and the great saphenous vein graft are generally harvested endoscopically, with a technique called endoscopic vessel harvesting or EVH. The open-bridging technique that requires two or more small incisions is another way to harvest the same.

• The right gastroepiploic artery from the stomach is not used much because of the difficulty in mobilizing it from the abdomen.

Conclusion

The coronary artery bypass graft is the treatment modality and the correction method for blocked and obstructed coronary arteries as well as cardiac arteries. The recovery period of coronary artery bypass grafting is different from patient to patient. It generally takes anywhere between six and twelve weeks for complete recovery. The diagnostic imaging techniques such as X-rays and other tests that can be taken during post-procedure consults and visits will show whether the treatment has been a success. If not, further measures may be required.