A CABG is a surgical procedure used in the management of coronary artery disease, commonly referred to as heart disease. Disease of the coronary arteries is the single largest cause of death in the western world.

What causes coronary artery disease?
To understand why coronary artery disease is so fatal it is necessary to know something about the workings of the heart.

The heart is a muscular organ consisting of four chambers: the right atrium, right ventricle, left atrium and left ventricle. The atria receive blood from the rest of the body and the ventricles pump blood to the rest of the body.
The blood supply of the heart itself is called the coronary arterial system and consists of two main blood vessels, called the right and left coronary artery.

Coronary artery disease reduces blood flow to a region of the heart muscle called the myocardium and gives rise to a wide variety of medical conditions from angina to heart attack (myocardial infarction).

Angina refers to the pain that arises from an area of heart muscle that is receiving an inadequate supply of oxygen. The commonest cause for this is diminished blood supply. It is usually described as gripping/squeezing pain or heaviness/tightness and is typically retrosternal (behind the breast bone) and may radiate to the jaw or arms.

Myocardial infarction refers to the cessation of blood flow to an area of heart muscle. This occurs when a diseased coronary blood vessel becomes blocked by a clot. The term infarction implies death of muscle tissue. Symptoms include chest pain (as with angina), which may be accompanied by shortness of breath (dyspnoea), sweating, nausea and palpitations.

What does a CABG involve?

CABG involves using a section of vein or artery from another part of the body to form a connection between the aorta and the diseased vessel. The join is made just beyond the obstruction, which is then bypassed allowing adequate blood flow. Until recently, the most commonly used vein for a coronary artery bypass was the Saphenous vein from the inside leg. Now, where possible, the internal mammary arteries are used.

Are there any alternatives to CABG?
If you have been diagnosed with heart disease, you will not necessarily need surgery. Treatment depends on the nature and severity of the disease and, where possible, your doctor will treat you medically.

The basic management of patients with heart disease is medical and involves the treatment of coexisting medical conditions such as Diabetes Mellitus, hypertension (high blood pressure) and dyslipidaemia (high cholesterol).
Prevention of symptoms is an important part of basic management and is mainly achieved with medications such as Beta Blockers, nitrates and calcium channel blockers.

PTCA (Percutaneous Transluminal Coronary Angioplasty) offers an alternative to surgery and involves dilation of coronary artery blockages by inflation of a small balloon within the obstructed vessel. PTCA is ideally suited to the treatment of single vessel blockages but is easily repeated and effective for symptom relief.

Advantages of CABG over PTCA include high efficacy in relief of symptoms, possibility of achieving complete revascularisation (restoration of blood supply) and improved survival in certain groups of patients.

Disadvantages include increased risk of surgical complications, longer hospital stay, longer postoperative recovery period, high financial cost and increased risk of a repeat procedure due to late graft closure.
You will only be considered for surgery if maximum medical treatment fails to control your symptoms and if the nature of your heart disease dictates that you are not suitable for PTCA.

What are the risks of CABG surgery?

CABG is a relatively safe procedure and the mortality rate is well below 1% in patients with no other significant medical conditions and normal left ventricular function. However, the mortality rate increases with age (greater than 75 years), worsening ventricular function, coexisting diseases and inexperience of the surgical team performing the procedure.

As with any surgical operation, CABG carries risks, which include:

• Strokes may occur in up to 2% of cases and more subtle neurological problems are commoner.
• Occlusion (blockage) of vein grafts is seen in 10% - 20% of cases within the first year after surgery. This falls to 2% per year during the subsequent five to seven years, and to 4% per year after that.
• 5% - 10% of patients experience heart attacks during the operation but in most cases they are small.
• Angina recurs in up to 25% of patients within three years of surgery.
• Aggressive lowering of LDL cholesterol has been shown to be beneficial after CABG.

What is the normal outcome of surgery?

In 90% of patients who have had CABG, the symptoms of angina are abolished or greatly reduced.

Within three years angina recurs in about 25% of patients but is rarely severe.
In cases where there is severe triple coronary vessel disease, impaired pump action of the left ventricle and in those with blockages of the left main coronary artery, CABG significantly reduces mortality irrespective of symptoms.