Coronary artery bypass graft surgery

Coronary artery bypass graft (CABG) surgery involves the placement of one or more graft between the aorta and the coronary artery circulation with the intention to revascularize a coronary artery. The graft is attached distally to the obstruction of the coronary artery, allowing blood from the aorta to bypass the obstruction and supply the ischaemic myocardium.

The graft in question is either arterial or venous, but patients most frequently receive some combination of the two. Arterial grafts are much more durable than venous graft and stay patent (open) for much longer. 98% of arterial grafts are patent after 10 years, while only 75 – 90% of venous grafts are patent in the first 18 months. As such, patients rarely receive only a venous graft nowadays, and a combination of one (or more) arterial grafts in addition to the venous graft is often used.

The most common venous graft used is the saphenous vein. The vein is surgically extracted from the leg, flipped upside down (so that the valves don’t occlude the blood flow), and then attached to the aorta and the coronary artery in question.

The most common arterial graft used is the left internal thoracic artery (internal mammary artery). Other options include the right internal thoracic artery and the radial artery.

Variations

CABG is typically performed “on-pump”. The patient is put on cardiopulmonary bypass temporarily to allow the heart to be safely stopped and operated on. After the operation is finished, the bypass is removed and the heart is started again. The heart is temporarily stopped with a cold potassium-rich cardioplegia solution, which stops the mechanical activity of the heart.

“Off-pump” CABG, where cardiopulmonary bypass (CPB) is not used, was developed to avoid the complications of cardiopulmonary bypass. However, studies have shown that off-pump CABG has higher mortality than on-pump. For this reason, on-pump is preferred unless there are strong indications for avoiding CPB.

Indications

CABG is mostly performed electively rather than acutely. It is used for the management of chronic coronary syndrome which is refractory to optimal medical therapy, or in which the coronary artery disease is severe. CABG may be used in the management of acute coronary syndrome in a few cases if PCI is deemed impossible.

The choice between PCI and CABG for chronic coronary syndrome is difficult and individualised. The following features favour CABG over PCI:

• Patients with diabetes
• Reduced LVEF (< 35%)
• Contraindications to DAPT
• Multi-vessel disease with intermediate or high SYNTAX score
• Coronary anatomy which will likely result in incomplete revascularization with PCI

Complications

The most important complication of CABG is graft failure (loss of graft patency). Other complications include myocardial infarction, stroke, wound infection, and death.