A coronary artery bypass graft, or CABG, is performed to improve circulation to the heart muscle in people with severe coronary artery disease.

In this procedure, a healthy artery or vein from another part of the body is connected, or grafted, to the blocked coronary artery.

The grafted artery or vein bypasses the blocked portion of the coronary artery, carrying oxygen-rich blood to the heart muscle.

One or more coronary arteries may be bypassed during a single operation.

Before the surgery, an intravenous line will be started and you may be given a medication to help you relax.

CABG procedures are done under general anesthesia, which will put you to sleep for the duration of the operation.

A breathing tube will be inserted through your mouth and into your throat to help you breathe.

A catheter will be placed in your bladder to drain your urine. Coronary artery bypass surgery generally takes three to six hours.

During a conventional bypass surgery, your surgeon begins by making an incision in the skin over your breast bone, or sternum.

He or she will then cut the sternum and move your ribcage in order to get to your heart.

Throughout the procedure, your circulatory system will be connected to a cardiopulmonary bypass pump, or heart-lung machine.

This machine temporarily performs the functions of your heart and lungs during the surgery,

allowing your heart to be stopped while the surgeon sews the grafts into place.

One of two blood vessels is typically used for the grafts:

the internal thoracic artery in the chest, or the saphenous vein in the leg.

For the internal thoracic artery graft,

your surgeon will leave the upper end attached to the subclavian artery and divert the lower end from your chest wall to your coronary artery,

just beyond the blockage.

Your surgeon will then sew the graft into place.

For the saphenous vein graft,

your surgeon will suture one end to the aorta and the other end to the narrowed artery,

just beyond the blockage.

With the grafts securely in place,

your surgeon will use electrical signals to restore the heartbeat and attach a temporary pacemaker to the heart.

Once your heart is again beating normally, the heart- lung machine will be disconnected.

Your surgeon will wire the breastbone back together, and suture the skin incision closed.

A temporary drainage tube will be placed through the skin, beneath the incision.

Two other types of CABG procedures have recently been developed:

off-pump and minimally invasive bypass surgery.

Off-pump CABG also is called “beating heart bypass grafting”

because the heart isn't stopped and a heart-lung machine isn't used.

Instead, a mechanical device is used to steady the part of the heart where grafting is being done.

Surgeons perform minimally invasive bypass procedures using specially designed instruments inserted through small incisions or “ports” in the chest.

These procedures sometimes require a heart-lung machine.

After surgery you will be taken to the intensive care unit.

The activity of your heart will be carefully monitored.

If necessary, the pacing wires will be used to temporarily control your heart rate.

The chest tube will remain in place to drain excess blood and air from the chest cavity.

Once you can breathe on your own, your breathing tube will be removed and replaced with an oxygen mask.

The bladder catheter will remain in place.

As you recover over the next three to four days, all of these devices will be gradually removed.