Surgery Information: Coronary Artery Bypass Graft Surgery

Sometimes referred to as CABG (“cabbage”), this procedure is performed to “bypass” blood around clogged arteries. Coronary arteries and their branches encircle the heart muscle supplying it with nourishment (oxygen carrying blood). These arteries often become clogged with a buildup of fat, cholesterol and other substances. When a coronary artery becomes clogged, blood supply to the area of heart muscle it feeds is reduced or stops completely. Without sufficient nourishment, that area of heart muscle is at risk of dying. Often, the result is angina (chest pain) or myocardial infarction (heart attack).

In performing a CABG, the surgeon makes an incision in the chest and exposes all or part of the heart. The location and length of incision depends on many factors (see “Approaches”). The most common approach is through the breast bone. The bypass may be performed with the heart beating (called “beating heart” or “off-pump”) or stopped. If the heart is to be stopped, surgeons use a heart-lung machine (called “cardiopulmonary bypass” ). This machine “bypasses” the heart completely – pumping oxygen rich blood from the lungs directly into the aorta (the large artery leaving the heart). With the heart “bypassed”, the surgeon can stop the heart using medication (“cardioplegia”), and work on a “still” heart.

Once the heart is exposed, the surgeon can proceed to work on the clogged coronary artery. To bypass the clogged area, the surgeon takes a blood vessel (artery or vein) from elsewhere in the body and constructs a “detour” around the clogged area. One or more of the following methods may be used.

• An artery (“internal mammary artery”) may be detached from the chest wall and the open end attached to the coronary artery below the blocked area.
• A section of artery or vein may be removed (“harvested”) from an area – generally the leg, or arm. One end is inserted into the aorta (a large artery attached to the heart) or other artery and the other end is attached to the coronary artery below the blocked area.
• If the area is localized , a patch of vein of artery can be used to enlarge the area of narrowing.

This “detour” provides a new path for blood to flow and nourish the threatened area. Often more than one coronary artery is clogged or there may be multiple sections clogged. This makes multiple bypasses necessary. For example, a “CABG x 4” refers to four bypasses.

In constructing the bypass, an artery or vein from the leg, or arm may be used. The arteries most frequently used are the arm (“radial artery”), abdomen (“gastro epiploic artery”), or chest (“internal mammary artery”). Veins are most frequently “harvested” from the leg (“saphenous vein”). It is preferable to use an artery rather than a vein. While the saphenous vein is most commonly used, it is prone to atherosclerosis (buildup of fat, cholesterol, and other substances).

Your surgeon will decide which artery or vein is best to use. Circumstances that might impact the decision include vessel size, number of bypasses needed, diabetes, previous CABG, previous breast surgery or radiation therapy, varicose vein removal, degree of stenosis or narrowing..

To remove the artery or vein, an incision is made over the vessel, the vessel is exposed and freed , and then removed. The area is then sutured closed. Two techniques for removal are available. One technique requires a long incision and the other several smaller incisions (called “endoscopic vein harvesting”).

Endoscopic Vein Harvesting

Endoscopic vein harvesting is the latest advance in vein removal. Generally, three small, inch-long incisions are made in the leg. A special instrument (“endoscope”), connected to a video camera, is inserted into the small incision. Using the video camera, a section of the vein is exposed, freed, and removed.

Is everyone a candidate? If the vein is very superficial (close to the surface) or very small, you may not be a candidate. The section of vein near the ankle is very difficult to harvest with this approach. The presence of varicose veins also makes it more difficult to harvest. (If the varicose veins have been removed, there is no vein to harvest).

• Benefits of this procedure include:
• Much smaller incision
• Less postoperative pain
• Fewer wound healing complications
• Minimal scarring
• Faster recovery time

Because the vein can be damaged in harvesting, this procedure requires a very experienced team. Our team specializes in endoscopic vein harvesting (85% of patients).

Approaches

Typical and newer approaches to opening the chest and exposing the heart include:

• Traditional median “sternotomy” – the incision is made mid-chest, the rib cage is separated, and the heart exposed.
• The rib cage (sternum) is reconnected with wire and the tissue and skin sutured closed.
• Minimally invasive (“MIDCAB” or “minimally invasive direct coronary artery bypass”). Not favored since it is very painful and gives limited exposure.

The type of approach, location and length of incision, depends on many factors, including the number and location of vessels to be operated on.

“Beating Heart” or “Off Pump” Surgery

Instead of operating on a still or motionless heart, the surgeon attaches the blood vessel to the coronary artery while the heart is still beating. A “stabilizing” device is generally used to reduce motion in the area of attachment. The surgeon may use a mini-thoracotomy approach (“MIDCAB”) or mid-sternal approach (OPCAB). The approach used depends on the number and location of vessels operated on. The risks and benefits of this approach are still being studied and not everyone is a candidate. Obvious benefits include reducing the risk of complications associated with the heart-lung machine. However, beating heart surgery is not without risks. The surface of the heart is exposed to injury from the devices used to stabilize the heart. Fewer grafts may be performed as some of the vessels may not be fully accessible. The incidence of re-intervention may be higher as the grafts performed may not be optimal. Diffuse disease and small vessels make beating heart surgery especially difficult and reduce the chance of successful outcome.

Mitral Valve Repair & Replacement

Depending on the degree and type of damage, the valve may be repaired or may require replacement. Repair is preferable to replacement when feasible. The natural tissue is much better and longer lasting with better preservation of heart function than any artificial valve. It also does not require blood thinning medicines. Incompetent mitral valves are the ones most commonly repaired. However, not all valves can be repaired. Valves that are diseased due to rheumatic fever are often both stenotic and regurgitant and beyond repair. Severely stenotic valves or valves with heavily calcified leaflets or annulus may also be irreparable.

Replacement options include a mechanical valve that requires blood thinning medicine to be taken for life [Coumadin], or a tissue valve [bovine pericardium] that does not need anticoagulation. Tissue valves have a tendency to wear out after 15-20 years. Repairs may be made to open a stenotic valve or correct a leaking valve. Stenotic valves can be repaired by mitral commisurotomy or balloon valvuloplasty. Repairs made on leaking or regurgitant valves include cutting out the area with the torn chordae [strings] and putting the valve leaflet back together again. A ring can be placed around the mitral valve to make it stop leaking..

Removal of cardiac tumours:

Atrial myxomas are the commonest tumours of the heart. They can cause strokes, shortness of breath and some irregularities of the heart rhythm . They occur mostly in the left atrium.

TMR [Transmyocardial Revascularisation]

In instances where no coronaries arteries are available to bypass and the heart muscle is viable TMR can be used to induce new blood vessels to develop. Laser has been used to make holes in the muscle of the heart. These holes close up but angiogenesis or new vessels are induced to grow . This can relieve angina. The laser technique has a mortality of 8% and produce irregularities of the heart rhythm that can be life threatening. A simpler technique that produces angiogenesis is to use a needle to produce the channels . It is cheaper and less risky. We are experimenting with this technique.

Coronary Endarterectomy

Coronary arteries can become completely blocked with plaque. Sometimes the only way to graft is to pull out the plug and do a bypass. This is called coronary endarterectomy. In the picture below is a specimen removed from the right coronary artery. It shows the main artery with some of its branches.

Coronary Patch Angioplasty

If the area of coronary narrowing is short and the rest of the vessel is healthy it can be patched using a piece of vein or artery.