Alternative names
Minimally invasive direct coronary artery bypass (MIDCAB); Off-pump coronary artery bypass (OPCAB); Beating heart surgery; RACAB (robot assisted coronary artery bypass); Keyhole heart surgery

Definition

Minimally invasive heart surgery refers to several approaches for bypassing critically blocked arteries that are less difficult and risky than conventional open-heart surgery (coronary artery bypass grafting - CABG). These approaches restore healthy blood flow to the heart without having to stop the heart and put the patient on a heart-lung machine during surgery.

Currently, there are three procedures that use this approach: Minimally Invasive Direct Coronary Bypass (MIDCAB), Off-Pump Coronary Artery Bypass (OPCAB), and Robotic Assisted Coronary Artery Bypass (RACAB). Each of these procedures has the potential benefit of avoiding complications associated with the heart-lung machine such as increased risk of stroke, lung complications, kidney complications, and problems with mental clarity and memory. Other benefits are faster recovery and reduced hospital costs.

MIDCAB is suitable for patients with blockage(s) in the arteries on the front of the heart - that is, the left anterior descending (LAD) artery and its diagonal branches. This procedure allows the surgeon to perform bypass surgery without splitting the breastbone. Unlike conventional open-heart bypass surgery, which requires a large incision, MIDCAB employs a tiny, 6-10 cm “keyhole” incision on the patient’s left chest to gain access to the heart. Surgeons may use MIDCAB incisions with or without the heart-lung machine.

With OPCAB, the surgeon makes a vertical incision in the chest the same as that used in conventional bypass surgery, and splits the breastbone. The difference is that the heart-lung machine is not used. A stabilizing device is used to restrict movement of small segments of the heart so that the surgeon can operate on it while it is still beating. This procedure enables the surgeon to perform multiple-vessel (4-5) bypass surgery on a beating heart.

RACAB is the latest advance in coronary surgery. Surgeons use a robotic device to enable coronary bypass without separating the breastbone at all. Surgeons do not have direct contact with the patient, but perform the operation while watching a videoscreen. As the technology becomes more advanced, the surgeon may perform coronary bypass from a distant site (that is, from another room or another geographical location).

Description

MIDCAB: This procedure offers the benefits of conventional CABG but produces less traumatic injury; the recovery may be closer to that experienced by angioplasty patients. Unfortunately, this procedure is limited to a small subset of patients requiring bypass surgery who need only 1-2 bypasses.

During the operation, the surgeon makes an incision approximately 6-10 cm long on the front of the chest toward the left side. The pectoral muscles are divided and a small portion of the front of the rib, the costal cartilage, is removed. The surgeon clamps off the internal mammary artery (IMA), which lies just beneath this cartilage, and frees its lower end. An opening is made in the pericardium, the sheath covering the heart.

A mechanical stabilizer is attached to the heart to reduce its movement, and the surgeon connects the mammary artery below the blockage to the left anterior descending (LAD) artery and/or one of its branches. Once the clamp on the mammary artery is released, blood can flow from the IMA through the LAD artery, bypassing the blockage and providing oxygen-rich blood to the heart muscle.

OPCAB: The use of this procedure has grown significantly because of its advantages over conventional CABG and the MIDCAB procedure. Compared with patients undergoing conventional CABG, those undergoing OPCAB require fewer blood transfusions, may have a decreased risk of stroke, have a shorter post-operative hospital stay, and may be able to return to normal activities more rapidly.

During the procedure, the surgeon opens the patient’s chest with a 12- to 14-inch incision over the breastbone and divides it to expose the heart. Simultaneously, the mammary artery and the greater saphenous vein from one of the patient’s legs or other blood vessels are “harvested” for use in the bypass procedure. Like the MIDCAB procedure, a mechanical heart stabilizer is employed to restrict the heart movement. With this procedure, bypasses can be constructed for any blocked arteries on the heart.

MIDCAB and OPCAB surgeries both take approximately 3-4 hours.

Indications
MIDCAB: Due to the limited size of the MIDCAB incision, only certain patients are eligible for the procedure:

1. Patients who have a blockage in one or two coronary arteries located on the front side of the heart, but are considered too high-risk for conventional bypass surgery or balloon angioplasty.
2. Patients who are otherwise healthy but have a blockage in one or two coronary arteries located on the front side of the heart.

In general, every patient with coronary artery disease is a candidate for OPCAB. However, for younger patients, for those who have small coronary arteries and need several bypasses, or those whose heart will not tolerate being manipulated during the procedure, it may be preferable to use the traditional CABG technique. Currently, the following patients with coronary artery disease are potential candidates for OPCAB:

1. Patients with poor heart function (very low ejection fraction).
2. Patients with severe lung disease (chronic obstructive pulmonary disease, COPD, and emphysema).
3. Patients with acute or chronic kidney disease.
4. Patients at high risk for stroke.
5. Patients with a calcified aorta.

Risks
Performing surgery on a beating heart (for both MIDCAB and OPCAB procedures) is technically more difficult than working on a heart that has been stopped with the help of the heart-lung machine. In addition, the stress on the heart during the procedure may lead to more heart muscle damage, lower blood pressure, irregular heart beat and potentially, brain injury if blood flow to the brain is reduced for too long during surgery. In some cases (usually less than 10%), it is necessary to convert to conventional CABG methods on an emergency basis.

Convalescence
MIDCAB and OPCAB patients typically spend one day in the surgical intensive care unit and then move to a regular surgery unit, where they receive cardiac rehabilitation. The average hospital stay is 3 days for MIDCAB patients and 5-7 days for OPCAB patients. In contrast, a hospital stay of 6-10 days is typical for conventional CABG patients.

Patients who have had MIDCAB have lower chest wound infection rates than patients who have undergone CABG or OPCAB. A smaller incision means less exposure and handling of tissue, which reduces the chance of infection.

MIDCAB patients recover more quickly than those who undergo CABG or OPCAB. Within 2 weeks, most MIDCAB patients can return to their normal activity level, compared with 2-3 months for patients who have had conventional surgery.

OPCAB patients have a recovery that in most respects is similar to that for CABG patients. Most are able to return to full activity, including work, 2-3 months after operation.

Medical Encyclopedia

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