Port Access CABG

Dateline: 01/18/98

Over the past month, we have discussed the concept of minimally invasive heart surgery, and the use of this novel technique in treating coronary artery disease , heart valve disease and birth defects of the heart. This week, we will discuss one of the types of CABG - Port Access procedures.

For more information on minimally invasive surgery, including coronary bypass operations, you can visit the MICAS website.

What is PACAB ?

Port-Access CABG, the most recent advance in Minimally Invasive Coronary Bypass surgery, attempts to combine the advantages of conventional CABG, including use of the heart-lung machine and cardioplegia, with MIDCAB. In this technique, using specially designed equipment inserted through multiple tiny incisions, the patient is hooked on to the heart-lung machine WITHOUT EVEN OPENING THE CHEST. The CABG procedure is carried out under cardioplegic arrest, using modified instruments to fashion the connection between the graft and coronary artery inside the chest cavity through these tiny incisions.
The benefits of PACAB stem from the limited incisions used to access the heart. No bone is divided, and very little muscle needs to be cut. With the heart stopped (and protected by cardioplegia), the anastomosis can be made with precision and on a steady non-beating heart. It is possible to place grafts to diseased coronary arteries in any part of the heart using this method.

How is PACAB done ?

PACAB is a new technique, with entirely new instruments that merit a short description to make the procedure easy to understand.

Instruments for PACAB

Ports
As the name implies, multiple "ports" provide access for CABG in this technique. Each "port" is a 1.5 cm. sized hollow metal tube, sealed with a valve at its outer end, that is inserted through a small incision in the chest wall. Specially modified instruments - such as needle-holders and forceps - can be passed through these ports inside the chest and used in the operation.

Telescope
This is a narrow tubular instrument with lenses used to visualize organs inside the thorax. Attached to a video camera, the telescope provides the operating team with a panoramic view of the inside of the chest, including the heart and coronary arteries.

Cannulae
These are plastic tubes used to connect the patient to the heart-lung machine. For the PACAB technique, these cannulae are made extra-long and thinner than usual, so that they can be passed through smaller blood vessels and guided to the heart.

Balloon Tipped Aortic Occlusion/Cardioplegia Catheter
This is a plastic tube (similar to any cardiac catheter used in diagnostic tests on the heart) with an inflatable balloon near the tip. When the catheter is positioned inside a blood vessel and the balloon is inflated, it occludes the artery or vein, producing an effect similar to an external clamp placed on this blood vessel.

The technique

The first step is to connect the patient to the heart-lung machine. This requires access to the venous and arterial systems. Venous access is obtained by

• a cannula threaded up the large vein in the groin (the femoral vein) and guided into the inferior vena cava
• a second cannula inserted into the jugular vein in the neck and pushed into the superior vena cava

Arterial access may be achieved by two methods

• the large artery in the groin (the femoral artery) may be cannulated
• through one of the ports in the chest, the aorta itself may be cannulated directly (there have been some complications with this technique recently)

Once the circulation has been supported artificially, a "telescope" device is inserted through a 1.5 cm. long "port". This telescope can be used to view the heart and other organs in the thorax. Two more similar incisions ("ports") are made in different parts of the chest wall through which instruments will be manipulated during the operation.

The long balloon-tipped catheter is passed into the femoral artery. By viewing its progress using x-ray monitors (fluoroscopy), it is manipulated into place in the root of the aorta. The balloon is then inflated. It occludes the lumen of the aorta, acting like a clamp. Through this same catheter, cardioplegia solution is injected. It passes through the aorta into the coronary arteries.

An alternative method to administer the cardioplegic solution exists. Another catheter is inserted into the jugular vein in the neck, and guided using fluoroscopy into the coronary sinus inside the heart. From here, cardioplegia solution may be delivered in a reverse ("retrograde") direction.

With the heart thus arrested and protected, the grafts are sewn onto the diseased coronary arteries using instruments that are passed through the multiple small "ports". This is a difficult procedure that needs some training to master.

Using port-access CABG, grafts can be placed to both right and left coronary artery systems safely. Both arterial and venous grafts can be used. The small incisions considerably reduce post-operative pain, but the ill-effects of the heart-lung machine are not avoided with this method.

For more information on minimally invasive surgery, including coronary bypass operations, you can visit the MICAS website.