Minimally Invasive Coronary Artery Surgery - MICAS

Dateline: 12/28/97

Last week I introduced you to the concept of Minimally Invasive Heart Surgery. This week I will focus on its practical application in the treatment of coronary artery disease. This discussion will compare the different techniques where the minimally invasive principle is used to bypass diseased coronary arteries. To better understand this section, I will first briefly describe the "conventional" operative procedure for Coronary Artery Bypass Grafting (CABG).

"Conventional" CABG

Conventional CABG is performed through a vertical incision down the front of the chest that splits the breast bone. It is an open heart operation. This means that the heart-beat is stopped temporarily while the circulation of blood is maintained artificially (by the "heart-lung machine"). The heart beat is then stopped, so that surgical connection between the graft and coronary artery can be achieved with greater ease and precision than if the heart were to continue moving.
To learn more about the technique of conventional CABG you can read my article on the topic.

Minimally Invasive Coronary Artery Surgery - MICAS

The different kinds of Minimally Invasive CABG have their own pros and cons, and are performed in different ways. There are three major kinds of MICAS.

• Off Pump CABG
• Minimally Invasive Direct CABG - MIDCAB
• Port Access CABG - PACAB

Off-Pump CABG - What is it ?

In many ways, off-pump CABG is similar to conventional CABG. The difference lies in the fact that the patient is NOT HOOKED ON TO THE HEART-LUNG MACHINE.

If there is one major drawback to using the heart-lung machine, it is this - the artificial circulation causes injury to the blood cells and all organ systems of the body. All the harmful effects of using a heart-lung machine are avoided by off-pump CABG.

Off-Pump CABG - How is it done ?

The surgeon opens the chest by a vertical midline incision splitting the breast bone (sternum). CABG is performed to the diseased coronary arteries in the conventional manner, using either vein or artery (ITA) grafts. To make the process easier, the heart may be transiently slowed down using drugs like Esmolol or Adenosine.
Learn more about off-pump CABG from my article on the topic.

Minimally Invasive Direct CABG (MIDCAB) - What is it ?

This quintessential minimally invasive operation is simple, yet elegant in concept. Not only does it do away with the need for the heart-lung machine to support the circulation during surgery, it also utilizes a tiny key-hole incision and avoids splitting the breast-bone as in the conventional CABG operation. Through this small access incision, the surgeon connects a graft to diseased coronary arteries on a beating heart without any artificial support to the circulation. It is truly MINIMALLY invasive.

A detailed description of the operation and techniques to stabilize the heart during the operation is a separate topic in itself, and you can read my article on the subject.

Port Access CABG (PACAB) - What is it ?

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.

For more information on the technique of PACAB, read my article on "How is PACAB done ?"

This overview on Minimally Invasive Coronary Bypass barely scratches the surface. More detailed accounts are available, and over the next few weeks we will probe deeper into this fascinating development. The next article in this series will be an analysis of the pros and cons of MICAS.

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