Minimally Invasive Heart Surgery for Birth Defects

Dateline: 01/11/98

Over the past three weeks, we have discussed the concept of minimally invasive heart surgery, and the use of this novel technique in treating coronary artery disease and in heart valve disease. This week, we will discuss its application in congenital heart disease.

In the field of congenital (birth defect) heart surgery, the techniques of minimal invasion have not yet been implemented in many areas for a variety of reasons. In this article, I will explain the practical use of the concept in two diseases - Patent Ductus Arteriosus (PDA) and Atrial Septal Defect (ASD).

Patent Ductus Arteriosus (PDA)

The ligation (tying off) of an abnormal connection between the aorta and pulmonary artery was first done surgically, using a long incision on one side of the chest - a lateral thoracotomy. Modifications allowed use of a much shorter incision, even avoiding division of any muscles of the chest wall (a muscle-sparing thoracotomy).

With the development of thoracoscopy as a safe procedure, surgeons started thinking of employing this technique in treating conditions like PDA. Using three or four tiny incisions ("ports") in the chest wall, specially designed instruments are inserted into the chest to view the PDA. The covering membranes are dissected off, and the PDA itself is isolated from surrounding tissues. After this is done, using an instrument called a "stapler", a clip made of metal or plastic is positioned across the PDA and closed. As the stapler is "fired" and the clip tightened, the lumen of the PDA is occluded, shutting off abnormal blood flow into the lungs.

The effect is almost identical to surgical ligation of the PDA, and has the added advantages of

• using a much smaller incision
• avoiding any muscle or tissue injury, allowing earlier discharge from hospital
• minimizing the pain of surgery, which is related to tissue damage
• being available even in the intensive care unit, where it can be used to treat extremely sick newborns with large PDA

The difficulties include

• learning a new technique
• inability to apply the clip securely in some cases, requiring conversion to an open operation

Results using this technique have been impressive, and in many centers it is offerred as an alternative to classical surgery for all patients with PDA.

Atrial Septal Defect (ASD)

The use of minimally invasive surgical techniques for ASD is a recent, and as yet "experimental" technique, whose efficacy remains to be proved in a larger population of patients. It is however an exciting and innovative method that merits discussion.

The operation employs the heart-lung machine to support the circulation during the operation. Heart-lung bypass is established by using an arterial cannula in the femoral artery in the groin, and two venous cannulas inserted into the jugular vein in the neck and the femoral vein in the groin. Surgical access to the heart is obtained through a small incision in the right side of the chest wall - a lateral thoracotomy.

After the circulation is supported, and the heart is stopped, the junctions of the great veins (SVC and IVC) with the heart are occluded using special "bull-dog" clamps. The right atrium is opened, and using special instruments with long handles, the ASD is visualized and closed by stitches. The right atrium is also then closed.

The operation has been performed only in older patients due to the difficulty in maintaining heart-lung bypass from smaller blood vessels in the periphery in tiny children. It has the advantages of a small, and more cosmetic incision, less post-operative pain and earlier discharge from hospital. The role of this technique as an alternative to classical operation remains to be proven.

Other birth defects have not been repaired using minimally invasive techniques. However, another exciting alternative concept in these patients is "Catheter based therapy", which will be the topic of another article in the near future.

That's all about minimally invasive congenital heart surgery. For more information on minimally invasive surgery, including coronary bypass operations, you can visit the MICAS website.