Minimally Invasive Heart Valve Surgery
Dateline: 01/04/98
Over the past two weeks, we have discussed the concept of minimally invasive heart surgery, and the use of this novel technique in treating coronary artery disease. This week, I will describe the treatment of heart valve disease using this method.
Traditional valve surgery
Valve disease requiring surgical repair is most commonly of the mitral and aortic valves. Many different disease processes damage heart valves, causing them to become blocked or leaky. Depending on how severely the valves are damaged, surgical repair or replacement with an artificial heart valve may be required. Conventionally, this is done by an open heart operation, using the heart-lung machine to bypass the circulation. A long incision down the midline of the chest is used, and the breast-bone (or sternum) is split down its length. Circulatory bypass is established using two tubes (cannulas), one for the arterial side and the other for the venous side of the circulation. In conventional open heart surgery for valve repair, the arterial cannula is positioned in the aorta, and the venous cannula may be placed in the right atrium - single venous cannula - or in the superior vena cava (SVC) and inferior vena cava (IVC) - dual venous cannulation.
For mitral valve surgery, access may be through the left atrium, or the right atrium (opening the inter-atrial septum). For the aortic valve, access is directly through an incision in the aorta.
Minimally Invasive Valve Surgery - How is it done ?
Since valve surgery (either repair or replacement) requires the heart chambers to be opened, it needs bypass of the circulation using the heart-lung machine. The surgical incision is however considerably smaller. It involves a 1.5 to 2 inch long opening in the upper part of the front of the chest. Through this tiny incision, the upper portion of the sternum (the manubrium) alone is split, and the cut extended side-ways into the space between the second and third ribs (intercostal space) like the letter "T".
But how can circulatory bypass be established through such a key-hole opening ?
As we just saw, this requires access to the venous and arterial systems. This is acheived by modified means. 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
- the aorta itself may be cannulated directly
Using these modifications, it is possible to safely establish circulatory bypass by hooking the patient to the heart-lung machine. The operation can now proceed.
Aortic Valve Surgery
The approach to the aortic valve is almost similar to a conventional procedure. The aorta is easily visible and accessible through the incision, albeit presenting an appearance different from what the surgeon is used to. The surgeon now sees the aortic valve from "directly above", but can operate upon it just as in a conventional operation. Aortic valve repair and also replacement with an artificial valve can be safely done, with only slightly more difficulty in surgical technique than the traditional method.
Mitral Valve Surgery
The surgical approach to the mitral valve is somewhat different with the minimal invasive method. The surgeon makes an opening in the roof of the left atrium, which is accessible just beside the aortic root. With strategically placed retention sutures, the surgeon can create adequate space to see and operate upon the mitral valve. Repair and replacement with an artificial valve can both be done, although the operation requires greater technical skill than the conventional one.
That's all about minimally invasive heart valve surgery. For more information on minimally invasive surgery, including coronary bypass operations, you can visit the MICAS website.
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