Midcab

Minimally invasive direct coronary artery bypass (MIDCAB) was introduced several years ago as truly minimally invasive cardiac surgery, in terms of not only incision size, but, far more importantly physiologically, the fact that CPB was not required. The key to the reliability of the procedure is a stabilizing device shaped as a sewing machine foot pad which straddles the target artery (Fig 9.2). This immobilizes the region, permitting an anastomosis on relatively fixed target. MIDCAB generally refers to left anterior descending artery (LAD) grafting with the left internal mammary artery (LIMA) via small left anterior thoracotomy. Prior to development of a reliable stabilizing device, anastomoses to vessels on a vigorously beating target required pharmacologic manipulation to slow, or even transiently arrest the heart rate. Even so, these beating heart cases led in some instances to unsatisfying anastomoses. The use of a reliable stabilizing device was a seminal event in making MIDCAB a more reliable and widely acceptable procedure.

The patient who is a MIDCAB candidate generally has single vessel disease in the left anterior descending artery (LAD) distribution, although right coronary

Fig.9.2. Retractor and stabilizer for MIDCAB procedures.

Fig.9.2. Retractor and stabilizer for MIDCAB procedures.

disease can also be bypassed with MIDCAB techniques. A small incision is made in the left anterior chest in the 4th intercostal space for LAD bypass. If necessary for exposure, the 4th costal cartilage may be excised. The left internal mammary artery is carefully identified and dissected cephalad using various commercially available exposure devices. The patient is moderately heparinized. The LAD is exposed, and vascular control achieved, generally with a proximally placed vessel loop p ositioned on a blunt needle. The stabilizer is positioned and the LAD opened. A vascular occluder may be inserted into the vessel. Alternatively, if the vessel is large and important, a vascular shunt may be placed to permit continued perfusion while maintaining vascular control and a bloodless field (Fig 9.3). A carbon dioxide blower is helpful to remove residual blood. It is helpful for the blower to be attached to a gentle saline aerosolizing device to prevent dessication of the target tissues. The internal mammary is grafted to the LAD. The quality of the anastomosis is immeasurably improved with the stabilizing device, with which patencies (at least short term) generally approach standard LIMA to LAD anastomoses on the arrested heart.

A concept which has been proposed for multivessel disease is the so-called "hybrid" procedure. This combines a MIDCAB procedure with endovascular coronary procedures (angioplasty, stenting) either in a simultaneous or staged manner. The concept generally does not coincide with conventional teaching that surgical coronary revascularization should be as complete as possible to prevent future coronary events. Furthermore, subsequent reoperation of failed angioplasty attempts is made much more difficult in the presence of a patent LIMA graft. Proponents of the hybrid procedure contend that the procedure is useful as a salvage maneuver in high risk patients who might not tolerate a prolonged coronary revascularization procedure on pump. Furthermore, they contend that the most important anastomosis that determines long term patient survival is the LIMA to LAD anastomosis. The hybrid procedure may have some indications. However, these must be selected cases. The hybrid procedure should be used judiciously and is not to be considered the mainstream of coronary revascularization methods.

Fig. 9.3. Intracoronary shunt to achieve vascular control while maintaining perfusion.
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