Off-pump coronary artery bypass and minimally invasive direct coronary artery bypass

Published on 07/02/2015 by admin

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Last modified 07/02/2015

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Off-pump coronary artery bypass and minimally invasive direct coronary artery bypass

Roxann D. Barnes Pike, MD

Definitions and indications

Cardiopulmonary bypass (CPB) can be avoided for coronary artery bypass grafting (CABG) by using either off-pump coronary artery bypass (OPCAB) or minimally invasive direct coronary artery bypass (MIDCAB). OPCAB involves CABG of one or more vessels accessed via a median sternotomy on the beating heart. MIDCAB consists of CABG done through a lateral anterior thoracotomy on the beating heart. The initial indication for MIDCAB was to treat patients with single-vessel disease that was not amenable to percutaneous transluminal coronary angioplasty and who wanted to avoid the deleterious effects of CPB.

In both techniques, each diseased artery is identified and immobilized, often using a specialized stabilization device. Improved results and more reliable and reproducible coronary anastomoses are achieved when mechanical stabilization devices are used (Figure 145-1). The stenotic segments are bypassed without the use of CPB or the need for cardioplegia or hypothermia.

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Figure 145-1 Example of an off-pump coronary artery bypass stabilization device.

Advantages and disadvantages of minimally invasive direct coronary artery bypass and off-pump coronary artery bypass

Advantages

The purported advantages of MIDCAB over the tradional approach for CPB include the avoidance of a median sternotomy with its associated risk of sternal wound infection and reduced musculoskeletal injury. OPCAB and MIDCAB can be used either as primary operations or as reoperations, and both avoid the adverse effects associated with the systemic inflammatory response syndrome in response to CPB and its deleterious effects, such as coagulation derangements, microvascular thromboembolism and endothelial dysfunction, arrhythmias, and multiorgan dysfunction. Cannulation, with manipulation and cross-clamping of the ascending aorta, required with CPB increases the risk of aortic dissection and of neurologic sequelae, such as neurocognitive dysfunction and stroke. A recent meta-analysis showed a significant reduction in perioperative stroke after OPCAB versus on-pump coronary revascularization. Other purported advantages of MIDCAB and OPCAB over conventional CPB include decreased surgical time, decreased need for transfusion, less atrial fibrillation, shorter hospital lengths of stay, and possibly decreased cost.

Disadvantages

The main disadvantage associated with the use of MIDCAB and OPCAB, compared with conventional CABG, is lack of optimal exposure of coronary vessels. MIDCAB allows the most limited exposure; therefore, fewer vessels can be grafted—often only the internal thoracic artery to the left anterior descending artery. Other vessels must be treated with angioplasty. OPCAB, however, allows grafting of multiple vessels. MIDCAB is also associated with more trauma to costal cartilages (with or without removal of rib segments) and more postoperative pain. Both procedures are associated with more hemodynamic instability (especially during displacement of the heart with OPCAB), which may pressure the surgeon to perform the procedure more quickly and, along with limited exposure, result in questionable anastomotic quality and completeness of revascularization. Patients will benefit from on-pump CABG if they have multiple lesions and their anatomy is complex. Patients who are not at increased risk for developing the complications associated with CPB have more effective revascularization if an on-pump CABG is performed. Overall, graft patency rate is higher and mortality is likely lower after on-pump CABG, compared with OPCAB.

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