A bypass operation may be referred to, depending on the number of coronary arteries bypassed, as a single, double, triple, quadruple, or quintuple bypass. Sextuple bypasses are not unheard of. In a double bypass, the left anterior descending (LAD) artery and the right coronary artery (RCA) might be bypassed. In a triple bypass, the LAD, RCA, and left circumflex (LCX) artery might be bypassed, and a quadruple bypass might involve the LAD, RCA, LCX, and the first diagonal artery of the LAD.
Contrary to popular belief, the number of bypasses performed in a single operation is not an indication of the severity of CAD. Someone with severe CAD may receive fewer bypasses due to a lack of target vessels; that is, vessels to which grafts may be attached. Coronary arteries may prove unsuitable for receiving grafts if they are too small or if the entire vessel has been damaged by arterial plaques. Prior to the surgery, the surgeon will review the coronary angiogram and any other diagnostic exams to identify blockages and estimate the number of bypass grafts required. However, the final decision isn't made until the surgeon examines the heart itself in the operating room.
Choice of Grafts
Which vessels are used as grafts depends a great deal upon the surgeon and hospital involved. Typically, however, surgeons prefer to use arteries as grafts whenever possible due to their higher rates of patency (that is, remaining unblocked) compared to veins. The internal thoracic artery, which has a patency rate at 10 years of above 90%, is frequently grafted to the LAD. A combination of other veins and arteries is used for other coronary arteries, particularly the radial artery from the arm and the saphenous vein from the leg.
Bypass surgery is minute, delicate work that requires loupe magnification and fine surgical instruments. In traditional open-chest bypass surgery, the veins or arteries are first removed and prepared for grafting. The surgeon then opens the chest. If the operation is "on-pump," the patient is connected to the heart-lung machine. The aorta is cross-clamped (in "off-pump" surgery, the aorta may be partially cross-clamped). A cold saline preparation is injected into the aorta and the coronary arteries to stop the heart.
Next, the diseased coronary artery is opened below (downstream from) the blockage. If the saphenous vein (or another vessel, other than the internal thoracic artery) is used as the graft, one end is sutured to this opening in the coronary artery and the other end is sutured to the aorta. If the internal thoracic artery is used, one end is connected to the coronary artery while the other remains attached to the aorta. The procedure is repeated on as many coronary arteries as necessary. Fine polypropylene thread is used for the suturing. The connection between the bypass graft and the artery must be perfect; there can be no leakage of blood.
If the heart has been stopped, it is given electrical shocks to start it pumping again after the grafts have been connected. The heart-lung machine is turned off, the heart and blood slowly return to normal body temperature, and the chest is closed.
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