Coronary artery bypass surgery
Coronary artery bypass surgery, also known as coronary artery bypass graft (CABG, pronounced "cabbage"), is a surgical procedure to treat coronary artery disease (CAD), the buildup of plaques in the arteries of the heart. It can relieve chest pain caused by CAD, slow the progression of CAD, and increase life expectancy. It aims to bypass narrowings in heart arteries by using arteries or veins harvested from other parts of the body, thus restoring adequate blood supply to the previously ischemic (deprived of blood) heart.
"Heart bypass" redirects here. For the technique to take over the function of the heart and lungs during surgery, see Cardiopulmonary bypass.
There are two main approaches. The first uses a cardiopulmonary bypass machine, a machine which takes over the functions of the heart and lungs during surgery by circulating blood and oxygen. With the heart in cardioplegic arrest, harvested arteries and veins are used to connect across problematic regions—a construction known as surgical anastomosis. In the second approach, called the off-pump coronary artery bypass (OPCAB), these anastomoses are constructed while the heart is still beating. The anastomosis supplying the left anterior descending branch is the most significant one and usually, the left internal mammary artery is harvested for use. Other commonly employed sources are the right internal mammary artery, the radial artery, and the great saphenous vein.
Effective ways to treat chest pain (specifically, angina, a common symptom of CAD) have been sought since the beginning of the 20th century. In the 1960s, CABG was introduced in its modern form and has since become the main treatment for significant CAD. Significant complications of the operation include bleeding, heart problems (heart attack, arrhythmias), stroke, infections (often pneumonia) and injury to the kidneys.
Coronary artery bypass graft
Coronary artery bypass graft, single bypass
Coronary artery bypass graft, double bypass.
Coronary artery bypass graft, triple bypass
Coronary artery bypass graft, quadruple bypass
Post-operative care[edit]
After the procedure, the patient is usually transferred to the intensive care unit (ICU), where intubations are removed if not already done in the operating theater. They usually exit the ICU by the following day, and four days later, if no complications occur, the patient is discharged from the hospital.[30]
A series of drugs are commonly used in early post-operative care. Dobutamine, a beta agent, can increase the cardiac output and is administered some hours after the operation. Beta blockers are used to prevent atrial fibrillation and other supraventricular arrhythmias. Pacing wires attached to both atria, inserted during the operation, may help prevent atrial fibrillation. Aspirin (80 mg) is used to prevent graft failure.[30] Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) are used to control blood pressure, especially in patients with low cardiac function (<40%). Amlodipine, a calcium channel blocker, is used for patients whose radial artery was used as a graft.[2]
After the discharge, patients may experience insomnia, low appetite, decreased sex drive, and memory problems. This effect is usually transient and lasts 6 to 8 weeks.[30] A tailored exercise plan is usually beneficial.[30]
Complications[edit]
The most common complications of CABG are postoperative bleeding, heart failure, atrial fibrillation (a form of arrhythmia), stroke, kidney dysfunction, and infection of the wound near the sternum.[38]
Postoperative bleeding occurs in 2–5% of cases and may require returning to the operating room;[42] the most common indicator is the amount of blood being drained by chest tubes, which are inserted during the operation to drain fluid or air from the chest. Bleeding may originate from the aorta, the anastomosis, an insufficiently sealed branch of the conduit, or from the sternum. Other causes include platelet abnormalities or their failure to clot—perhaps due to the bypass or to the rebound heparin effect, which occurs when the anti-coagulant heparin is administered at the beginning of surgery and reappears in the blood after its neutralization by protamine.[43]
Low cardiac output syndrome (LCOS) can occur in up to 14% of CABG patients. According to its severity, LCOS is treated with inotropes, an intra-aortic balloon pump (IABP), optimization of pre-load and afterload, or correction of blood gauzes and electrolytes. The aim is to maintain a systolic blood pressure above 90 mmHg and a cardiac index of more than 2.2 L/min/m2.[38] LCOS is often transient.[42] Myocardial infarction can occur after the operation because of either technical or patient-specific factors. Its incidence is difficult to estimate due to varying definitions, but most studies place its occurrence at between 2% and 5%. The incidence is also dependent on whether it is isolated CABG (average, 4%, range, 0.3%–10%) or a combined operation (average, 2.0%, range, 0.7%–12%).[44] New electrocardiogram features, such as Q waves or ultrasound-documented alternation of cardiac wall motions, are indicative. Ongoing ischemia might prompt emergency angiography and PCI or re-operation.[45][42] Immediate coronary angiography offers the most expeditious modality not only for diagnosis but also for potential reintervention.[46] Echocardiography is less valuable for the detection or confirmation of postoperative myocardial ischemia.[47] Arrhythmias can also occur, most-commonly atrial fibrillation (incidence of 20–40%) that is treated with correcting electrolyte balance, and rate and rhythm control.[42][38] However, arrhythmia such as ventricular tachycardia or fibrillation can be a sign of postoperative myocardial ischemia that is treated depending on the cause.[48]
Adverse neurological effects occur after CABG in about 1.5% of patients.[42] They can manifest as type-1 deficits—focal deficits such as stroke or coma—or type-2 global deficits such as delirium caused by CPB, hypoperfusion, or cerebral embolism.[38] Cognitive impairment has been reported in up to 80% cases after CABG at discharge and lasts for a year in up to 40% of cases. The cause remains unclear; CPB is an unlikely cause because even in CABG patients without CPB, as in off-pump CABG, and PCI patients, the incidence is the same.[38][39]
Infections, such as wound infections in the sternum (superficial or deep) are most commonly caused by Staphylococcus aureus, and may complicate the post-operation process. The harvesting of both two thoracic arteries is a risk factor because it significantly impairs the perfusion of blood through the sternum.[38] Pneumonia can also occur.[42] Complications in the gastrointestinal tract have been described and are most commonly due to medications administered during the operation.[39]