"Heart bypass" redirects here. For the technique to take over the function of the heart and lungs during surgery, see Cardiopulmonary bypass.
Coronary artery bypass surgery
Early in a coronary artery bypass operation, during vein harvesting from the legs (left of image) and the establishment of bypass (placement of the aorticcannula) (bottom of image). The perfusionist and heart-lung machine are on the upper right. The patient's head (not seen) is at the bottom.
Three coronary artery bypass grafts, a LIMA to LAD and two saphenous vein grafts – one to the right coronary artery system and one to the obtuse marginal system.
There are many variations on terminology, in which one or more of "artery", "bypass" or "graft" is left out. The most frequently used acronym for this type of surgery is CABG (pronounced 'cabbage'), pluralized as CABGs (pronounced 'cabbages'). More recently[when?] the term aortocoronary bypass (ACB) has come into popular use. CAGS (coronary artery graft surgery, pronounced phonetically) should not be confused with coronary angiography (CAG).
Arteriosclerosis is a common arterial disorder characterized by thickening, loss of elasticity, and calcification of arterial walls, resulting in a decreased blood supply.
Atherosclerosis is a common arterial disorder characterized by yellowish plaques of cholesterol, lipids, and cellular debris in the inner layer of the walls of large and medium-sized arteries.
Illustration depicting single, double, triple, and quadruple bypass
The terms single bypass, double bypass, triple bypass, quadruple bypass and quintuple bypass refer to the number of coronary arteries bypassed in the procedure. In other words, a double bypass means two coronary arteries are bypassed (e.g. the left anterior descending (LAD) coronary artery and right coronary artery (RCA)); a triple bypass means three vessels are bypassed (e.g. LAD, RCA, left circumflex artery (LCX)); a quadruple bypass means four vessels are bypassed (e.g. LAD, RCA, LCX, first diagonal artery of the LAD) while quintuple means five. Bypass of more than four coronary arteries is uncommon.
A greater number of bypasses does not imply a person is "more sick", nor does a lower number imply a person is "healthier." A person with a large amount of coronary artery disease (CAD) may receive fewer bypass grafts owing to the lack of suitable "target" vessels. A coronary artery may be unsuitable for bypass grafting if it is small (< 1 mm or < 1.5 mm depending on surgeon preference), heavily calcified (meaning the artery does not have a section free of CAD) or intramyocardial (the coronary artery is located within the heart muscle rather than on the surface of the heart). Similarly, a person with a single stenosis ("narrowing") of the left main coronary artery requires only two bypasses (to the LAD and the LCX). However, a left main lesion places a person at the highest risk for death from a cardiac cause.
The surgeon reviews the coronary angiogram prior to surgery and identifies the lesions (or "blockages") in the coronary arteries. The surgeon will estimate the number of bypass grafts prior to surgery, but the final decision is made in the operating room upon examination of the heart.
Both PCI and CABG are more effective than medical management at relieving symptoms, (e.g. angina, dyspnea, fatigue). CABG is superior to PCI for some patients with multivessel CAD
The Surgery or Stent (SoS) trial was a randomized controlled trial that compared CABG to PCI with bare-metal stents. The SoS trial demonstrated CABG is superior to PCI in multivessel coronary disease.
The SYNTAX trial was a randomized controlled trial of 1800 patients with multivessel coronary disease, comparing CABG versus PCI using drug-eluting stents (DES). The study found that rates of major adverse cardiac or cerebrovascular events at 12 months were significantly higher in the DES group (17.8% versus 12.4% for CABG; P=0.002). This was primarily driven by higher need for repeat revascularization procedures in the PCI group with no difference in repeat infarctions or survival. Higher rates of strokes were seen in the CABG group.
The FREEDOM (Future Revascularization Evaluation in Patients With Diabetes Mellitus—Optimal Management of Multivessel Disease) trial will compare CABG and DES in patients with diabetes. The registries of the nonrandomized patients screened for these trials may provide as much robust data regarding revascularization outcomes as the randomized analysis.
A study comparing the outcomes of all patients in New York state treated with CABG or percutaneous coronary intervention (PCI) demonstrated CABG was superior to PCI with DES in multivessel (more than one diseased artery) coronary artery disease (CAD). Patients treated with CABG had lower rates of death and of death or myocardial infarction than treatment with a coronary stent. Patients undergoing CABG also had lower rates of repeat revascularization. The New York State registry included all patients undergoing revascularization for coronary artery disease, but was not a randomized trial, and so may have reflected other factors besides the method of coronary revascularization.
A meta-analysis with over 6000 patients showed that coronary artery bypass was associated with lower risk for major adverse cardiac events compared to drug-eluting stenting. However, patients had a higher risk of stroke events.
The 2004 ACC/AHA CABG guidelines state CABG is the preferred treatment for:
Disease of all three coronary vessels (LAD, LCX and RCA).
Diffuse disease not amenable to treatment with a PCI.
The 2005 ACC/AHA guidelines further state: CABG is the preferred treatment with other high-risk patients such as those with severe ventricular dysfunction (i.e. low ejection fraction), or diabetes mellitus.
Prognosis following CABG depends on a variety of factors, and successful grafts typically last 8–15 years. In general, CABG improves the chances of survival of patients who are at high risk (generally triple or higher bypass), though statistically after about five years the difference in survival rate between those who have had surgery and those treated by drug therapy diminishes. Age at the time of CABG is critical to the prognosis, younger patients with no complicating diseases doing better, while older patients can usually be expected to suffer further blockage of the coronary arteries.
The value of coronary artery bypass surgery in rescuing someone having a heart attack (by immediately alleviating an obstruction) is clearly defined in multiple studies, but studies have failed to find benefit for bypass surgery vs. medical therapy in stable angina patients. The artery bypass can temporarily alleviate chest pain, but does not increase longevity. The "vast majority of heart attacks do not originate with obstructions that narrow arteries".
Loss of mental function is a complication of bypass surgery in elderly people, and might influence procedure cost benefit considerations.
Several factors may contribute to immediate cognitive decline. The heart-lung blood circulation system and the surgery itself release a variety of debris, including bits of blood cells, tubing, and plaques. For example, when surgeons clamp and connect the aorta to tubing, resulting emboli block blood flow and cause mini strokes. Other heart surgery factors related to mental damage may be events of hypoxia, high or low body temperature, abnormal blood pressure, irregular heart rhythms, and fever after surgery.
A safer and more permanent and successful way to prevent heart attacks in patients at high risk is to exercise, give up smoking, take "drugs to get blood pressure under control and drive cholesterol levels down to prevent blood clotting". Longer term, behavioral and medication treatment may be the only way to avoid vascular related loss of mental function.
Illustration of a typical coronary artery bypass surgery. A vein from the leg is removed and grafted to the coronary artery to bypass a blockage.
Coronary artery bypass surgery during mobilization (freeing) of the right coronary artery from its surrounding tissue, adipose tissue (yellow). The tube visible at the bottom is the aortic cannula (returns blood from the HLM). The tube above it (obscured by the surgeon on the right) is the venous cannula (receives blood from the body). The patient's heart is stopped and the aorta is cross-clamped. The patient's head (not seen) is at the bottom.
The patient is brought to the operating room and moved on to the operating table.
An anaesthetist places a variety of intravenous lines and injects a painkilling agent (usually fentanyl) followed within minutes by an induction agent (usually propofol) to render the patient unconscious.
In the case of "off-pump" surgery, the surgeon places devices to stabilize the heart.
If the case is "on-pump", the surgeon sutures cannulae into the heart and instructs the perfusionist to start cardiopulmonary bypass (CPB). Once CPB is established, the surgeon places the aortic cross-clamp across the aorta and instructs the perfusionist to deliver cardioplegia (a special potassium-mixture, cooled) to stop the heart and slow its metabolism. Usually the patient's machine-circulated blood is cooled to around 84 °F (29 °C)
The heart is restarted; or in "off-pump" surgery, the stabilizing devices are removed. In cases where the aorta is partially occluded by a C-shaped clamp, the heart is restarted and suturing of the grafts to the aorta is done in this partially occluded section of the aorta while the heart is beating.
Nurses in the ICU focus on recovering the patient by monitoring blood pressure, urine output and respiratory status as the patient is monitored for bleeding through the chest tubes. If there is chest tube clogging, complications such as cardiac tamponade, pneumothorax or death can ensue. Thus nurses closely monitor the chest tubes and under take methods to prevent clogging so bleeding can be monitored and complications can be prevented.
After awakening and stabilizing in the ICU (approximately one day), the person is transferred to the cardiac surgery ward until ready to go home (approximately four days).
Grafts can become diseased and may occlude in the months to years after bypass surgery is performed. Patency is the chance that a graft remains open. A graft is considered patent if there is flow through the graft without any significant (>70% diameter) stenosis in the graft.
Graft patency is dependent on a number of factors, including the type of graft used (internal thoracic artery, radial artery, or great saphenous vein), the size or the coronary artery that the graft is anastomosed with, and, of course, the skill of the surgeon(s) performing the procedure. Arterial grafts (e.g. LITA, radial) are far more sensitive to rough handling than the saphenous veins and may go into spasm if handled improperly.
Generally the best patency rates are achieved with the in-situ left internal thoracic artery (the proximal end is left connected to the subclavian artery) with the distal end being anastomosed with the coronary artery (typically the left anterior descending artery or a diagonal branch artery). Lesser patency rates can be expected with radial artery grafts and "free" internal thoracic artery grafts (where the proximal end of the thoracic artery is excised from its origin from the subclavian artery and re-anastomosed with the ascending aorta). Saphenous vein grafts have worse patency rates, but are more available, as the patients can have multiple segments of the saphenous vein used to bypass different arteries.
Veins that are used either have their valves removed or are turned around so that the valves in them do not occlude blood flow in the graft. LITA grafts are longer-lasting than vein grafts, both because the artery is more robust than a vein and because, being already connected to the arterial tree, the LITA need only be grafted at one end. The LITA is usually grafted to the left anterior descending coronary artery (LAD) because of its superior long-term patency when compared to saphenous vein grafts.
Patients undergoing coronary artery bypass surgery will have to avoid certain things for eight to 12 weeks to reduce the risk of opening the incision. These are called sternal precautions. First, patients need to avoid using their arms excessively, such as pushing themselves out of a chair or reaching back before sitting down. To avoid this, patients are encouraged to build up momentum by rocking several times in their chair before standing up. Second, patients should avoid lifting anything in excess of 5–10 pounds. A gallon (U.S.) of milk weighs approximately 8.5 pounds, and is a good reference point for weight limitations. Finally, patients should avoid overhead activities with their hands, such as reaching for sweaters from the top shelf of a closet or reaching for plates or cups from the cupboard.
Postperfusion syndrome (pumphead), a transient neurocognitive impairment associated with cardiopulmonary bypass. Some research shows the incidence is initially decreased by off-pump coronary artery bypass, but with no difference beyond three months after surgery. A neurocognitive decline over time has been demonstrated in people with coronary artery disease regardless of treatment (OPCAB, conventional CABG or medical management). However, a 2009 research study suggests that longer term (over 5 years) cognitive decline is not caused by CABG but is rather a consequence of vascular disease.
Pericardial tamponade: Blood collection around the heart that compresses the heart and causes poor body and brain perfusion. Chest tubes are placed around the heart and lung to prevent this. If the chest tubes become clogged in the early post operative period when bleeding is ongoing this can lead to pericardial tamponade, pneumothorax or hemothorax.
Patients who have a coronary artery bypass surgery need regular monitoring from a physician. Among the changes in monitoring are five years after the surgery the addition of a regular cardiac stress test even when there is no change in the patient's status.
The first coronary artery bypass surgery was performed in the United States on May 2, 1960, at the Albert Einstein College of Medicine-Bronx Municipal Hospital Center by a team led by Dr. Robert H. Goetz and the thoracic surgeon, Dr. Michael Rohman with the assistance of Dr. Jordan Haller and Dr. Ronald Dee. In this technique the vessels are held together with circumferential ligatures over an inserted metal ring. The internal mammary artery was used as the donor vessel and was anastomosed to the right coronary artery. The actual anastomosis with the Rosenbach ring took fifteen seconds and did not require cardiopulmonary bypass. The disadvantage of using the internal mammary artery was that, at autopsy nine months later, the anastomosis was open, but an atheromatous plaque had occluded the origin of the internal mammary that was used for the bypass.[verification needed]
However, Goetz's has been cited by others, including Kolesov, as the first successful human coronary artery bypass. Goetz's case has frequently been overlooked. Confusion has persisted for over 40 years and seems to be due to the absence of a full report and to misunderstanding about the type of anastomosis that was created. The anastomosis was intima-to-intima, with the vessels held together with circumferential ligatures over a specially designed metal ring. Kolesov did the first successful coronary bypass using a standard suture technique in 1964, and over the next five years he performed 33 sutured and mechanically stapled anastomoses in Leningrad (now St. Petersburg), USSR.
Dr. René Favaloro, an Argentine surgeon, achieved a physiologic approach in the surgical management of coronary artery disease—the bypass grafting procedure—at the Cleveland Clinic in May 1967. His new technique used a saphenous veinautograft to replace a stenotic segment of the right coronary artery. Later, he successfully used the saphenous vein as a bypassing channel, which has become the typical bypass graft technique we know today; in the U.S., this vessel is typically harvested endoscopically, using a technique known as endoscopic vessel harvesting (EVH). Soon Dr. Dudley Johnson extended the bypass to include left coronary arterial systems. In 1968, Doctors Charles Bailey, Teruo Hirose and George Green used the internal mammary artery instead of the saphenous vein for the grafting.
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