Coronary artery bypass surgery
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2008-06-28T17:30:32Z
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{{Redirect|Heart bypass|the technique to take over the function of the heart and lungs during surgery|Cardiopulmonary bypass}}
[[Image:Coronary artery bypass surgery Image 657C-PH.jpg|thumb|right|300px|Early in a '''coronary artery bypass surgery''' during vein harvesting from the legs (left of image) and the establishment of bypass (placement of the [[aorta|aortic]] [[cannula]]) (bottom of image). The [[perfusionist]] and [[heart-lung machine]] (HLM) are on the upper right. The patient's head (not seen) is at the bottom.]]
[[Image:Coronary artery bypass surgery Image 657B-PH.jpg|thumb|right|300px|'''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 [[Heart-lung machine|HLM]]). The tube above it (obscured by the [[cardiac surgeon|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.]]
'''Coronary artery bypass surgery''', also '''coronary artery bypass graft surgery''', and colloquially '''heart bypass''' or '''bypass surgery''' is a [[surgery|surgical procedure]] performed to relieve [[Angina pectoris|angina]] and reduce the risk of death from [[Coronary heart disease|coronary artery disease]]. [[artery|Arteries]] or [[vein]]s from elsewhere in the patient's body are [[medical grafting|grafted]] to the [[coronary artery|coronary arteries]] to bypass [[atherosclerosis|atherosclerotic]] [[stenosis|narrowings]] and improve the [[blood]] supply to the [[coronary circulation]] supplying the [[myocardium]] (heart muscle). This surgery is usually performed with the heart stopped, necessitating the usage of [[cardiopulmonary bypass]]; techniques are available to perform CABG on a beating heart, so-called "off-pump" surgery.
==History==
The technique was pioneered by [[Argentina|Argentine]] [[cardiac surgeon]] [[René Favaloro]] at the [[Cleveland Clinic]] in the late 1960s.<ref>Captur G. Memento for Rene Favaloro. Tex Heart Inst J. 2004;31(1):47-60. PMID 15061628. [http://www.pubmedcentral.gov/articlerender.fcgi?tool=pubmed&pubmedid=15061628 Free Full Text].</ref>
Currently, about 500,000 CABGs are performed in the United States each year.
==Terminology==
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'),<ref>American Heart Association. Heart Bypass Surgery. URL: http://www.americanheart.org/presenter.jhtml?identifier=4484. Accessed on March 26, 2006.</ref> pluralized as '''CABGs''' (pronounced 'cabbages'). More recently the term '''aortocoronary bypass (ACB)''' has come into popular use. '''CAGS''' (Coronary Artery Graft Surgery, pronounced phonetically) has been used (primarily outside the [[United States]]) and should not be confused with [[Coronary angiography|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.
===Number of bypasses===
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|left anterior descending (LAD)]] coronary artery and [[right coronary artery|right coronary artery (RCA)]]); a triple bypass means three vessels are bypassed (e.g. LAD, RCA, [[left circumflex artery|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. Less commonly more than four coronary arteries may be bypassed.
A greater number of bypasses does not imply a person is "sicker," nor does a lesser number imply a person is "healthier."<ref>{{cite journal |author=Ohki S, Kaneko T, Satoh Y, ''et al'' |title=[Coronary artery bypass grafting in octogenarian] |language=Japanese |journal=Kyobu geka. The Japanese journal of thoracic surgery |volume=55 |issue=10 |pages=829–33; discussion 833–6 |year=2002 |pmid=12233100 |doi=}}</ref> A person with a large amount of [[coronary artery disease|coronary artery disease (CAD)]] may receive fewer bypass grafts due to the lack of suitable "target" vessels. A coronary artery may be unsuitable for bypass grafting it 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 coronary artery|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.{{Fact|date=February 2007}}
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.
==Indications for CABG==
Several alternative treatments for coronary artery disease exist. They include:
* Medical management ([[statins]], [[antihypertensive]]s, [[smoking cessation]], tight [[blood sugar]] control in [[diabetes mellitus|diabetics]])
* [[Percutaneous coronary intervention]] (PCI)
Both PCI and CABG are more effective than medical management at relieving symptoms,<ref name=rihal>{{cite journal |author=Rihal C, Raco D, Gersh B, Yusuf S |title=Indications for coronary artery bypass surgery and percutaneous coronary intervention in chronic stable angina: review of the evidence and methodological considerations |journal=Circulation |volume=108 |issue=20 |pages=2439–45 |year=2003 |pmid=14623791 |doi=10.1161/01.CIR.0000094405.21583.7C}} [http://circ.ahajournals.org/cgi/content/full/108/20/2439 Full Free Text].</ref> (e.g. [[Angina pectoris|angina]], [[dyspnea]], [[fatigue (medical)|fatigue]]). CABG is superior to PCI in multivessel CAD (more than one diseased artery),<ref name="SoS 2002">{{cite journal |author=SoS Investigators |title=Coronary artery bypass surgery versus percutaneous coronary intervention with stent implantation in patients with multivessel coronary artery disease (the Stent or Surgery trial): a randomised controlled trial |journal=Lancet |volume=360 |issue=9338 |pages=965–70 |year=2002 |pmid=12383664 |doi=10.1016/S0140-6736(02)11078-6}}</ref> although the ARTS II registry suggests PCI with [[drug-eluting stent]]s (DES) may be not inferior to CABG.
The ARTS II registry compared a cohort of patients treated with DES and contemporary medical management to the historical CABG cohort in the ARTS I trial and concluded drug-eluting stenting is not inferior to CABG for treatment of multivessel coronary disease.<ref>http://www.medscape.com/viewarticle/501424</ref> The Surgery or Stent (SoS) trial was a randomized controlled trial that compared CABG to PCI with [[coronary stent|bare-metal stent]]s. The SoS trial demonstrated CABG is superior to PCI in multivessel coronary disease.<ref name="SoS 2002">{{cite journal |author=SoS Investigators |title=Coronary artery bypass surgery versus percutaneous coronary intervention with stent implantation in patients with multivessel coronary artery disease (the Stent or Surgery trial): a randomised controlled trial |journal=Lancet |volume=360 |issue=9338 |pages=965–70 |year=2002 |pmid=12383664 |doi=10.1016/S0140-6736(02)11078-6}}</ref>
No randomized trial comparing CABG and DES has been completed, although two trials of DES versus CABG are currently enrolling patients - SYNTAX (Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery) and FREEDOM (Future Revascularization Evaluation in Patients With Diabetes Mellitus—Optimal Management of Multivessel Disease). The registries of the nonrandomized patients screened for these trials may provide as much robust data regarding revascularization outcomes as the randomized analysis.<ref>{{cite journal |author=Desai ND |title=Pitfalls assessing the role of drug-eluting stents in multivessel coronary disease |journal=Ann. Thorac. Surg. |volume=85 |issue=1 |pages=25–7 |year=2008 |pmid=18154771 |doi=10.1016/j.athoracsur.2007.08.063}}</ref>
A recent 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 heart disease|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.<ref name="Hannan 2008">{{cite journal |author=Hannan EL, Wu C, Walford G, ''et al'' |title=Drug-eluting stents vs. coronary-artery bypass grafting in multivessel coronary disease |journal=N. Engl. J. Med. |volume=358 |issue=4 |pages=331–41 |year=2008 |pmid=18216353 |doi=10.1056/NEJMoa071804}}</ref> 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.
The 2004 [[American College of Cardiology|ACC]]/[[American Heart Association|AHA]] CABG guidelines state CABG is the preferred treatment for:<ref name="2004 ACC CABG">{{cite journal |author=Eagle KA, Guyton RA, Davidoff R, ''et al'' |title=ACC/AHA 2004 guideline update for coronary artery bypass graft surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for Coronary Artery Bypass Graft Surgery) |journal=Circulation |volume=110 |issue=14 |pages=e340–437 |year=2004 |pmid=15466654 |doi=}}</ref>
* Disease of the [[left main coronary artery]] (LMCA).
* Disease of all three coronary vessels ([[left anterior descending|LAD]], [[circumflex artery|LCX]] and [[right coronary artery|RCA]]).
* Diffuse disease not amendable to treatment with a PCI.
The 2005 ACC/AHA guidelines further state:
CABG is the likely the preferred treatment with other high-risk patients such as those with severe ventricular dysfunction (i.e. low [[ejection fraction]]), or [[diabetes mellitus]].<ref name="2004 ACC CABG">{{cite journal |author=Eagle KA, Guyton RA, Davidoff R, ''et al'' |title=ACC/AHA 2004 guideline update for coronary artery bypass graft surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for Coronary Artery Bypass Graft Surgery) |journal=Circulation |volume=110 |issue=14 |pages=e340–437 |year=2004 |pmid=15466654 |doi=}}</ref>
==Prognosis==
Prognosis following CABG depends on a variety of factors, but successful grafts typically last around 10-15 years. In general, CABG improves the chances of survival of patients who are at high risk (meaning those presenting with angina pain shown to be due to ischemic heart disease), but statistically after about 5 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 have a high probability of greater longevity. The older patient can usually be expected to suffer further blockage of the coronary arteries.{{Fact|date=January 2008}}
==Procedure (Simplified)==
#The patient is brought to the [[operating room]] and moved onto the operating table.
#An [[anaesthetist]] places a variety of [[intravenous]] lines and injects an induction agent (usually [[propofol]]) to render the person unconscious.
#An [[endotracheal tube]] is inserted and secured by the anesthetist or assistant (e.g. [[respiratory therapist]] or [[nurse anesthetist]]) and [[mechanical ventilation]] is started.
#The chest is opened via a [[median sternotomy]] and the heart is examined by the surgeon.
#The bypass grafts are harvested - frequent conduits are the [[internal thoracic artery|internal thoracic arteries]], [[radial artery|radial arteries]] and [[saphenous vein]]s. When harvesting is done, the patient is given [[heparin]] to prevent the blood from clotting.
#In the case of "[[OPCAB|off-pump]]" surgery, the surgeon places devices to stabilize the heart.
#If the case is "on-pump", the surgeon sutures [[Cardiopulmonary bypass#Cannulae|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]] to stop the heart.
#One end of each graft is sewn onto the [[coronary artery|coronary arteries]] beyond the [[coronary artery disease|blockages]] and the other end is attached to the [[aorta]].
#The heart is restarted; or in "off-pump" surgery, the stabilizing devices are removed. In some cases, 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.
#[[Protamine]] is given to reverse the effects of [[heparin]].
#The [[sternum]] is wired together and the incisions are [[suture]]d closed.
#The person is moved to the [[intensive care unit]] (ICU) to recover. After awakening and stabilizing in the ICU (approximately 1 day), the person is transferred to the cardiac surgery [[ward]] until ready to go home (approximately 4 days).
==Minimally Invasive CABG==
Alternate methods of minimally invasive coronary artery bypass surgery have been developed in recent times. [[Off-pump coronary artery bypass surgery]] (OPCAB) is a technique of performing bypass surgery without the use of [[cardiopulmonary bypass]] (the heart-lung machine). Further refinements to OPCAB have resulted in [[minimally invasive direct coronary artery bypass surgery]] (MIDCAB), a technique of performing bypass surgery through a 5 to 10 cm incision.
==Conduits used for bypass==
The choice of conduits is highly surgeon and institution dependent. Typically, the left [[internal thoracic artery]] (LITA) (previously referred to as ''left internal mammary artery'' or ''LIMA'') is grafted to the [[left anterior descending]] artery and a combination of other arteries and veins is used for other coronary arteries. The right internal thoracic artery (RITA), the [[great saphenous vein]] from the leg and the [[radial artery]] from the forearm are frequently used. The [[right gastroepiploic artery]] from the [[stomach]] is infrequently used given the difficult mobilization from the [[abdomen]].
===Graft patency===
Grafts can become diseased and may occlude in the months to years after bypass surgery is performed. Patency is a term used to describe the chance that a graft remain 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 (the proximal end is left connected to the [[subclavian artery]]) left internal thoracic 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 [[valve]]s 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.<ref>Kitamura S, Kawachi K, Kawata T, Kobayashi S, Mizuguchi K, Kameda Y, Nishioka H, Hamada Y, Yoshida Y. [Ten-year survival and cardiac event-free rates in Japanese patients with the left anterior descending artery revascularized with internal thoracic artery or saphenous vein graft: a comparative study] Nippon Geka Gakkai Zasshi. 1996 Mar;97(3):202-9. PMID 8649330.</ref><ref>Arima M, Kanoh T, Suzuki T, Kuremoto K, Tanimoto K, Oigawa T, Matsuda S. Serial Angiographic Follow-up Beyond 10 Years After Coronary Artery Bypass Grafting. Circ J. 2005 Aug;69(8):896-902. PMID 16041156. [http://www.jstage.jst.go.jp/article/circj/69/8/896/_pdf Free Full Text].</ref>
==Sternal Precautions==
Patients undergoing coronary artery bypass surgery will have to avoid certain things to avoid 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 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.
==Complications==
People undergoing coronary artery bypass are at risk for the same complications as any surgery, plus some risks more common with or unique to CABG.
===CABG associated===
*[[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).
*[[Nonunion]] of the [[sternum]]; [[internal thoracic artery]] harvesting devascularizes the sternum increasing risk.
*[[Myocardial infarction]] due to embolism, [[hypoperfusion]], or graft failure.
*Late graft [[stenosis]], particularly of [[Great saphenous vein|saphenous vein]] grafts due to [[atherosclerosis]] causing recurrent [[Angina pectoris|angina]] or [[myocardial infarction]].
*[[Acute renal failure]] due to embolism or hypoperfusion.
*[[Stroke]], secondary to embolism or hypoperfusion.
===General surgical===
*[[Infection]] at incision sites or [[sepsis]].
*[[Deep vein thrombosis]] (DVT)
*[[Anesthesia|Anesthetic]] complications such as [[malignant hyperthermia]].
*[[Keloid]] scarring
*[[Chronic pain]] at incision sites
*[[Chronic stress]] related illnesses
*[[Death]]
==See also==
* [[Angioplasty]]
* [[Cardiothoracic surgery]]
* [[Dressler's syndrome]]
* [[Hybrid bypass]]
* [[Totally endoscopic coronary artery bypass surgery]]
==References==
{{reflist}}
==External links==
* [http://cardiacsurgery.ctsnetbooks.org/current.shtml#PART_III__ISCHEMIC_HEART_DISEASE Ischemic Heart Disease] section in ''Cardiac Surgey in the Adult''
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{{Cardiac surgery}}
[[Category:Cardiac surgery]]
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