View source for Vascular bypass

{{short description|Type of surgical grafting}}
{{Infobox medical intervention
| name         = Vascular bypass
| synonym      =Vascular graft
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| specialty    = Vascular surgery, Cardiac surgery
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A '''vascular bypass''' is a [[surgery|surgical procedure]] performed to redirect [[Circulatory system|blood flow]] from one area to another by reconnecting blood vessels. Often, this is done to bypass around a diseased artery, from an area of normal blood flow to another relatively normal area. It is commonly performed due to inadequate blood flow ([[ischemia]]) caused by [[atherosclerosis]], as a part of [[organ transplantation]], or for [[vascular access]] in [[hemodialysis]]. In general, someone's own [[vein]] (autograft) is the preferred graft material (or conduit) for a vascular bypass, but other types of grafts such as [[polytetrafluoroethylene]] (Teflon), [[polyethylene terephthalate]] (Dacron), or a different person's vein ([[Allotransplantation|allograft]]) are also commonly used. [[Artery|Arteries]] can also serve as vascular grafts. A surgeon sews the graft to the source and target vessels by hand using [[surgical suture]], creating a [[surgical anastomosis]].

Common bypass sites include the [[heart]] ([[coronary artery bypass surgery]]) to treat coronary artery disease, and the legs, where [[Popliteal bypass surgery|lower extremity bypass surgery]] is used to treat [[peripheral vascular disease]].

==Medical uses==

===Cardiac bypass===
{{Main|Coronary artery bypass surgery}}
Cardiac bypass is performed when the arteries that bring [[blood]] to the [[heart muscle]] (coronary arteries) become clogged by [[Atheroma|plaque]].<ref>{{cite web|title=What Is Coronary Artery Bypass Grafting|url=https://www.nhlbi.nih.gov/health/health-topics/topics/cabg|website=www.nhlbi.nih.gov|publisher=National Institutes of Health — National Heart, Lung, and Blood Institute|access-date=11 November 2016}}</ref><ref name="AHA">{{cite web|url=http://www.americanheart.org/presenter.jhtml?identifier=4484/|title=Bypass Surgery, Coronary Artery|access-date=8 April 2010}}</ref> Such a condition may cause chest pain from [[angina pectoris]] or a heart attack. Dimensional aspects, material selection, and manufacturing methods influence mechanistic behaviours of artificial grafts and chosen to receive artery-like behaviour <ref>Zia, A.W., Liu, R. & Wu, X. Structural design and mechanical performance of composite vascular grafts. Bio-des. Manuf. (2022). https://doi.org/10.1007/s42242-022-00201-7</ref>

===Leg (lower extremity) bypass===
{{Main|Popliteal bypass surgery}}
In the legs, bypass grafting is used to treat [[peripheral vascular disease]], [[acute limb ischemia]], [[aneurysm]]s and [[Trauma (medicine)|trauma]]. While there are many anatomical arrangements for vascular bypass grafts in the lower extremities depending on the location of the disease, the principle is the same: to restore blood flow to an area without normal flow. <ref name="Femoropopliteal bypass">{{cite web |title=Femoropopliteal bypass surgery |url=https://patient.uwhealth.org/healthwise/article/en-us/aa118144 |website=patient.uwhealth.org}}</ref>

For example, a femoral-popliteal bypass ('''"fem-pop"''') might be used if the [[femoral artery]] is occluded. A fem-pop bypass may refer to the above- or below-knee popliteal artery. Other anatomic descriptions of lower extremity bypasses include:
* '''"fem-fem"''' - femoral to femoral bypass, e.g. from right to left. Used when there is no inflow to one femoral artery (i.e., the iliac artery on the receiving side is diseased) but there is aortic flow.
* '''"aorto-bifem"''' - aortic to both femoral arteries. Used when there is disease at the [[aortic bifurcation]], known as [[Leriche syndrome]], or in both iliac arteries.
* '''"ax-bifem"''' - [[axillary artery]] to both femoral artery bypass. Either axillary artery can be used as the origin of the bypass. Used when patient cannot tolerate a more invasive and higher risk aorto-bifem, or when removing an infected aortic graft such as an [[EVAR]] device.
* '''"fem-tib"''' - femoral to one of the three tibial arteries ([[Anterior tibial artery|Anterior]], [[Posterior tibial artery|Posterior]] or [[Fibular artery|Peroneal]]). Used for disease of the femoral and tibial arteries, this procedure is used most frequently in people with [[diabetes]], which tends to create disease in the tibial arteries rather than the more [[Anatomical terms of location#Proximal and distal|proximal]] arteries.<ref>{{cite journal|last=Aboyans|first=V.|author2=Lacroix, P.|author3=Criqui, M.H.|title=Large and Small Vessel Atherosclerosis: Similarities and Differences|journal=Progress in Cardiovascular Diseases|date=Sep–Oct 2007|volume=50|issue=2|pages=112–125|pmid=17765473|doi=10.1016/j.pcad.2007.04.001}}</ref>
* a '''"DP"''' bypass - any vascular bypass where the target is the [[dorsalis pedis artery]] on the [[Dorsum (anatomy)|dorsum]] of the foot. It is used in similar situations to those described for the fem-tib bypass.

===Hemodialysis access===
{{Main|Vascular access}}
[[File:Blausen 0050 ArteriovenousGraft.png|thumb|300px|An arteriovenous graft serving as a fistula for hemodialysis access]]

A vascular bypass is often created to serve as an access point to the [[circulatory system]] for [[hemodialysis]]. Such a bypass is referred to as an [[arteriovenous fistula]] if it directly connects a [[vein]] to an [[artery]] without using synthetic material.<ref name="Cochrane HD access">{{cite journal |title=Cochrane review - hemodialysis access preoperative eval | date=2015 | doi=10.1002/14651858.CD007013.pub2 | pmid=26418347 | last1=Kosa | first1=S. D. | last2=Al-Jaishi | first2=A. A. | last3=Moist | first3=L. | last4=Lok | first4=C. E. | journal=The Cochrane Database of Systematic Reviews | issue=9 | pages=CD007013 | pmc=6464998 }}</ref>

===Cerebral artery bypass===
In the skull, when blood flow is blocked or a damaged [[cerebral artery]] prevents adequate blood flow to the [[brain]], a cerebral artery bypass may be performed to improve or restore flow to an oxygen-deprived (ischemic) area of the brain.<ref name="MayField">{{cite web|url=http://www.mayfieldclinic.com/PE-CerebralBypass.htm|website=mayvfieldclinic.com|publisher=Mayfield Brain and Spine|title=What is Cerebral Bypass Surgery?|access-date=8 April 2010}}</ref>

There are two main types of cerebral artery bypass: direct and indirect. Direct revascularization is also known as EC-IC bypass because it involves directly connecting an extracranial artery outside the brain to an intracranial artery inside the brain. This is also sometimes called STA-MCA bypass because the superficial temporal artery and the middle cerebral artery are the most commonly used arteries for the surgery.<ref>{{cite web |title=Direct Revascularization |url=https://stanfordhealthcare.org/medical-conditions/brain-and-nerves/moyamoya/treatments/direct-revascularization.html |website=Stanford Healthcare |publisher=Stanford Medicine |access-date=17 November 2023}}</ref> STA-MCA bypass surgery has been shown to be ineffective in reducing the risk of ischemic stroke in an international, randomized clinical trial.<ref name = "ECIC">{{cite journal |last1=Barnett |first1=HJM |last2=The EC/IC bypass study group |title=Failure of extracranial-intracranial arterial bypass to reduce the risk of ischemic stroke. Results of an international randomized trial |journal=New England Journal of Medicine |date=1985 |volume=313 |issue=19 |pages=1191–1300 |doi=10.1056/NEJM198511073131904 |pmid=2865674}}</ref> Indirect revascularization involves placing part of an artery, in the case of EDAS (encephaloduroarteriosynangiosis), or part of a muscle, in the case of EMS (encephalomyosynangiosis), on the surface of the brain and allowing it to revascularize the brain through new vessel growth. Both types of indirect revascularization typically take 3-6 months to see effects.<ref>{{cite web |title=Indirect Revascularization |url=https://stanfordhealthcare.org/medical-conditions/brain-and-nerves/moyamoya/treatments/indirect-revascularization.html |website=Stanford Healthcare |publisher=Stanford Medicine |access-date=17 November 2023}}</ref>

When several arteries are blocked and several bypasses are needed, the procedure is called multiple bypass. The number of bypasses needed does not always increase the risk of surgery, which depend more on the patient's overall health.

==Evaluation==

Prior to constructing a bypass, most surgeons will obtain or perform an imaging study to determine the severity and location of the diseased blood vessels. For cardiac and lower extremity disease, this is usually in the form of an [[angiogram]]. For hemodialysis access, this can be done with ultrasound. Occasionally, a [[CT angiogram]] will take the place of a formal angiogram.<ref>{{cite journal |last1=Menzoian |first1=JO |last2=La Morte |first2=WW |last3=Cantelmo |first3=NL |last4=Doyle |first4=J |last5=Sidawy |first5=AN |last6=Savenor |first6=A |title=The preoperative angiogram as a predictor of peripheral vascular runoff. |journal=American Journal of Surgery |date=September 1985 |volume=150 |issue=3 |pages=346–52 |doi=10.1016/0002-9610(85)90076-5 |pmid=4037194}}</ref>

==Contraindications==
The lack of an adequate venous conduit is a relative contraindication to bypass surgery, and depending on the area of disease, alternatives may be used. Medical conditions such as [[ischemic heart disease]] or [[chronic obstructive pulmonary disease]] that increase the risk of surgery are also relative contraindications. For coronary and peripheral vascular disease, lack of "runoff" to the distal area is also a contraindication because a vascular bypass around one diseased artery to another diseased area does not solve the vascular problem.<ref>{{cite journal |last1=Mannick |first1=JA |title=Femoro-popliteal and femoro-tibial reconstructions. |journal=The Surgical Clinics of North America |date=August 1979 |volume=59 |issue=4 |pages=581–96 |doi=10.1016/s0039-6109(16)41882-7 |pmid=157542}}</ref>

If a patient is deemed to be too high-risk to undergo a bypass, he or she may be a candidate for [[angioplasty]] or [[stent]]ing of the relevant vessel.<ref name="UpToDate LEB">{{cite journal |title=UpToDate: Lower extremity bypass techniques |website=www.uptodate.com |url=https://www.uptodate.com/contents/management-of-chronic-limb-threatening-ischemia?sectionName=COUNSELING%20THE%20HIGH-RISK%20PATIENT&search=angioplasty%20vs%20bypass&topicRef=15194&anchor=H3044923355&source=see_link#H3300240228}}</ref>

==Techniques==

===Standard techniques===
Dogma in vascular bypass technique says to obtain [[Anatomical terms of location#Proximal and distal|proximal]] and [[Anatomical terms of location#Proximal and distal|distal]] control. This means that in a vessel with flow through it, a surgeon must have exposure of the furthest and nearest extents of the blood vessel in which the bypass is being created, so that when the vessel is opened, blood loss is minimized. After the necessary exposure, clamps are usually used on both the proximal and distal end of the segment. Exceptions exist where there is no blood flow through the target vessel at the area of proposed entry, as is the case with an intervening occlusion.

If the organ perfused by an artery is sensitive to even temporary occlusion of blood flow, such as in the brain, various other measures are taken.<ref name="Cochrane carotid shunt">{{cite journal |title=Cochrane review - carotid shunting | date=2022 | doi=10.1002/14651858.CD000190.pub4 | pmid=35731671 | last1=Chuatrakoon | first1=B. | last2=Nantakool | first2=S. | last3=Rerkasem | first3=A. | last4=Orrapin | first4=S. | last5=Howard | first5=D. P. | last6=Rerkasem | first6=K. | journal=The Cochrane Database of Systematic Reviews | volume=2022 | issue=6 | pages=CD000190 | pmc=9216235 }}</ref>

===ELANA===
{{Main|Excimer laser-assisted nonocclusive anastomosis}}
In [[neurosurgery]], excimer laser assisted non-occlusive anastomosis (ELANA) is a technique used to create a bypass without interrupting the blood supply in the recipient blood vessels. This reduces the risk of stroke or a rupture of an [[aneurysm]].

==Risks and complications==
Several complications can arise after vascular bypass.<ref>{{cite web|title=What Are the Risks of Coronary Artery Bypass Grafting?|url=https://www.nhlbi.nih.gov/health/health-topics/topics/cabg/risks|website=nhlbi.nih.gov|publisher=National Institutes of Health — National Heart, Lung, and Blood Institute|access-date=11 November 2016}}</ref>

Risks of the bypass:{{cn|date=July 2024}}
* '''Acute graft occlusion''' is the occlusion (blockage) of a vascular bypass graft shortly after the bypass is performed. Its causes, which are distinct from those of [[vein graft failure|chronic graft occlusion]], include technical failure (e.g. [[Surgical anastomosis|anastomotic]] stricture, incomplete [[valve lysis]] in non-reversed vein) and thrombosis. It is rare, but almost always requires [[Surgery#terminology|reoperation]].

General risks of surgery:{{cn|date=July 2024}}
* [[Hemorrhage]] (bleeding)
* [[Infection]]
* [[Embolism]]

==Recovery==
Immediately following coronary artery or neurosurgical vascular bypass surgery, patients recover in an [[intensive care unit]] or [[coronary care unit]] for one to two days. Provided that recovery is normal and without [[Complication (medicine)|complications]], they can move to a less intensively monitored unit such as a [[step-down unit]] or a [[Medical ward|ward bed]]. Depending on the extent of the surgery, recovery from a leg bypass may start from a step-down or ward bed. [[Monitoring (medicine)|Monitoring]] immediately after bypass surgery focuses on signs and [[symptom]]s of bleeding and graft occlusion. If bleeding is detected, treatment can range from [[Blood transfusion|transfusion]] to [[Surgery#terminology|reoperation]]. Later on in the hospital course, common complications include [[Infection#Primary versus opportunistic|wound infections]], [[pneumonia]], [[urinary tract infection]], and graft occlusion.<ref name=NIHafter>{{cite web|title=What To Expect After Coronary Artery Bypass Grafting|url=https://www.nhlbi.nih.gov/health/health-topics/topics/cabg/after|website=nhlbi.nih.gov|publisher=National Institutes of Health — National Heart, Lung, and Blood Institute|access-date=11 November 2016}}</ref>

At discharge, patients are often prescribed oral painkillers, and should be prescribed a [[statin]] and an [[Antiplatelet drug|anti-platelet medication]] if not contraindicated and their bypass was performed for [[atherosclerosis]], (e.g., [[peripheral vascular disease]] or [[coronary artery disease]]). Some patients start feeling normal after one month, while others may still experience problems several months after the procedure.<ref name=NIHafter/>

During the first twelve weeks after most bypass operations, patients are advised to avoid heavy lifting, house work, and strenuous recreation like [[golf]], [[tennis]], or [[Swimming (sport)|swimming]] while their surgical wounds heal, particularly the sternum after coronary bypass.<ref name=NIHafter/><ref name="ehealth">{{cite web|url=http://www.ehealthmd.com/library/cardiacbypass/CB_life.html|title=Life After Bypass Surgery|access-date=8 April 2010}}</ref>

Part of the recovery after any bypass surgery includes regular visits to a physician to monitor the patient's recovery. Normally a follow-up visit with a surgeon is scheduled for two to four weeks after surgery. The frequency of these visits gradually lessens as the patient's health improves.<ref name=NIHafter/>

For vascular bypass operations performed for atherosclerosis, the operation does not cure the metabolic problem that led to the vascular disease. Lifestyle changes that include [[quitting smoking]], making [[diet (nutrition)|diet]] changes, and getting regular exercise are required to cure the underlying condition.<ref name=NIHafter/><ref>{{cite web|url=http://www.medic8.com/healthguide/articles/heartbypasssurgery.html|title=Heart Bypass Surgery|access-date=8 April 2010}}</ref>

==References==
{{reflist|2}}

==External links==
* {{Commonscatinline}}

{{Cardiac procedures}}
{{Vascular procedures}}
{{Organ transplantation}}

[[Category:Implants (medicine)]]
[[Category:Neurosurgery]]
[[Category:Vascular surgery|Bypass]]