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SECTION 7 Technical aspects ofcoronary artery bypass graft surgery368
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7. Lawrie GM, Morris GC, Silvers A, Wagner WF, Baron AE,
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8. Takanashi S, Fukui T, Miyamoto Y. Coronary endarterectomy in
the le anterior descending artery. J Cardiol. 2008;52(3):261– 8.
9. Vohra HA, Kanwar R, Khan T, Dimitri WR. Early and late
outcome aer o- pump coronary artery bypass gra surgery with
coronary endarterectomy:a single- center 10- year experience.
Ann orac Surg. 2006;81(5):1691– 6.
10. Walley VM, Byard RW, Keon WJ. A study of the sequential
morphologic changes aer manual coronary endarterectomy. J
orac Cardiovasc Surg. 1991;102(6):890– 4.
11. Wang J, Gu C, Yu W, Gao M, Yu Y. Short- and long- term
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and coronary artery bypass graing:a meta- analysis of 63,730
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12. Marinelli G, Chiappini B, Di Eusanio M, Di Bartolomeo R,
Caldarera I, Marrozzini C, etal. Bypass graing with coronary
endarterectomy:immediate and long- term results. J orac
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13. Byrne JG, Karavas AN, Gudbjartson T, Leacche M, Rawn
JD, Couper GS, etal. Le anterior descending coronary
endarterectomy:early and late results in 196 consecutive patients.
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14. Kato Y, Shibata T, Takanashi S, Fukui T, Ito A, Shimizu Y. Results of
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Endarterectomy of the le coronary system. Analysis of a 10year
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53
Redo coronary artery bypassgraing
Faisal G. Bakaeen and Lars G. Svensson
Introduction
Patients who undergo redo coronary artery bypass graing (CABG)
are older, have more comorbidities, and a greater atherosclerotic
burden than those who undergo primary CABG. In addition, redo
CABG is technically more demanding than primary CABG. Sternal
re- entry may be challenging because of the proximity of cardiovascular structures, including previous bypass gras that could be at
risk for injury. Furthermore, dissecting out the heart for cardiopulmonary bypass (CPB) and exposing the coronary targets may
be complicated by scar tissue and suboptimal dissection planes,
with additional risk of injury to patent conduits or inadvertent manipulation of diseased conduits that can result in thromboembolic
complications and ischaemia. Eective myocardial protection is
important in redo CABG, but anatomical limitations must be overcome in patients with severe diuse native disease or areas supplied
by occluded gras. In addition, patent le internal thoracic arteries
(LITAs) in redo CABG patients introduce an extra level of complexity in intraoperative management.
Frequency of redo CABG cases has declined over time, reducing
the experience of surgeons in managing them. According to the
Society of oracic Surgeons Adult Cardiac Surgery Database, cumulative incidences of any redo CABG in patients aged 65years
or older were low:0.1%, 0.6%, 1.3%, and 1.7%, at 1, 5, 10, and
18years aer surgery, respectively. is nding is multifactorial
and likely due to improved medical care, aggressive percutaneous
interventions, and use of the LITA to the le anterior descending
coronary artery (LAD) and other arterial gras with improved
gra patency.
e purpose of this chapter is to review work- up and management options for patients undergoing redo CABG, with emphasis
on safe and eective operative strategies that improve outcomes.
derive no survival benet from reintervention. Reintervening in patients with a patent LITA- to- LAD gra may be warranted to relieve
symptoms, without expecting a survival benet.
In addition to routine testing that primary CABG patients undergo,
preoperative testing to assess the availability and quality of conduits
is particularly important for redo CABG patients in whom concerns
exist about the availability of adequate conduits. Internal thoracic arteries (ITAs) may be imaged at the time of diagnostic coronary angiography, providing useful information about their integrity and ruling
out the possibility of their injury during previous surgery. Flow in the
in situ ITA may also be detected by transthoracic ultrasound scanning.
Routine use of preoperative multidetector computed tomography
angiography in redo CABG is recommended to detect high- risk
ndings, such as proximity of cardiovascular structures and conduits
to the posterior table of the sternum, ascending aorta calcication,
and pseudoaneurysms. Adoption of preventive surgical strategies
in such risky scenarios can enhance the safety of reoperations and
improve outcomes.
Previous endoscopic vein harvesting makes it dicult to determine how much vein was previously harvested. Ultrasonographic
vein mapping provides useful information about the size and quality
of the greater and lesser saphenous veins available for harvest. e
Allen test or more sophisticated transcutaneous pulse oximetry
testing is used to determine if radial arteries could be used. Recent
instrumentation for diagnostic coronary angiography precludes use
of the accessed radial artery.
Finally, the importance of a complete and well- performed coronary angiogram cannot be overemphasized. is is essential to detect potential targets that are underlled or completely missed if the
angiographic technique is inadequate.
Operativestrategy
Patient selection and preoperativetesting
Patients with LAD disease with or without an occluded LAD gra
stand to benet the most from redo CABG, especially if a LITA
is available and the distal LAD is a good target. Patients with patent LITA- to- LAD gras who develop non- LAD territory jeopardy
Patients should be prepped and draped in the usual fashion.
Debrillation paddles should be secured in place in case a shock
must be delivered before the heart is completely dissected out.
Routine monitoring lines are placed, including a Swan– Ganz catheter, especially if there is ventricular dysfunction. Transoesophageal
echocardiography (TOE) is used routinely in all CABG cases. Some
SECTION 7 Technical aspects ofcoronary artery bypass graft surgery370
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surgeons routinely expose the femoral artery and vein in case emergency cardiopulmonary bypass may be needed.
Our preference is to perform revascularization using the onpump technique, but o- pump surgery is used selectively in certain
anatomical and physiological scenarios where avoiding ascending
aorta manipulation and CPB may be benecial. Examples include
porcelain or heavily diseased ascending aortas, alternative access
CABG (see following section), and cirrhosis or liver dysfunction.
Other operative strategies, including on- pump beating heart
CABG or hypothermic cardiac brillatory arrest, are used sparingly
if the preference is to avoid aortic clamping and cardioplegic arrest.
Cannulation strategy and cardiopulmonarybypass
Cut- down and exposure of the femoral artery and vein should be
considered if the need for CPB arises before the heart is exposed for
central cannulation. Alternatively, femoral vessels may be accessed
percutaneously with or without ultrasound guidance, with wires or
catheters le in place ready for a Seldinger technique insertion of
percutaneous cannulas should the need arise.
When CPB before sternal re- entry is indicated, our preference is
to use a gra sewn to the right axillary artery for inow and a percutaneous femoral cannula advanced into the superior vena cava with
TOE guidance for venous drainage (Fig. 53.1).
e right side of the heart is dissected out rst aer exposing the
distal aorta, starting at the diaphragmatic surface, where the tissue
planes tend to be more easily dened. Next, the aorta is dissected to
allow cannulation and clamping. Ano- touch technique is recommended when handling diseased venous conduits to minimize risk
of atheromatous plaque embolization.
Dissection of the le side of the heart is best performed on CPB,
starting at the diaphragm and sweeping up to the LITA and vein
bypasses. e LITA is best located superiorly medial to the lung
(Fig. 53.2). Dissection of the latter o the mediastinal structures
and LITA is usually accomplished through a user- friendly dissection plane. Astrip of pericardium may be le attached to the LITA
and heart if adhesions are intense, to minimize the risk of injuring
the LITA. e LITA is controlled with a bulldog clamp aer the
aorta is clamped. If the LITA cannot be exposed, systemic cooling
to 22°C is an option. In this scenario, retrograde cardioplegia is especially useful.
Full dissection and mobilization of the entire heart is usually
needed to expose the coronary targets, especially in the circumex
territory. Old gras are helpful in guiding the surgeon to the target
vessels, but, in general, nding targets in redo CABG is more challenging than primary cases because of scar tissue.
Sternal re- entry and cardiacdissection
Safe sternal re- entry is carefully planned and guided by preoperative computed tomography angiography. Use of an oscillating saw is
recommended. e anterior sternal table is cut rst, followed by a
deeper cut towards the posterior table. Sternal wires may be cut and
le in place to help gauge the depth of the saw blade, and then removed (Fig. 53.1). Sternal edges are lied by an assistant, and edges of
the sternum are gently pushed apart by the saw blade to facilitate their
separation. Going on- pump before sternal re- entry decompresses the
heart and allows it to fall away from the sternum with ease, potentially reducing risk of injury. oracotomy counter- incisions are used
in rare circumstances to allow direct access for dissecting structures
away from the posterior sternal table ahead of sternal re- entry.
Electrocautery and scissors are then used to complete division of
the posterior table and free up the sternal edges to allow placement
of a retractor. Care should be taken to avoid injury to the lungs or
other vital structures. Minor injuries to the lungs such as denuding
of the parenchyma can be managed conservatively, but deeper lacerations require suture repair or stapling o the damaged segment.
Dissection on the le side is usually limited at this stage to avoid
injury to a patent LITA and is best performed when the patient is
ready for or on CPB.
A patent right ITA crossing the midline to a LAD may be at risk
of injury if close to the posterior table of the sternum. Leaving the
posterior table of the sternum intact and carefully completing the
sternotomy working from caudad to cephalad towards the area at
risk can allow for enough space to allow for safe sharp dissection
of the ITA with or without a layer of periosteum attached to it. e
team should be ready to go on bypass and have a salvage strategy in
place should the ITA be injured.
bb
aa
dd
cc
Fig.53.1 Axillary cannulation and right femoral cannulation are useful in
high- risk scenarios where sternal re- entry and mediastinal dissection are
best performed on CPB. An oscillating saw is used for controlled re- entry.
The Cleveland Clinic Center for Medical Art & Photography © All Rights Reserved.
Fig.53.2 Dissection of patent LITA graft best identified medial to
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the lung.
53 Redo coronary artery bypassgrafting 371
appropriate selection of target vessels to avoid competitive ow and
enhance radial gra patency is important. Gastroepiploic arteries
pose challenges related to limited gra length, variation in size,
small distal diameter, and vulnerability to spasm and are rarely used
in North America and Europe, although some centres in Asia use
them and report good outcomes.
Construction of the anastomosis is performed distal to the occlusive disease and beyond the previous gra; hence, longer conduits
are generally needed than in primary CABG. Sequential graing
and composite arterial constructs (Fig. 53.3) can help maximize
areas supplied by arterial conduits and conserve conduit requirements. In certain patients with appropriate anatomy, and depending
on the quality of the tissues, recycling of patent arterial gras is a
useful option. Diseased but non- occluded venous gras from previous surgery are not ligated, to minimize the potential risk of ischaemia when ow through a new arterial gra may be insucient
because of ‘immaturity’ or potential perioperative spasm.
Myocardialprotection
Myocardial protection is the cornerstone of successful redo CABG.
Cardioplegia is administered antegrade and retrograde. e latter is
particularly helpful in accomplishing good myocardial protection
because antegrade delivery may not reach myocardial territories
with compromised arterial inow. Retrograde cardioplegia will
oen ush out embolic material from atheromatous diseased vein
gras. If diculty is encountered in placing the retrograde cannula
through the right atrial wall and with manual and TOE guidance,
then double venous cannulation is used with control of the superior
and inferior vena cavae, and the cannula is placed into the coronary
sinus under direct vision and secured with a purse- string suture that
is snared down.
Myocardial temperature monitoring is a useful adjunct to conrm adequate cooling and myocardial protection. Systemic cooling
(typically 28°C) may be used for supplementary protection, but a
lower temperature is required if patent ITAs are not controlled and
continue to perfuse the heart.
Choice ofconduit and graftingstrategy
aa
dd
bb
cc
e conduit of choice for LAD revascularization is a LITA if it was
not used in the primary operation. Alarge Cleveland Clinic study
demonstrated that LITA- to- LAD graing at reoperation is safe and
confers a risk- adjusted survival advantage. LITA graing of the
LAD at reoperation resulted in an absolute mortality risk reduction
of 6.0% and a hazard ratio of 0.85. If there is a large territory involved
supplied by a patent vein gra, it is wise to leave the vein gra intact.
Additional arterial gras should be considered, especially in
younger patients with favourable risk proles. In patients in whom
the LITA had been previously used, harvesting the right ITA
does not appear to increase the risk of deep sternal wound infection. Radial graing in redo CABG has been associated with improved outcomes. Patency of radial arteries is diminished when
they are graed to vessels that are not severely stenosed. erefore,
Fig.53.3 Acomposite arterial graft configuration off the LITA pedicle
conserves on conduit length and maximizes the number of targets
receiving arterial grafting.
The Cleveland Clinic Center for Medical Art & Photography © All Rights Reserved.
SECTION 7 Technical aspects ofcoronary artery bypass graft surgery372
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Proximal anastomoses are performed with a single aortic clamp
and may be taken o the hood of previous gras or o fresh areas of
the aorta if space allows.
old gras when present. Once the target vessel is identied, attention is usually turned to the proximal anastomosis. Advantages of
performing the proximal anastomosis rst include more precise
gra length measurement, the opportunity to ush atherosclerotic
Alternative (non- sternotomy) approaches
forredoCABG
debris from the gra before completing the distal anastomosis, and
immediate establishment of ow upon completion of the distal
anastomosis.
In addition to preoperative computed tomography angiography
In patients with a patent LITA- to- LAD gra and signicant myocardial ischaemia in a sizable non- LAD territory not amenable to
percutaneous intervention, sternal- sparing alternative surgical
strategies with or without CPB may be considered. Such strategies
can reduce risk of cardiac injury and damage to patent gras and
avoid manipulation of the ascending aorta, especially if calcied or
diseased. O- pump redo CABG for the circumex and its branches
via a le posterolateral thoracotomy is a useful option in the armamentarium of cardiac surgeons.
Our approach to a le thoracotomy redo CABG includes doublelumen endotracheal tube placement. Aer conduit harvesting, the
patient is repositioned in a right lateral decubitus position with the
pelvis externally rotated (45°) to allow access to the femoral vessels should cannulation for CPB become necessary. e le lung is
deated, and an incision is made in the fourth or h intercostal
space. e lung is dissected free and the inferior pulmonary ligament incised. In the presence of a patent LITA- to- LAD bypass, the
anteromedial aspect of the lung is dissected from the pericardium
only enough to locate the circumex target. In such instances, the
LITA gra is usually not encountered.
e pericardium is opened posterior to the phrenic nerve.
Limited dissection is performed to locate the target vessel, tracing
assessment of the descending aorta, the aorta is assessed further by
TOE or epiaortic echocardiography. Heparin (10,000 units) is administered and the activated clotting time maintained at longer than
300 seconds. e proximal anastomosis is constructed with aid of a
side- biting clamp on the descending aorta. If the descending aorta
is signicantly diseased, the le subclavian artery is used for inow.
In the case of a patent LITA- to- LAD gra, a test occlusion of the
subclavian artery is conducted before proceeding with the proximal
anastomosis.
e distal anastomosis is completed using a proximal snare and
an o- pump stabilizing platform. Acarbon dioxide blower is used to
aid visualization. Endovascular shunts are not routinely used. Gras
originating from the le subclavian artery and proximal descending
aorta are routed anterior to the pulmonary hilum (Fig. 53.4). Gras
are examined with the lung inated to ensure a smooth course with
no kinking.
Minimally invasive direct CABG for the right coronary artery
and its branches utilizing the right gastroepiploic artery via a
subxiphoid incision has been reported to have good outcomes,
but experience with this approach is limited. We have used this
approach selectively to bypass large branches of the right coronary
ar ter y.
Fig.53.4 Redo CABG via left posterolateral thoracotomy. The pericardium is opened posterior to the phrenic nerve, and the distal anastomosis is
constructed to an obtuse marginal vessel distal to the previous venous graft. The new vein graft lies anterior to the hilum of the lung.
The Cleveland Clinic Center for Medical Art & Photography © All Rights Reserved.
53 Redo coronary artery bypassgrafting 373
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Outcomes
Technical diculties associated with redo CABG are reected in
most published reports in the increased perfusion and ischaemic
times despite fewer bypass gras compared with primary CABG.
e challenges of adequate myocardial protection and higher incidence of incomplete revascularization contribute to a higher incidence of postoperative low cardiac output syndrome and increased
morbidity and mortality in redo CABG.
Nationally, according to the Society of oracic Surgeons risk
model, redo CABG is associated with increased perioperative mortality (odds ratio, 3.1 vs rst operation). However, CABG outcomes
can approach those of primary CABG for risk- matched patients in
centres with large experience, including our centre. e importance of experience in reoperative CABG cannot be overstated.
Routine post- CABG care includes optimal medical therapy and
secondary preventative strategies to optimize short- and long- term
outcomes.
REFERENCES
1. Yau TM, Borger MA, Weisel RD, Ivanov J. e changing pattern
of reoperative coronary surgery:trends in 1230 consecutive
reoperations. J orac Cardiovasc Surg. 2000;120(1):156– 63.
2. Bakaeen FG. Invited commentary. Ann orac Surg. 2011;92(4):
1267– 8.
3. Fosbøl EL, Zhao Y, Shahian DM, Grover FL, Edwards FH,
Peterson ED. Repeat coronary revascularization aer coronary
artery bypass surgery in older adults:the Society of oracic
Surgeons’ national experience, 1991– 2007. Circulation.
2013;127(16):1656– 63.
4. Subramanian S, Sabik JF 3rd, Houghtaling PL, Nowicki ER,
Blackstone EH, Lytle BW. Decision- making for patients
with patent le internal thoracic artery gras to le anterior
descending. Ann orac Surg. 2009;87(5):1392– 8.
5. Kamdar AR, Meadows TA, Roselli EE, Gorodeski EZ, Curtin RJ,
Sabik JF, etal. Multidetector computed tomographic angiography
in planning of reoperative cardiothoracic surgery. Ann orac
Surg. 2008;85(4):1239– 45.
6. Sabik JF 3rd, Raza S, Blackstone EH, Houghtaling PL, Lytle BW.
Value of internal thoracic artery graing to the le anterior
descending coronary artery at coronary reoperation. J Am Coll
Cardiol. 2013;6(3)1:302– 10.
7. Svensson LG, Mumtaz MA, Blackstone EH, Feng J, Banbury MK,
Sabik JF, etal. Does use of a right internal thoracic artery increase
deep wound infection and risk aer previous use of a le internal
thoracic artery? J orac Cardiovasc Surg. 2006;131(3):609– 13.
8. Zacharias A, Schwann TA, Riordan CJ, Durham SJ, Shah AS,
Engoren M, Habib RH. Late outcomes aer radial artery versus
saphenous vein graing during reoperative coronary artery
bypass surgery. J orac Cardiovasc Surg. 2010;139(6):1511– 8.
9. Aldea GS, Bakaeen FG, Pal J, Fremes S, Head SJ, Sabik J, etal.
e Society of oracic Surgeons clinical practice guidelines on
arterial conduits for coronary artery bypass graing. Ann orac
Surg. 2016;101(6):801– 9.
10. El Oumeiri B, Glineur D, Price J, Boodhwani M, Etienne PY,
Poncelet A, etal. Recycling of internal thoracic arteries in
reoperative coronary surgery:in- hospital and midterm results.
Ann orac Surg. 2011;91(4):1165– 8.
11. Turner FE, Lytle BW, Navia D, Loop FD, Taylor PC, McCarthy
PM, etal. Coronary reoperation:results of adding an internal
mammary artery gra to a stenotic vein gra. Ann orac Surg.
1994;58(5):1353– 5.
12. Azoury FM, Gillinov AM, Lytle BW, Smedira NG, Sabik JF.
O- pump reoperative coronary artery bypass graing by
thoracotomy:patient selection and operative technique. Ann
orac Surg. 2001;71(6):1959– 63.
13. Shahian DM, etal. e Society of oracic Surgeons 2008 cardiac
surgery risk models:part1— coronary artery bypass graing
surgery. Ann orac Surg. 2009;88(1 Suppl):S2– 22.
14. Sabik JF, 3rd, Blackstone EH, Houghtaling PL, Walts PA, Lytle
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5 4
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Avoiding stroke duringcoronary artery
bypassgra ing
Gil Bolotin , Michael J. Mack , Antonino Di Franco , John D. Puskas, and Zvi Peled
Background
Stroke is the most devastating non- cardiac complication of cardiac
surgery. It is second only to heart failure as a cause of morbidity and
mortality and increases signi cantly the likelihood of requiring
long- term care.
prolonged hospitalization, and long- term disability) were described
as the main concern of patients undergoing invasive procedures
by Sun and colleagues in a survey involving 3112 cardiac patients
in 2018.
Periprocedural neurological events during cardiac surgery remain
prevalent, with stroke reported in 2– 5% of patients undergoing cardiac surgery and increasing to more than 10% in octogenarians.
Large single- centre studies and the most recent data from the
Society of oracic Surgeons Adult Cardiac Surgery Database (STSACSD) show a perioperative mortality close to 20% for patients who
su ered a stroke a er coronary artery bypass gra ing (CABG).
–
Stroke sequelae (with speci c reference to death,
–
,
Mechanisms
e mechanisms by which stroke occurs following CABG are well
established. It is likely that the cause is multifactorial in many cases.
e aetiology of stroke varies depending on the speci c timing of
its occurrence. Intraoperative stroke is mainly due to embolism,
hypoperfusion, and generalized in ammatory and hypercoagulable
states. In contrast, stroke in the early postoperative period ( rst
7 days) is largely caused by arrhythmias and haemodynamic instability while stroke in the late phase (beyond 7days) is primarily
predicted by the overall atherosclerotic risk pro le of patient and the
development of postoperative atrial brillation. Anaemia is also
strongly associated with the risk of adverse perioperative and postoperative outcomes, including stroke.
Embolism
Adverse neurological outcomes following CABG are o en attributed to micro- and macro- emboli. e most common source of emboli is the ascending aorta in which atherosclerosis is documented
in more than 50% of CABG patients. Atheromatous material may
be dislodged during surgical manipulation (cannulation, crossclamping, side- biting, decannulation) in on- pump CABG,
demonstrated by a number of studies utilizing both intra- aortic
embolic lters and Doppler techniques. ese studies con rmed
a substantial risk of embolization at the time of aortic clamping/
unclamping.
Other sources for emboli may be cardiac, such as in the case of
pre- existing or new- onset atrial brillation or preoperative/ perioperative acute transmural myocardial infarction causing le ventricular systolic dysfunction and promoting formation of thrombus
on the injured endocardial surface of the le ventricle.
ere is also a threat of macro- or microscopic air emboli from
the bypass machine or from routine surgical manipulations themselves, such as inadvertent air during ushing of the coronaries and
the opening of the aorta during distal and proximal anastomosis.
Microemboli are distributed in proportion to blood ow; thus, reduced cerebral blood ow reduces microembolic injury although it
may increase the risk of hypoperfusion. Massive air embolism may
cause great ischaemic injury, but gaseous microemboli may also directly damage the endothelium, in addition to blocking blood ow, as
shown in a rabbit model.
,
,
as
Hypoperfusion
Cerebral hypoperfusion resulting from hypotension during surgery,
pre- existent large or small vessel intra- or extracranial vascular stenosis, or chronic hypertensive changes may cause haemodynamic or
‘watershed’ strokes.
In a study evaluating a total of 98 patients with postoperative
stroke, Gottesman etal. found that bilateral watershed strokes
were diagnosed in 48% of magnetic resonance imaging and 22% of
computed tomography (CT) scans; of note, a decrease in mean arterial pressure of 10mmHg or more was shown to be an important
predictor of watershed strokes (odds ratio (OR) 4.06, 95% con dence interval (CI) 1.03– 15.98).
Hypoperfusion may accompany or be accentuated by the systemic
in ammatory response, which may also be a presumed source of
neurological injury.
–
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Hypercoagulablestate
A systemic hypercoagulable state occurs aer any major surgery
due to vessel manipulation, dehydration leading to elevated blood
viscosity, and activation of the coagulation cascade. Conventional
cardiopulmonary bypass (CPB) interferes with normal haemostasis
by diluting haemostatic cells and proteins, through reinfusion of
shed blood, and through activation in the bypass circuit surface of
multiple systems including platelets, the kallikrein– kinin system,
and brinolysis. In the setting of CPB, soluble and circuit- bound
brin provide a huge surface for plasminogen activation to occur,
leading to a 10- to 100- fold increase in plasmin generation shortly
aer the commencement of CPB,; moreover, plasmin generation,
along with brin degradation, remains increased 10- to 20- fold
throughout the duration of CPB. During on- pump CABG surgery,
although systemic anticoagulation is routine during CPB, the need
for heparin reversal and the use of antibrinolytic agents, and sometimes blood products such as fresh frozen plasma and platelets, can
create a transient hypercoagulable state, which may contribute to
stroke risk.
Meticulous assessment of medical history and physical examination before any cardiac surgery is mandatory. Identication of
previously unrecorded issues, such as claudication, absent pulses
suggesting peripheral vascular disease, audible bruits suggesting carotid stenosis, and atrial brillation allow a tailored approach to risk
reduction. All patients should be assessed by a risk score, such as the
EuroSCORE (http:// www.euroscore.org) or the STS score (https://
www.sts.org):a high morbidity and mortality score for a given patient will also indicate a higher probability of developing perioperative stroke.
Concomitant carotid arterydisease
Some centres perform routine screening carotid duplex ultrasonography in all patients before CABG while other centres perform it
only in selected cases. is imaging method should be strongly considered in patients who have peripheral artery disease, have a history
of stroke or transient ischaemic attack (TIA), or if an audible bruit
is found at the time of physical examination. It is also important in
patients with signicant smoking history or le main coronary disease, since both conditions are associated with a higher incidence of
carotid stenosis.,
Risk factors forstroke
To date, however, studies are inconclusive and oen contradictory regarding the indications for carotid endarterectomy
prior to or during CABG. European guidelines support carotid
Cardiovascular and cerebrovascular risk factors largely overlap and
include among others age, dialysis dependency, severe chronic lung
disease, emergency surgery, and atherosclerotic burden in the coronary artery and other vascular beds., Many patients who are
scheduled for CABG will have signicant carotid stenosis, and almost 50% of patients who need carotid interventions have concomitant ischaemic coronary disease.–
With reference to the specic setting of CABG, known independent risk factors for intraoperative stroke are a calcied ascending aorta (OR 2.0, 95% CI 1.2– 3.3), emergency operation (OR
3.1, 95% CI 2.1– 4.8), age (OR 8.5, 95% CI 3.2– 22.0), history of
smoking (OR 1.6, 95% CI 1.1– 2.2), peripheral and carotid arterial
disease (OR 2.0, 95% CI 1.5– 2.6), hypertension (OR 1.8, 95% CI
1.2– 2.8), history of neurological events (OR 2.1, 95% CI 1.5– 3.0),
redo surgery (OR 1.4, 95% CI 1.02– 1.79), moderate or severe le
ventricular dysfunction (OR 1.5, 95% CI 1.15– 1.94), and preoperative atrial brillation (OR 2.4, 95% CI 1.4– 4.2).
Marked hypotension during surgery carries an 8.4- fold increased
risk for intraoperative stroke; similarly, manipulation of a severely
diseased ascending aorta carries an increased risk of neurological
complications (OR 5.32, 95% CI 3.44– 8.22). Furthermore, Likosky
etal. showed among 11825 patients undergoing CABG that a prolonged bypass time was a strong predictor of stroke, especially with
durations of at least 114 minutes (adjusted OR 2.36).
revascularization in CABG patients where there is a recent history
of stroke/ TIA (<6months) (classIIa, level of evidence (LOE) B); carotid revascularization might be considered in case of neurologically asymptomatic patients with bilateral 70– 99% carotid stenosis
or 70– 99% carotid stenosis and contralateral occlusion (IIb, LOE
C), provided that a multidisciplinary evaluation of the patients
is performed. Similarly, American guidelines support carotid
revascularization in patients scheduled for CABG in case of previous stroke/ TIA and signicant (50– 99%) carotid artery stenosis
(IIa, LOE C), while it could be considered in those with no history
of stroke/ TIA but with bilateral severe (70– 99%) carotid stenoses
or a unilateral severe carotid stenosis with a contralateral occlusion
(IIb, LOE C). ere is no widely recognized advantage in performing a combined carotid endarterectomy and coronary bypass
procedure, unless both vascular beds are causing active unstable
symptoms. While it has been argued that carotid stenting may be
benecial,,, management of aggressive antiplatelet therapy aer
carotid stenting may complicate the timing and performance of
CABG surgery.
Knowledge of the presence of carotid stenosis is important even
if revascularization of the carotid arteries is not planned. During
CABG in such patients, sustained hypotension should be scrupulously avoided; it is also recommended to maintain a relatively high
mean arterial blood pressure before, during, and aer the interval of
CPB, in order to optimize cerebral blood ow.–
Strokeprevention
e main strategy to reduce the risk of adverse neurological events
is to individualize perisurgical management strategies for high- risk
patients. Screening for the above- mentioned risk factors is crucial
to identify patients who are at higher risk of neurological complications, allowing formal identication and focused mitigation against
pre- existing risk factors.
Preoperative assessment oftheaorta
Evaluation of the ascending aorta to detect calcication and atherosclerotic plaques is essential for the operative plan. During surgery,
plaques or calcium debris from a pathological aorta can be dislodged,
resulting in emboli to the cerebral arteries, causing ischaemia.
Signs of a calcied aorta can be detected in a preoperative chest Xray and on the preoperative coronary angiogram. If calcication is
detected or there is concern about a diseased aorta, a CT scan of the
54 Avoiding stroke duringcoronary artery bypassgrafting 377
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chest (without contrast) is suggested to further demonstrate the location, extent, and severity of the disease and to help plan surgery.
Preoperative CT (as opposite to intraoperative techniques, e.g.
epiaortic scanning) allows discussion of alternate strategies before
sternotomy is performed; this, in turn, can lead to signicant alteration of surgical strategy, as demonstrated by Lee and co- workers.
ese authors reported stroke rates of 3.04% and 0.73% in the pre-
and post- CT periods (P=0.05), respectively, highlighting the potential for improvement in patient outcomes.
Planning surgery for a patient with a signicantly calcied aorta
entails carefully choosing the cannulation site and minimizing aortic
clamping. An alternative cannulation site, such as the right axillary
artery, may be preferable to cannulating a very calcied ascending
aorta. Another alternative is to choose an o- pump approach and
particularly in combination with a no- touch aortic technique (see
following section).
Intraoperative assessment and manoeuvres toreduce
risk ofstroke
Several monitoring modalities are available and are suggested to reduce the incidence of neurological complications. Transoesophageal
echocardiography may be used to detect potential risk factors for
stroke during surgery, such as plaques in the aorta or aortic dissection, thrombi in the heart chambers (especially in the le atrial appendage in a patient with atrial brillation), patent foramen ovale,
vegetations on the valves in patients suering from endocarditis, and
retained air in the heart at the end of CPB.– It must be emphasized, however, that transoesophageal echocardiography is limited
in the assessment of the distal ascending aorta due to a blind spot
caused by the trachea and, therefore, it is less helpful for cannulation
and clamp site assessment.
e use of intraoperative epiaortic ultrasound (EAUS) is gaining
popularity worldwide. Routine EAUS has a classIIa (LOE B) recommendation in the latest European Guidelines although it is not yet a
universal standard. EUAS is a very fast and economic tool to supplement aortic palpation, to localize endoluminal atheroma (which is
not palpable), and, in some cases, to modify intraoperative decisions
about placement of the cross- clamp and choosing among alternative
sites for cannulation or avoiding any aortic manipulation. EAUS was
found to be almost 50% more sensitive than manual aortic palpation
in detecting aortic disease. Some observational studies showed reduced rates of stroke using EAUS- guided decision- making. To date,
however, there is no randomized trial conrming these data.
EAUS can detect both anterior and posterior endoluminal atherosclerotic plaques that are not manually palpable, and therefore
identify sites that are free of atherosclerosis to safely place the aortic
cannula, clamps, and bypass gras.
Other available intraoperative imaging technologies include
transcranial Doppler and electroencephalography. In both cases,
however, there is no convincing evidence that they reduce the incidence of neurological complications., Monitoring with nearinfrared spectroscopy assesses cerebral tissue oxygenation and can
identify cerebral malperfusion, although evidence is lacking concerning its benet in reducing complications.
e avoidance of CPB by performing o- pump CABG has been
proposed as a way to reduce the risk of stroke, especially in the setting
of severe calcication of the ascending aorta— as currently recommended by European guidelines. However, the role of o- pump
CABG in reducing that risk in the general population of patients
undergoing CABG has been controversial.,
Avoidance of any aortic manipulation may be safer in patients
with severe atherosclerosis or even mandatory in patients with a
porcelain aorta. Single or sequential T- or Y- gras from an internal thoracic artery, or vein gras anastomosed to arch vessels can
be used to avoid performing proximal anastomosis to a calcied ascending aorta.
A study by Moss etal. demonstrated that completely avoiding
aortic manipulation, by using in situ internal thoracic arteries, compared to using a clamp or a clampless device (such as a Heartstring®
proximal seal system (Maquet/ Getinge, Cardiovascular LLC, San
Jose, CA, USA)) to perform the proximal anastomosis, reduced the
overall incidence of stoke by more than 50%., Arecent network
meta- analysis showed that anaortic o- pump CABG was associated
with the lowest risk of stroke compared to all other CABG strategies; however, by denition this approach is not possible with
on- pump CABG. us, while minimization of aortic manipulation
is a classI(LOE B) recommendation in the most recent European
guidelines, in on- pump CABG this is achieved by careful selection
of cannulation site, single application of the aortic cross- clamp, and
routine avoidance of side- biting or partial occlusion clamps.
Using carbon dioxide in the operative eld, for ooding the pericardial wall or for dispersing blood from the coronary artery during
suturing of distal anastomoses, is thought to reduce the likelihood
of harmful gaseous emboli since carbon dioxide is absorbed much
more quickly than nitrogen- rich air.
In patients with known intracardiac thrombi or vegetations,
aortic cross- clamping before cardiac manipulation is recommended
to avoid dislodging embolic material to the systemic circulation.
Cardiopulmonary bypassmanagement
All aspects of CPB can inuence the risk of cerebral injury during
the procedure, especially the temperature, the acid– base status,
venous and arterial blood ows, and blood pressure.
e ecacy of lters in the CPB circuit is controversial because
the optimal pore size has yet to be determined. Small pores lter
macro- emboli more eciently but limit overall ow rates. e
Northern New England Cardiovascular Disease Study Group published innovative techniques using a small- pore venous reservoir
and arterial line lter to eliminate microemboli generated in CPB
circuits; overall, changes in CPB techniques and circuit components, including lter size and type of pump, resulted in a reduction
in more than 75% of cerebral microemboli.
Hypothermia has a protective eect on the brain and the temperature is usually reduced to about 32°C during CABG. However, this
has not been widely standardized, and some surgeons cool patients
to only 34°C for routine CABG surgery, while others cool to 30°C or
even 28°C, without a strong evidence base to support this practice.
It is more widely agreed that rewarming should be done very gradually to prevent hyperthermia and air embolus formation caused by
a decrease in gas solubility.
Mean arterial pressure should be preserved in the range of 65–
80mmHg which is usually well tolerated. In elderly patients, patients who suer from hypertension, or those with known carotid
stenosis, it might be preferable to maintain a higher mean arterial
pressure above 80mmHg. Some surgeons recommend a mean arterial pressure on CPB that is always above 65mmHg or the patient’s
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