Key-words:
Dual-image videoangiography - endarterectomy - in vivo optical spectroscopy - intraoperative
shunt
Introduction
Stroke is the third cause of disability and third leading cause of death in the world.[[1]] Approximately 20%–30% of all strokes are caused by extracranial carotid artery
stenosis. The prevalence of carotid stenosis is 7% in women and 9% in men. Stenosis
is predominantly due to atherosclerosis. The major risk factors of atherosclerosis
include dyslipidemia, hypertension, diabetes, obesity, cigarette smoking, advanced
glycation end products (AGEs), and its receptors AGEs (RAGE and soluble RAGE), lack
of exercise, and C-reactive protein.[[2]] Extensive research in the past has identified carotid stenosis as a powerful predictor
of stroke. The severity of stenosis is universally accepted to be directly proportional
to an increased risk of future stroke.[[3]],[[4]]
DeBakey performed the first successful carotid endarterectomy (CEA) in 1953, but his
seminal work, however, was only published in 1975.[[5]] North American Symptomatic CEA Trial (NASCET) and European Carotid Surgery Trial
(ECST) are the two largest well-consolidated trials that defined the indications and
outcome of CEA in carotid stenosis patients.
Materials and Methods
We have operated a total of 14 patients in our institute from 2015 to 2018. Two patients
have undergone bilateral CEA. The male to female ratio is 13:1. 13 (92.8%) patients
had a positive history of hypertension. Four (28.5%) patients were symptomatic, and
10 (71.5%) were asymptomatic; with an average percentage of carotid stenosis being
81.2% in symptomatic and 76.6% in asymptomatic patients. Intraoperative monitoring
was done with (Somanetics, Inc., Troy, MI) in vivo optical spectroscopy (INVOS).[[6]] Furui's double-balloon shunt system produced by Inter medical. Co, Ltd., was used
to maintain blood flow from a common carotid artery (CCA) to internal carotid artery
(ICA), thus preventing cerebral ischemia in selected cases with significantly lateralized
cerebral oximetry (CO) recordings. Dual-image videoangiography (DIVA) was used intraoperatively
to visualize the extent of plaque. It helps in planning the arterotomy and also provides
the detail of extent of resection after the removal of plaque.
Illustrative case
A 60-year-old man presented with the transient ischemic attack. Carotid Doppler and
three-dimensional (3D) computed tomography angiography (CTA) were done which showed
>60% left carotid artery stenosis [[Figure 1]]. CEA was planned and executed as explained below.
Figure 1: (a) Doppler and (b) three-dimensional computed tomography angiography, showing significant
carotid artery stenosis
Position and preparation
The patient under general anesthesia was positioned supine with his head turned right
and in extension, on a horseshoe for better exposure of the left side of the neck.
Cranial strips of the INVOS monitor were placed over the patient's forehead and fixed
properly. This continuously monitors the rSO2 intraoperatively. Skin marking was done
along the medial border of the sternocleidomastoid (SCM) followed by painting and
draping [[Figure 2]].
Figure 2: Patient positioned in horseshoe headrest, with in vivo optical spectroscopy cranial
strips over the frontal region and skin marking over the medial border of SCM. In
vivo optical spectroscopy - in vivo optical spectroscopy, SCM - Sternocleidomastoid
Neck dissection
On lateralizing the SCM, hypoglossal nerve, and carotid sheath were seen. CCA, ICA,
and ECA were dissected clearly after ligating the common facial vein from the internal
jugular vein. Carotid sinus block was administered by injecting a small dose of the
local anesthetic agent directly into the sinus. DIVA was performed before the opening
of the carotid artery, which showed a filling defect, demarcating the extent of the
atherosclerotic plaque intraoperatively [[Figure 3]].
Figure 3: (a) Carotid sinus block with local anesthesia, (b) Dual-image videoangiography showing
the extent of atherosclerotic plaque
In vivo optical spectroscopy and shunt placement
The temporary clip was placed over the ipsilateral ICA for about 30 s; following which
there was a significant reduction in the CO recording. The rS02 reduced from 75 to
62, i.e., 17.3% reduction from the baseline value [[Figure 4]]. Therefore, we planned for a temporary shunt tube insertion between CCA and ICA,
which maintained the cerebral blood flow during the entire time of the procedure and
thus prevented cerebral ischemia. Furui's shunt tube system was prepared and inserted
into the CCA and ICA. Distal balloons of the shunt were inflated with 0.5 ml of normal
saline, and vascular clips were applied subsequently to keep the tubes from sliding
out and to prevent the blood leakage around the sides of the tube. After successful
shunt placement, the INVOS recordings came back to baseline value.
Figure 4: In vivo optical spectroscopy recordings, (a) baseline value, (b) after occlusion
of the left internal carotid artery for 30 s, rSO2 reduced from 75 to 62, i.e., 17.3%
reduction in baseline value
Arterotomy and excision of plaque
ECA, CCA, and ICA were clamped, respectively. Arterotomy was done from the CCA to
ICA; the plaque was identified and dissected all around, away from the arterial wall
and excised completely [[Figure 5]]. We used 6–0 prolene to suture the arterotomy wound from ICA toward CCA and then
from CCA to ICA with shunt tube in situ, subsequently, shunt tubes were removed and
suturing was completed. DIVA was done after the removal of all temporary clips which
showed improvement in blood flow with no filling defect in comparison to the preoperative
assessment [[Figure 6]]. Postoperative period was uneventful. Postoperative 3D-CTA showed an increase in
the diameter of the operated carotid artery with improved blood flow and no filling
defect [[Figure 7]].
Figure 5: Furui's shunt inserted into common carotid artery and internal carotid artery, followed
by excision of atherosclerotic plaque
Figure 6: (a) Completely sutured arteriotomy wound, (b) postprocedural Dual-image videoangiography
showing improved flow
Figure 7: Postoperative three-dimensional computed tomography angiography shows an increase
in the diameter of the carotid with improved blood flow
Results
In our series of 14 patients with 16 CEA procedures, continuous INVOS monitoring was
used in 12 CEA procedures. Of the 12 only 5 (41.6%) needed an intraoperative shunt.
A shunt was not used in 7 (58.3%) CEA procedures, where there were no changes in the
intraoperative CO, and these patients had an uneventful postoperative period. INVOS
monitoring not only reduced the use of routine shunt but also reduced the total surgical
time and aided in preventing neurological complications. DIVA was used in 12 CEA cases,
which helped in demarcating the atherosclerotic plaque and helped in deciding the
extent of resection of the plaque intraoperatively. Although intraoperative shunting
was not required in all the cases, it was found highly useful in cases with significantly
reduced rsO2 values to prevent postoperative deficits.
Postoperative carotid Doppler and CTA were done in all the patients. The preoperative
and postoperative vessel caliber was compared in all patients. The diameter of the
involved artery was significantly larger postoperatively thus proving the efficacy
of the procedure. There was no morbidity or mortality in our series.
Discussion
Symptomatic and asymptomatic carotid artery stenosis
A patient with carotid artery stenosis is considered symptomatic if the patient has
transient or permanent focal neurologic symptoms (visual field defect, hemiparesis/plegia,
and aphasia in the case of dominant [usually left] hemisphere involvement). Nonspecific
symptoms such as dizziness, generalized subjective weakness, syncope or near-syncope
episodes or blurred vision, in patients with carotid artery stenosis, do not qualify
as symptomatic ischemic events. These patients are considered asymptomatic even in
the presence of high-grade carotid artery stenosis.[[7]]
Diagnosis
Carotid auscultation should be a part of the routine physical examination of the patient.
Although carotid bruit has limited value in the diagnosis of carotid artery stenosis,
they are good markers of generalized atherosclerosis. Since Japan has a higher incidence
of intracranial aneurysms and cerebrovascular diseases, routine head and neck imaging
are a part of the screening protocol. Doppler ultrasonography is a noninvasive and
the first imaging tool used to screen carotid artery stenosis. Compared to catheter
angiography, Doppler ultrasonography has a sensitivity of 86% and a specificity of
87% for the detection of hemodynamically significant carotid artery stenosis. DSA
is the gold standard for defining the degree of stenosis and the morphologic features
of the offending plaque. 3D-CTA and magnetic resonance angiography have gained increasing
popularity for use in the diagnosis of carotid artery stenosis, often replacing conventional
catheter angiography.[[8]],[[9]]
Indications and benefits of carotid endarterectomy
Symptomatic patients according to NASCET [[10]],[[11]] is with >70% carotid stenosis, and there is also a proven benefit in symptomatic
patients with a moderate (50%–69%) degree of stenosis in preventing ipsilateral stroke
during a 2-year period. ECST [[12]] showed benefits of CEA in symptomatic patients with >80% (corresponding NASCET
= 60%) carotid stenosis. In asymptomatic carotid atherosclerosis study [[13]] and [[14]] (asymptomatic carotid surgery trial) trials, patients <75 years of age with asymptomatic
a significant carotid artery stenosis (≥60%), successful CEA reduced the 10-year risk
of ipsilateral stroke with significant reduction in perioperative mortality and morbidity
as compared to deferred CEA.
Technique
Most surgeons prefer selective shunting during carotid cross-clamping while performing
a CEA. Selective shunting necessitates the use of a monitoring system to detect cerebral
ischemia. Various monitoring systems such as transcranial Doppler (TCD), electroencephalograms,
and INVOS are available to detect the cerebral blood flow and impending ischemia.
A Cochrane review in 2002 concluded that the available data were too limited to support
or refute the use of routine or selective shunting in CEA, and no one method of monitoring
selective shunting has been shown to produce better outcomes.[[15]]
Cuadra et al.[[16]] used the INVOS-4100 CO during 42 consecutive CEAs in 40 patients to measure the
effect of carotid clamping and shunting on rSO2. Although this study showed statistically
significant changes in rSO2 as a result of clamping and shunting of the carotid artery,
they were not convinced in using CO as a sole monitor for deciding on an intraoperative
shunt.
Recent studies compared CO to other monitors such as TCD in performing CEA and found
CO has a better correlation compared to the TCD. CO is more accurate than TCD in predicting
the need for carotid shunting.[[17]]
INOS [[Figure 8]] uses infrared light in the range of 650–1100 nm.[[18]],[[19]] This noninvasive monitoring system detects the hemoglobin oxygen saturation of
blood in the brain of an individual. DIVA utilizes the intravenous indocyanine green
with near-infrared fluorescence, which is visualized in a single monitor.[[20]],[[21]] It helps in identifying the atherosclerotic occlusion by opaque or nonglowing area
in the monitor. Postprocedural DIVA delineates the extent of plaque resection.
Figure 8: In vivo optical spectroscopy cerebral oximetry with cranial strips
The Furui's shunt system consists of a flexible silicone tube which is 20 cm long,
equipped with silicone rubber balloons at both ends. Each balloon can be inflated
individually, with saline of about 0.5ml to prevent bleeding from the gaps between
the tube and the carotid arteries. Clamps are placed around the common and ICA to
avoid further leakage, thus preventing blood loss which in turns reduces the possibility
of ischemia and gives a bloodless field for the procedure.[[22]],[[23]]
Carotid stenting (CAS) was introduced as a treatment to prevent stroke in 1994. The
carotid revascularization endarterectomy versus stenting trial [[24]] is the largest trial comparing CAS and CEA in symptomatic and asymptomatic carotid
stenosis patients. CAS and CEA had similar short- and long-term outcomes. During the
periprocedural period, there was a higher risk of stroke in CAS and a higher risk
of myocardial infarction in CEA patients. Patients <70 years of age had lesser complications
with CAS compared to people >70 years of age, who tolerated CEA well.[[25]],[[26]]
Conclusion
CEA should be considered for symptomatic patients with >70% of carotid stenosis and
also with 50%–69% stenosis if no other etiologic basis for the ischemic symptoms can
be found. CEA should be considered in asymptomatic patients with >60% stenosis. Continuous
INVOS monitoring is mandatory for the decision of the use of intraoperative shunt,
which reduces the perioperative morbidity and mortality significantly. More randomized
controlled trials are necessary to help clarify the indications and benefits of these
procedures for different subgroups of patients with carotid artery disease.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
