Fig. 35.5 Diagram showing lesions in the aortic arch and aortic arch branches of the patient

Question 6

In this stage, what kind of intervention do you recommend?

A.Anti-coagulation with heparin, then warfarin

B.Balloon angioplasty of the left vertebral artery

C.Stenting of both common carotid arteries followed by dual anti-platelet therapy

D.Bypass surgery to restore the cerebral blood flow

E.Carotid endarterectomy

Wedecidedtoperformbypasssurgeryfortherevascularizationofarchvesselswithdiffuse involvements.

Question 7

What surgical treatment would you recommend for this patient?

A.Ascending aorta-to-left carotid bypass

B.Ascending aorta-to-bicarotid bypass

Fig. 35.6  Three-dimensional volume-rendered CT angiography image showing (a) pre-operative and (b) post-operative findings of aortic arch branches. The external ring-supported polytetrafluoroethylene (PTFE) graft from the ascending aorta to the left internal carotid artery is shown

C.  Descending thoracic aorta-to-left carotid bypass D.  Right axillary-to-left carotid bypass

Inthispatient,theascendingaortadidnotshowFDGuptakeon18-FDGPETscanswhereas CT angiography and duplex ultrasonography showed intimomedial thickening of the right proximal internal carotid artery. We decided to perform ascending aorta-to-left-carotid bypass using an external ring-supported polytetrafluoroethylene (PTFE) graft (Fig. 35.6b).

Question 8

What complications can occur after carotid reconstructive surgery in this patient?

A.  Intracranial hemorrhage B.  Anastomotic restenosis C.  Anastomotic aneurysm D.  All of above

The patient’s post-operative course was uneventful and she had complete resolution of the visualsymptom.Shereportedconsiderableimprovementinherdailyactivities.Sixmonths later, a follow-up CT angiography revealed patency of the aorto–monocarotid bypass. She was placed on prednisolone (15 mg/day), methotrexate (15 mg/week) and clopidogrel (75 mg/day) postoperativerly. Her ESR/CRP values remained within upper normal limits. Patency of the bypass was confirmed by CT angiography during a 2-year follow-up.

35.1  Commentary

TA is a chronic vasculitis of the aorta and its major branches, with unknown aetiology. Women are affected in 80–90% of cases, with an age of onset usually between 10 and 40 years. It is common in Asia and Mexico but rare in Europe and North America. The rarity of the disease results in low clinical awareness in Western countries. The American College of Rheumatology has established diagnostic criteria for TA (Table 35.1).1 [Q1] Our patient’s clinical findings fulfill five out of six diagnostic criteria. The early diagnosis of TA can be difficult because early symptoms such as fatigue, malaise, weight loss, arthralgia and low-grade fever are non-specific. However, careful examination of the arteries at an early stage can detect a weak pulse, BP discrepancy between the arms, or bruits over the neck, supraclavicular and infraclavicular areas, or the abdomen. This early systemic phase is followed by a late chronic ischaemic phase in which vascular lesions progress slowly over years or decades (Fig. 35.7) with the development of collateral circulation. The incidence of ischaemic symptoms is relatively low compared with arteriosclerosis, despite the extensive steno-occlusive vasculopathy. Detection of bruits or decreased pulses

Table 35.1  American College of Rheumatology (1990) criteria for the diagnosis of Takayasu’s arteritis

1.Age at disease onset <40 years:Development of symptoms or findings related to TA at age <40 years

2.Claudication of extremities:Development and worsening of fatigue and discomfort in muscles of one or more extremity while in use, especially the upper extremities

3.Decreased brachial artery pulse:Decreased pulsation of one or both brachial arteries

4.BP difference >10 mmHg:Difference of >10 mmHg in systolic BP between arms

5.Bruit over the subclavian arteries or aorta:Bruit audible on auscultation over one or both subclavian arteries or the abdominal aorta

6.Arteriogram abnormalities:Arteriographic narrowing or occlusion of the entire aorta, its primary branches or large arteries in the proximal upper or lower extremities, not caused by arteriosclerosis, fibromuscular dysplasia or similar causes; the changes are usually focal or segmental

For purposes of classification, a patient shall be said to have TA if at least three of these six criteria are present. The presence of any three or more criteria yields a sensitivity of 90.5% and a specificity of 97.8%. (Adapted from Ref. 1.)

BP, blood pressure (systolic; difference between arms).

Fig. 35.7 Diagram showing progression of vascular lesions in the aortic arch branches in patients with Takayasu arteritis. (a) The initial vascular lesions frequently occur in the left middle or proximal subclavian artery. (b, c) As the disease progresses, the left common carotid, vertebral, brachiocephalic, right middle or proximal subclavian artery, right carotid and vertebral arteries and aorta might also be affected (Adapted from Ref. 26)

in a young woman narrows the differential diagnosis to TA. The differential diagnosis includes giant cell arteritis, atherosclerosis and fibromuscular dysplasia. [Q1]

Clinical manifestations of TA include systemic symptoms such as fatigue, weight loss and low-grade fever, myalgia and arthralgia. Vascular inflammation may lead to pain such as carotodynia. Most symptoms, however, are the result of ischaemia to organs supplied by stenotic vessels. Patients may have TIAs or strokes, visual aberration, symptoms of vertebrobasilar insufficiency, limb claudication, angina or renovascular hypertension, among others.2 TA should be ruled out in young female patients with hypertension. Aortic regurgitation, prevalent in Korea and Japan, is often associated with aortic root dilation.3

Laboratory results reflect the underlying inflammatory process but are mostly non-specific. A normochromic normocytic anaemia suggestive of a chronic disease is present in most patients.Thewhitebloodcellcountisusuallynormalormildlyelevated.Acutephasereactants, such as an elevated ESR and increased serum CRP, are a reflection of the inflammatory process. Although the blood tests are not always precise or reliable indicators of disease activity, they are most frequently used blood test to assess disease activity of TA. [Q1:C]

With contrast angiography, primary arteriographic abnormalities are smooth-walled, tapered, focal or narrowed areas with some areas of dilation. Collateral circulation is often prominent because of the chronic nature of the disease. Arteriography can define the location and appearance of the arterial lesion and might also allow a subsequent therapeutic approach through the same arterial puncture [Q2: A]. However, it does not evaluate mural changes and is an invasive test associated with some risks. Therefore, if a therapeutic intervention is not anticipated, a less invasive imaging technique may be preferred. CT angiography or MRI of the aorta can reveal the mural changes as well as luminal changes in evaluating large arteries.4,5 At present, CT or MRI scans appear to be definitive for most patients [Q2: C, D]. When diagnosing or evaluating TA, we start with duplex ultrasonography of the carotid artery because duplex scan is non-invasive, has no risk and could disclose luminal and mural changes of the aortic arch branches. [Q2: B] Duplex ultrasonography is particularly useful for the assessment of the common carotid arteries, displaying a resolution of 0.1–0.2 mm.6 In patients with TA, the typical lesion identified by

ultrasonography is a long, smooth, homogenous concentric thickening of the arterial wall in contrast to an atherosclerotic plaque shown to be non-homogenous, often calcified and associated with an irregular wall.7

Althoughimagingisoptimalatthecommoncarotidandvertebralarteries,assessmentof the proximal subclavian and distal internal carotid arteries is limited by overlying tissues.

Underlying systemic hypertension is often missed, as the BP measured in the upper extremities may underestimate the true BP, as a consequence of the subclavian/axillary artery involvements. [Q3: A] It is important to measure BP in all four extremities. [Q3: B] Hypertension develops in more than one half of cases because of renovascular hypertension caused by the narrowing of the renal artery, and by narrowing and decreased elasticity of the aorta and branches [Q3:C]. In the case of atypical coarctation of the aorta, the upper arm BP is elevated. [Q3: D] In rare patients with TA, BP measurements from all four extremities are falsely low because of stenosis or occlusion of extremity arteries combined with atypical coarctation. In such patients, adequate control of BP could be judged by the absence of left ventricular hypertrophy or hypertensive retinopathy. If such a patient has a mitral regurgitation, left ventricular systolic pressure (equal to aortic systolic pressure) can be estimated by mitral regurgitant Doppler flow.

TA usually involves the proximal neck vessels with diversion of the distal flow or collateral filling of distal vessels. Changes in cerebral haemodynamics in relation to occlusive cerebral vascular lesions are not fully understood. Visual disturbances, such as blurring or visual dimming, occur in 8–13% of patients with TA. Permanent loss of vision is unusual in this disease. Stroke and TIAs occur in 5% and 20% of cases, respectively.8 Carotid stenosis and occlusion are frequently asymptomatic, and isolated subclavian stenosis seldom requires revascularization because of the general adequacy of the collateral circulation. [Q4: A] Therefore, it is uncertain when it might be appropriate to revascularize any stenosis of the arch vessels. Our indications of supra-aortic artery revascularizations are symptomatic stenosis >70%, severe dizziness or ocular symptom, episodes of stroke or TIA. [Q4: B, C, D, E] Occlusive lesions of all four cervical arteries usually have disabling symptoms. Only a minority of patients needs intervention in arch vessels. In the Mayo Clinic, over 27 years, 6% of all patients with TA (16/251) required a bypass of the arch vessels for cerebral ischaemia.9 For the last 15 years in our institute, 7% of patients with TA (15/205) needed arch vessel bypass operations.

Ideally, interventions should be performed when the disease is inactive to minimize the risks of restenosis or anastomotic dehiscence. A recent study using serial angiography found that intervention performed on patients with stable disease and post-interventional treatment with immunosuppressive drugs were independent variables determining the maintenance of arterial patency.10 Therefore, controlling disease activity is important before performing any revascularization. However it is not always possible to follow the principle due to urgency of intervention.

Clinical, laboratory and imaging findings of the patient suggested that she has moderately active arteritis.In the early active phase,arterialstenosis might reverseand ischaemic symptoms can improve in response to immunosuppressive therapy. Evaluation of disease activity in patients with TA is challenging. Clinical features do not correlate with acutephase reactants in ~50% of cases. Imaging modalities do not always correlate with clinical and laboratory parameters. Up to 45% of patients in clinical remission have histological

cerebrovascular insufficiency caused by TA. Two key points in carotid artery revascularization surgery for TA are the need to perform surgery in a quiescent phase of the disease, and selecting disease-free segments for anastomosis. Accordingly, it is important to determine the degree of activity of the vasculitis and co-existing morbidities such as renovascular hypertension. The clinician must select the target artery(s) to be revascularized, and determine the optimal site for the inflow artery for the bypass surgery and bypass conduit before the operation. In patients with co-existing severe uncontrolled renovascular hypertension caused by co-existing renal artery stenosis, we recommend renal artery intervention first before carotid artery reconstruction, to avoid cerebral hyperperfusion syndrome after carotid surgery. For this purpose, renal artery angioplasty is often recommended.

In patients with bilateral common carotid artery occlusion, some prefer to perform unilateral carotid reconstruction while others recommend bilateral carotid revascularizations. The proponents of unilateral carotid revascularization for patients with bilateral common carotid occlusion argue for the hypothetical advantage of a lower risk of cerebral hyperperfusion syndrome compared with bilateral carotid revascularization. [Q7: A] Proponents of bilateral carotid reconstruction argue for the expected advantages of greater cerebral blood flow after surgery compared with unilateral carotid reconstruction and a lower risk of recurrent cerebrovascular insufficiency when one of the grafts is occluded. [Q7: B] However, there has been no comparative study between unilateral and bilateral carotid artery reconstructions in patients with TA.

To select an optimal site of the proximal anastomosis free of an active lesion, easy access and the risk of late progression of the disease should be considered in patients with TA. Operative findings and pre-operative imaging studies (contrast-enhanced CT, contrast angiography, ultrasonography, MRI and PET scans) are used for the selection of the dis- ease-free inflow artery.

The ascending aorta is often selected as an inflow artery during carotid artery reconstruction because involvement of disease is relatively uncommon at this segment of the aorta, and the risk of late development of anastomotic stenosis is lower than in cases using an aortic branch (e.g., the subclavian or axillary artery) as an inflow artery. [Q7: C, D] However, in patients with critical brain ischaemia, partial clamping of the ascending aorta can further compromise cerebral blood flow. To avoid this potential risk, the descending aorta can be selected as an inflow site for carotid revascularization surgery.18 Regarding the bypass conduit, some recommend autogenous vein grafts,19,20 while others prefer to use prosthetic grafts.21,22

Two categories of complication can develop after carotid artery reconstruction in patients with TA. One involves neurologic complications, which can occur during the operation or early post-operative period. The other category of late complications which are associated with the graft material, anastomosis site or progression of vasculitis. Most patients who undergo carotid revascularization have multiple and extensive extracranial carotid and vertebral artery occlusive lesions. During the operation, further ischaemia of brain can develop from neck tilting and aortic and carotid artery clamping. However, most patients can tolerate the surgery owing to extensive collateral circulation in the neck.

Cerebral hyperperfusion syndrome (CHS) can develop after carotid artery reconstruction in patients with severe brain ischaemia. It is believed that CHS results from a sudden increase of cerebral blood flow in conditions of impaired cerebral autoregulation, to