Takayasu Arteritis: Follow-up Investigations

1. Clinical Assessment

• Blood pressure (both arms) — detect new asymmetry (>10 mmHg difference) suggesting progressive subclavian or aortic disease
• Peripheral pulse examination — loss or reduction of previously palpable pulses indicates disease progression
• Auscultation for bruits — over carotid, subclavian, renal, and aortic territories
• Symptoms review — claudication (upper > lower limb), carotidynia, headache, visual symptoms, renovascular hypertension, chest/abdominal pain

2. Laboratory Investigations

Key point: ESR and CRP are unreliable markers of vascular disease activity. Normal inflammatory markers do not exclude active arteritis, and imaging remains essential for relapse detection. — Brenner and Rector's The Kidney; Current Surgical Therapy 14e

3. Imaging Investigations

3a. MRI / MR Angiography (MRA) — Preferred modality for TA

• MRI is the preferred imaging modality per EULAR 2023 recommendations for TA
• Demonstrates wall oedema (active inflammation), wall thickening, gadolinium enhancement, and structural changes (stenosis/aneurysm)
• MRA provides luminography — identifies stenoses, occlusions, aneurysms, and collaterals
• No ionising radiation — preferred for serial follow-up studies (especially in young women)
• Limitation: Wall changes do not always correlate with disease activity; gadolinium avoidance needed in renal impairment

3b. CT Angiography (CTA)

• High-resolution assessment of vessel wall thickening, calcification, stenosis, aneurysms
• Preferred when MRI is contraindicated or unavailable
• Limitation: Radiation exposure — a concern given repeated imaging in young patients
• May demonstrate mural thickening with enhancement during active inflammation

3c. ¹⁸F-FDG PET/CT or PET/MRI

• Detects metabolically active vascular inflammation even before structural changes appear
• Particularly useful to differentiate active ("hot") from burned-out ("cold") disease
• Used for evaluating suspected relapse and assessing response to therapy
• Limitation: Not validated as a reliable measure of disease activity in follow-up; FDG uptake may reflect chronic remodelling; not widely available; radiation exposure

Braunwald's Heart Disease — TA imaging: (A) Granulomatous inflammation on histology; (B) Colour Doppler ultrasound of subclavian artery; (C) ¹⁸FDG-PET showing thoracic/abdominal aortic uptake; (D) MR angiography showing bilateral subclavian/axillary stenosis

3d. Vascular Ultrasound (Duplex/Colour Doppler)

• Assesses carotid, subclavian, axillary, and renal arteries for wall thickening, flow velocity (stenosis), and intima-media thickness
• Useful at bedside and in serial monitoring — no radiation
• Detects the "macaroni sign" (circumferential wall thickening) in large vessels
• Limited to accessible vessels; operator-dependent; cannot image thoracic aorta directly

3e. Conventional (Catheter) Angiography

• Previously the gold standard; now largely replaced by CTA/MRA
• Provides luminography only — no vessel wall information
• Reserved for pre-intervention planning (angioplasty, stenting, bypass)
• Noninvasive imaging is preferred per ACR/VF 2021 and EULAR guidelines

Summary: Imaging Choice by Purpose

4. Echocardiography

• Assess for aortic root dilation and aortic regurgitation (AR) — occurs in ~18% of TA patients due to ascending aortic inflammation
• AR requiring valve replacement affects approximately 15% of patients
• Also evaluates left ventricular function, coronary artery origins (coronary arteritis), pulmonary arterial pressure (pulmonary artery involvement in up to 50%)
• Annual or biennial echocardiography is recommended in patients with aortic involvement

5. Blood Pressure Monitoring

• Serial bilateral arm BP measurement at every visit
• Ambulatory blood pressure monitoring (ABPM) for accurate assessment where subclavian/axillary disease affects peripheral readings
• Renal artery stenosis is a common cause of renovascular hypertension — renal duplex Doppler or CTA/MRA of renal arteries if BP is difficult to control

6. Ophthalmologic Review

• Indicated in patients with carotid/vertebral involvement or symptoms
• Fundoscopy for hypertensive retinopathy, retinal vein/artery occlusion, optic atrophy
• Visual field assessment if visual symptoms occur

7. ACR/VF 2021 Recommendations for Monitoring (TA in Remission)

• Strong recommendation: Long-term clinical monitoring over no monitoring in patients in apparent remission
• Inflammatory markers (ESR/CRP) to assist monitoring, acknowledging limitations
• Noninvasive imaging over catheter angiography
• In remission with asymptomatic elevation of inflammatory markers: increase monitoring frequency rather than automatically escalating immunosuppression
• In remission with new vascular inflammation on imaging (new stenosis or wall thickening): conditionally recommend treating with immunosuppression

8. EULAR 2023 Imaging Recommendations (Relevant to TA Follow-up)

• MRI is the preferred imaging modality for TA (both diagnosis and follow-up)
• FDG-PET, CT, or ultrasound are acceptable alternatives
• Imaging not routinely recommended for follow-up — use when relapse is suspected or inflammatory markers are unreliable
• MR-angiography, CT-angiography, or ultrasound for long-term structural damage monitoring at sites of prior vascular inflammation

Summary Table: Follow-up Investigations in TA