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............................................................................................................................................................................. • CMR/CCT is useful for detailed evaluation of supravalvular anatomy, in particular, when multilevel LVOTO is present or for (pre-operative) assessment of coronary artery anatomy and other aortic or aortic branch lesions (e.g. carotid and renal artery stenosis), and central and branch PAs. • Cardiac catheterization: haemodynamic assessment is recommended when non-invasive quantification remains uncertain. • Genetic evaluation, with counselling and subsequent testing using micro-array techniques to diagnose WilliamsBeuren syndrome and sequencing of the elastin gene in non-syndromic presentations, is useful.

4.5.2.4 Surgical/catheter interventional treatment Surgery is the primary treatment: the operative mortality rate for fibrous diaphragm and hourglass deformity is <5%. Since the coronary arteries are under high pressure, surgery might be considered earlier than in patients with valvular AS, particularly when no valve substitute is required. Following operative repair, the survival rate has been reported to be 8085% at 20 years.181 AR may be present in 25% of patients, but usually it is not progressive after surgical relief of SupraAS.

4.5.2.5 Follow-up recommendations Lifelong and regular follow-up, including echocardiography, is required to determine progression of obstruction (rare), LV size/ function, and development of symptoms, as well as after surgery to detect late restenosis, development of aneurysm (CMR/CCT), and the occurrence or progression of CAD. Follow-up should include evaluation in specialized ACHD centres. 4.5.2.6 Additional considerations

• Exercise/sports: see valvular AS (section 4.5.1). • Pregnancy: See valvular AS (section 4.5.1). Male and female patients with WilliamsBeuren syndrome and elastin gene mutations have a 50% transmission risk (family screening recommended). • IE prophylaxis: recommended only for high-risk patients (see section 3.4.6).

4.5.3 Subaortic stenosis 4.5.3.1 Introduction and background Subaortic stenosis (SubAS) occurs as an isolated lesion, but is frequently associated with aortic valve disease, VSD, AVSD, or Shone complex (multilevel left heart obstruction). It may also develop after repair of these lesions. It is caused by a fibrous ridge/ring in the LVOT proximal to the aortic valve or as a fibromuscular narrowing. SubAS has to be differentiated from obstructive hypertrophic cardiomyopathy.

4.5.3.2 Clinical presentation and natural history The clinical course is highly variable. The presence of associated CHD, particularly a VSD, is related with SubAS progression; age seems not to play a role in disease. AR is frequent but rarely haemodynamically significant or progressive.182 Although infrequent, sudden death has been reported in SubAS patients.

4.5.3.3 Diagnostic work-up See section 3.3 for general principles. Clinical findings mainly include a systolic ejection murmur at the left sternal border without systolic ejection click. A diastolic murmur refers to AR. • Echocardiography visualizes LVOT anatomy, associated aortic valve abnormality, degree of AR, LV function, LVH, and associated lesions. With Doppler echocardiography, the severity of the subvalvular obstruction is determined, but Doppler-derived gradients may overestimate the obstruction and may require confirmation by cardiac catheterization. Occasionally, TOE is necessary to better demonstrate the membrane or ring. 3D TOE can be helpful to characterize the complex LVOT anatomy and estimate the area of obstruction by planimetry. • CMR may be useful to characterize complex LVOTO anatomies, especially in patients with poor acoustic window.

4.5.3.4 Surgical/catheter interventional treatment Surgical treatment is the only effective intervention and involves a complete resection of the fibrous ridge/ring and parts of the muscular base along the left septal surface. Fibromuscular or tunnel-type SubAS requires more extensive resection or a Konno procedure. Surgical results are good, but restenosis may occur. In patients with low surgical risk and morphologically well suited to repair, the threshold for intervention is lower than in aortic valve stenosis since no valve implant is required. In the case of moderate or severe AR, the aortic valve must be repaired or replaced at the time of surgery.

4.5.3.5 Follow-up recommendations Lifelong regular follow-up, including echocardiography, is required in the non-operated state to determine progression of obstruction, AR, and LV hypertrophy, function, and size. Regular post-operative follow-

Recommendations for intervention in supravalvular aortic stenosis

Recommendations Classa Levelb

In patients with symptoms (spontaneous or on exercise test) and mean Doppler gradient >_40 mmHg, surgery is recommended. I C In patients with mean Doppler gradient <40 mmHg, surgery is recommended when one or more of the following findings are present:  Symptoms attributable to obstruction (exertional dyspnoea, angina, syncope).  LV systolic dysfunction (EF <50% without other explanation).  Surgery required for significant CAD or valvular disease. I C Patients with mean Doppler gradient >_40 mmHgc  but without symptoms, LV systolic dysfunction, LVH, or abnormal exercise test  may be considered for repair when the surgical risk is low. IIb C

CAD = coronary artery disease; EF = ejection fraction; LV = left ventricle/ventricular; LVH = left ventricular hypertrophy. aClass of recommendation. bLevel of evidence. cDoppler-derived gradients may overestimate the obstruction and may need confirmation by left heart catheterization. Downloaded from academic.oup.com/eurheartj/article/42/6/563/5898606 by guest on 07 October 2026