Table A3.

Description of case reports of mitral valve replacement in MPS patients.

Case	Type	Age/Sex	Presentation	Pre-op Findings	Device/Other Procedures	Surgical Notes	Outcome	Author Comments
Brazier (2015) [68]	I-HS	24 F	Paroxysmal dyspnoea, and stridor; On ERT	Severe MS: 0.9 cm2, ΔP 14.5 mmHg; 8 cm LA appendage aneurysm; PAP 50 mmHg	17 mm SJM (inverse AV); LA aneurysm resection	High MAP maintained due to concern for spinal ischaemia from previous occipitocervical fusion	Small paravalvular leak. Tracheostomy removed 15 d PO; D/C 37 d PO; NYHA Class I at 10mo F/U	-Small and rigid annulus. -Poor tissue quality. -Need for MDT preop planning for fibreoptic intubation and planned open tracheostomy. -Steroids used to prevent post-extubation laryngeal oedema.
Encarnacion (2017) [72]	I-HS	32 F	Reduced functional capacity; Previous Konno root enlargement; 21 mm SJM AVR; PO 42 d redo for suspected endocarditis; On ERT	MV tethered and thickened; MS: ΔP 12 mmHg; MR; EF 60%	25 mm SJM	Uneventful	PO 6 d echo: well-seated valve, ΔP 7.7 mmHg; AV well seated, ΔP 15 mmHg;	-Example of disease progression in spite of ERT. -Unknown if ERT can alter progression of valve disease. -VP shunt in situ: avoid entering pleural space to prevent infection. -Prudent to use mechanical valve to prevent future reintervention.
Manna (2021) [72]	I-HS	44 M	MV restenosis; Previous AVR, MV commissurotomy; On ERT	ns	ns; “Toilet of aortic prosthesis”; Removal of subvalvular fibrous tissue; AVN ablation pacing	ns	Normal life at 1 yr F/U.	-One of the longest living MPS I pts. -History suggests valve disease is stabilised or unresponsive to ERT. -MPS patients will likely need valve surgery because of longer lifespan since ERT.
Fischer (1999) [100]	I-S	35 M	Severe MS; SJM AVR 12 years previously.	MV and chordae thickening and calcification; MS: 1.2 cm2, ΔP 10 mmHg; Mild MR; Aortic prosthesis: ΔP 41 mmHg; EF 60%; PAP 55 mmHg	SJM	Extensive irregular thickening and calcification of MV and chordae.	Improved cardiopulmonary function at 6 mo F/U	-Small valve annulus -Difficulty in inserting adult prosthesis
Kitabayashi (2007) [65]	I-S	41 F	Exertional dyspnoea, NYHA III	Severely thickened and fused chordae, leaflets and papillary muscles; Severe MS: 0.90 cm2; Large LA: 49 mm; Mild AS and TR; EF 66%; PAP 52 mmHg	20 mm ATS	Difficult intubation with macroglossia and short neck; Difficulty identifying leaflet/annulus border; Reinforcement of suture line with equine pericardial patch between valve ring and LA wall; Annulus hard/not pliable.	ECMO/IABP due to severe diastolic LV dysfunction; Removed 3 d PO; Good valve function at 11 mo F/U.	-Small valve insertion due to small body size and annulus -Poor tissue quality and annulus flexibility. -Equine pericardial patch may be useful adjunct to prevent valve dehiscence and leakage. -IABP useful for low diastolic dysfunction. -MPS causes multivalvular disease; Other lesions need to be monitored.
Bhattacharya (2005) [75]	II	28M	Acute HF precipitated by new onset AF; Chronic MS	MV commissural fusion, thickened leaflets with subvalvular involvement; MV: 0.95 cm2	23 mm SJM	Thickened leaflets and chordae;	PO IABP and adrenaline; Elective tracheostomy; prolonged PO ventilation due to persistent bibasal atelectasis; D/C 18 d; Good LV function at 18 mo F/U	-Intubation difficult due to macroglossia and short tracheal length. -LMA used and ET tube passed through it. -Surgery complicated by poor tissue quality, small chambers and small mediastinum. -No clear demarcation of annulus and valve leaflets. -Tracheostomy due to risk of obstruction from macroglossia -Preoperative planning is important.
Lee (2013) [101]	II	25 M	Severe dyspnoea, NYHA IV	Thickened MV leaflets and subvalvular structures, commissural fusion; Severe MS: 0.6 cm2, ΔP 27 mmHg; PAP 63 mmHg	25 mm SJM	ns	Stable condition at 1 yr F/U; Started on ERT	-Difficult to differentiate rheumatic MS and MS secondary to MPS by echocardiography. -Diffuse and general thickening of MV and subvalvular structures, restrictive motion of leaflets may suggest MPS.
Ribeiro (2014) [102]	III-A	6 F	Anasarca and pneumonia	Severe MR; rupture of chordae; LV dilation	Biological prosthesis	ns	Mild AR and normalised LV function; Died at 13 from aspiration pneumonia	-
Marwick (1992) [103]	VI	25 F	Progressive exertional dyspnoea	MV rigidity, with commissural fusion; MS: 0.83 cm2, ΔP 18 mmHg	2 M Starr–Edwards 6120	MV: thickened, nodular, and calcified	Moderate AS at 3 yr F/U; Improved functioning	-Valve involvement similar to rheumatic fever with nodular thickening along free margin and shortening of chordae. -Cardiac involvement should be considered in progressive dyspnoea.
Bell (2018) [56]	VI	29 F	Symptomatic severe MV disease; On ERT	Severe MR; MV thickening, prolapsed leaflets; MV ΔP 10 mmHg; PAP 25 mmHg	21 mm Medtronic Standard pivot (inverted AV prosthesis)	ns	D/C 6 d PO; No obvious regurgitation at 10 mo F/U	-Mitral annular tissue is more friable. -Anchoring of prosthesis is more difficult. -Felt pledgets can be used to reinforce periprosthetic sutures. -Small annulus may require an inverted aortic prosthesis. -Consider extra-annular patches and mitral ring enlargement.

Abbreviations: ΔP = mean transvalvular pressure gradient; AR = aortic regurgitation; AS = aortic stenosis; AV = aortic valve; AVT = aortic valve thickening; D/C = discharge; EF = ejection fraction; ERT = enzyme replacement therapy; ET = endotracheal; F/U = follow-up; IABP = intra-aortic balloon pump; LA = left atrium; LMA = laryngeal mask airway; LV = left ventricle; MPS = mucopolysaccharidoses; MR = mitral regurgitation; MS = mitral stenosis; MV = mitral valve; MVT = mitral valve thickening; ns = none stated; NYHA = New York Heart Association functional classification; PAP = pulmonary artery pressure; PO = post-operative; SJM = St Jude Medical mechanical prosthesis; TR = tricuspid regurgitation.