bicuspid aortic valve and aortopathy
TRANSCRIPT
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Bicuspid AV & Aortopathy
Dr Cheng He
Cardiothoracic Trainee, Royal Australasian College of Surgeons
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BAV - Anatomy• 2 unequal-sized cusps
• Raphe - site of fusion identifiable in most cases
• Size of cusps: • Fused > non-fused
counterpart • 2 ‘normal’ cusps > 1 fused
cusp
Morphologic patterns depend on fusion configuration
Roberts,AmJCardiol1970;26:72-83SieversetalJTCS2007;133:1226-33
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BAV - Epidemiology• Incidence: 0.5%-2%
• M:F 3:1 • Sporadically • Familial
• Turner - 30% have BAV • Occur with other congenital CVS malformations
• Coarctation of aorta - 50% • Hypoplastic LHS
BAV represents a complex disease of the aorta and cardiac development
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BAV - Pathogenesis
Padangetal.CircCardiovascGenet.2012;5:569-580.
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ClemenGetal.AmJMedGenet1996;62:336-8.Glicketal.AmJCardiol1994;73:400-4.HunGngtonetal.AmJCardiol1997:30;1809.Padangetal.CircCardiovascGenet.2012;5:569-580.
Genetics• Autosomal dominant, variable penetrance • 9% prevalence in first-degree relatives
• 24% if >1 person affected
• Causal genes largely unknown • NOTCH1 (9q34.3)
• BAV + accelerated calcium deposition
BAV - Pathogenesis
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BAV - Classification
SieversetalJTCS2007;133:1226-33
Surgical - Sievers
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BAV - ClassificationEcho - Schaffers
SchaffersetalHeart2008;94:1634–1638
Valve: PS SAX
R+L R+N L+N
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BAV - Classification
Kangetal.JACC2013;6:150-61
MDCT - Kang
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BAV - ClassificationWhy?
• Valve morphology - Natural history
• Associated aortopathies
• Comparison of reports on BAV
• Appropriate surgical intervention
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BAV - DiagnosisAuscultation
• Functionally normal BAV - Ejection murmur/click at LLSB or apex
• Murmurs of AS/AR/Coarctation
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BAV - DiagnosisTransthoracic Echo
• Sensitivity 92%, Specificity 96% • Accuracy inverse to calcification
• Findings: • Raphe • Systolic doming & eccentric closure line
(LAX) • Evaluate in systole; raphe may appear
trileaflet
Ayadetal.AmJCardiol2011;108:1589.Diastole Systole
Raphe
Doming
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BAV - Natural History• Valvular dysfunction - AS, AR, endocarditis
• Aortopathy
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BAV - Natural History
MichelenaetalCirculaGon.2008;117:2776-2784.)
Survival of asymptomatic patients with BAV
Identical to expected survival of matched population
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BAV - Natural History
MichelenaetalCirculaGon.2008;117:2776-2784.)
Medical events
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BAV - Natural History
MichelenaetalCirculaGon.2008;117:2776-2784.)
20-yr BAV rate
BAV incidence
rate*
Non-BAV incidence
rate*
AVR 24% 1370 19
*In pt-yrs (per 100,000)
AVR performed at younger ages49±20 (BAV) vs 67±16 yrs (tricuspid)
No aortic dissections during follow-up
Surgical events
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BAV - Natural History
MichelenaetalCirculaGon.2008;117:2776-2784.)
Predictive factors (medical & surgery): • Age ≥50 yrs • Valve degeneration at diagnosis
Aorta surgery predicted by: • Ascending aorta ≥40 mm at baseline
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BAV - Natural History
Tzemosetal.JAMA;2008:300;11:1317-1325.
The largest study (n=642) in symptomatic/asymptomatic BAV pts: 10-year 96% survival
Similar to normal population
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BAV - Natural History
Tzemosetal.JAMA;2008:300;11:1317-1325.
Independent predictors of primary cardiac events: Age ≥30 yrs
Moderate/Severe ASModerate/Severe AR
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BAV - Natural History
What is common in both these studies? • Independent prognostic significance of age and baseline
valvular dysfunction
Many patients proceed to have some sort of intervention
Does surgery in BAV pts alter its presumed natural history?
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BAV - Natural History• Valvular dysfunction - AS, AR, endocarditis
• Aortopathy
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Surgical series of 932 resected aortic valves for AS:
• 49% had BAV
• Age at intervention • BAV: 67±11 • Tricuspid: 74±8
BAV - AS
Robertsetal.CirculaGon.2005;111:920-925.
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BAV - AS
Robertsetal.CirculaGon.2005;111:920-925.
Disease progression • Similar degenerative changes as seen in tricuspid
valves • Exacerbated by BAV folding/creasing/turbulent flow • Results in accelerated disease progression
• Most common reason for valve replacement
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BAV - AS
Fernandesetal.JACC2007:2211-4.
Influence of valve morphology • 310 patients with BAV
• 202 (65%): R-L fusion, 108 (35%): R-N fusion • Follow-up 14±7 yrs • 49 (16%) had interventions • Freedom from intervention: 64% R-N vs. 91% R-L • AS more progressive in R-N pts
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BAV - AR
Sabetetal.MayoClinProc.1999Jan;74(1):14-26Tzemosetal.JAMA;2008:300;11:1317-1325MichelenaetalCirculaGon.2008;117:2776-2784.)
Less frequent occurrence than AS• Surgical series of 542 pts who underwent AVR (1991-1996):
• 13% (pure AR) vs 75% (pure AS) • Mean age:
• 46 yrs (AR) vs 65 yrs (AS)
Low intervention rates• Olmsted county (Michelena): 47% had some degree of AR at baseline; 3% had
intervention for severe AR • Toronto study (Tzemos): 21% had moderate/severe AR at baseline; 6% had
intervention for symptomatic AR
Mechanisms• Valve prolapse • Aortic root/annular dilatation • Endocarditis
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BAV - Endocarditis
Tzemosetal.JAMA;2008:300;11:1317-1325MichelenaetalCirculaGon.2008;117:2776-2784.)
Recent studies suggest low incidence: • Olmsted county:
• 2% per year incidence • Toronto study:
• 0.3% per year incidence
AHA guidelines no longer suggest bacterial endocarditis prophylaxis, except if prior history of endocarditis.
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BAV - Aortopathy
Siuetal.JAmCollCardiol2010;55:2789-800.Tadrosetal.CirculaGon2009;119:880-90.
Prevalence of Aortic Dilation • 20% - 84% amongst pts with BAV
• Differences in study populations • Assessment techniques • Aortic-size thresholds • Heterogenous nature of the disease
• Children with BAV have larger ascending aorta & enlarges faster cf matched tricuspid controls
• All segments of ascending aorta are larger in adults with BAV cf tricuspid controls
• Independent of BP, peak aortic velocities, LV ejection time
• Prevalence of tubular ascending aorta dilation increases with age:
<30 yrs 30-39yrs 40-49yrs 50-60yrs >60yrs
56% 74% 85% 91% 88%
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BAV - Aortopathy
Vermaetal.NEJM2014370;20
Patterns of Aortic Dilation
Type 1: Dilation of tubular ascending aorta primarily along convexity with mild-moderate root dilation.
Most common; associated with R-L cusp fusion & AS
Type 2: Isolated tubular ascending aorta dilation, which may extend into the arch, with relative sparing of
aortic root. Associated with R-N cusp fusion.
Type 3: Root phenotype - isolated root dilation, normal tubular/arch dimensions.
Rarer; associated with younger age at diagnosis; genetic.
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BAV - Aortopathy
Vermaetal.NEJM2014370;20Yasudaetal.CirculaGon2003;108;supp;291-4
PathophysiologyGenetic evidence • Aortopathy prevalent in 1st degree relatives of BAV pts • Aortic dimension differences in BAV cf controls in spite of
haemodynamic variable adjustments • Aortic dilation in BAVs (incl. children) without AS/AR • Progressive aortic dilation with or without AVR
Deficiency of Fibrillin 1; Increased matrix metalloproteinases - loss of integrity in extracellular matrix
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BAV - Aortopathy
Barkeretal.CircCardiovascImaging2012;5:457-66.Hopeetal.Radiology2010;255:53-61.MichelenaetalCirculaGon.2008;117:2776-2784.)Tzemosetal.JAMA;2008:300;11:1317-1325.Vermaetal.NEJM2014370;20
PathophysiologyHaemodynamic evidence Recent MRI studies - • Abnormal transvalvular-flow patterns despite apparent normally
functioning BAVs • Regional increases in wall-shear stress
However, valve morphology did not predict events in population studies
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BAV - Aortopathy
HardikaretalJACC:CardiovascularImaging2013;6;12:1311-20Robicesketal.HSRProcIntensiveCareCardiovascAnaesth2012;4:109-18.
Pathophysiology
Robicsek et al: No histological differences of foetal BAV vs
control aortic tissue
Genetic predilection compounded by
haemodynamic insults?
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BAV - Aortopathy
MichelenaetalCirculaGon.2008;117:2776-2784.)Tzemosetal.JAMA;2008:300;11:1317-1325.Vermaetal.NEJM2014370;20
Natural HistoryAscending aortic aneurysm:
• At 25yrs: 26% will develop aneurysm (≥45 mm ascending aorta)
BAV: 84.9/10,000 pt-yrs
All population: 1.04/10,000 pt-yrs
Age-adjusted RR: 86.2
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BAV - Aortopathy
HardikaretalJACC:CardiovascularImaging2013;6;12:1311-20
Natural HistoryAscending aortic aneurysm:
• Rate of growth higher in persons with BAV c/f tricuspid valve • Tricuspid: 0.16 mm/yr uniformly over 6 decades • BAV: 0.20 - 1.9 mm/yr
Accelerating rate of aortic dimension increase with increasing age
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BAV - Aortopathy
Michelenaetal.JAMA2011;306(10):1104-1113
Natural HistoryAscending aortic aneurysm: Predictors
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BAV - Aortopathy
Michelenaetal.JAMA2011;306(10):1104-1113Tzemosetal.JAMA;2008:300;11:1317-1325.
Natural HistoryAortic dissection • Toronto study:
• 0.1% per pt-yrs over 9yrs • 5/642 pts (3 type A, 2 type B)
• Olmsted County study: • At 25yrs: 0.5% risk of dissection
• 2/416 pts (1 type A, 1 type B) • 3.1 cases/10,000 person-yrs
• Pts >50yrs age: 17.4 cases/10,000 person-yrs • Baseline aneurysm: 44.9 cases/10,000 person-yrs
• 7% longer-term rate of dissection • RR 8.4
No dissections when aortic diameter <45mm or normal functioning aortic valve
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BAV - Aortopathy
Girdauskasetal.JThoracCardiovascSurg2014;147:276-82
Natural HistoryAortic dissection Risk after AVR - 153 BAV pts vs 172 TAV pts: • 3 dissections over 3566 pt-yrs
• All in TAV group • Reoperation rates lower in BAV cf TAV: 3% vs 5%
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BAV - AortopathyNatural HistoryAortic dissection Low rates in contemporary series - • Serial surveillance • Surgery changes natural history of BAV
Does size really matter? • Changes in 2014 AHA guidelines reflect the low incidence observed
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BAV - ManagementSurveillanceClass I [AHA] • Annual aortic imaging if
• Aortic dilation >4.5 cm • Rapid rate of change in aortic diameter • Family history of dissection
Screening • First-degree family members of pts with BAV
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BAV - ManagementMedical• Scarce evidence of efficacy
• No evidence for altering natural history in BAV • AHA recommendation
• Dilated aortic root/ascending aorta: • ACEI/ARB & BB to reduce SBP to the lowest tolerated
levels • AS/AR:
• Treatment of systemic hypertension
Current trial: Atenolol and Telmisartan in BAV aortopathy - RCT
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BAV - ManagementRepair of BAV• Attractive given young cohort of BAV pts with AI • No RCTs of repair vs replacement • When to consider:
• Regurgitant valves • Pliable leaflets • Minimal fibrosis/calcification • No more than mild cusp thickening • Minor fenestrations
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BAV - Management
Repair of BAV• Effective height:
• Height to which central free margin of cusp rises over the aortic insertion line of cusp
• N = 9-10mm • Prolapse: <6-7mm
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BAV - ManagementRepair of BAV - TechniquesRestore cusp integrity • Closing tears/perforations by direct suture or autologous
pericardial patching
Line-up discloses presence of tissue redundancy
Sufficient tissue; closure of cleft
Excess tissue; triangular resection, plication
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BAV - ManagementRepair of BAV - TechniquesDeficient tissue • Overcorrecting free margin of the conjoint cusp to a length
shorter than free margin of reference cusp • Increases systolic doming
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BAV - ManagementRepair of BAV - TechniquesCommissural repair
Resuspension of detached commissure -pledgeted sutures & plication
Misalignment & splaying -pledgeted oblique Cabrol-like stitch
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BAV - ManagementBAV repair with dilated annulus:
Bavariaetal.STS2013.AnnThorSurg.Aicheretal.CirculaGon2011;123:178-185
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BAV - ManagementFailure of BAV repair in dilated annulus irrespective of SCA or Remodelling style root
Aicheretal.CirculaGon2011;123:178-185
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BAV - ManagementBentall's
Survival similar to age/sex matched controls at 12 yrs
Etzetal.AnnThoracSurg2007;84:1186-94
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BAV - Management
Ross ProcedureConcern regarding intrinsic wall abnormalities of the pulmonary artery in BAV pts
Etzetal.AnnThoracSurg2007;84:1186-94
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BAV - ManagementAHA 2014: Surgical Intervention Class 1Diameter of the aortic sinuses or ascending aorta is greater than 5.5 cm [B]
Class 2aDiameter of the aortic sinuses or ascending aorta is greater than 5.0 cm and a risk factor for dissection is present (family history of aortic dissection or if the rate of increase in diameter is 0.5 cm per year) [C]
Replacement of the ascending aorta is reasonable in patients with a bicuspid aortic valve who are undergoing aortic valve surgery because of severe AS or AR if the diameter of the ascending aorta is greater than 4.5 cm. [C]