TRICUSPID ATRESIA. Dr Vivek pillai. Defined as congenital absence or agenesis of the tricuspid valve, with no direct communication between the right atrium and right ventricle. Incidence : 0.06 per 1000 live births Prevalence :in clinical series of congenital heart disease is 1- 2.4 %.
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TRICUSPID ATRESIA Dr Vivekpillai
Defined as congenital absence or agenesis of the tricuspid valve, with no direct communication between the right atrium and right ventricle. • Incidence : 0.06 per 1000 live births • Prevalence :in clinical series of congenital heart disease is 1- 2.4 %.
HISTORY • First reported by Kreysig in 1817. • Clinical features reported by Bellet and Stewart in 1933. • Also by Taussig and Brown in 1936.
EMBRYOLOGY • During early embryogenesis,the process of expansion of the inlet portion of the right ventricle coincides with development of the AV valves. • Failure of this process of inlet expansion is the pathogenetic mechanism for the usual muscular variety of tricuspid atresia.
The less common variety , with well formed but fused leaflets,occurs if the embryological insult occurs later in gestation. • If valve fusion is incomplete, tricuspid stenosis develops.
ANATOMY • The most common type of tricuspid atresia is muscular . • It is characterized by a dimple or a localized fibrous thickening in the floor of the right atrium at the expected site of the tricuspid valve. • The muscular variety constitutes 89% of cases.
In the membranous type (6.6%), the atrioventricular portion of the membranous septum forms the floor of the right atrium at the expected location of the tricuspid valve. • This particular type appears to be associated with absent pulmonary valve leaflets.
Minute valvar cusps are fused together in the valvar type (1%). • In the Ebstein type (2.6%), fusion of the tricuspid valve leaflets occurs; attachment is displaced downward, and plastering of the leaflets to the right ventricular wall occurs.
The atrioventricular canal type is extremely rare (0.2%). -a leaflet of the common atrioventricular valve seals off the only entrance into the right ventricle.
The right atrium is enlarged and hypertrophied. • An interatrial communication is necessary for survival. • This communication most commonly is a stretched patent foramen ovale.
A true ASD is much less common and when present is almost always in the ostium secundum location. • Rarely, the patent foramen ovale is obstructive and may form an aneurysm of the fossa ovalis, which is sometimes large enough to produce mitral inflow obstruction
The left atrium may be enlarged, especially when the pulmonary blood flow is increased. • The mitral valve is morphologically normal; it is rarely incompetent and has a large orifice. • The left ventricle is enlarged and hypertrophied but usually morphologically normal
The right ventricle is small and hypoplastic. • In patients with a large VSD or TGA, the size of the right ventricle may be larger, but, even in these patients, the right ventricle is smaller than normal.
VSD in tricuspid atresia • Associated VSD is common with TA, seen in about 90% of individuals during infancy. • Is usually perimembranous but also may occur in the muscular septum or as a component of an atrioventricular septal defect, although the latter is rare. • At birth the VSD is usually restrictive,permitting adequate but not excessive pulmonary blood flow .
This advantage is often lost, as 40% of these defects close spontaneously/ decrease in size-”acquired pulmonary atresia” • The majority of defects close in the first yr of life. • These restrictive VSD’S cause subpulmonic obstruction in pts with normally related great arteries, and subaortic obstruction in pts with TGA.
Classification Proposed by Kuhne and later modified Type 1 : normally related great arteries (70 – 80%) a. intact ventricular septum with pulmonary atresia( 9%) b. small ventricular septal defect and pulmonary stenosis( 51%) c. large ventricular septal defect without pulmonary stenosis ( 9%)
Type ii : D-transposition of great arteries (12 – 25%) a. ventricular septal defect with pulmonary atresia( 2%) b. ventricular septal defect with pulmonary stenosis( 8%) c. ventricular septal defect without pulmonary stenosis(18%)
Type 3 :L- Transposition or malposition of great arteries (3-6%) associated complex lesions, ie., truncus arteriosus, endocardial cushion defect
ADDITIONAL CARDIOVASCULAR ABNORMALITIES- 20% • Coarctation of aorta – 8% • Persistent left SVC • Juxtaposition of atrial appendages-50% of TA with TGA. • Right aortic arch • Abnormalities of mitral apparatus- cleft in AML,malattachment of the valve,direct attachment of the mitral leaflets to papillary muscles.
PHYSIOLOGY-TA WITH NRGA • Obligatory rt to left shunt at atrial level. • LA receives both the entire systemic and pulmonary venous return. • The entire mixture flows into the LV which is the sole pumping chamber for the pulmonary and systemic circulation.
When the great arteries are normally related,pulm artery blood flow is usually reduced as the restrictive VSD, is a zone of subpulmonic stenosis. • LV overload is curtailed but at the cost of cyanosis. • This is so in 90% of cases.
In TGA • The VSD is almost always non-restrictive and pulmonary stenosis is usually absent. • Low PVR results in abundant pulmonary arterial blood flow. • Minimal cyanosis,marked LV volume overload. • If these pts have a restrictive vsd,or infundibular narrowing→diminished syst circulation→metabolic acidosis and shock.
SEX PREDILECTION • Tr. Atresia with normally related great arteries have an equal frequency in males and females. • If TGA is present→male preponderance. • No male preponderance with juxtaposition of atrial appendages.
GENETICS • Although specific genetic causes of the malformation remain to be determined in humans, the FOG2 gene may be involved in the process. • This has however been validated only in animal studies. • Familial recurrence is low , and recurrence in siblings is only about 1%.
OVERALL ACTUARIAL SURVIVAL IN INFANTS WITH TRICUSPID ATRESIA • 1 year- 72%. • 5 years- 52%. • 10 years- 46%
NATURAL HISTORY • Few infants with tr. Atresia and normally related gr . Arteries with an intact ventricular septum survive beyond 6 months of age without surgical palliation. • Intense hypoxia and death ensue unless the ductus is patent, or adequate systemic to PA collaterals are present , either of which are unlikely.
TR. ATRESIA WITH NRGA AND SMALL VSD. • The VSD in such patients closes spontaneously or is excessively obstructive, so that majority of patients die by one year. • Rarely, a favorable balance is achieved b/w the presence of VSD and pulm . Blood flow , permitting survival from 2nd to 5th decades.
TR. ATRESIA WITH NRGA AND LARGE VSD. • Pts with TA , normally related great arteries and large VSD do not fare well • Excessive pulmonary arterial flow results in vol. overload of LV and CCF. • Pts have lived to ages 4 to 6 years. • In exceptional cases, long survivals have been reported between ages 32 and 45 yrs.
TR. ATRESIA WITH TGA • Same poor longevity patterns hold when TA occurs with complete transposition and large VSD. • TA with TGA with subaortic stenosis( restrictive VSD) is an ominous combination. • Exceptional survivals to mid-late teens have been recorder. • problems related to increased longevity-I.E,brain abscess, paradoxical embolism
Physical examination- appearance • Dysmorphic facies-occasionally “cat-eye” syndrome or congenital coloboma may be seen.
JVP • Increase in the A wave amplitude , due to the restrictive interatrial communication. • Y descent is slow • In LVF, A and V waves increase in amplitude.
Precordium • LV impulse without a RV impulse in a cyanotic patient. • A gentle RV impulse in pt with TA ,complete transposition and a well dev RV . • Palpable thrill if VSD is restrictive.
AUSCULTATION • First heart sound is single . • Second usually single, but a soft delayed pulmonic component is occasionally present. • TA with normally related great arteries, prominent systolic murmur originates at the site of restrictive VSD – holosystolic, maximal at the mid to lower left sternal edge.
TA with complete transposition and increased pulmonary blood flow • Holosystolic murmur – across VSD • S2 – single but always loud • S3 • MDM • 4th heart sounds are rare in any of the varieties of tricuspid atresia.
Pulmonary vascular resistance – high • VSD murmur vanishes • Soft midsystolic murmur- anterior aortic root • Rarely, the loud second component from the dilated hypertensive posterior pulmonary trunk is heard.
TA with complete transposition, coexisting pulmonic or subpulmonic stenosis – midsystolic murmur – loudness and length vary inversely with degree of obstruction
ECG • Tall peaked right atrial P waves are usually seen • Biatrial P – if left atrial volume is↑ due to ↑PBF. • PR interval- normal. • QRS axis – left and superior ( type 1 pts) • Absence of RV forces in precordial leads
CHEST X-RAY-TA WITH NRGA AND SMALL VSD • Pulmonary vascularity reduced. • Pulmonary artery segment – inconspicuous. • Heart size – normal. • Right cardiac border, esp in LAO projection – superior convexity caused by enlargement of RA and its appendage.
Inferior border – flat or receding owing to absence of RV. • LAO – Humped appearance of right cardiac border and a prominent left cardiac silhouette
TA with complete transposition and no obstruction • Lungs – plethoric • LV, LA, RA – enlarged • Right cardiac border seldom has distinctive hump-shaped contour – RV is relatively well developed
TA with complete transposition and PS • Pulmonary blood flow is normal or reduced • Ascending aorta and pulmonary trunk are not border forming (narrow vascular pedicle)
ECHOCARDIOGRAM • Presence of an imperforate linear echo density in the location of normal TV • Presence of two great arteries and semilunar valves