Atrezja trójdzielna – Patofizjologia i mechanizm

Atrezja trójdzielna
Patofizjologia i mechanizm

Atrezja trójdzielna to wrodzona wada serca charakteryzująca się całkowitym brakiem zastawki trójdzielnej, co skutkuje brakiem połączenia między prawym przedsionkiem a prawą komorą. Wada ta występuje z częstością około 1,03 na 10 000 żywych urodzeń i stanowi 1-2% wszystkich wrodzonych wad serca. Patogeneza opiera się na zaburzeniu rozwoju zastawek przedsionkowo-komorowych w okresie embriogenezy, prowadząc do hipoplazji prawej komory. Przepływ krwi jest możliwy dzięki obligatoryjnemu przeciekowi prawo-lewemu na poziomie przedsionków (ASD lub PFO), a obecność ubytku przegrody międzykomorowej (VSD) oraz stan zastawki płucnej determinują stopień sinicy i ryzyko niewydolności serca. Wyróżnia się trzy typy atrezji trójdzielnej w zależności od relacji wielkich naczyń: typ I (70-80%) z prawidłowym położeniem, typ II (około 30%) z przełożeniem wielkich naczyń (TGA) oraz typ III z rzadkim skorygowanym przełożeniem wielkich naczyń. Przeżycie noworodków zależy od obecności odpowiednich przecieków i przepływu płucnego, z 1-rocznym przeżyciem na poziomie 72% i 10-letnim 46%.

Patogeneza atrezji trójdzielnej

Atrezja trójdzielna jest wrodzoną wadą serca charakteryzującą się całkowitym brakiem zastawki trójdzielnej, co prowadzi do braku połączenia między prawym przedsionkiem a prawą komorą. Występuje z częstością około 1,03 na 10 000 żywych urodzeń, stanowiąc około 1-2% wszystkich wrodzonych wad serca¹². Patogeneza tej wady nie jest w pełni poznana, jednak wiadomo, że rozwija się ona we wczesnym okresie embriogenezy serca.

Zaburzenia rozwojowe w embriogenezie

Atrezja trójdzielna powstaje w wyniku zaburzenia prawidłowego rozwoju zastawek przedsionkowo-komorowych wywodzących się z poduszeczek wsierdzia. Podczas wczesnej embriogenezy, w procesie ekspansji części napływowej prawej komory, dochodzi jednocześnie do rozwoju zastawek przedsionkowo-komorowych. Niepowodzenie w tym procesie ekspansji jest mechanizmem patogenetycznym prowadzącym do najczęściej występującej, mięśniowej postaci atrezji trójdzielnej³⁴. W większości przypadków ujście trójdzielne objawia się jako zagłębienie w prawym przedsionku, występujące w formie mięśniowej.

Rzadziej spotykana postać atrezji trójdzielnej, z dobrze uformowanymi, ale zrośniętymi płatkami zastawki, pojawia się, gdy zaburzenie embriologiczne występuje później w okresie ciąży. Jeśli zrost płatków jest niepełny, rozwija się zwężenie zastawki trójdzielnej⁵. W rzadziej występujących przypadkach dochodzi do fuzji częściowo odwarstwowionych płatków, co prowadzi do tworzenia błon, obserwowanych w typie Ebsteina⁶.

Podłoża genetyczne

Chociaż dokładna przyczyna atrezji trójdzielnej pozostaje nieznana, badania wskazują na możliwe powiązania genetyczne. Wada ta została stwierdzona w przypadkach anomalii chromosomalnych, takich jak mikrodelecje 22q11, 4q31, 8p23 i 3p. Zidentyfikowano również geny potencjalnie zaangażowane w jej rozwój: ZFPM2, HEY2, NFATC1, NKX2.5 i MYH6⁷. Badania na modelach zwierzęcych łączą geny ZFPM2/FOG2 i HEY2 z patogenezą atrezji trójdzielnej⁸⁹. Częstość występowania rodzinnego jest jednak niska, a ryzyko powtórzenia się u rodzeństwa wynosi tylko około 1%¹⁰.

Atrezja trójdzielna została również opisana w związku z zespołami Alagille’a i Ellis-Van Crevelda¹¹. Wykazuje także związek z zespołem VATER, trisomią i zespołem DiGeorge’a¹².

Mechanizm patofizjologiczny

W atrezji trójdzielnej z powodu braku zastawki trójdzielnej nie istnieje bezpośrednie połączenie między prawym przedsionkiem a prawą komorą. To zaburzenie przepływu krwi ma kluczowe znaczenie dla patofizjologii tej wady i determinuje jej objawy kliniczne.

Zaburzenia przepływu wewnątrzsercowego

W sercu z atrezją trójdzielną krew żylna powracająca z organizmu przez żyły główne górną i dolną do prawego przedsionka nie może przepłynąć do prawej komory z powodu braku zastawki trójdzielnej. W tej sytuacji konieczne jest istnienie ubytku w przegrodzie międzyprzedsionkowej (ASD, atrial septal defect) lub drożnego otworu owalnego (PFO, patent foramen ovale), co stanowi obligatoryjne połączenie umożliwiające przeżycie¹³¹⁴.

Krew z prawego przedsionka przepływa przez ubytek przegrody międzyprzedsionkowej do lewego przedsionka, a następnie do lewej komory. W lewym przedsionku następuje mieszanie się krwi żylnej (o niskiej zawartości tlenu) z krwią utlenowaną powracającą z płuc przez żyły płucne. Ta mieszana krew dostaje się do lewej komory, która funkcjonuje jako jedyna pompa, mieszając powrót żylny systemowy i płucny¹⁵.

Z powodu obligatoryjnego przecieku prawo-lewego na poziomie przedsionków, saturacja krwi w lewym przedsionku jest zmniejszona¹⁶. Dalszy przepływ krwi wewnątrz serca zależy od obecności lub braku innych towarzyszących anomalii, takich jak ubytek przegrody międzykomorowej (VSD), zwężenie zastawki płucnej lub przełożenie wielkich naczyń.

Rola ubytku przegrody międzykomorowej

W większości przypadków atrezji trójdzielnej występuje ubytek przegrody międzykomorowej (VSD), który umożliwia przepływ krwi z lewej komory do hipoplastycznej prawej komory i dalej do tętnicy płucnej¹⁷. Wielkość VSD oraz obecność zwężenia zastawki płucnej mają istotny wpływ na przepływ krwi do płuc.

Gdy VSD jest duży i nie ma zwężenia zastawki płucnej, przepływ krwi do płuc może być prawidłowy, co skutkuje normalnym utlenowaniem i zmniejszoną sinicą¹⁸. Jednak jeśli VSD jest zbyt duży, może dojść do nadmiernego przepływu krwi do płuc, co z kolei prowadzi do niewydolności serca¹⁹²⁰.

Natomiast w przypadku współistnienia zwężenia zastawki płucnej lub atrezji płucnej, przepływ krwi do płuc jest ograniczony, co skutkuje nasiloną sinicą²¹. W takiej sytuacji przepływ płucny może być zależny od drożności przewodu tętniczego (PDA, patent ductus arteriosus)²².

Typy atrezji trójdzielnej i ich mechanizmy

Atrezja trójdzielna jest klasyfikowana w zależności od związku pomiędzy komorami a wielkimi naczyniami (aortą i tętnicą płucną) na kilka typów.

W typie I, który występuje najczęściej (70-80% przypadków), wielkie naczynia mają prawidłowe położenie. Aorta odchodzi od lewej komory, a tętnica płucna od hipoplastycznej prawej komory²³²⁴. W tej sytuacji przepływ krwi z lewej komory odbywa się przez aortę oraz, jeśli istnieje VSD, przez ubytek do prawej komory i dalej do tętnicy płucnej. Jeśli VSD jest mały lub występuje zwężenie zastawki płucnej, przepływ płucny jest zmniejszony, co prowadzi do nasilonej sinicy. Większość pacjentów z tym typem prezentuje sinicę²⁵.

W typie II (około 30% przypadków) występuje przełożenie wielkich naczyń (TGA). Tętnica płucna odchodzi od lewej komory, a aorta od małej, hipoplastycznej prawej komory²⁶²⁷. W tym przypadku przepływ do aorty zależny jest od wielkości VSD. Jeśli VSD jest zbyt mały, może dojść do zwężenia podzastawkowego aorty i spadku rzutu serca. W odpowiedzi ciśnienie w lewej komorze wzrasta, co zwiększa przepływ płucny, prowadząc do niewydolności serca i nadciśnienia płucnego. Pacjenci z tym typem często nie wykazują sinicy²⁸.

W typie III występuje skorygowane przełożenie wielkich naczyń²⁹. Jest to najrzadziej spotykany typ.

Koarktacja aorty lub przerwany łuk aorty są często związane z atrezją trójdzielną i występują częściej w przypadku przełożenia wielkich naczyń³⁰.

Konsekwencje hemodynamiczne

Lewa komora w atrezji trójdzielnej stanowi większość masy komorowej. Z powodu przeciążenia objętościowego (lewa komora otrzymuje cały powrót żylny) oraz przewlekłego niedotlenienia, może dojść do upośledzenia funkcji komorowej, co prowadzi do włóknienia, zmniejszenia frakcji wyrzutowej, poszerzenia pierścienia mitralnego i niedomykalności zastawki mitralnej³¹.

Przeżycie noworodków z atrezją trójdzielną zależy od obecności odpowiedniego przecieku na poziomie przedsionków (ASD lub PFO) oraz od przepływu płucnego, który może być zapewniony przez VSD lub drożny przewód tętniczy. Bez tych alternatywnych dróg przepływu krwi, śmierć nastąpiłaby wkrótce po urodzeniu³².

Ogólne przeżycie u niemowląt z atrezją trójdzielną wynosi 72% w 1. roku życia, 52% w 5. roku życia i 46% w 10. roku życia³³. Nieliczne niemowlęta z atrezją trójdzielną i prawidłowo ułożonymi wielkimi naczyniami z nieuszkodzoną przegrodą międzykomorową przeżywają ponad 6 miesięcy bez interwencji chirurgicznej. Intensywna hipoksja i śmierć następują, chyba że przewód tętniczy pozostaje drożny lub obecne są odpowiednie naczynia oboczne tętniczo-płucne³⁴.

Wpływ na rozwój prawej komory

W atrezji trójdzielnej brak przepływu krwi przez zastawkę trójdzielną prowadzi do hipoplazji prawej komory. Rozwój komór serca jest stymulowany przez przepływ krwi przez nie, a ponieważ w tej wadzie krew nie przepływa przez zastawkę trójdzielną do prawej komory, pozostaje ona mała i niedorozwinięta³⁵³⁶.

Stopień hipoplazji prawej komory jest zmienny i często związany z wielkością ubytku przegrody międzykomorowej. W niektórych przypadkach prawa komora może być praktycznie nieobecna. Ta hipoplazja prawej komory ma kluczowe znaczenie dla funkcjonowania serca jako całości i determinuje podejście terapeutyczne³⁷.

Atrezja trójdzielna, ze względu na hipoplazję prawej komory, klasyfikowana jest jako wada serca z pojedynczą komorą funkcjonalną. Oznacza to, że lewa komora musi przejąć funkcję całego serca, czyli pompować krew zarówno do krążenia systemowego, jak i płucnego³⁸.

Podsumowanie patogenezy

Atrezja trójdzielna jest złożoną wrodzoną wadą serca, której patogeneza obejmuje brak rozwoju zastawki trójdzielnej, co prowadzi do braku połączenia między prawym przedsionkiem a prawą komorą. W konsekwencji obserwujemy hipoplazję prawej komory, obligatoryjny przeciek prawo-lewy na poziomie przedsionków oraz zmienny przepływ płucny w zależności od towarzyszących anomalii.

Mechanizm przepływu krwi wewnątrz serca jest uzależniony od obecności i wielkości ubytków w przegrodach międzyprzedsionkowej i międzykomorowej, a także od relacji między komorami a wielkimi naczyniami. Te czynniki determinują stopień sinicy, ryzyko niewydolności serca oraz ogólne rokowanie u pacjentów z atrezją trójdzielną.

Chociaż dokładna etiologia tej wady pozostaje nieznana, badania wskazują na możliwe podłoże genetyczne. Leczenie wymaga wieloetapowego podejścia chirurgicznego, mającego na celu odtworzenie prawidłowego przepływu krwi, przy czym ostatecznym etapem jest zazwyczaj operacja Fontana, tworząca krążenie typu Fontana³⁹.

Kolejne rozdziały

Zapraszamy do dalszego czytania naszego leksykonu.

Wybierz kolejny rozdział z menu poniżej, aby otworzyć nową podstronę kompedium wiedzy i uzyskać szczegółowe informację o leku, substancji lub chorobie.

Materiały źródłowe

#1 Tricuspid Atresia | Boston Children’s Hospital
https://www.childrenshospital.org/conditions/tricuspid-atresia
Tricuspid atresia is a congenital heart defect, occurring in two out of every 10,000 live births. Relatively rare, it accounts for about 1 to 2 percent of all cases of congenital heart disease. […] In tricuspid atresia, lack of development of the tricuspid valve prevents oxygen-poor (blue) blood from passing from the right atrium to the right ventricle and on to the lungs as it should. Instead, blood passes from the right atrium to the left atrium and then to the only pumping chamber, the left ventricle. […] Most often, tricuspid atresia occurs sporadically with no clear reason for its development. Some congenital heart defects may have a genetic link, causing heart problems to occur more often in certain families.
#2 Tricuspid Atresia: Background, Pathophysiology, Etiology
https://emedicine.medscape.com/article/158359-overview
Tricuspid atresia is the third most common form of cyanotic congenital heart disease, with a prevalence of 1.03 per 10,000 live births. The deformity consists of a complete lack of formation of the tricuspid valve with absence of direct connection between the right atrium and right ventricle. […] Three types of tricuspid atresia are described, depending on the associated relationship of the great vessels. In type I, the great arteries are related normally; in type II, the great arteries are d-transposed; and in type III, the great arteries are l-transposed. The types are further subclassified according to the presence or absence of ventricular septal defects and pulmonary valve pathology. […] With the absence of the tricuspid valve and no continuity between the right atrium and right ventricle, venous blood returning to the right atrium can exit only by an intra-atrial communication. Because of the obligatory right-to-left shunt at the level of the atria, saturation of the left atrial blood is diminished.
#3 Tricuspid Atresia – StatPearls – NCBI Bookshelf
https://www.ncbi.nlm.nih.gov/books/NBK554495/
Tricuspid atresia is a congenital heart defect that results in cyanosis due to the absence of communication between the right atrium and ventricle caused by the complete agenesis of the tricuspid valve. […] The root cause of this condition lies in abnormal heart development during embryogenesis without any confirmed genetic predisposition. […] The pathogenesis of tricuspid atresia is not fully understood, but it occurs due to the disruption of the normal development of the atrioventricular valves from the endocardial cushion. […] In most patients, the tricuspid inlet manifests as a dimple in the right atrium, presenting in a muscular form. […] In less common occurrences, a fusion involves partially delaminated leaflets, resulting in the formation of membranes, as observed in the Ebstein type.
#4 Tricuspid atresia | PPT
https://www.slideshare.net/slideshow/tricuspid-atresia-230184837/230184837
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. […] Overall actuarial survival in infants with tricuspid atresia is 1 year- 72%. 5 years- 52%. 10 years- 46%. […] Few infants with tricuspid atresia and normally related great 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 pulmonary artery collaterals are present, either of which are unlikely.
#5 Tricuspid atresia | PPT
https://www.slideshare.net/slideshow/tricuspid-atresia-230184837/230184837
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. […] Overall actuarial survival in infants with tricuspid atresia is 1 year- 72%. 5 years- 52%. 10 years- 46%. […] Few infants with tricuspid atresia and normally related great 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 pulmonary artery collaterals are present, either of which are unlikely.
#6 Tricuspid Atresia – StatPearls – NCBI Bookshelf
https://www.ncbi.nlm.nih.gov/books/NBK554495/
Tricuspid atresia is a congenital heart defect that results in cyanosis due to the absence of communication between the right atrium and ventricle caused by the complete agenesis of the tricuspid valve. […] The root cause of this condition lies in abnormal heart development during embryogenesis without any confirmed genetic predisposition. […] The pathogenesis of tricuspid atresia is not fully understood, but it occurs due to the disruption of the normal development of the atrioventricular valves from the endocardial cushion. […] In most patients, the tricuspid inlet manifests as a dimple in the right atrium, presenting in a muscular form. […] In less common occurrences, a fusion involves partially delaminated leaflets, resulting in the formation of membranes, as observed in the Ebstein type.
#7 Orphanet: Tricuspid atresia
https://www.orpha.net/en/disease/detail/1209
A rare congenital heart malformation characterized by absence of the tricuspid valuvar annulus (absent right atrioventricular connection/junction) or an imperforate tricuspid valve leading to severe hypoplasia of right ventricle (functionally univentricular heart). The malformation is associated with normally related great arteries (70 to 80% of cases) or transposed great vessels, an obligatory interatrial connection that is crucial for survival (patent oval foramen or atrial septal defect ostium secundum type), ventricular septal defect (VSD), pulmonary outflow obstruction (pulmonary atresia, stenosis or hypoplasia), aortic coarctation and/or aortic arch interruption. […] Etiology is still largely unknown. Tricuspid atresia results from an arrest in cardiac development at an early stage, when the atrioventricular canal is supported only by the primary (left) ventricle and there is no connection between the right atrium and the developing right ventricle. Tricuspid atresia is found in chromosomal anomalies such as 22q11, 4q31, 8p23 and 3p microdeletions. Some genes have been recognized as potentially involved: ZFPM2, HEY2, NFATC1, NKX2.5, and MYH6. Tricuspid atresia has also been reported in association with Alagille and Ellis Van Creveld syndromes.
#8 Tricuspid Atresia | Thoracic Key
https://thoracickey.com/tricuspid-atresia-4/
The true embryologic basis for TA remains elusive, as is the case with many congenital heart defects. It appears to be related to a result of malalignment of the ventricular septum in relation to the atria and endocardial cushions. […] Animal studies in mice associate ZFPM2/FOG2 and HEY2 genes in the pathogenesis of TA.
#9 Tricuspid atresia | PPT
https://www.slideshare.net/slideshow/tricuspid-atresia-230184837/230184837
Tricuspid atresia with normally related great arteries have an equal frequency in males and females. If transposition of great arteries is present, there is male preponderance. […] 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%.
#10 Tricuspid atresia | PPT
https://www.slideshare.net/slideshow/tricuspid-atresia-230184837/230184837
Tricuspid atresia with normally related great arteries have an equal frequency in males and females. If transposition of great arteries is present, there is male preponderance. […] 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%.
#11 Orphanet: Tricuspid atresia
https://www.orpha.net/en/disease/detail/1209
A rare congenital heart malformation characterized by absence of the tricuspid valuvar annulus (absent right atrioventricular connection/junction) or an imperforate tricuspid valve leading to severe hypoplasia of right ventricle (functionally univentricular heart). The malformation is associated with normally related great arteries (70 to 80% of cases) or transposed great vessels, an obligatory interatrial connection that is crucial for survival (patent oval foramen or atrial septal defect ostium secundum type), ventricular septal defect (VSD), pulmonary outflow obstruction (pulmonary atresia, stenosis or hypoplasia), aortic coarctation and/or aortic arch interruption. […] Etiology is still largely unknown. Tricuspid atresia results from an arrest in cardiac development at an early stage, when the atrioventricular canal is supported only by the primary (left) ventricle and there is no connection between the right atrium and the developing right ventricle. Tricuspid atresia is found in chromosomal anomalies such as 22q11, 4q31, 8p23 and 3p microdeletions. Some genes have been recognized as potentially involved: ZFPM2, HEY2, NFATC1, NKX2.5, and MYH6. Tricuspid atresia has also been reported in association with Alagille and Ellis Van Creveld syndromes.
#12 Tricuspid Atresia: Symptoms, Treatment & Prognosis
https://my.clevelandclinic.org/health/diseases/14789-tricuspid-atresia
Tricuspid atresia is a congenital heart defect (present at birth) that occurs when the tricuspid valve doesn’t form. The tricuspid valve is normally between two chambers on the right side of your heart, the right atrium (upper chamber) and right ventricle (lower chamber). […] With tricuspid atresia, you have solid tissue instead of the tricuspid valve. This sheet of tissue blocks blood flow from the right atrium to the right ventricle, where blood would normally go. Because of this blockage, the right ventricle is usually small and underdeveloped. The other valve on the right side (pulmonary valve) between the right ventricle and your lungs can also be underdeveloped. […] Although tricuspid valve atresia has known risk factors, the exact causes of it are unknown. Congenital heart diseases develop while a fetus is in the uterus and heart development is taking place. This can start in the first six weeks of your pregnancy. […] Tricuspid atresia has a connection with VATER syndrome, trisomy and DiGeorge syndrome.
#13 Tricuspid Atresia | Lurie Children’s
https://www.luriechildrens.org/en/specialties-conditions/tricuspid-atresia/
In this condition, there’s no tricuspid valve. That means no blood can flow from the right atrium to the right ventricle. As a result, the right ventricle is small and not fully developed. The child’s survival depends on there being an opening in the wall between the atria called an atrial septal defect (ASD) or patent foramen ovale (PFO). Otherwise, the blood returning from the body to the right atrium gets stuck in the right atrium and cannot return to the body. Since blood cannot get to the body, death occurs unless something is done to create an ASD or PFO. […] The other problem with this defect is that no blood can get to the pulmonary arteries because the right ventricle is usually undeveloped or nonexistent. There are special cases of tricuspid atresia with a hole between the ventricles (ventricular septal defect, VSD, and/or transposition of the great arteries, TGA). These are complex heart defects with a combination of defects which can change the types of treatment needed although they are overall similar.
#14 Tricuspid atresia – Wikipedia
https://en.wikipedia.org/wiki/Tricuspid_atresia
Tricuspid atresia is a form of congenital heart disease whereby there is a complete absence of the tricuspid valve. Therefore, there is an absence of right atrioventricular connection. This leads to a hypoplastic (undersized) or absent right ventricle. This defect occurs during prenatal development, when the heart does not finish developing. It causes the systemic circulation to be filled with relatively deoxygenated blood. The causes of tricuspid atresia are unknown. […] Tricuspid atresia is caused by complete absence of the tricuspid valve. The underlying cause of this absence remains unknown. This prevents direct blood flow between the right atrium and the right ventricle. […] As there is no communication between the right atrium and the right ventricle, there must be an atrial septal defect to allow blood to flow into the left cardiac chambers. Due to the lack of blood flow into the right ventricle, it will be hypoplastic. In most cases, there will also be a ventricular septal defect allowing some blood into the pulmonary circulation. Due to the lack of blood flow into the pulmonary circulation, there is poor oxygenation of blood, leading to progressively worsening cyanosis.
#15 Congenital Defects Tutorial – Congenital Heart Defects | Atlas of Human Cardiac Anatomy
https://www.vhlab.umn.edu/atlas/congenital-defects-tutorial/right-heart-lesions/tricuspid-atresia.shtml
Tricuspid atresia refers to a defect where the tricuspid valve is absent and the right ventricle is variably hypoplastic. An ASD is always present and can be restrictive. It can be classified into three types which have implications for clinical manifestations and surgical correction (St. Louis): 1) Type I includes those without transposition of the great arteries, 2) Type II includes those with transposition of the great arteries, and 3) Type III refers to those with congenitally corrected transposition of the great vessels. Each of these types can be subdivided based on the degree of obstruction to pulmonary blood flow: […] When the tricuspid valve is absent, blood from the right atrium usually passes through a patent foramen ovale to the left atrium and left ventricle. In more rare cases, it may also pass through an ASD. Atresia of the tricuspid valve results in both the pulmonary and systemic venous returns passing through the foramen ovale and into the left atrium and left ventricle which functions as a single ventricle, mixing systemic and pulmonary venous return.
#16 Tricuspid Atresia: Background, Pathophysiology, Etiology
https://emedicine.medscape.com/article/158359-overview
Tricuspid atresia is the third most common form of cyanotic congenital heart disease, with a prevalence of 1.03 per 10,000 live births. The deformity consists of a complete lack of formation of the tricuspid valve with absence of direct connection between the right atrium and right ventricle. […] Three types of tricuspid atresia are described, depending on the associated relationship of the great vessels. In type I, the great arteries are related normally; in type II, the great arteries are d-transposed; and in type III, the great arteries are l-transposed. The types are further subclassified according to the presence or absence of ventricular septal defects and pulmonary valve pathology. […] With the absence of the tricuspid valve and no continuity between the right atrium and right ventricle, venous blood returning to the right atrium can exit only by an intra-atrial communication. Because of the obligatory right-to-left shunt at the level of the atria, saturation of the left atrial blood is diminished.
#17 Tricuspid atresia – Symptoms & causes – Mayo Clinic
https://www.mayoclinic.org/diseases-conditions/tricuspid-atresia/symptoms-causes/syc-20368392
Many babies born with tricuspid atresia also have a hole between the lower heart chambers. This hole is called a ventricular septal defect (VSD). If this occurs, some blood can flow through the hole directly to the main lung artery. The amount of blood going to the lungs depends on the size of the VSD and whether the pulmonary valve is narrowed. If the VSD is large, too much blood can move to the lungs. This can cause heart failure.
#18 Tricuspid Atresia: Background, Pathophysiology, Etiology
https://emedicine.medscape.com/article/158359-overview
The intracardiac blood flow in tricuspid atresia further depends on the presence or absence of pulmonary arterial pathology. In the absence of pulmonary atresia or pulmonary valve stenosis, the volume of blood to the lungs may be normal with normal oxygenation occurring, resulting in reduced cyanosis. In contrast, with accompanying pulmonary artery or valve stenosis, pulmonary blood flow is reduced, resulting in increased cyanosis. […] The left ventricle comprises most of the ventricular mass in tricuspid atresia. Because of volume overload (the left ventricle receives all the venous return) and persistent hypoxemia, decreased ventricular function may result in fibrosis, decreased ejection fraction, mitral annular dilatation, and mitral insufficiency.
#19 Tricuspid atresia – Symptoms & causes – Mayo Clinic
https://www.mayoclinic.org/diseases-conditions/tricuspid-atresia/symptoms-causes/syc-20368392
Many babies born with tricuspid atresia also have a hole between the lower heart chambers. This hole is called a ventricular septal defect (VSD). If this occurs, some blood can flow through the hole directly to the main lung artery. The amount of blood going to the lungs depends on the size of the VSD and whether the pulmonary valve is narrowed. If the VSD is large, too much blood can move to the lungs. This can cause heart failure.
#20 Tricuspid Atresia
https://scts.org/patients/congenital/procedures/37/tricuspid_atresia/
However, the valve between the right ventricle and the pulmonary artery (pulmonary valve) might be narrowed, which can reduce blood flow to the lungs. If the pulmonary valve isn’t narrowed and if the ventricular septal defect is large, too much blood can flow to the lungs, which can lead to heart failure.
#21 Tricuspid Atresia: Background, Pathophysiology, Etiology
https://emedicine.medscape.com/article/158359-overview
The intracardiac blood flow in tricuspid atresia further depends on the presence or absence of pulmonary arterial pathology. In the absence of pulmonary atresia or pulmonary valve stenosis, the volume of blood to the lungs may be normal with normal oxygenation occurring, resulting in reduced cyanosis. In contrast, with accompanying pulmonary artery or valve stenosis, pulmonary blood flow is reduced, resulting in increased cyanosis. […] The left ventricle comprises most of the ventricular mass in tricuspid atresia. Because of volume overload (the left ventricle receives all the venous return) and persistent hypoxemia, decreased ventricular function may result in fibrosis, decreased ejection fraction, mitral annular dilatation, and mitral insufficiency.
#22 Tricuspid atresia pathophysiology – wikidoc
https://www.wikidoc.org/index.php/Tricuspid_atresia_pathophysiology
Tricuspid atresia occurs during prenatal development. In tricuspid atresia, there is no continuity between the right atrium and right ventricle. Inferior vena cava and superior vena cava collect venous nonoxygenated blood into the right atrium. Through atrial septal defect (ASD), blood come into the left atrium, then left ventricle andaorta. This blood is a mixture of saturated and unsaturated O2. If there is a ventricular septal defect (VSD), this mixed blood in the left ventricle flows into the right ventricle, then via pulmonary artery reaches pulmonary bed and becomes oxygenated, then returns back into the left atrium viapulmonary veins. In diminished pulmonary blood flow whether the flow is dependent on patent ductus arteriosus (PDA), the mixed-blood in aorta flows from this passage intopulmonary artery and pulmonary bed. In the presence of normal positioning of great arteries, cyanosis is more prominent and is affected by the size of VSD. Transpositioning great arteries (TGA) and subaortic stenosis are other associated anomalies.
#23 Tricuspid Atresia – Pathophysiology – Management – TeachMePaeds
https://teachmepaediatrics.com/cardiology/congenital-heart-defects/tricuspid-atresia/
The tricuspid valve is absent and the right ventricle is hypoplastic due to absence of the inflow into the right ventricle. In the vast majority of cases there will be a ventricular septal defect (VSD) present and the size of this will affect the size of the right ventricular cavity. In all cases there must be an inter-atrial communication to allow systemic venous return out of the heart via the left atrium and ventricle. […] In 70% of cases the great arteries are normally related and so the pulmonary artery arises from the hypoplastic right ventricle. Most commonly in this situation, there is a small VSD present and hypoplasia of the pulmonary arteries. This therefore results in decreased pulmonary blood flow. […] In 30% of cases, the great arteries are transposed and so the pulmonary artery arises from the left ventricle and the valve is of normal calibre. There can be a tendency for pulmonary over-circulation however the main concern is if the VSD is restrictive, systemic perfusion will be poor. […] Coarctation of the aorta or interrupted aortic arch are commonly associated abnormalities and are more common if there is tricuspid atresia with transposed great vessels.
#24 Tricuspid atresia pathophysiology – wikidoc
https://www.wikidoc.org/index.php/Tricuspid_atresia_pathophysiology
Tricuspid atresia is classified according to the connection between ventricles with great arteries (aorta, pulmonary) into two subgroups: Normal connection between ventricles with the aorta and pulmonary artery which is the common type and is consistent with 70%-80% of cases. Most patients are cyanotic. […] Aorta originated from small right ventricle and the pulmonary artery comes from the left ventricle. Heart failure and pulmonary hypertension are common and patients are not cyanotic. Flow in the aorta is dependent on ventricular setrum defect(VSD) size. Subaortic stenosis and aortic arch anomalies are common.
#25 Congenital Defects Tutorial – Congenital Heart Defects | Atlas of Human Cardiac Anatomy
https://www.vhlab.umn.edu/atlas/congenital-defects-tutorial/right-heart-lesions/tricuspid-atresia.shtml
When the great vessels are normally related (Type I), blood passes from the left ventricle out the aorta and through a VSD to the right ventricle and pulmonary artery. Closure of the septal defect, combined with restriction by the pulmonary valve and limited right ventricular outflow due to hypoplasia, results in a progressive decrease in pulmonary blood flow. The patent ductus arteriosus provides a time-limited source of blood to the pulmonary artery, as it typically closes on schedule a few days after birth. […] When the great vessels are transposed (Type II), blood from the left ventricle passes out the pulmonary artery and through a VSD into the aorta. Closure of the septal defect leads to subaortic stenosis and a decrease in cardiac output. To compensate, pressure in the left ventricle increases which, in turn, increases pulmonary outflow leading to congestive heart failure. […] Most patients with tricuspid atresia present with cyanosis that increases in severity over a period of months as VSDs and the ductus arteriosus constrict. As the degree of cyanosis worsens, infants may also begin to have cyanotic spells.
#26 Tricuspid Atresia – Pathophysiology – Management – TeachMePaeds
https://teachmepaediatrics.com/cardiology/congenital-heart-defects/tricuspid-atresia/
The tricuspid valve is absent and the right ventricle is hypoplastic due to absence of the inflow into the right ventricle. In the vast majority of cases there will be a ventricular septal defect (VSD) present and the size of this will affect the size of the right ventricular cavity. In all cases there must be an inter-atrial communication to allow systemic venous return out of the heart via the left atrium and ventricle. […] In 70% of cases the great arteries are normally related and so the pulmonary artery arises from the hypoplastic right ventricle. Most commonly in this situation, there is a small VSD present and hypoplasia of the pulmonary arteries. This therefore results in decreased pulmonary blood flow. […] In 30% of cases, the great arteries are transposed and so the pulmonary artery arises from the left ventricle and the valve is of normal calibre. There can be a tendency for pulmonary over-circulation however the main concern is if the VSD is restrictive, systemic perfusion will be poor. […] Coarctation of the aorta or interrupted aortic arch are commonly associated abnormalities and are more common if there is tricuspid atresia with transposed great vessels.
#27 Tricuspid atresia pathophysiology – wikidoc
https://www.wikidoc.org/index.php/Tricuspid_atresia_pathophysiology
Tricuspid atresia is classified according to the connection between ventricles with great arteries (aorta, pulmonary) into two subgroups: Normal connection between ventricles with the aorta and pulmonary artery which is the common type and is consistent with 70%-80% of cases. Most patients are cyanotic. […] Aorta originated from small right ventricle and the pulmonary artery comes from the left ventricle. Heart failure and pulmonary hypertension are common and patients are not cyanotic. Flow in the aorta is dependent on ventricular setrum defect(VSD) size. Subaortic stenosis and aortic arch anomalies are common.
#28 Congenital Defects Tutorial – Congenital Heart Defects | Atlas of Human Cardiac Anatomy
https://www.vhlab.umn.edu/atlas/congenital-defects-tutorial/right-heart-lesions/tricuspid-atresia.shtml
When the great vessels are normally related (Type I), blood passes from the left ventricle out the aorta and through a VSD to the right ventricle and pulmonary artery. Closure of the septal defect, combined with restriction by the pulmonary valve and limited right ventricular outflow due to hypoplasia, results in a progressive decrease in pulmonary blood flow. The patent ductus arteriosus provides a time-limited source of blood to the pulmonary artery, as it typically closes on schedule a few days after birth. […] When the great vessels are transposed (Type II), blood from the left ventricle passes out the pulmonary artery and through a VSD into the aorta. Closure of the septal defect leads to subaortic stenosis and a decrease in cardiac output. To compensate, pressure in the left ventricle increases which, in turn, increases pulmonary outflow leading to congestive heart failure. […] Most patients with tricuspid atresia present with cyanosis that increases in severity over a period of months as VSDs and the ductus arteriosus constrict. As the degree of cyanosis worsens, infants may also begin to have cyanotic spells.
#29 Congenital Defects Tutorial – Congenital Heart Defects | Atlas of Human Cardiac Anatomy
https://www.vhlab.umn.edu/atlas/congenital-defects-tutorial/right-heart-lesions/tricuspid-atresia.shtml
Tricuspid atresia refers to a defect where the tricuspid valve is absent and the right ventricle is variably hypoplastic. An ASD is always present and can be restrictive. It can be classified into three types which have implications for clinical manifestations and surgical correction (St. Louis): 1) Type I includes those without transposition of the great arteries, 2) Type II includes those with transposition of the great arteries, and 3) Type III refers to those with congenitally corrected transposition of the great vessels. Each of these types can be subdivided based on the degree of obstruction to pulmonary blood flow: […] When the tricuspid valve is absent, blood from the right atrium usually passes through a patent foramen ovale to the left atrium and left ventricle. In more rare cases, it may also pass through an ASD. Atresia of the tricuspid valve results in both the pulmonary and systemic venous returns passing through the foramen ovale and into the left atrium and left ventricle which functions as a single ventricle, mixing systemic and pulmonary venous return.
#30 Tricuspid Atresia – Pathophysiology – Management – TeachMePaeds
https://teachmepaediatrics.com/cardiology/congenital-heart-defects/tricuspid-atresia/
The tricuspid valve is absent and the right ventricle is hypoplastic due to absence of the inflow into the right ventricle. In the vast majority of cases there will be a ventricular septal defect (VSD) present and the size of this will affect the size of the right ventricular cavity. In all cases there must be an inter-atrial communication to allow systemic venous return out of the heart via the left atrium and ventricle. […] In 70% of cases the great arteries are normally related and so the pulmonary artery arises from the hypoplastic right ventricle. Most commonly in this situation, there is a small VSD present and hypoplasia of the pulmonary arteries. This therefore results in decreased pulmonary blood flow. […] In 30% of cases, the great arteries are transposed and so the pulmonary artery arises from the left ventricle and the valve is of normal calibre. There can be a tendency for pulmonary over-circulation however the main concern is if the VSD is restrictive, systemic perfusion will be poor. […] Coarctation of the aorta or interrupted aortic arch are commonly associated abnormalities and are more common if there is tricuspid atresia with transposed great vessels.
#31 Tricuspid Atresia: Background, Pathophysiology, Etiology
https://emedicine.medscape.com/article/158359-overview
The intracardiac blood flow in tricuspid atresia further depends on the presence or absence of pulmonary arterial pathology. In the absence of pulmonary atresia or pulmonary valve stenosis, the volume of blood to the lungs may be normal with normal oxygenation occurring, resulting in reduced cyanosis. In contrast, with accompanying pulmonary artery or valve stenosis, pulmonary blood flow is reduced, resulting in increased cyanosis. […] The left ventricle comprises most of the ventricular mass in tricuspid atresia. Because of volume overload (the left ventricle receives all the venous return) and persistent hypoxemia, decreased ventricular function may result in fibrosis, decreased ejection fraction, mitral annular dilatation, and mitral insufficiency.
#32 Tricuspid atresia | PPT
https://www.slideshare.net/slideshow/tricuspid-atresia-230184837/230184837
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. […] Overall actuarial survival in infants with tricuspid atresia is 1 year- 72%. 5 years- 52%. 10 years- 46%. […] Few infants with tricuspid atresia and normally related great 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 pulmonary artery collaterals are present, either of which are unlikely.
#33 Tricuspid atresia | PPT
https://www.slideshare.net/slideshow/tricuspid-atresia-230184837/230184837
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. […] Overall actuarial survival in infants with tricuspid atresia is 1 year- 72%. 5 years- 52%. 10 years- 46%. […] Few infants with tricuspid atresia and normally related great 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 pulmonary artery collaterals are present, either of which are unlikely.
#34 Tricuspid atresia | PPT
https://www.slideshare.net/slideshow/tricuspid-atresia-230184837/230184837
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. […] Overall actuarial survival in infants with tricuspid atresia is 1 year- 72%. 5 years- 52%. 10 years- 46%. […] Few infants with tricuspid atresia and normally related great 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 pulmonary artery collaterals are present, either of which are unlikely.
#35 Tricuspid Atresia – Stanford Medicine Children’s Health
https://www.stanfordchildrens.org/en/topic/default?id=tricuspid-atresia-90-P01819
Tricuspid atresia (TA) is a heart defect present at birth (congenital). It occurs when the tricuspid valve doesnt form. […] In tricuspid atresia, the tricuspid valve does not form as it should. Development of the ventricles is helped by blood flowing through them. Because blood does not pass through the tricuspid valve, the right ventricle remains small. […] Some congenital heart defects may be passed down through families (genetic defects). Most of the time, there is no known cause for tricuspid atresia.
#36 Tricuspid Atresia (TA) | Valley Children’s Healthcare
https://www.valleychildrens.org/services/heart/conditions-we-treat/tricuspid-atresia
Tricuspid atresia (TA) is a heart defect present at birth (congenital). It occurs when the tricuspid valve doesnt form, or only partly forms. Normally the tricuspid valve is located between the right upper chamber (atrium) and the right lower chamber (ventricle) of the heart. Instead of a valve, a piece of tissue forms that restricts blood flow between the right atrium and right ventricle. The defect keeps low oxygenated blood from flowing normally into the right atrium to the right ventricle, and to the lungs where the blood becomes oxygenated. With TA, there is mixing of low oxygenated blood with oxygenated blood. This means not enough oxygen in the blood is carried to the body. This may cause a blue coloring of the skin or lips. […] In TA, the tricuspid valve doesn’t form as it should. Development of the ventricles is helped by blood flowing through them. Because blood doesn’t pass through the tricuspid valve, the right ventricle remains small. […] Some congenital heart defects may be passed down through families (genetic defects). Most of the time, there is no known cause for TA.
#37 Tricuspid Atresia – Pediatric Heart Specialists
https://pediatricheartspecialists.com/heart-education/15-congenital-heart-defects/188-tricuspid-atresia
Tricuspid atresia is a type of congenital heart disease in which the tricuspid valve fails to develop properly. Typically there is simply a plate of tissue where the normal tricuspid valve should be. This results in no direct communication between the right atrium and right ventricle. […] Tricuspid atresia is almost invariably associated with some sort of hypoplasia, or underdevelopment of the right ventricle, due to the lack of adequate blood flow. […] Tricuspid atresia is classified as a cyanotic form of congenital heart disease. Cyanotic congenital heart disease refers to those heart defects that result in decreased or inadequate blood flow to the lungs. […] In tricuspid atresia, because blood cannot pass from the right atrium to the right ventricle, it must flow across a hole between the two atria (termed a foramen ovale or atrial septal defect), where it then enters the left atrium and left ventricle.
#38 Tricuspid Atresia | SpringerLink
https://link.springer.com/10.1007/978-3-031-07563-6_56
Tricuspid atresia is a rare congenital heart disease; however, a common defect in the subset of univentricular heart lesions. The absence of communication between the right atrium and ventricle due to tricuspid valve atresia results in a functionally univentricular heart necessitating palliative procedures, performed in a stepwise fashion towards a Fontan circulation. […] This chapter reviews the incidence, pathology, natural history, genetics, presentation, diagnosis, and management, both medical and surgical, of this congenital heart disease.
#39 Tricuspid Atresia | SpringerLink
https://link.springer.com/10.1007/978-3-031-07563-6_56
Tricuspid atresia is a rare congenital heart disease; however, a common defect in the subset of univentricular heart lesions. The absence of communication between the right atrium and ventricle due to tricuspid valve atresia results in a functionally univentricular heart necessitating palliative procedures, performed in a stepwise fashion towards a Fontan circulation. […] This chapter reviews the incidence, pathology, natural history, genetics, presentation, diagnosis, and management, both medical and surgical, of this congenital heart disease.