Endocardial cushion defect pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

Overview

AV canal connects the atria to the ventricles. At four to five weeks of gestation, the superior and inferior endocardial cushions of the common AV canal fuse. Results in the formation of the mitral and tricuspid valve and the AV septum. Any failure of fusion results in endocardial cushion defect. Pathophysiology of endocardial cushion defects depends upon level of left to right shunting and degree of shunting. Incompetent AV valves in endocardial cushion defect results in regurgitation. There is a strong association between AV canal defects and Down syndrome

Pathophysiology

Physiology

AV canal connects the atria to the ventricles.^[1]
At four to five weeks of gestation, the superior and inferior endocardial cushions of the common AV canal fuse.^[2]
Results in the formation of the mitral and tricuspid valve and the AV septum.

Pathophysiology

Pathophysiology of endocardial cushion defects depends upon

Level of left to right shunting
Degree of shunting


	Level of left-to-right shunting	Pathophysiology
Complete defect	At the atrial and ventricular levels	↑ pulmonary blood flow Leading to heart failure and ↑ PVR
Partial defect	At the level of the primum atrial septal defect	Volume overload of the right atrium and ventricle and pulmonary vasculature. Pulmonary artery pressures are usually normal. Minimal symptoms
Transitional defect	Shunting is minimal Due to a small and restrictive ventricular septal defect.	Similar to those of partial canal defect

AV valve regurgitation

AV valves are incompetent in endocardial cushion defect resulting in regurgitation
- In complete defects, regurgitation through LV to LA or RV to RA.
- In partial defects, most of the regurgitation is from LV to LA through the cleft in the anterior mitral valve leaflet.

Genetics

There is a strong association between AV canal defects and Down syndrome.^[3]

Chromosome 21 has been designated an AV canal critical region.
Trisomy 21 have an AV canal defect, usually the complete form

Associated Conditions

Common cardiac conditions associated with endocardial cushion defect include:^[4]^[5]

References

↑ Wenink AC, Zevallos JC (January 1988). “Developmental aspects of atrioventricular septal defects”. Int. J. Cardiol. 18 (1): 65–78. doi:10.1016/0167-5273(88)90031-9. PMID 3343065.
↑ VAN MIEROP LH, ALLEY RD, KAUSEL HW, STRANAHAN A (January 1962). “The anatomy and embryology of endocardial cushion defects”. J. Thorac. Cardiovasc. Surg. 43: 71–83. PMID 13924605.
↑ Korenberg JR, Bradley C, Disteche CM (February 1992). “Down syndrome: molecular mapping of the congenital heart disease and duodenal stenosis”. Am. J. Hum. Genet. 50 (2): 294–302. PMC 1682442. PMID 1531166.
↑ Peoples WM, Moller JH, Edwards JE (1983). “Polysplenia: a review of 146 cases”. Pediatr Cardiol. 4 (2): 129–37. doi:10.1007/BF02076338. PMID 6878069.
↑ Karl TR (January 1997). “Atrioventricular septal defect with tetralogy of Fallot or double-outlet right ventricle: surgical considerations”. Semin. Thorac. Cardiovasc. Surg. 9 (1): 26–34. PMID 9109222.

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[pmid3343065-1] Wenink AC, Zevallos JC (January 1988). “Developmental aspects of atrioventricular septal defects”. Int. J. Cardiol. 18 (1): 65–78. doi:10.1016/0167-5273(88)90031-9. PMID 3343065.

[pmid13924605-2] VAN MIEROP LH, ALLEY RD, KAUSEL HW, STRANAHAN A (January 1962). “The anatomy and embryology of endocardial cushion defects”. J. Thorac. Cardiovasc. Surg. 43: 71–83. PMID 13924605.

[pmid1531166-3] Korenberg JR, Bradley C, Disteche CM (February 1992). “Down syndrome: molecular mapping of the congenital heart disease and duodenal stenosis”. Am. J. Hum. Genet. 50 (2): 294–302. PMC 1682442. PMID 1531166.

[pmid6878069-4] Peoples WM, Moller JH, Edwards JE (1983). “Polysplenia: a review of 146 cases”. Pediatr Cardiol. 4 (2): 129–37. doi:10.1007/BF02076338. PMID 6878069.

[pmid9109222-5] Karl TR (January 1997). “Atrioventricular septal defect with tetralogy of Fallot or double-outlet right ventricle: surgical considerations”. Semin. Thorac. Cardiovasc. Surg. 9 (1): 26–34. PMID 9109222.

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