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Ventricular septal defect
Synonyms: Inter-ventricular communication
Definition: a congenital anomaly which consist in a communication between both ventricles through the inter-ventricular septum. The communication allows a shunt between the two ventricular cavities.
Prevalence: about 0,6 to 1,9 per 1000 live births (7) and about 30% of all structural heart defects. Ventricular septal defect is the most common congenital heart defect diagnosed in the first year of life (1) and also a most frequently heart defect detect prenatally (5).
Pathogenesis: likely multifatorial. Different etiologies could be responsible for different types of Ventricular Septal Defect. Perimembranous ventricular defect could be the consequence of an imbalance of intracardiac blood flow affecting the heart prior to completion of ventricular septation. It is also speculated that muscular ventricular septal defect could form by excessive cellular death (apoptosis) leading to septal perforation. Multifatorial inheritances as well as classical Mendelian patterns of inheritance are applicable in exceptional families (6)
Associated anomalies: it is commonly found as part of complex cardiac lesions. Ventricular Septal Defect is part of the Tetralogy of Fallot, so this diagnosis should be suspect when the pulmonary artery is smaller than expected in the presence of a ventricular septal defect.
Ventricular Septal Defect can be part of other complex congenital heart diseases such transposition of the great arteries and double-outlet right ventricle. Other associations include sub-aortic stenosis, aortic valve stenosis, coarctation of the aorta and interrupted aortic arch. Extra cardiac anomalies associated include chromosomal anomalies in over 40% (2)
Anatomy: the localization of the defect is about 70% perimembranous, about 25% muscular and mixed in 5%. The inter-ventricular septum can be divided into 4 sections: the inlet, membranous, trabecular and outlet (5).
Pathology: an isolated ventricular septal defect can be well tolerated and not causes many haemodynamic disturbances in utero. The pressure in both ventricles is similar, and even large ventricle septal defects could cause small bidirectional shunts. After birth, a left-to-right shunt occurs when the pulmonary resistance decreases.
Diagnosis: the fetal ventricular septum is easily seem in the four chamber view. Since the membranous part of the septum is thin, the ventricular septum could be no visible toward the internal crux of the heart. This may lead to a false diagnosis (7)
When the ultrasound beam perpendicular to the ventricular septum, the different parts of the septum can be visualized in detail. The use of color flow Doppler imaging may augment the ability to identify the ventricular septal defect. Since the pressure is similar in the fetal right and left ventricles, the potential pressure gradient across a septal defect is small. Color flow velocity should be reduced.
Prognosis : most infants are asymptomatic at birth (3). Isolated perimembranous and muscular ventricular septal defect show a high rate of spontaneous closure in utero (4) which is no correlation between the size of the defect. Posnatally, the closure has more chance of occurrence in the small defects.
Management: an amnio could be recommended because of the association with chromosomal anomalies, mainly Trisomy 21, 18 and 13 (2). A careful ultrasound evaluation is necessary. Diagnosis in the third trimester does not alter obstetrical management.
(1) Anderson RH, Macartney FJ, Shinebiurne EA, Tynan M, Ventricular septal defects. In: Pediatric cardiology, Anderson RH, ed. London,UK:Mcgraw_hill, 1987:565-90.
(2) Allan LD, Sharland GK, Milburn A, et al. Prospective diagnosis of 1006 consecutive cases of congenital heart disease in the fetus. J Am Coll Cardiol 1994;23:1452-1458
(3) Hoffman JIE. Natural history of congenital heart disease. Problems in assessment, with special reference to ventricular septal defects. Circulation 37:97, 1968.
(4) Paladini D, Palmieri S, Lamberti A, Teodoro A, Martinelli P, Nappi C. Characterization and natural history of ventricular septal defects en the fetus. Obst Ginecol 2000; 16:118-122.
(5) Ibanez Fernandes A, Diez Tomaz JJ, Barreiro Davina J, Rodriguez Soarez J, Crespo Hernandez M. An Pediatr (Barc) 2004 Feb; 60(2):148-52.
(6) Clark EB (1987). Mechanism in the pathogenesis of congenital cardiac malformations. In. Pierpont MEM, Moller JH (eds) Genetics of cardiovascular disease. Martinus Nijhoff, Boston, pp 3-11.
(7) Canale JM, Sahn DJ, Allen HD et al. Factors affecting real-time cross-sectional echocardiograph imaging of perimembranous ventricular septal defects. Circulation 1981;63:689-697