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CARDIAC DEVELOPMENT AND CONGENITAL HEART DEFECTS

Congenital heart defects are structural and/or functional abnormalities of the heart present at birth, resulting from an alteration in normal cardiac development during embryonic life. They represent the most common group of congenital malformations, with an incidence of approximately 8-10 cases per 1,000 live births. ---

Cardiac Ontogenesis and Septation

Heart development begins in the third week of embryonic life with the formation of the primitive cardiac tube, which subsequently undergoes folding and subdivision, giving rise to the cardiac chambers.

Role of Neural Crest Cells

Neural crest cells are essential for the formation of the conotruncal region and the separation of the truncus arteriosus into the aorta and pulmonary artery. Defects in their migration are associated with congenital heart defects such as Tetralogy of Fallot and Persistent Truncus Arteriosus.

Molecular Factors in Heart Development

Heart development is regulated by several transcription factors and molecular signals:

Atrial Septum

Atrial separation begins in the fourth week with the growth of the septum primum, which extends from the roof of the primitive atrium downward. Initially, there is an opening, the ostium primum, which progressively closes with the fusion of the endocardial cushions. Before complete closure, a second opening, the ostium secundum, forms to maintain interatrial communication.
From the right atrium, the septum secundum subsequently develops, leaving the foramen ovale open, allowing fetal blood flow between the atria. After birth, the foramen ovale closes due to changes in pressure gradients.

Interventricular Septum

In the fourth week, the interventricular septum develops with:

Fetal Circulation and Transition to Postnatal Life

During fetal life, blood circulation differs significantly from postnatal circulation, as the placenta serves as the organ responsible for gas exchange, replacing pulmonary function.

Adaptations at Birth

With the first breath, the lungs expand, pulmonary vascular resistance drops dramatically, and pulmonary blood flow increases. This results in:

Prenatal Diagnosis and Neonatal Screening

Fetal echocardiography, performed between the 18th and 22nd weeks of gestation, is the primary tool for prenatal diagnosis of congenital heart defects. After birth, neonatal screening using pulse oximetry is recommended to identify critical congenital heart defects requiring early intervention.

Classification of Congenital Heart Defects

    References
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  2. Hoffman J.I., Kaplan S. The incidence of congenital heart disease. Journal of the American College of Cardiology. 2002;39(12):1890-1900. doi:10.1016/S0735-1097(02)01886-7.
  3. Reller M.D., Strickland M.J., Riehle-Colarusso T., Mahle W.T., Correa A. Prevalence of congenital heart defects in metropolitan Atlanta, 1998-2005. The Journal of Pediatrics. 2008;153(6):807-813. doi:10.1016/j.jpeds.2008.05.059.
  4. Van der Linde D., Konings E.E.M., Slager M.A., et al. Birth prevalence of congenital heart disease worldwide: a systematic review and meta-analysis. Journal of the American College of Cardiology. 2011;58(21):2241-2247. doi:10.1016/j.jacc.2011.08.025.
  5. Geva T., Martins J.D., Wald R.M. Atrial Septal Defects. The Lancet. 2014;383(9932):1921-1932. doi:10.1016/S0140-6736(13)62145-5.