Embryonic Heart Development

Anatomy

• The cardiovascular system is the first to function in the embryo as it ensures embryonic nutrition.
• The heart develops from the mesoderm embryonic germ layer.
• The heart tube is derived from the cardiogenic plate.
• The fusion of two endocardial heart tubes form the primitive heart tube.
• Three primary sources involved in heart development are the heart tube, myoepicardial mantle, and pericardial sac.
• Looping is the process of folding the heart tube into its characteristic shape.
• The first chamber to appear during heart development is the bulbus cordis.
• The last chamber to develop during heart formation is the sinus venosus.
• The atrioventricular canal forms between the atria and ventricles.
• The sinus venarum within the right atrium is formed by the right horn of the sinus venosus.
• The septum that forms the foramen ovale is the septum primum.
• Failure of septum primum and septum secundum fusion after birth results in patent foramen ovale
• The aorticopulmonary (truncal) septum separates the aorta and pulmonary trunk.
• The membranous part of the interventricular septum is derived from the septum intermedium and conus septum.
• The tricuspid valve originates from endocardial cushions.
• Dextrocardia occurs as a result of a failure in heart looping.
• Persistent truncus arteriosus occurs due to the failure of the aorticopulmonary septum to develop.
• Tetralogy of Fallot comprises pulmonary stenosis, overriding aorta, right ventricular hypertrophy, and ventricular septal defect (absence of atrial septal defect).
• Coarctation of the aorta is associated with a narrowed segment of the aorta.
• Transposition of the great vessels occurs due to a failure of the aorticopulmonary septum to spiral.
• The neural crest cells contribute to the formation of the interventricular septum (membranous part).
• The coronary sinus develops from the left sinus venosus horn.
• The primitive ventricle gives rise to the left ventricle.
• The fossa ovalis is a remnant of the septum primum.
• Aortic stenosis results from a fusion of aortic cusps.
• The primary heart field is derived from the lateral plate mesoderm.
• The second heart field forms structures including the right ventricle and outflow tracts.
• The aortic sac contributes to the development of the ascending aorta.
• Ventricular septal defect is the most common congenital heart defect.
• The left sinus venosus horn gives rise to the coronary sinus.
• Functionally for fetal circulation, the foramen ovale allows oxygenated blood flow from the right to left atrium.
• Failure of the aorticopulmonary septum to spiral causes transposition of the great vessels.
• The ductus arteriosus connects the aorta and pulmonary trunk in fetal circulation.
• The endocardial cushions are essential for the formation of atrioventricular valves and septa.
• Absorbed pulmonary veins form the smooth-walled part of the left atrium.

Clinical

• Ostium secundum is the most common type of atrial septal defect (ASD).
• Eisenmenger syndrome is the likely complication when a patient with ventricular septal defect (VSD) presents with cyanosis in late childhood.
• Patent ductus arteriosus is associated with a continuous 'machine-like' murmur congenital heart defect.
• Ostium primum ASD is most commonly associated with Down syndrome.
• The degree of right ventricular outflow tract (RVOT) obstruction determines the degree of cyanosis in Tetralogy of Fallot.
• A boot-shaped heart is the characteristic chest X-ray finding in Tetralogy of Fallot.
• Squatting during episodes of cyanosis is most characteristic of Tetralogy of Fallot.
• Patent ductus arteriosus after Eisenmenger syndrome develops typically results in lower extremity cyanosis only after birth.
• Blalock-Taussig shunt is a palliative surgical treatment for Tetralogy of Fallot.
• Placing a child in the knee-chest position and giving oxygen is the initial treatment for a hypercyanotic spell in a child with Tetralogy of Fallot.