Aortic Valve Stenosis Quiz

Embryological Development of the Heart

• The primitive pulmonary vein incorporates into the wall of the left atrium and sends two branches to each lung.
• Atrial growth eventually incorporates all four branches into the wall.
• These branches meet with developing venous plexuses near the lungs.

Septation of the Outflow Tracts

• At 6 weeks, conotruncal ridges (cushions) begin to form and grow distally and spiral.
• When the two conus swellings have fused, the septum divides the conus into an anterior and posterior portion, forming the outflow tracts of the right and left ventricles.

Aortic Arches

• Pharyngeal arches develop, each with its own pair of arteries from the aortic sac.
• 1st to 6th arches develop cranial to caudally over 3-4 weeks.
• Each arch terminates in the paired dorsal aorta.

Fates of Embryological Structures

• Sinus venosus: Right atrium (smooth part) and Coronary sinus
• Primitive Atrium: Right and Left Atria
• Bulbus cordis:
  • Proximal 1/3: Right Ventricle
  • Middle 1/3: Conus cordis (Infundibulum) and Aortic vestibule
  • Distal 1/3: Proximal Aorta and Pulmonary trunk
• Endocardial cushions: AV valves, Membranous IV septum, Lower IA septum, Spiral septum

Congenital Heart Defects (CHD)

• Patent foramen ovale: Defect in septum secundum, causing blood to bypass the pulmonary circulation.
• Patent ductus arteriosus: Connection between the 6th aortic arch and left dorsal aorta, allowing oxygenated blood to bypass the pulmonary circulation.

Foetal Circulation

• Ductus venosus: Oxygenated blood from the placenta through the umbilical vein bypasses the liver and enters the inferior vena cava.
• Foramen ovale: Bypasses the pulmonary circulation, allowing oxygenated blood to flow directly from the right atrium to the left atrium.
• Ductus arteriosus: Bypasses the pulmonary circulation, allowing oxygenated blood to flow directly from the pulmonary artery to the aorta.

Congenital Heart Defects (CHD)

• Acyanotic: Ventricular Septal Defect (VSD), Atrial Septal Defect (ASD), Patent Ductus Arteriosus (PDA)
• Cyanotic: Tetralogy of Fallot (TOF), Transposition of the Great Arteries

Clinical Features and Management of CHD

• Ventricular Septal Defect (VSD):
  • Small VSDs: May close on their own
  • Medium to large VSDs: Require closure to prevent complications
• Patent Ductus Arteriosus (PDA):
  • Small PDA: May close on its own
  • Large PDA: Requires closure to prevent complications
• Atrial Septal Defect (ASD):
  • Small ASDs: May close on their own
  • Medium to large ASDs: Require closure to prevent complications
• Tetralogy of Fallot (TOF):
  • Palliative surgery: Modified Blalock–Taussig shunt to increase pulmonary blood flow
  • Definitive surgery: Closure of VSD and relief of right ventricular outflow tract obstruction### Congenital Heart Defects
• Atrioventricular Septal Defect (AVSD): occurs when there is a hole between the chambers of the heart and problems with the valves that control blood flow between the upper and lower chambers of the heart
• Presentation: detected during antenatal ultrasound screening or routine echocardiography screening in a newborn infant with Down syndrome
• Symptoms: cyanosis at birth or heart failure at two weeks to three weeks of life, with no murmur heard
• Management: treat heart failure medically and surgical repair at three to six months of age

Heart Valve Defects

• Atresia: occurs when a valve does not form correctly and lacks a hole for blood to pass through
• Stenosis: occurs when the flaps of a valve thicken, stiffen, or fuse, and the valve cannot fully open
• Regurgitation: occurs when a valve does not close tightly, and blood leaks back through the valve

Pulmonary Valve Stenosis

• Definition: narrowing of the pulmonary valve, which allows blood to flow from the right ventricle into the pulmonary artery
• Symptoms: most children with this defect have no signs or symptoms other than a heart murmur
• Diagnosis: ejection systolic murmur is best heard at the upper left sternal edge
• Treatment: balloon valvuloplasty, which is successful in 85% of cases

Aortic Valve Stenosis

• Definition: occurs when there is a problem with the aortic valve, which allows blood to flow from the left ventricle into the aorta
• Symptoms: depend on the severity of the obstruction, may present with chest pain or syncope
• Diagnosis: small-volume, slow-rising pulses, carotid thrill, ejection systolic murmur maximal at the upper right sternal edge
• Treatment: balloon valvuloplasty in older children, surgical valvotomy or valve replacement in others

Left Heart Outflow Obstruction

• Definition: occurs when there is a blockage in the left side of the heart that prevents blood from flowing out of the heart and to the rest of the body
• Symptoms: heart failure, shock, and collapse, often at around two days of age
• Treatment: surgical repair or balloon dilation

Coarctation of the Aorta

• Definition: occurs when the aorta is narrowed or blocked, which can reduce blood flow to the lower body
• Symptoms: absent femoral pulses, severe heart failure, and metabolic acidosis
• Treatment: surgical repair or balloon dilation### Heart Development
• Conus cordis and truncus arteriosus develop concurrently, not sequentially
• Heart defects occur in approximately 8 in 1,000 births
• Causes of heart defects include genetic and teratogenic factors, such as Rubella virus, social drugs, thalidomide, insulin-dependant diabetes, and hypertension, as well as genetic syndromes like Down's, DiGeorge, and trisomy 18
• Craniofacial abnormalities are linked to cardiac malformation due to neural crest cells

Formation of Endocardial Tube

• Initial nourishment and oxygenation occur via diffusion
• Heart is the first functional organ in the embryo, developing around days 22-25
• Splanchnic lateral plate mesoderm produces angiogenic cells, leading to blood islands and the primary heart field
• Day 17: Splanchnic lateral plate mesoderm produces angiogenic cells
• Day 18: Endothelial lined tubes surrounded by myocytes form
• Day 20: Two sides of the horseshoe fuse to form a single heart tube, ventral to the gut tube

Heart Tube Development

• Day 22: Myocardial cells infiltrate cardiac jelly, begin contraction and electrical activity
• Days 22-24: Heart tube folding occurs
• Days 28: Folding complete, left medial view, anterior view
• Formation of trabeculae in primitive ventricle and bulbus cordis

Septation

• Day 23-35: Endocardial cushion cells from neural crest, dorsal and ventral cushions meet, forming left and right AV canals
• Day 30: Remodelling of ventricle wall, erosion and remodelling in ventricular wall leads to trabeculae
• Day 34-35: Muscular growth forms inferior part of AV septum
• Superior part derived from endocardial cushions, completed by about 8 weeks

Atrial Septation

• Day 26-33: Septum primum forms, separation but maintains pulmonary bypass
• Day 33-37: Septum secundum forms, crescentic growth never entirely complete
• Formation of foramen ovale

Congenital Conditions

• Ventricular septal defect (VSD): defect in membranous or muscular portion of IV septum
• Tetralogy of Fallot: unequal division of conus cordis, anterior displacement of aortic origin
• Transposition of great vessels: failure of aorticopulmonary septum to spiral
• Coarctation of aorta: narrowing of aorta, usually distal to origin of left subclavian artery

ECG Interpretation

• Identity, standardization
• Rate calculation
• Rhythm analysis
• P wave analysis
• PR interval analysis
• QRS complex analysis
• QT interval analysis
• ST segment analysis
• T wave analysis
• Axis determination
• Abnormal components
• Formulation of interpretation

Note: The study notes have been organized into sections to facilitate easy understanding and review of the material.