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Formation of the Heart and Heart Defects


									Formation of the Heart and
             Heart Defects

                       Michele Kondracki
          Learning Objectives

 Review anatomy of the heart

 Formation of the Heart

 Congenital heart defects

 Development stages for infants and children
Review of Anatomy
How does the Heart Form?
       Formation of the Heart
 Mesoderm divides into two layers
   Mesoderm = one of the primary germ cell layers in the early

 Heart precursor cells come from one of those two
  mesoderm layers (cardiogenic mesoderm)

 Heart precursor cells form a single
  heart tube by day 22 of
       Formation of the Heart
 These cells differentiate into the endocardium and
   Endocardium = innermost layer that lines the heart chambers
    and valves valves
   Myocardium = the muscular layer of the atria and ventricles

 The heart tube grows and elongates

 Primitive heart begins to form around day 22-23
       Formation of the Heart
 The heart tube begins to bulge into primitive heart
  chambers and undergoes right ward looping

 Followed by proper valve positioning and chamber
     Congenital Heart Defects

 Abnormalities in heart present at birth

 Affects 8:1000 live births

 Examples:
   Ventricular Septal Defect
   Atrial Septal Defect
   Coarctation of the Aorta
   Tetralogy of Fallot
   Transposition of the Great Arteries
  Ventricular Septal Defect (VSD)

 Most common congenital cardiac anomaly

 There is a hole between the two ventricles

 Hole can vary in size and location

 Oxygenated blood forced through hole from left ventricle to
  right ventricle then returns to the lungs even though it already
  carries oxygen
 Consequences
   Volume load causes enlargement of both ventricles and the
     pulmonary artery and exposes right ventricle and pulmonary
     arteries to high pressures
    VSD Signs and Symptoms

 Heart murmur

 Difficulty maintaining weight

 Increased breathing rate

 Lower energy and easy tiring
           Atrial Septal Defect

 Hole in the septum between the atria

 Blood flows through the hole primarily from left to right

 Causes increased blood volume in right atrium so more
  blood goes to the lungs than normal
    ASD: Signs and Symptoms

 Usually no symptoms in children

 If very large can cause fatigue, poor growth

 In adulthood can lead to pulmonary hypertension, atrial
  arrhythmias or congestive heart failure

 Usually a split S2 (second heart sound)

 Murmur heard as large amount of blood forced through
  normal size pulmonary valve
      Coarctation of the Aorta

 Common in patients with some chromosomal anomalies
  (Turner’s syndrome)

 Due to narrowing of the aorta

 Left ventricle has to work harder to force blood through
  narrow aorta
Coarctation of the Aorta
Coarctation of the aorta: Signs

 Depends on degree of narrowing
   Severe – possible heart failure in first days of life
   Mild – progressive left ventricular hypertrophy (thickening of
     the muscle)

 Weak pulses in the legs of the infant (femoral artery pulse)
  and increased pressure in upper extremities
            Tetralogy of Fallot

 Combination of four heart defects
   Pulmonary stenosis – narrowing of pulmonic valve that
    impedes blood flow from right ventricle to pulmonary artery
   VSD
   Overriding aorta – Aorta is enlarged and appears to arise
    from both right and left ventricles
   Right ventricular hypertrophy – due to pumping at high
                       Tetralogy of Fallot

    Overriding aorta

Pulmonary stenosis


         RV hypertrophy
    Tetralogy of Fallot: Signs and

 Usually diagnosed in the first few weeks of life

 Loud murmur

 Cyanosis due to pulmonary stenosis

 Rapid breathing in response to low oxygen
       Transposition of the Great
 The aorta and pulmonary artery arise from the wrong
 Oxygen poor blood from body to the RA and RV is pumped
  out of the aorta to the body
 Oxygen rich blood from the lungs to the LA and LV is sent
  back to the lungs through the pulmonary artery
 VSD is common with Transposition of Great Arteries and
  allows for some blood mixing but not enough to give
  adequate oxygen to all organs
Transposition of the Great
          Signs and Symptoms
 Cyanosis during first hours/days of life

 Rapid breathing due to lack of oxygen

 If untreated, 50% will die in the first months of life, and
  90% in the first year
           Helpful Information for Case
General guidelines for a child's growth rates include:


   2 weeks - regains birth weight and then gains about 1 1/2 - 2 pounds a month

   3 months - gains about 1 pound a month

   5 months - doubles birth weight

   1 year - triples birth weight and then gains about 1/2 pound a month

   2 years - quadruples birth weight and then gains about 4-5 pounds a year

    9-10 years - increased weight gain as puberty approaches, often about 10 pounds a year


    0-12 months - grows about 10 inches (25 cm)

    1-2 years - grows about 5 inches (13 cm)

    2-3 years - grows about 3 1/2 inches a year most children will double their birth height by 3-4
    years of age

    3 years to puberty - grows about 2 inches (5cm) a year

Thank you!

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