Lecture 9

• Dextrocardia:

  heart sits on right side of chest instead of left

  may result from abnormal cardiac looping however exact cause unknown

  can occur in isolation or in conjunction w/ other major organs

  
• Patent Ductus Arteriosus (PDA)

  ductus arteriosus does not lose up so blood from aorta goes to pulmonary trunk

  thus mix of arterial and venous blood

  oxygenated blood goes back to lungs and back to heart increases workload of heart

  lead to pulmonary hypertension, ventricular hypertrophy, heart failure

  
• ductus arteriosus kept open by prostaglandins

  treatment can consist of prostaglandin inhibitors or surgical implantation of a device to close passageway

  
• Atrial Septul Defects (ASD)

  failure of septum secundum fusing after birth - patent foramen ovale

  1. Primum ASD
  2. Secumdum ASD

  
• Patent Foramen Ovale occurs 1 in 4 people

  typically asymptomatic - pressure left atrium forces septum primum against septum secundum and so closes gap

  if pressure higher in right atrium, push weaker septum primum open and allow blood shunt from right to left
• Premature closure of foramen ovale, closes during prenatal life, results in hypertrophy of right side heart and underdevelopment of left, death usually occurs shortly afte birth
• Secundum ASD:

  most common type ASD

  casued by excessive apoptosis in septum primum or inadequate development of septum secundum meaning overlap of ostium seundum and foramen ovale

  blood shunted from left to right lead to right atrium or ventricle enlargement

  small defects asymptomatic; larger require surgical repair
• Common atrium; rare cardiac defect w/ complete absense atrial septum

  failure development of septum primum and septum secundum
• Ventricular Septal Defect (VSD)

  most common congenital heart defect

  often associated w/ other congenital malformations

  affect muscular or membranous part interventricular septum

  defects affecting muscular part interventricular septum often resolves themselves as child grows

  ventricular septal defects allows left to right shunting blood

  result in pulmonary hypertension and hypertrophy of right ventricle
• Conotruncal septal defects:

  conotruncal swellings form conotruncal septum rely on migration neural crest cells from neural tube

  septation defects of truncus arteriosus include:

  1. persistent truncus arteriosus
  2. transposition of great vesels
  3. tetralogy of fallot
• persistent truncus arteriosus:

  contruncal septum completely absent so cannot fuse with interventricular septum

  undivided truncus in communication w/ both ventricles - receives oxygenated and deoxygenated blood

  symptoms include cyanosis, lethargy, brethlessness and delayed growth

  must be corrected surgically or result in heart failure & death w/i 2 years

  
• Transposition of great vessels:

  conotruncal septum not form in spiral but instead runs straight down

  aorta arises from right ventricle and pulmonary artery from left ventricle

  incompatible w/ life unless accompanying shunt such as VSD, patent foramen ovale or patent ductus arteriosus exists
• Tetralogy of fallot:

  four abnormalities caused by same defect

  unequal division of truncus arteriosus caused by anterior displacement of aorticpulmonary septum this causes:

  1. pulmonary stenosis
  2. right ventricular hypetrophy due higher pressure on right hand side
  3. overriding aorta
  4. VSD

  
• Coarction of aorta:

  narrowing aorta, generally happens near ductus arteriosus cause unknown

  classifised in relation to position of ductus arteriosus eg.

  1. Preductal
  2. Postductal

  
• preductal coarctation (infantile type)

  during developmeny, ductus arteriosus compensates for narrowing

  PDA following birth

  differential cyanosis, upper body and head well perfused, lower body cyanotic

  
• postductal coarctation (adult type)

  more common type, relies on presence of collateral circulation

  subclavian artery -> internal thoracic artery -> anterior intercostal artery -> posterior intercostal artery -> descending aorta

  vessels appear larger than normal enable greater blood flow

  hypertension upper half body, hypotension lower half body