RCS 29 - Cardiovascular Pathology 5

Question 1

Describe the basics of normal fetal circulation to, from, and through the heart.

Answer 1

1. Blood is oxygenated at the placenta
2. Oxygenated blood is carried via the umbilical vein > ductus venosus > inferior vena to right atrium of the heart
3. Blood is shunted from the RA to the LA via the foramen ovale, some blood will make it down in the RV
4. Most of the RV blood that is pumped into the pulmonary artery is shunted to the aorta via the ductus arteriosus

Question 2

Describe how the foramen ovale and ductus arteriosus normally close.

Answer 2

• When the baby breaths, the lungs inflate, causing pulmonary resistance (and right sided heart pressure) to drop drastically. This causes blood flow through the foramen ovale to stop and the septum primum to close of the foramen ovale.
• The patency of the ductus arteriosus is only maintained by the continued production of prostaglandins by the placenta. These PGs are metabolized when they reach the lungs. The drastic increase in blood oxygenation causes the placenta to stop producing PGs. This, in combination with placental separation and the continued PG breakdown in the lungs causes the ductus arteriosus to close off within 15hrs of life.

Question 3

List the three major categories of cardiac congenital malformations

Answer 3

1. Righ to Left Shunts
2. Left to Right Shunts
3. Obstructions

Question 4

What are the cardinal features of right to left and left to right shunts?

Answer 4

• Right to Left Shunts
  
  • Cyanosis
  • Oligemic Lung Fields - decrease in vascularity
• Left to Right Shunts
  
  • Plethoric lung fields - increase in vascularity
  • Pulmonary HTN
  • Right sided heart failure (CHF)

Question 5

List the major types of right to left shunt congenital cardiac malformations seen at birth and after birth.

Answer 5

• At birth
  
  • Tetralogy of Fallot
  • Transposition of the great vessels
  • Truncus arteriosus
  • Tricuspid atresia
  • Total anomalous pulmonary venous connection
• After birth (occurs when right-sided pressures increase)
  
  • ASD
  • VSD
  • PDA

Question 6

Name and describe the most common form of cyanotic congenital heart disease?

Answer 6

• Tetralogy of Fallot
  
  • VSD
  • Pulmonary Stenosis (degree determines prognosis)
  • Overriding aorta
  • Right ventricular hypertrophy

Question 7

What are the clinical features of TOF?

Answer 7

• Usually present by 6 months
• Dyspnea on exertion
• Cyanosis
• Squatting (increases PVR so more blood is shunted through pulmonary circulation)
• Polycythemia (which can cause a cerebral thrombosis)
• Infective endocarditis (the abnormal blood flow in the heart can damage the endocardium)
• Oligemic lung fields
• Often associated with Down’s Syndrome

Question 8

Facts to know about transposition of the great vessels

Answer 8

• Aorta comes off RV and pulmonary artery comes off LV
• Incompatible with life unless a VSD or PDA is present (allowing for mixing), in which case the dominant clinical finding is cyanosis

Question 9

Facts to know about persistent truncus arteriosus

Answer 9

• Typically the truncus arteriosus partitions into the aorta and pulmonary artery. That fails to happen with this condition
• Essentially a VSD
• Main feature is cyanosis

Question 10

Facts to know about tricuspid atresia

Answer 10

• Complete occlusion of the tricuspid leading to an underdeveloped RV and a larger than normal mitral valve
• Incompatible with life unless both an ASD and VSD are present, bet even then the child will be cyanotic from birth with a high chance of mortality

Question 11

Facts to know about total anomalous pulmonary venous connections (TAPVC)

Answer 11

• Pulmonary vein somehow feeds into the RA instead of the LA. Usually by joining with the left inominate (aka - brachiocephalic) vein, coronary, sinus, or directly with the RA.
• Incompatible with life unless an ASD is present
• Cyanosis is key feature

Question 12

Name the most common congenital heart defect. List the facts we need to know about it.

Answer 12

• VSD
  
  • Associated with Trisomy 21 (Down), 13 (Patau), and 18 (edwards)
  • Most commonly occurs in the membranous part of the septum (region towards the top of the septum) instead of the muscular part
  • Most VSDs close spontaneously in childhood
  • Clinical Features - pulmonary HTN, CHF, and a pansystolic murmor
  • If right sided pressure increases enough, the L to R shunt becomes a R to L shunt. This is known as Eisenmenger Complex