DIT review - Cardiology 1

Question 1

Describe the steps of atrial septation

Answer 1

• (1) Septum primum grow toward endocardial cushion, narrowing foramen (ostium) primum
• (2) Foramen secundum forms in septum primum (foramen primum disappears)
  
  • Perforations in the septum primum eventually fuse together to become the foramen secundum
• (3) Septum secundum develops as foramen secundum maintains R-to-L shunt
• (4) Septum secundum expands and covers most of the foramen secundum
  
  • The residual foramen in the septum secundum is the foramen ovale
• (5) Remaining portion of septum primum form valve of foramen ovale
• (6) Septum secundum and septum primum fuse to form the atrial septum
• (7) Foramen ovale usually closes soon after birth because in increased LA pressure

Question 2

Derivatives of the 1st aortic arch

Answer 2

• Part of maxillary artery

Question 3

Derivatives of 2nd aortic arch

Answer 3

• Stapedial artery and hyoid artery

Question 4

Derivatives of 3rd aortic arch

Answer 4

Common carotid artery and proximal part of internal carotids

Question 5

Derivatives of 4th aortic arch

Answer 5

• On left – aortic arch
• On right – proximal part of R subclavian

Question 6

Derivatives of 6th aortic arch

Answer 6

• Proximal part of pulmonary arteries
• On left – ductus arteriosus

Question 7

What are the 3 shunts involved in fetal circulation + describe fetal circulation

Answer 7

Ductus venosus, foramen ovale, ductus arteriosus

• Umbilical vein carries oxygenated blood from placenta to liver
  
  • In the liver there is mixing of oxygenated blood from umbilical vein with deoxygenated blood from lower extremities
  • Some blood from umbilical vein goes to liver into hepatic circulation while some blood is shunted directly into the IVC via ductus venosus, bypassing hepatic circulation
• Blood goes from IVC to RA
  
  • In the RA, blood can either go into the RV or straight into the LA via foramen ovale
• Blood that went to the RV then enters the pulmonary artery
  
  • In the pulmonary artery, blood can either go to the lungs, or go through the ductus arteriosus which will shunt the blood directly into the descending aorta
    
    • This shunt is due to the high fetal pulmonary artery resistance

Question 8

Describe the transition from fetal circulation to adult circulation (e.g. closure of shunts)

Answer 8

• When the infant takes a breath, this decreases intrathoracic pressure, thus decreasing resistance in pulmonary vasculature
• Decreased resistance leads to more blood entering the pulmonary artery (less leaving through ductus arteriosus), and thus more blood entering the LA
• Increased LA pressure causes closure of the foramen ovale
• Highly oxygenated blood in the aorta causes closure of ductus arteriosus

Question 9

Cardiac disorders associated with Turner syndrome

Answer 9

• Coarctation of aorta
• Bicuspid aortic valve

Question 10

Cardiac disorders associated with Down Syndrome

Answer 10

• Endocardial cushion defect (ASD and VSD)
  
  • Complete atrioventricular canal defect

Question 11

Cardiac disorders associated with DiGeorge Syndrome

Answer 11

• Tetralogy of Fallot
• Truncus arteriosus

Question 12

Cardiac disorders associated with Marfan syndrome

Answer 12

Aortic insufficiency due to abnormal aortic valve

Question 13

Defect and heart sound heard in atrial septal defect

Answer 13

• Most commonly due to ostium secundum defect
• Loud S1; wide, fixed split S2
• Symptoms range from none to heart failure

Question 14

Heart sounds associated with patent ductus arteriosus

Answer 14

• Due to decreased pulmonary vascular resistance after birth, shunt becomes left to right
• Continuous “machine-like” murmur

Question 15

What drug do you use to keep the PDA open and to close it?

Answer 15

• Indomethacin closes PDA
• PGE keeps PDA open

Question 16

Describe the pathogenesis of Eisenmenger syndrome

Answer 16

• Uncorrected L-to-R shunt = increased pulmonary blood flow = remodeling of vasculature = pulmonary arterial HTN = right ventricular hypertrophy = increase RV pressure = shunt become R-to-L
• Causes late cyanosis, clubbing, and polycythemia

Question 17

Location and presentation of infantile aortic coarctation

Answer 17

• Coarctation is proximal to ductus arteriosus
  
  • Associated with PDA
• Presentation:
  
  • Lower extremity cyanosis in infants – blood going to LE is deoxygenated (from RV to pulmonary artery to PDA)
• Associated with Turner syndrome

Question 18

Location and presentation of adult aortic coarctation

Answer 18

• Coarctation is distal to ductus arteriosus
• Presentation:
  
  • HTN in upper extremities and hypotension with weak pulses in lower extremities
  • “Notching” of ribs on X-ray
    
    • Collateral arteries form and engorged intercostal erode ribs

Question 19

Complications of aortic coarctation

Answer 19

• Heart failure, increased risk of cerebral hemorrhage, aortic rupture, endocarditis

Question 20

What other defect is often associated with persistent truncus arteriosus

Answer 20

• Failure of truncus arteriosus to divide into pulmonary trunk and aorta
• Usually associated with VSD

Question 21

What is required in order for life in an infant with transposition of great vessels

Answer 21

• Not compatible with life unless a shunt is present to allow mixing of blood (e.g. VSD, PDA, or patent foramen ovale)
• Defect = 2 closed loop circuits
  
  • LV enters into the pulmonary trunk
  • RV enters into the aorta

Question 22

Describe the defect and required shunting in tricuspid atresia

Answer 22

• Absence of tricuspid valve and hypoplastic RV
• Requires 2 shunts:
  
  • ASD to get blood from RA to LA
  • VSD to get blood from LV to RV so it can go to the lungs

Question 23

What are the defects in tetralogy of fallot

Answer 23

• 4 defects:
  
  • (a) Pulmonary valve stenosis
  • (b) RV hypertrophy
  • (c) VSD
  • (d) Overriding aorta (sitting over VSD)

Question 24

Describe presentation of Tetralogy of Fallot

Answer 24

• “Tet spells”
  
  • Cyanosis exacerbated by increased R-to-L shunt due to crying fever, exercise
• Symptoms relieved by squatting
  
  • Increased SVR = R-to-L shunt becomes L-to-R shunt = improved cyanosis
• Will see a boot-shaped heart on X-ray due to RV hypertrophy

Question 25

Describe the defect in Total anomalous pulmonary venous return (TAPVR)

Answer 25

• Pulmonary veins drain into R heart circulation (e.g. SVC, coronary sinus, RA)
• Associated with ASD and sometimes PDA to allow for R-to-L shunting

Question 26

Describe the defect in Ebstein anomaly

Answer 26

• Displacement of tricuspid valve leaflets downward into RV, “atrializing” the RV
• Associated with tricuspid regurgitation and right HF
• Most patients have a patent foramen ovale with a R to L shunt
• Can be caused by lithium exposure in utero

Question 27

Equation for Cardiac output

Answer 27

• CO = Stroke volume (SV) x Heart rate (HR)

Question 28

Equation for stroke volume and causes of changes in SV

Answer 28

• SV = end-diastolic volume (EDV) – end-systolic volume (ESV)
• Change of stroke volume:
  
  • Contractility = increased SV
  • Increased afterload = decreased SV
  • Increased preload = increased SV

Question 29

What is Fick Principle

Answer 29

• CO = (Rate of O2 consumption) / (arterial O2 content – venous O2 content)

Question 30

Equation for mean arterial pressure

Answer 30

• MAP = CO (Q) x Total peripheral resistance (TPR)
• MAP = (2/3 diastolic pressure) + (1/3 systolic pressure)

Question 31

Equation for pulse pressure

Answer 31

• PP = Systolic pressure – Diastolic pressure
  
  • PP is proportional to SV

Question 32

Equation for ejection fraction

Answer 32

• = what your heart can pump out / what your heart can hold
• EF = (stroke volume) / (end-diastolic volume)

Question 33

How is CO maintained in early and sustained exercise

Answer 33

• Early exercise:
  
  • CO maintained due to increased HR and increased SV
• Sustained exercise:
  
  • CO maintained due to increased HR
  • SV plateaus