Congenital Hearth Disease - Shunts and Obstructions Flashcards
Segmental Analysis
-start with great veins and follow normal path of blood, ensuring that normal connectivity exists and that all valves are existant
Deoxygenated Blood Oxygenation %
~70%
Oxygenated Blood Oxygenation %
~95%
Shunts, Two Basic Types
Intracardiac and Extracardiac
Intra-cardiac Shunts
- atrial septal defect
- ventricular septal defect
- atrioventricular septal defect
Extra-cardiac Shunts
- patent ductus arteriosus
- aorto-pulmonary window
Atrial Septal Defects
- most common -> defect in secundum
- defect can occur in various parts of septum, eg. secundum, primum, sinus venosus, coronary sinus
- defect in one region may affect surrounding structures, eg. defect in primum often affects tricuspid valve
- secundum can be closed percutaneously
Ventricular Septal Defects
- can occur in different areas of septum, eg. muscular, membranous, inlet, outlet
- muscular defects are most common in childhood, often closes spontaneously
Patent Ductus Arteriosus
- connection between aorta and pulmonary artery
- in fetal state, blood shunts from right to left
- usually closes at birth
- if stays open, blood shunts from left to righ
Flow Direction in Shunts Determinants
- relative compliance (related to stiffness) between the two chambers
- pressure differential between the two chambers
- size of the defect
Left to Right Shunts
- acyanotic
- ASD’s
- VSD’s
- AVSD’s
- PDA’s
Right to Left Shunts
- cyanotic
- Eisenmenger’s Syndrome (AVSD, VSD, PDA)
- Tetralogy of Fallot
Mixed Shunts
- cyanotic
- transposition of the great arteries
Left to Right Shunts Physiological Implications
- pulmonary overcirculation
- pulmonary HTN
- left sided chamber dilation
- left sided chamber dysfunction
- clinical heart failure
- arrhythmias
Left to Right Shunts Oxygenation Changes
- see jump in oxygenation in right ventricle and pulmonary artery due to mixing of blood with VSD
- see jump in oxygenation in pulmonary artery with PDA
Eisenmenger’s Syndrome
- long-term left to right sided shunting produces excessive pulmonary over circulation
- eventually pressures on right side of heart increase to point that they cause reverse shunting
- left to right shunt becomes a right to left shunt
Tetralogy of Fallot
- RV hypertrophy
- overriding aorta
- pulmonary outflow tract obstruction
- VSD
Right to Left Shunting
-obstruction of outflow tract produces R -> L shunting in TOF
Right to Left Shunts Oxygenation Changes
-see lower oxygenation in blood returning to right side of heart and in right sided chambers, normal oxygenation in pulmonary vein and left atrium, drop in oxygenation in left ventricle and aorta
Transposition of the Great Arteries
- aorta coming off right ventricle, pulmonary artery off left ventricle
- results in two independent circuits of circulation that don’t mix, need ASD/VSD/PDA to have mixing of blood and maintain survival
- ASD can be created to allow mixing of blood for interim
- cyanotic heart disease - inadequate oxygenation of blood in systemic circuit
TGA Oxygenation Changes
- see low oxygenation (mid 60’s) in right side of heart and in aorta
- see high oxygenation in left side of heart and pulmonary tracts
Obstruction
- anatomic obstruction to blood flow
- subvalvular, valvular or supravalvular level
Obstruction Complications
- no changes in oxygenation states usually
- if severe obstruction, periphery may extract more oxygen than normal from blood, producing higher deoxygenation in blood returning to right side of heart
- major issue is pressure gradient across obstruction and hemodynamic effect on upstream chamber
Aortic Coarctation Physiological Implications
- hypertension
- hypoperfusion of distal tissues
- left side of heart having to work harder, get dilation and dysfunction
- heart failure
- no change in oxygenation status of blood in system
