Lec 08 Cyanotic Congenital Heart Diseases Flashcards
Maternal infection that predisposes to PDA or pulmonary stenosis?
Rubella.
Other environmental insults which can lead to CHDs
- Teratogenic Drugs
- X-ray/Irradiation
- Low O2 Tension/Chronic Hypoxia (higher altitude, higher predisposition to CHD)
Changes in Fetal Circulation after Birth
- Gas exchange from placenta to lungs
- Interruption of umbilical cord
- Expansion of the lungs
– Increase SVR due to removal of placenta – Closure of ductus venosus – Decreased PVR, increase PBF, decrease PAP – Functional closure of foramen ovale due to increase LAP; RAP decreases after closure of ductus venosus – PDA closes with increased O2 saturation
This test is used to differentiate cardiac and pulmonary causality of cyanosis
Hyperoxic test:
> If PO2 150-200 mmHG ->pulmonary
> If PO2 cardiac
Malformations in Tetralogy of Fallot:
- Large unobstructed VSD which can be sub-aortic or subpulmonic
- Pulmonary stenosis (may occur in singles or in combination) and can be Subvalvar, Supravalvar, Valvar or infundibular (most common)
- Overriding Aorta (becaue of the VSD). Aorta is also anteriorly displaced
- Right Ventricular Hypertrophy – physiologic adaptation due to pulmonary stenosis and VSD where LV systemic becomes equal to RV systemic
Clinical Features:
- Cyanosed – often progressive
- Retarded growth NOT mental development
- Clubbing of fingers and toes
- Often squat to improve pulmonary blood flow
- Liable to cyanotic spells – infundibular stenosis goes to
spasm cutting off blood flow to the lungs
• Hyperpnoea
What is a Pink Tetrad?
The stenosis is very mild so the patient only has mild cyanosis as well (Remember! The degree of cyanosis is directly correlated with the degree of stenosis)
Appearance of heart in CXR in Tetralogy of Fallot
boot-shaped
- due to upliftment of the right ventricle and convexation of the main pulmonary artery
- however, people with TOF can still have normal CXR
Natural History of TOF?
- CYANOSIS in the form of a hypoxic spell; Tet spells
- Relieved by squatting - POLYCYTHEMIA - Compensatory mechanism (since our body detects our need for oxygen, we produce more
hemoglobin; but our problem is the pulmonary stenosis not this -> increase in blood viscosity -> more prone to thrombosis -> embolization - CEREBROVASCULAR ACCIDENTS (CVA); brain abscess - Because of the VSD, bacteria in systemic venous return mixes with blood in LV -> bacteria can go straight to the brain.
* Important to instruct any patient with structural cardiac defect to always have healthy teeth - INFECTIVE ENDOCARDITIS - Any structural abnormality of the heart is a set-up for infective endocarditis.
Medical management for Tetralogy of Fallot:
- Prevent Fe Deficiency
- Phlebotomy (remove blood to make baby less
polycythemic)
- Propanolol for hypoxic spells
Surgical management for Tetralogy of Fallot
- Can now be done in infancy but still with criteria
o Palliative:
> SHUNTS (BTS-Blalock Taussig Thomas Shunt, central) - like creating a PDA - so there is continuous flow from the aorta to pulmonary artery
> STENT - keep the PDA open (no need for shunts!)
Definitive management for TOF?
- VSD closure
- Infundibulectomy - Excision of the conus arteriosus, especially of hypertrophied myocardium encroaching on the ventricular outflow tract -> to relieve effects of stenosis
- Trans-annular patching - patch covers part of the wall of the right ventricle as well as widening the pulmonary artery and pulmonary valve.
Requirement: normal size of pulmonary artery
In Transposition of the Great Arteries,
- Aorta connects to the ___ ventricle
- Pulmonary artery to the ___ ventricle
- Aorta on the RIGHT ventricle
- Pulmonary artery on the LEFT ventricle
- 5% of CHDs - least common
CXR appearane of Transposition of Great Arteries?
Egg-shaped with Hypervascular Markings
- appearance is a bit similar to TOF since both have Right Ventricular Hypertrophy. The main difference is that in TOF, the markings around the heart are HYPOVASCULAR because of decreased pulmonary blood flow. In contrast, in TGA, there are Hypervascular Markings because there is preferential flow towards the lungs. (Though circuit is parallel so TGA is a worse condition and patient would be progressively cyanotic)
The best shunt for a patient with Transposition of the Great Arteries?
ASD the best! Since pressure in RA=RV
unrestricted communication
o VSD problem: restricted flow not as effective as
large VSD of ToF
o PDA problem: high pulmonary vascular resistance in newborn good; pulmonary vascular resistance in adult is low thus not as effective
Heart sounds in patients with TGA
Single S2, soft systolic murmur - -> aorta is anterior to pulmonary artery so during auscultation, only one sound is heard
Management for a patient with TGA?
Management
• Palliative
> Prostaglandin – prevent closure of PDA
> Create inter-atrial communication
§ Balloon Atrial Septostomy (BAS) – Rashkind
§ Blade septosomy -
§ Atrial septosomy - Block Hanlon
• Definitive
> Atrial switch - Senning/Mustard (not done
anymore)
> Arterial switch –Jatene procedure
