Tetralogy of Fallot Flashcards
What is cyanotic congenital heart disease?
- Cyanotic CHD occurs when deoxygenated blood enters systemic circulation due to R-L or bidirectional shunting or mal position of the great arteries
- One of the most common causes of cyanosis in new-borns = cyanotic CHD
What is cyanosis?
Bluish colour of skin and mucous membrane due to insufficient blood oxygen
Most common cyanotic heart lesions?
- Tetralgy of Fallot
- Tricuspid Atresia
- Total Anomalous Pulmonary Venous Return (TAPVR)
- Transposition of Great Arteries (TGA)
- Truncus Arteriosus
What is Tetralogy of Fallot?
- Cono-truncal-septal anomaly results when anterior and superior deviation of the outlet IVS
- Leads to malalignment of the outlet ventricular septum as well as unequal division of ventricular outflow tracts and great arteries
What are the four cardiac abnormalities in TOF?
- Subaortic VSD (large mal-alignment VSD)
- Dilated, overriding aorta
- RVOTOB (narrowing and obstruction of RVOT)
- RVH
How does subaortic VSD occur in TOF?
Occurs as cono-truncal septum and trabecular and inlet septum do not line up and connect
How does dilated, overriding aorta occur in TOF?
Anterior displacement of mono-truncal septum leads to rightward shift of the aorta, so the aorta straddles VSD and opens over both RV and LV
How does RVOTOB occur in TOF?
Results from crowding of sub-pulmonary outflow by muscular and fibrous tissues of the abnormal outlet ventricular septum
What may RVOTOB be due to?
- Stenosis or hypoplasia of the PV
- Hypoplasia of MPA and/or MPA branches
- Combination of these
How does RVH occur in TOF?
Occurs as compensatory mechanism to increased RV pressure due to RVOTOB
Circulatory pathway in TOF?
- Deoxygenated blood from IVC/SVC –> RA –> RV
- From RV, blood ejected through stenotic PV, to lungs where it is oxygenated –> pulmonary veins –> LA –> LV –> aorta
- Overriding aorta receives oxygenated blood from LV and deoxygenated blood from RV
Circulatory Pathway: What is the degree of cyanosis dependent on in TOF?
- Degree of mixing dependent on RVOTOB
- More severe obstruction, more blood delivered from RV –> aorta = greater degree of cyanosis
Variants of TOF?
- TOF + pulmonary atresia
- TOF + absent pulmonary valve
- TOF + double outlet RV
- TOF + AV canal defect
Associated lesions of TOF?
- Right aortic arch
- Coronary artery anomalies
- ASD
- Additional VSDs
Syndromes associated with TOF?
- DiGeorge Syndrome
- Down syndrome
- Foetal Alcohol Syndrome
- Goldenhar Syndrome
- Holt-Oram Syndrome
Diagnosing TOF?
- Diagnosed on echo by detecting the four associated abnormalities
- Use of turbulent flow in RVOTOB, CW to identify PG across PV, and measurement of pulmonary annulus
TOF Repair?
- Patch closure of VSD
- Relief of RVOTOB (achieved by RVOT widening via trans-annular patch)
Role of Echo Post TOF Repair?
- Residual VSDs
- PR Severity
- RVOT: aneurysms, obstruction
- RV and LV; size and systolic function
- Aortic root: progressive dilatation quite common
- ? AR: AR can occur secondary to aortic root dilatation
Assessing AR in TOF?
- Colour jet area
- P1/2t; intensity of jet compared with forward flow
- PW abdominal aorta: looking for pan-diastolic flow reversal
- PW descending thoracic aorta: looking for pan-diastolic flow reversal
Post-op complications of TOF?
- RV failure
- Severe PR
- Persistent RVOTOB
Post-Op Complications of TOF: RV Failure
- RV almost always dilated with some degree of systolic dysfunction
- RV Anterior-Posterior Diameter (APd): if RV diameter appears larger than LV diameter at level of papillary muscle in PSAX, RV considered severely dilated
- CMR best for assessing RV post TOF repairs
- RV strain can also be used
- Global longitudinal peak systolic strain (GLPSS): average of 3 x septal and 3 x free wall segments
- Longitudinal peak systolic strain (LPSS): average of 3 RV free wall segments only
Post-Op Complications of TOF: Severe PR
- Very common post TOF repair
- Severe for ‘free’ PR can be easily missed as PR jet is low velocity, so PR flow appears laminar on CFI; PR duration may only appear in early diastole and be brief
Severe PR Parameters?
- Jet width/annulus ratio ≥ 70%
- Dense jet, PHT < 100ms (due to increased RV diastolic pressure caused by PR into RV)
- Early termination of PR flow
- Diastolic flow reversal in PA branches
- Dilated RV
Significance of PR: Class 1?
PV replacement (surgical or percutaneous) for relief of symptoms is recommended for patients with repaired TOF and moderate or greater PR with cardiovascular symptoms not otherwise explained
Significance of PR: Class 2a?
PV replacement (surgical or percutaneous) is reasonable for preservation of ventricular size and function in asymptomatic patients with repaired TOF and ventricular enlargement or dysfunction and moderate or greater PR
Post-Op Complications of TOF: Persistent RVOT Obstruction
- See congenital PS notes
- Can see pulmonary bifurcation from SSN SAX by rotating to 3-4o’clock position
- If a high TR velocity: search for RVOT or PA obstruction at some level
PR slope and duration in severe PR?
- Dependent on RV compliance
- Steep PR slope and early termination of PR signal = marked increase in RVEDP
- May occur with 1) severe PR or 2) restrictive RV physiology
