Murmur of Tetrology of Fallot is generated at the level of
- Aortic root
- Any of the above
Answer : RVOT.
RVOT is the classical site of TOF murmur , but there is a rider . The murmur of TOF is inversely proportional to the degree of RVOT obstruction. (Contrary to VPS with intact IVS) .In severe TOF especially during spells the murmur attenuate dramatically and may disappear altogether. Hence a silent and quiet heart do not necessarily indicate a mild form of TOF .
Other possibilities also exist.
- The VSD in TOF is large and do not restrict blood flow on either direction . Rarely restrictive VSD can generate a murmur across VSD.
- Aortic flow is increased in all severe cases of TOF ( Highest in pulmonary atresia and VSD) Hence there is always a possibility of a soft systolic flow murmur across Aortic valve .
- Other rare cause for systolic murmur is due to prolapse of tricuspid valve that occludes the VSD potentially causing TR and in the process may convert the VSD into restrictive type.
- One more cause for systolic murmur is sub Infundibular anomalous muscle bundles criss crossing the RV body .
- Peripheral pulmoanry arterial stenosis is recognised cause for distant faint systolic murmur.
- Diastolic murmurs can also occur in TOF . Absent pulmonary valve and aortic regurgitation can result in diastolic murmurs .
Question for analysis
What happens to TOF murmur during squatting ?