I know ,there is a VSD out there ! but I am unable to get the gradient across it.This situation can be quiet common .The reasons could be technical, anatomical or hemodynamic.
As a rule , if we hear a pan-systolic murmur clinically , one must be able to catch a good Doppler spectrum somewhere by echocardiography . However , If the murmur is restricted to early or mid to late systole, VSD jet is often attenuated in echocardiography .
In the following situations , VSD jets may not record a distinctive Doppler spectra. Invariably the velocity is low , spectrum is short, less intense , lacks good shape and borders are hazy !
- A closing VSD
- A Small muscular VSD
- VSD with Severe pulmonary hypertension
- VSDs with muscle bundle criss crossing
- Double chambered right ventricle (DCRV, where VSD usually drains to high pressure chamber.)
- VSD associated RVOT obsruction (Note: classical TOF VSD will never generate a murmur)
- VSD with sinus of valsalva aneurusms ( Doppler jet can be really difficult to record )
- Inlet VSDs are missed because convectional views of echo are perpendicular to these inlet jets.(Short axis better )
- Another common situation is post STEMI VSR.Both a small apical VSD or multi tract VSD associated with infero posterior STEMI gradients are difficult to obtain.
What is inference ?
Doppler spectrum will help detect small VSDs and color doppler will not miss even a tiny VSD.Doppler spectrum across VSD is dependent many factors other than the presence of VSD. However some large VSDs are detected better by 2D echo rather than doppler signals.
Presence of a Anatomical VSD does not imply it should generate a noise.The murmur as well as Doppler signals are primarily determined by the pressure difference on either side of VSD. After all , one of the largest VSD that we encounter