The most famous and popular view in clinical echocardiography is para sternal long axis view.It gives us an instant information about the status of left atrium , left ventricle and aorta.Left atrium appears to be seen in full. Still , one should realise it is far from truth.There is a huge blind spot for left atrium in this view .
For a complete imaging of LA one need to do a short axis view at aortic level, and of course a 4 chamber view . All these three views put together , can at best give a 80% exploration of LA .The rest of the 20%( some times vital !) can be seen only be transesophageal echo .
Why para sternal long axis fail to give even glimpse of the 4 pulmonary veins ?
- Pulmonary veins are probably , the most vital structure in LA . There are 4 veins , generally arranged in 2 pairs
- Unfortunately all these 4 veins does not interrupt the ultrasound beam in this view .The beam in para sternal view crosses the anterior and lateral surfaces and to a very small area of inter atiral septum( IAS )
- These enter the posterior surface of the LA in an oblique angle . The angle of entry is widely variable .Some times they need to run a parallel course with LA posterior wall . This makes recognition and delineation of PV from LA very difficult ..
- Since all 4 pulmonary veins are located in the posterior aspect of LA , they are best visualized either in apical 4 chamber (Right pulmonary veins) or short axis views(Left pulmonary veins)
When can pulmonary veins visible in PS- LAX view ?
When PVs take an abnormal course like in TAPVC or when they enter coronary sinus etc .
Rarely , huge LA enlargement may pull or push the PVs and make them visible in LAX view.
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Dr.S.Venkatesan MD 
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