Particulate matter in the inferior vena cava
It is well-recognized that a dilated IVC in endurance athletes is a physiologic adaptation to repeated, intermittent volume loading and does not reflect an increased right atrial pressure. Interestingly, in one study, swimmers were found to have bigger IVCs than other athletes (mean diameter 2.66 cm vs 2.17 cm). As you may recall, generally, we consider >2.1 cm as dilated. It is also commonly seen in young, thin, and active individuals. Below image is a nice example that is obtained from a healthy, trained athlete with resting heart rate in 40s-50s bpm. The maximal diameter of the IVC is >2.1 cm. However, as expected, hepatic and portal vein Doppler are normal.
The interesting thing here is not just the size of the IVC but the echogenic things floating within the vessel. It’s called particulate matter (PRM) and is often observed in patients with no known cardiac pathology who are not tachycardic. Below is another example from Kerut, et al paper.
On the other hand, spontaneous echo contrast (known as ‘smoke’) is seen in cases of stasis and heart failure – likely due to rouleaux (stacked RBCs) formation. It appears as a swirling gray haze of variable density; conversely, PRM particles tend to be larger, more discrete and move faster.
Below is an example of smoke in the IVC obtained from a patient with right heart failure. Note associated abnormal VExUS waveforms suggestive of venous congestion.
Below images are obtained from a patient with severely reduced LV ejection fraction. In addition to IVC, smoke is also seen in the left heart chambers (apical3-chamber view shown).
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