Answer: B) Obstructive

The IVC here exhibits significant collapsibility (which was confirmed to be true collapsibility by two independent expert scanners, and not just lateral translation with respiration).

A collapsible IVC makes obstructive shock much less unlikely (though not impossible – collapsible IVCs have been reported in patients with massive PE, for example). It’s also very important to note that respiratory effort can confound IVC collapsibility – a patient breathing very hard and generating significant negative inspiratory intrathoracic pressure can manage to collapse even a “distended” IVC.

The right ventricle was dilated which may prompt consideration of a massive pulmonary embolus; however, note from the history the patient was not hypoxic or in respiratory distress. Also, in looking at the interventricular septum in the PSAX view, a “D-shaped” septum was only produced during diastole (volume overload), rather than in systole (pressure overload, which would be typically observed when pulmonary arterial pressure acutely elevate). Note that these findings are not definitive, however; and regardless of any other disease processes at play in this case, the R heart certainly deserves some attention and careful consideration!

Answer: A) Obtain a transthoracic echocardiogram

Given the clinical circumstances, the lesion is most likely an infected vegetation (infective endocarditis).

However, there is a differential diagnosis for such endocardial lesions, including thrombi, intracardiac masses, etc. Although there are certain sonographic features for each, it is BEYOND the scope of POCUS to definitively characterize these lesions (and indeed, often not possible even on diagnostic echocardiography).

At this point, it would be prudent to obtain a diagnostic echocardiogram to elucidate salient features of this lesion for a diagnosis, assess for the presence of other lesions (eg. tricuspid valve is the most common valve affected for those who use injection drugs), and potential sequelae (eg. valvular regurgitation).

A transthoracic echocardiogram would be a reasonable initial test given the adequate windows. However, in cases where TTE is inconclusive and clinical suspicion is high, proceeding with TEE is appropriate.

Answer: C) Unable to tell

The clinical question here is whether the patient would be tolerant to volume expansion (as opposed to volume responsiveness – whether their cardiac output would increase in response to fluids. This will be discussed more in a future case!).

This issue is often not straightforward and was debated by several of our POCUS faculty. As in the rest of medicine, in POCUS things are not always black and white – and the shades of grey require careful consideration to reconcile with the rest of the clinical picture.

Possible indicators of volume tolerance in this case were the patient’s dry lungs (lack of B-lines) and good LV function; as well as the very collapsible IVC despite the presence of significant tricuspid regurgitation.

Note, however, that the greatest risk with volume expansion in this patient is not left heart failure resulting in pulmonary edema, but right heart failure. Given the RV dilation and severe TR, most of us said we would be very cautious about giving this patient any additional fluids, in spite of the collapsible IVC. The RV is very poorly tolerant of volume overload, and this patient could get into trouble very quickly with aggressive volume administration. Excess volume administration to a failing right heart leads to increased RV size, decreased RV function, impaired LV filling, and low cardiac output.