Correct!
5. 1 and 4
The 99mTc-MAA study does show relatively homogeneous tracer distribution within the lungs, indicating a low likelihood of pulmonary embolism; however, this is not the most interesting or relevant finding on this examination. Rather, the study shows tracer activity within the brain (Figure 4, Panel B) and the kidneys (Figure 4, Panel C), which indicates systemic tracer embolization, and is diagnostic of right-to-left shunting. Such shunting does not localize the level of the shunt- it could be intracardiac or extracardiac- but it does indicate a physiologically significant right-to-left shunt is present.
An echocardiographic bubble study was performed and the findings were consistent with the presence of a pulmonary shunt. Measurement the shunt fraction using the 100% oxygen method indicated a shunt fraction of 20%.
What is the appropriate next step for the evaluation / management of this patient?