Final answer:
The next best step for isolated RSVP on echo in young patients is to evaluate for an ASD. This can be done through a transthoracic echocardiogram. If an ASD is confirmed, further evaluation and treatment may be necessary.
Step-by-step explanation:
The next best step for isolated RSVP on echo in young patients is to evaluate for an atrial septal defect (ASD). Isolated right superior vena cava (RSVC) drainage is a rare congenital anomaly that can lead to an ASD. A transthoracic echocardiogram can help visualize the RSVC and assess for any accompanying defects.
If an ASD is confirmed, it may require further evaluation and treatment. This can include additional imaging studies like cardiac catheterization to assess the anatomy and size of the ASD, and potential surgical repair or closure of the defect.