If a patient has PHTN with a dilated IVC (3cm) that collapses 50% with sniff, what is the estimated RA pressure?

In this scenario, the key is understanding how the inferior vena cava (IVC) diameter and its collapsibility during respiration are evaluated to estimate right atrial (RA) pressure.

A dilated IVC that measures 3 cm suggests that the RA pressure is elevated because increased pressure in the right heart or complications such as pulmonary hypertension can lead to distension of the IVC. The collapse of the IVC by 50% during a sniff test indicates that while there is some degree of filling pressure in the right atrium, it is not excessively elevated.

Generally, a collapsibility of 50% correlates with an estimated RA pressure of around 10 to 15 mmHg. However, considering we have a dilated IVC combined with 50% collapse, it leans towards the higher end of this range. Thus, a pressure of approximately 15 mmHg is consistent with these findings, making B the most appropriate answer.

This knowledge aligns with echocardiographic assessments where IVC measurement and its dynamics are crucial for estimating right-sided heart pressures, particularly in patients with conditions like pulmonary hypertension.