What is the recommended action if a patient has a suspected right-to-left cardiac shunt during lung perfusion imaging?

In the case of a suspected right-to-left cardiac shunt during lung perfusion imaging, the appropriate action is to decrease the number of particles administered.

When a right-to-left shunt is present, particles can bypass the pulmonary circulation and enter systemic circulation directly, which could lead to complications such as embolism or adverse effects if too many particles are introduced. The standard protocol in such scenarios is to reduce the particle count to minimize the risk of these particles entering the systemic blood flow. Additionally, using fewer particles can still provide adequate imaging information while safeguarding the patient’s health.

The other approaches, such as increasing the number of particles or performing the imaging test immediately without adjusting for the shunt, would not be advisable as these could exacerbate the risk of complications during the imaging procedure. Administering the standard particle count could also pose a hazard in the presence of the shunt, as it does not consider the altered hemodynamics and the potential for particles to bypass normal filtration in the lungs.