Hypoxia related to PFO: A case report of MRI findings (QF_FR_100)

Description of Clinical Presentation: A 73-year-old man with a chronic smoking history presented to an urgent care clinic with a complaint of dizziness. The patient was found to be profoundly hypoxemic requiring high-flow nasal cannula initially presumed to be from chronic obstructive pulmonary disease exacerbation. The initial chest CT scan did not show pulmonary parenchymal or vascular disease. Failure in improvement of hypoxemia and normal chest CT findings prompted a transthoracic echocardiogram which showed normal biventricular function, atrial septal aneurysm, and right to left shunt on agitated saline study. The tricuspid regurgitation jet was insufficient for the assessment of pulmonary pressures. A presumptive diagnosis of right-to-left shunt in the context of possible pulmonary hypertension was made. A cardiac MRI was performed to characterize the nature of the shunt.

Diagnostic Techniques and Their Most Important Findings: MRI was performed to characterize the nature of the shunt. Cine SSFP images showed normal biventricular function and interatrial septal aneurysm. A stack of cines interrogating the interatrial septum showed distorted septal geometry from an enlarged aortic root. Phase contrast sequences yielded a Qp:Qs of 0.6 consistent with the right-to-left shunt. Post-contrast inversion recovery sequences showed focal transmural enhancement of mid inferior wall suggestive of embolic infarction. Diagnosis of right-to-left shunt from a patent foramen ovale was made. foramen ovale was made. Right heart catheterization showed normal pulmonary arterial pressures (22/14 mmHg), normal pulmonary vascular resistance (1.7 WU), and a right-to-left shunt with Qp: Qs of 0.6. The patient underwent PFO closure with a 35 mm Amplatzer device with complete resolution of hypoxia. In subsequent follow-up visits, the patient showed normal oxygen saturation and denied symptoms.

Learning Points from this Case: This case highlights the occurrence of a right-to-left shunt from a PFO in the setting of altered septal geometry and with the absence of pulmonary hypertension. A high index of suspicion is required as it is curable with PFO closure. CMR aids in the diagnosis and characterization of anatomy.