Patent Foramen Ovale Mediated Right-to-Left Shunt: The Role of Hepatic Venous Flow

A 74-year-old male with known pulmonary fibrosis, follicular lymphoma, sleep apnea, and truncal obesity, reported progressive exertional dyspnea. During a 6-minute walk test, his oxygen saturation dropped from 94% to 86% postexercize. CT chest suggested subpleural reticulation with ground-glass opacities; dilated ascending aorta and root (both 41 mm), and resultant compressed right atrium (RA) (Figure 1A). A VQ scan did not identify any significant perfusion defect. His hemoglobin was 180 g/L (hematocrit-51%). Transthoracic echocardiography demonstrated a positive bubble test, both at rest and post-Valsalva maneuver (Supplemental Video 1). A transesophageal echocardiogram confirmed compressed RA characterized by reduced distance between the limbus and the posterior wall of the atrium (Figure 1B, C). His mean RA and LA pressures were 6- and 15 mm Hg respectively. Bilateral pulmonary venous saturation was 95% to 96%, whereas the aortic saturation was 91% suggestive of intracardiac right-to-left shunt. Superior and inferior vena cava (IVC) angiograms demonstrated opacification of the RA, RV, and pulmonary artery, without any significant shunting through a patent foramen ovale (PFO) (Supplemental Videos 2 and 3, Figure 1D, E). As the intracardiac shunt was suspected, we performed a hepatic venogram that demonstrated right-to-left shunt through the PFO (Figure 1F, Supplemental Video 4). Transcatheter closure of a PFO using a 30 mm Gore PFO occluder device eliminated the shunt and normalized systemic saturation. The in-utero IVC just below the diaphragm receives blood from the following: (1) the distal inferior vena cava, (2) the ductus venosus, (3) the portal vein, and (4) the hepatic veins, each with different oxygen saturations. In contrast to the general belief that there is an adequate mixture of this blood in the cephalic portion of the IVC, it is preferentially the highly oxygenated ductus venosus blood that selectively streams through the foramen ovale,1Edelstone D.I. Rudolph A.M. Preferential streaming of ductus venosus blood to the brain and heart in fetal lambs.Am J Physiol. 1979; 237: H724-H729https://doi.org/10.1152/ajpheart.1979.237.6.H724Crossref PubMed Google Scholar whereas the IVC flow enters into the right ventricle. In adults, hepatic vein drains ∼25% to 30% of the total cardiac output; hepatic venous saturation is lower than that from superior vena cava and IVC. Altered geographical relationships between venous drainages and cardiac structures can create a “perfect storm” allowing streaming of venous flow through a PFO. Although this patient had pulmonary fibrosis, careful workup identified a PFO-mediated right-to-left shunt. Transcatheter closure resolved systemic desaturation. This is the first case describing the role of hepatic venous flow in PFO-mediated right-to-left shunting and systemic desaturation. •PFO commonly produces intermittent right-to-left shunting due to episodic elevation of RA pressure.•Altered anatomic relationships between venous drainages and cardiac structures can induce PFO shunting.•In the setting of novel pathoanatomic conditions, redirected hepatic vein flow can cause R-L shunting through a PFO. The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. This work was not supported by funding agencies in the public, commercial, or not-for-profit sectors.

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.