49. Case Report: Platypnea-Orthodeoxia secondary to a PFO – Allegheny Health Network

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Patient Summary

A 64 y/o female with a history of venous and arterial embolism on anticoagulation, known PFO, and obesity presented after a fall. There was no loss consciousness, pre-syncopal symptoms, chest pain, aura, weakness, or palpitations. She had no recent preceding illness. When she arrived in the ED she was hypoxic to 87% on ambulation on room air and required 4L of nasal cannula O2 supplementation. The AGH CardioNerds were consulted!

On examination, the team noted that upon sitting up the patient would desaturate to the mid 80% but when lying down oxygen saturation would improve to 95%! Her ECG demonstrated a RBBB and no acute ST-T changes. TTE was obtained and showed normal LV and RV function and size, no valvular disease, and a likely PFO on an agitated saline study. Cardiac MRI revealed mild RV hypertrophy and Qp:Qs of 0.8 (right/pulm cardiac output < left/systemic cardiac output, indicating right to left shunting). RHC showed normal right-sided pressures. A right femoral vein bubble study was done showing torrential right to left shunting! She underwent PFO closure and her platypnea-orthodexia resolved; she was discharged on room air.

Case Media

Episode Schematics & Teaching

The CardioNerds 5! – 5 major takeaways from the #CNCR case

1. Platypnea-orthodeoxia syndrome (POS) is when dyspnea (Platypnea) and hypoxia (Orthodeoxia) are present in the upright position, but improve upon lying flat. One cause is ARLIAS, or Acute Right-to-Left Inter-Atrial Shunting, which requires an anatomic component (I.e., ASD or PFO) and a functional component (I.e., PH, PE, RV failure) for Right-to-Left shunting to occur
2. A PFO, or patent foramen ovale is a common congenital defect and typically will not lead to hypoxia unless there is right to left shunting. Typically flow is left to right due to an LA to RA pressure gradient and lower compliance of the RV.
3. Remember when evaluating for a PFO with agitated saline, the timing of the appearance of bubbles is important! Early appearance of bubbles (seen in less than 5 beats of the cardiac cycle, think about intra-cardiac shunt. Delayed opacification (> 5 to 6 beats) occurs when the bubbles slowly build in the LV with each successive beat as they circulate to the LV and suggests extra-cardiac shunt.
4. Cardiac MRI is helpful in quantifying the shunt fraction (Qp:Qs). This is the ratio of pulmonary flow (Qp) to systemic flow (Qs), where hemodynamically significant Left-to-Right shunt is > 1.5, especially when we see RA/RV dilation. Qp/Qs < 1.1 indicates net R to L shunt. Other ways to measure a Qp:Qs are echocardiogram (less accurate) and right heart catheterization.
5. If there remains clinical concern for PFO with right to left shunting without evidence of a clear functional cause clinically or by catheterization (I.e., no evidence of high PA pressures, pericardial effusion, constrictive pericarditis), consider a right femoral vein bubble study. Upper extremity agitated saline enters the RA via the SVC; however, patients with prominent eustachian valve at the IVC can have blood flow directed towards the interatrial septum. This will be demonstrated on femoral vein bubble study!

Educational Video

References

• Cheng, T. O. (2002). Mechanisms of platypnea-orthodeoxia: what causes water to flow uphill. Circulation, 105(6), e47.
• Tobis, J. M., & Abudayyeh, I. (2016). Platypnea-orthodeoxia syndrome: an overlooked cause of hypoxemia.
• Sanikommu, V., Lasorda, D., & Poornima, I. (2009). Anatomical factors triggering platypnea‐orthodeoxia in adults. Clinical Cardiology: An International Indexed and Peer‐Reviewed Journal for Advances in the Treatment of Cardiovascular Disease, 32(11), E55-E57.

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