Platypnea-Orthodeoxia Syndrome
A 70-year-old man presented with shortness of breath for 2 days. His shortness of breath worsened when sitting up or when straining during defecation or urination. He denied chest pain, cough, hemoptysis, orthopnea, leg swelling, or fever. His medical history included 80 pack per year cigarette smoking habit, chronic obstructive pulmonary disease, stage IIA lung adenocarcinoma diagnosed 14 weeks before presentation, and Guillain-Barre syndrome which was diagnosed and treated 6 weeks before presentation. His surgical history included right pneumonectomy 10 weeks prior to presentation.
Physical examination. The patient was hypoxemic while wearing a nonrebreather facemask. His pulse oximetry measurement was 80% sitting upright and 90% lying supine. The patient was alert, tachypneic, and tachycardic. Blood pressure was normal. He had no jugular venous distention, clear breath sounds on the left side, decreased breath sounds on the right side, regular cardiac rhythm without murmurs, and no lower extremity edema or erythema.
Laboratory testing. The patient was admitted to the ICU for refractory hypoxemic respiratory failure. He required high-flow supplemental oxygen with FiO2 ranging from 0.65 to 1.0 to maintain a pulse oximetry measurement greater than 90%. His EKG showed only sinus tachycardia. Arterial blood gas measurement while breathing FiO2 of 1.0 showed pH 7.50, PaCO2 24 mm Hg, PaO2 50 mm Hg, and arterial oxyhemoglobin saturation of 83%. The patient’s hemoglobin was 16.6 g/dL. Portable chest x-ray revealed chronic post-pneumonectomy changes but was otherwise normal (Figure 1).
Figure 1. A frontal portable radiograph of the chest demonstrated chronic shift of the mediastinum from left to right after right-sided pneumonectomy. There were no acute abnormalities identified in the left lung.
Evaluation for acute pulmonary embolism with a CT chest with contrast was negative. Transthoracic echocardiography using intravenous agitated saline contrast demonstrated no intracardiac shunting. But the imaging was technically limited by suboptimal windows. Given the high suspicion for intracardiac shunting as the cause for platypnea-orthodeoxia syndrome in this patient, further testing with transcranial Doppler ultrasound using intravenous agitated saline contrast was completed. Right-to-left embolic events were detected, most notably during Valsalva maneuver. A quantitative scintigraphic shunt study (Figure 2) was also done, confirming right-to-left shunting (shunt fraction of 19%).
Outcome of the case. The patient subsequently underwent cardiac catheterization, which demonstrated a patent foramen ovale (PFO), right-to-left shunting, and normal mean pulmonary artery pressure of 12 mm Hg. The PFO was closed percutaneously with a septal occluder. The patient’s oxygen requirement improved rapidly and dramatically. He required no supplemental oxygen after PFO closure. After discharge, he followed-up with his oncologist and completed adjuvant chemotherapy for non–small cell lung cancer.
Figure 2. A quantitative scintigraphic right-to-left shunt study using radiolabeled 99mTc macroaggregated albumin demonstrated uptake diffusely in the brain and kidneys, signifying transit of radiotracer from the right circulation to the left.
Discussion. Platypnea-orthodeoxia syndrome after pneumonectomy is a rare but established postoperative occurrence.1 The mechanisms by which platypnea-orthodeoxia syndrome develops are not entirely resolved, although an interatrial communication is a key factor.2,3 It can develop even with normal right-sided heart pressures.4 There is usually an asymptomatic interval between pneumonectomy and clinical detection of platypnea-orthodeoxia syndrome.5 The patient described above developed platypnea and orthodeoxia approximately 2 months after pneumonectomy. This case demonstrates that a high index of suspicion in the proper clinical context is needed to make the diagnosis. Expedited diagnosis and management have important implications for the patient, since platypnea-orthodeoxia syndrome can be completely reversible.4
References:
1.Ng SY, Sugarbaker DJ, Frendl G. Interatrial shunting after major thoracic surgery: a rare but clinically significant event. Ann Thoracic Surg. 2012;93(5):1647-1651.
2. Holcman K, Cameron SJ, Laskurain E, et al. Breathtaking: platypnea-orthodeoxia syndrome. Am J Med. 2014;127(6):491-493.
3.Cheng TO. Mechanisms of platypnea-orthodeoxia: what causes water to flow uphill? Circulation. 2002;105(6):e47.
4.Chen GP, Goldberg SL, Gill EA. Patent foramen ovale and the platypnea-orthodeoxia syndrome. Cardiol Clin. 2005;23(1):85-89.
5.Smeenk FW, Postmus PE. Interatrial right-to-left shunting developing after pulmonary resection in the absence of elevated right-sided heart pressures. Chest. 1993;103(2):528-531.