To the Editor:
We hypothesize that right-to-left interatrial shunt (RTLIAS), platypnea-orthodeoxia syndrome (POS), and paradoxical embolization may exacerbate coronavirus disease 2019 (COVID-19) in select patients with a patent foramen ovale (PFO).1 We therefore read the description by Fabre and colleagues2 of the clinical course of a 45-year-old woman with COVID-19 and a PFO with great interest. A pulmonary embolism and a thrombus straddling the PFO developed, and she died despite embolectomy and extracorporeal membrane oxygenation.2 We suspect that RTLIAS may have contributed to her refractory hypoxia and that the initial improvement with prone positioning raises the possibility of POS.
Positional hypoxia while upright that improves with recumbency is characteristic of POS, a syndrome described in 25% of reported patients with RTLIAS.3 Recognition of POS is important, because simple repositioning can reduce the requirement for respiratory support.3 Because the prevalence of PFO is high (20%-30%),3 the absence of reports describing RTLIAS and POS in patients with COVID-19 suggests that these phenomena are being overlooked. Bubble-contrast echocardiography, a minimally invasive bedside test, can detect interatrial defects and RTLIAS.3
The evidence base to guide management of RTLIAS is limited. Patients with RTLIAS respond poorly to positive end-expiratory pressure, are ventilated longer, and receive more interventions for refractory hypoxia.4 Whereas some therapies for refractory hypoxia exacerbate RTLIAS,4 repositioning, reducing airway pressures, and medical treatment of pulmonary hypertension (eg, nitric oxide, nitrates, and sildenafil) may reduce or reverse RTLIAS.
In select patients, surgical or percutaneous PFO closure could improve hypoxia, reduce the need for invasive ventilation, and prevent paradoxical embolization. However, acute cor pulmonale develops in some patients after PFO closure. Furthermore, hypoxia may improve spontaneously as the functional trigger for RTLIAS resolves, so closure is not always required.
Studies of COVID-19, PFO, and RTLIAS are urgently required to improve patient outcomes. Such data may be relevant to other pulmonary diseases and could redefine the treatment paradigm of refractory hypoxia.
References
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