Economy Class Syndrome, Patent Foramen Ovale and Stroke

Abstract

Whether air travel in a patient with patent foramen ovale (PFO) is a risk factor for cerebral embolism is unresolved. This is illustrated by a recent case report of the Massachusetts General Hospital in the New England Journal of Medicine of deep venous thrombosis (DVT) and stroke associated with air travel. The discussant concluded that because of the relatively short flight “it seems unlikely that air travel was a major risk factor.” 1 Schwamm L.H. Jaff M.R. Dyer K.S. Gonzalez R.G. Huck A.E. Case 13-2016. N Engl J Med. 2016; 374: 1671-1680 Crossref PubMed Scopus (5) Google Scholar This may well be true for DVT per se, the risk of which has been shown to increase with duration of the flight. 2 Lapostolle F. Surget V. Borron S.W. Desmaizières M. Sordelet D. Lapandry C. Cupa M. Adnet F. Severe pulmonary embolism associated with air travel. N Engl J Med. 2001; 345: 779-783 Crossref PubMed Scopus (364) Google Scholar However, the patient under discussion had a PFO with documented right-to-left shunting. Air travel is not only a risk for DVT secondarily to prolonged immobility during which blood pools in the legs (the so-called economy class syndrome 3 Cruickshank J.M. Gorlin R. Jennett B. Air travel and thrombotic episodes: the economy class syndrome. Lancet. 1988; 2: 497-498 Abstract PubMed Scopus (218) Google Scholar ) but in a patient with PFO also because of altitude exposure. Even in well-pressurized planes, oxygen levels correspond to altitude levels of up to 8,000 feet. At these levels, right-to-left shunting through the PFO distinctly increases because of an increase in pulmonary artery pressure. 4 Allemann Y. Hutter D. Lipp E. Sartori C. Duplain H. Egli M. Cook S. Scherrer U. Seiler C. Patent foramen ovale and high-altitude pulmonary edema. JAMA. 2006; 296: 2954-2958 Crossref PubMed Scopus (102) Google Scholar , 5 Rimoldi S.F. Ott S. Rexhaj E. de Marchi S.F. Allemann Y. Gugger M. Scherrer U. Seiler C. Patent foramen ovale closure in obstructive sleep apnea improves blood pressure and cardiovascular function. Hypertension. 2015; 66: 1050-1057 Crossref PubMed Scopus (17) Google Scholar Obviously increased shunting across the PFO may facilitate paradoxical embolism. Contrary to the aforementioned statement, it is likely that air travel was indeed the triggering event in the patient under discussion, leading to increased shunting across the PFO and as consequence to paradoxical embolism and acute ischemic stroke.