PHILADELPHIA—Long-distance air and land travel is a risk factor for patent foramen ovale (PFO)–related stroke, researchers reported at the 66th Annual Meeting of the American Academy of Neurology.
“The coexistence of additional risk factors potentiates the risk associated with immobilization,” said MingMing Ning, MD, Codirector of the Cardio-Neurology Division and Director of the Clinical Proteomics Research Center at the Massachusetts General Hospital in Boston. “PFOs are highly prevalent in the general population, but they are usually only discovered after a stroke, so effective risk assessment and prevention are key.”
PFO—a “back door to the brain”—is an important risk factor for embolic strokes, noted Dr. Ning. She and her colleagues previously found that PFO not only may cause paradoxical emboli, but it also promotes an acquired hypercoagulable state in peripheral blood due to persistent venous–arterial mixing. PFO is also associated with other nontraditional risk factors for stroke.
“Economy class syndrome,” which refers to the hypothesis that passengers with less legroom during long-distance flights have an increased risk of deep vein thrombosis due to immobility, has not been studied prospectively in PFO-related stroke. Prior research has shown that as many as 10% of healthy air travelers develop asymptomatic deep vein thrombosis after prolonged flights and that 25% of the general population has a PFO. Therefore, the investigators hypothesized that long-distance travelers may have an increased risk of PFO-related stroke.
Dr. Ning’s prospective study included 896 consecutive patients (51% female) who were evaluated at the Massachusetts General Hospital’s Cardio-Neurology Clinic. Eleven percent of the subjects had a history of land or air travel within one week prior to their stroke (average travel time, seven hours). Long-distance travel before stroke was more common in subjects younger than 55, compared with long-distance travel in those older than 55 (13% vs 6%, respectively).
Dr. Ning’s group found that patients with novel stroke risk factors had a significantly shorter average time of travel before their strokes, compared with patients without these risk factors. For example, travel time before stroke was 3.0 hours for patients with hypercoagulable state versus 7.4 hours for patients without clotting disorders, 4.4 hours for patients with migraine with aura versus 9.3 hours for patients without migraine, and 5.2 hours for patients with pelvic venous abnormalities such as May–Thurner syndrome versus 7.0 hours for patients without such abnormalities. The prevalence of traditional risk factors such as hypertension and diabetes was similar between the two groups.
Reducing the risk of a PFO-related stroke is not simply a matter of closing a PFO, said Dr. Ning. “PFO-related stroke is a multiorgan disease that not only affects the brain, but also the heart, lung, blood, and peripheal vasculature,” she commented. “We need to carefully tailor treatment using new modifiable and inherited risk factors. For example, patients who are going to become pregnant may develop a higher risk of venous clotting if they have May–Thurner anatomy. To individualize care for each one of our patients is the goal. Some patients would really benefit from deep vein thrombosis prophylaxis. Simple statistics indicate that one of four healthy persons has a PFO, and one of 10 healthy travelers may develop deep vein thrombosis after prolonged flights. So just taking an aspirin before you get on a flight, from a public health perspective, will help a lot of patients without even knowing whether they have a PFO.”