Provoked Right-to-Left Shunt in Patent Foramen Ovale Associates With Ischemic Stroke in Posterior Circulation

BACKGROUND AND PURPOSE: Right-to-left shunt (RLS) via the patent foramen ovale is an important cause of cryptogenic stroke. The Valsalva maneuver provokes or enhances RLS, but RLS can also occur during normal respiration. This study examined whether the ischemic lesion pattern differs depending on the character of RLS. METHODS: All consecutive patients with a patent foramen ovale (diagnosed by transesophageal echocardiography) who had a cryptogenic stroke and underwent transcranial Doppler-patent foramen ovale test (monitoring of microbubbles in the right middle cerebral artery by transcranial Doppler after hand-agitated saline injection) were divided according to whether RLS was constant (microbubbles detected both at baseline and after the Valsalva maneuver) or provoked (microbubbles detected only after the Valsalva maneuver). The groups were compared in terms of clinical and imaging characteristics. RESULTS: Seventy-six patients met the eligibility criteria: 50 had constant RLS and 26 had provoked RLS. Provoked RLS patients were significantly younger. The ischemic lesions in provoked RLS patients were located predominantly in the vertebro-basilar circulation (73.1% versus 28.0%; P=0.002), whereas constant RLS patients were more likely to have multicirculatory lesions (16.0% versus 0.0%; P=0.045). After adjusting for confounders, provoked RLS associated independently with a vertebro-basilar lesion location (OR=3.306; P=0.03). CONCLUSIONS: The predominance of posterior-circulatory infarction in provoked RLS patients suggests that the Valsalva maneuver may promote RLS and paradoxical embolization to the posterior circulation.