Characteristics of patent foramen ovale associated with cryptogenic stroke. A biplane transesophageal echocardiographic study.

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Abstract
Patent foramen ovale is associated with ischemic stroke in patients without a clearly identifiable etiology for stroke (cryptogenic stroke). Paradoxical embolization is thought to be a potential mechanism. However, patent foramen ovale is also found in patients with known cause of stroke. Therefore, using contrast transesophageal echocardiography, we characterized the patent foramen ovale in cryptogenic stroke patients to assess morphological factors that may contribute to paradoxical embolization. Contrast transesophageal echocardiographic studies of 74 consecutive patients referred for ischemic stroke were reviewed. Twenty-three patients with patent foramen ovale were identified. These patients were classified as having strokes of determined origin or cryptogenic strokes according to criteria developed for the Stroke Data Bank of the National Institute of Neurological Disorders and Stroke. Separation of septum primum from secundum and the number of microbubbles appearing in left atrium were then quantitated. These parameters were compared between patients with cryptogenic stroke and those with known cause of stroke. The patent foramen ovale dimension was significantly larger in patients with cryptogenic stroke compared with patients with an identifiable cause of stroke (2.1 +/- 1.7 mm versus 0.57 +/- 0.78 mm [mean +/- SD]; P < .01). The number of microbubbles was also greater in patients with cryptogenic stroke compared with patients with an identifiable cause of stroke (13.9 +/- 10.7 versus 1.6 +/- 0.8 [mean +/- SD]; P < .0005). Patients with cryptogenic stroke have larger patent foramen ovale with more extensive right-to-left interatrial shunting than patients with stroke of determined cause. Transesophageal echocardiographically identifiable characteristics of patent foramen ovale may be important in defining the clinical significance of individual patent foramina.