Patent Cardiac Foramen Ovale: Stroke Risk and Closure

With increasingly sophisticated detection technology, patent cardiac foramen ovale has emerged from the arcane shadows of clinicopathologic conferences, where its diagnosis as a cause of embolic stroke was a challenge to the discussants (1). Given the common difficulties in finding a cause for ischemic stroke (2), demonstration of patent foramen ovale seems an acceptable explanation to most clinicians (3). No longer rarely diagnosed, patent foramen ovale is being increasingly documented by transesophageal echocardiography (TEE). The condition is best demonstrated by passage of microbubbles through the patent foramen ovale after intravenous injection of agitated saline. These same microbubbles, which spread widely through the systemic circulation, also reach the circle of Willis intracranially, a finding easily documented through transcranial Doppler techniques (4, 5).

Given the small size of brain arteries, difficulties in finding the source of particles that can cause an embolic stroke are not surprising. Candidate sources include the great vessels leading to the brain, the aortic arch, heart valves, and ventricular or atrial walls, as well as venous particles passing through a patent foramen ovale. Because of the many sources and the possible small particle size, even a detailed search often finds no mechanisms for recurrent stroke. The term cryptogenic stroke was introduced to classify such cases (6). Many reports in the literature assume that when several potential causes are uncovered, only one and not the others is the actual cause; this assumption continues to affect clinical practice. Not least among such examples is Chiari's famous 1905 case report (7). His patient, studied at autopsy, had the first reported case attributed to embolism from carotid ulceration. However, this woman also had a patent foramen ovale. To which cause would her stroke be attributed today?

The circumstances allowing passage of an embolus through a patent …