Low frequency of clinically silent circulating emboli in patients with mitral valve prolapse or patent foramen ovale detected by bigated transcranial Doppler ultrasound.

Patent foramen ovale (PFO), but not uncomplicated mitral valve prolapse (MVP), is a possible source of cardiac embolism to the brain. There are only a few reports on the frequency of clinically silent circulating microemboli in these two conditions. We performed 1-hour recordings of one middle cerebral artery in 4 patients with MVP and 14 patients with PFO to detect circulating microemboli. For the identification of microembolic signals we used blinded off-line evaluation and bigated transcranial Doppler sonography (sampling from two different depths in the vessel). Microembolic signals were detected conventionally in 3 out of 14 patients with PFO (3, 8, and 14 microemboli/h), and in none out of the 4 patients with MVP. The absence of microembolic signals in patients with MVP and the low frequency of microemboli in patients with PFO reflect the different embolic potential of these two cardiac abnormalities.