Detection and Measurement of Functional Impact of Patent Foramen Ovale in case of Paradoxical Embolism

A paradoxical embolism may be the cause of a stroke in case of patent foramen ovale when other potential causes have been excluded. While transesophageal echocardiography (TEE) remains the gold standard, bed-side diagnosis for the neurologist is possible by means of transcranial echocardiography using a contrast agent that does not pass the lung. Previous studies have found the ultrasound test for right-to-left shunt (RLS) being g most sensitive when injection of contrast agent (preferable Echovist® due to higher sensitivity) is performed 5 seconds before a Valsalva maneuver. Quantification can be obtained by counting of the microbubbles observed at the middle cerebral artery or can follow an arbitrary 4-step categorization scheme according to the count of microbubbles (0, 1–10, 11–50 and „shower“ where single microbubbles cannot be discriminated). In case of negative TEE examination, exclusion of non-cardiac RLS (e.g., pulmonary shunts) can be considered, however, reports of paradoxical embolism through non-cardiac RLS are rare. A correlation between functional impact of PFO and size of lesion could not be demonstrated in a study of 87 patients. In a follow-up study of 90 patients, there was no association of functional impact of RLS with recurrence rate, but due to the low recurrence (<1.6%/year) this might be the consequence of lack of power. Decisions about secondary prophylactic treatment should consider morphological issues such as atrial septal aneurysm and anamnestic details such as history of recent cerebrovascular ischemic event. and other causes of stroke such as hypertension, since a recent study found patients with hypertension after assumed paradoxical embolism being at increased risk for stroke recurrence. If hypertension in these patients is a concurrent or a supplementing cause of stroke still remains unclear.