The aim of the project is to identify new risk indicators of PFO. The evaluation of the R-L shunt is based on the newly developed precise measurement technique. Moreover, this measurement of R-L shunt is feasible in a case when R-L shunt is present only intermittently. Multicentric study with 150 patients.

The aim of the proposed project is to identify new risk indicators of PFO. The evaluation of the R-L shunt is based on the newly developed precise measurement technique. Moreover, this measurement of R-L shunt is feasible in a case when R-L shunt is present only intermittently.

Detection and quantification of R-L shunt will be realized by the original INNTHERM® ® system (Innova Medical s.r.o., Velká Dobrá). This system is based on the principle of thermodilution.

The basic assumption of our study is the hypothesis, that the size of the R-L shunt (and especially its maximum size during intra-abdominal pressure increase) is a risk factor for the development of paradoxical embolism (from pulmonary to systemic circulation). The most critical consequence of paradoxical embolism is the development of ischemic stroke.

Such measurement with an unequivocal accuracy has never been done so far, due a lack of technology precise enough.

Precise quantification of R-L shunt will allow a more accurate prediction of high-risk patients, especially after correlation with commonly used methods. PFO is now an indication for implantation of percutaneous occlusion device only in case of secondary prevention of stroke, i.e. in a group of patients who have had an ischemic stroke.

Prospectively, precise and better identification of a risk group of these patients could lead to cost reduction of treatment. This cost reduction is crucial for young working-age patients who can be treated before a major irreversible brain injury occurs.

A parameter applicable in primary prevention saves the cost of ischemic stroke treatment and other systemic embolism; additionally it will contribute to cost reduction during aftercare treatment.

Inclusion Criteria:

1. Male and female patients aged ≥18 and < 60 years
2. Cryptogenic stroke or Systemic embolization due to paradoxical embolization via Patent Foramen Ovale
3. The patient indicated for occlusion of PFO with catheter occluder

Exclusion Criteria:

1. Inability to perform spiroergometry
2. Inability to perform Transesophageal echocardiography (TEE)
3. Inability to perform proper Valsalva maneuver
4. Inability to understand and/or signed informed consent form
5. Contraindication of Patent Foramen Ovale occlusion by any medical reason or patient refusal