Cryptogenic stroke. Part 2: paradoxical embolism

Cryptogenic stroke (CS) is defined as a subtype of stroke associated with a heterogeneous group of pathogenetic mechanisms that remained undetermined in the course of advanced diagnostic research. One third or fourth of the ischemic strokes is cryptogenic. Paradoxical embolism is considered the important cause of cryptogenic stroke and transient ischaemic attack (TIA) in young patients. It may occur via the following: patent foramen ovale (PFO), atrial septal defect (ASD), and pulmonary arteriovenous malformation (PAVM). When interviewing patients with suspected paradoxical embolism to obtain their health history, a practitioner should consider factors associated with Valsalva maneuvers, deep vein thrombosis/PE or predisposing conditions or situations, as well as symptoms of hereditary hemorrhagic telangiectasia (telangiectasia of the skin and mucous membranes, hemorrhagic syndrome) and pulmonary arteriovenous malformations (PAVMs) (shortness of breath, hemoptysis). If paradoxical embolism is suspected, it is necessary to conduct a stepwise diagnostic search, including transcranial Doppler ultrasound with bubble test, contrast-enhanced transesophageal echocardiography, and CT angiopulmonography. Diagnosis of relevant clinical conditions involves a search of atrial tachyarrhythmias, deep vein thrombosis, and thrombophilia. As the pathogenetic role of ASD and PAVMs in the development of embolic cryptogenic stroke is beyond doubt, the clinical significance of PFO should be determined taking into account several factors, including the presence of deep vein thrombosis/PE, the severity of the right-left shunt, the presence of ASD, the RoPE score, and detection of thrombophilia. The secondary prevention techniques of ischemic stroke or TIA with underlying PFO should be selected on a case-by-case basis, depending on the clinical significance of the anomaly, comorbid pathology, life expectancy of the patient: endovascular occlusion, anticoagulant or antiplatelet therapy. The secondary prevention with underlying ASD and LAVM includes surgical techniques such as endovascular occlusion or open surgery followed by monitoring of their effectiveness.