The paradoxical embolism phenomenon in patients with embolic cryptogenic stroke

Abstract

Patent foramen ovale (PFO) is an important cause of embolic cryptogenic stroke (ECS) in young patients. The main mechanism in this case is paradoxical embolism (PE), the basis for which is a right-to-left (R-L) shunt.Objective: to comparatively characterize patients who have undergone ECS, with and without an R-L shunt, as evidenced by transcranial Doppler with the bubble test (TCD-BT).Patients and methods. In 40 patients with acute ECS, an R-L shunt was sought using TCD-BT, followed by transesophageal echocardiography (TEE). The left atrial volume index (LAVI) was additionally calculated. Brain damage was analyzed by probabilistic mapping of foci according to magnetic resonance imaging.Results and discussion. The mean age of the examined patients was 51.5 (39.5–60.0) years; of them there were 22 women and 18 men. An RL shunt was detected in 24 (60.0%) of patients with cryptogenic embolism that was mainly grades 2 and 3 (41.0 and 35.0%). TEE could visualize PFO (1.0 to 5.5 mm in size) in 16 (40%) patients and atrial septal aneurysm in 3 (7.5%). PFO was not found in 5 patients with positive results of TCD-BT, which may suggest that there is either a pulmonary shunt or a false-negative TEE. The patients with an R-L shunt versus those without an R-L-shunt showed lower LAVIs (23.9 and 26.5 mL/m2) (p=0.016). This fact may additionally confirm the causative role of PFO in the development of stroke, whereas higher LAVIs in the non R-L shunt subgroup should alert to the presence of atrial cardiopathy and initiate an appropriate diagnostic search for latent atrial fibrillation. According to the presence or absence of an R-L shunt, the groups did not significantly differ in gender, age, and clinical characteristics of the stroke. In patients with PFO, a lesion focus was most commonly localized in the middle cerebral artery bed (35.3%), cerebellum (23.5%), and posterior cerebral artery (17.6%). Five (29.0%) patients were ascertained to have several foci of acute stroke. There was a trend towards the larger size of cerebral infarction foci and their specific localization in the vertebrobasilar bed in PE, which determined the high (35.3%) incidence of ataxia with the onset of the disease.Conclusion. PE causes ECS in 60.0% of cases. The distinctive feature of patients with an R-L shunt is lower LAVIs and a trend towards the larger size of cerebral infarction foci and their specific localization in the vertebrobasilar bed.

Keywords

• paradoxical embolism
• patent foramen ovale
• cryptogenic stroke