Significant association of atrial vulnerability with atrial septal abnormalities in young patients with ischemic stroke of unknown cause

Background and Purpose-Atrial septal abnormalities have been associated wit h cryptogenic ischemic stroke in young patients, but the causal link has no t yet been established. Paradoxical embolism is considered the most likely mechanism but is rarely proven. It can be hypothesized that, in those patie nts, paroxysmal atrial arrhythmias, potentially favored by the anatomic abn ormalities, can be another cause of thrombus formation and subsequent embol ism to the brain, In this study we assessed the relationship between atrial vulnerability, reflecting arrhythmogenic properties of the atria, and atri al septal abnormalities in young patients with cryptogenic ischemic stroke. Methods-We enrolled 62 consecutive patients aged <55 years who had ischemic stroke of unknown cause and transesophageal echocardiography to assess atr ial septal aneurysm (ASA) or patent foramen ovale (PFO) (ie, atrial septal abnormalities). These patients underwent electrophysiological study to meas ure atrial refractoriness and conduction time defining a vulnerability inde x (ie, latent atrial vulnerability) and to assess the inducibility of susta ined (lasting >60 seconds) atrial fibrillation with the use of programmed a trial stimulation. Actual atrial vulnerability was defined by the presence of both latent vulnerability and inducibility of sustained atrial fibrillat ion lasting >60 seconds. Results-We found atrial vulnerability in 58% of patients with atrial septal abnormalities and in 25% of patients without (odds ratio = 4.1 [95% CI, 1. 3 to 12.7; P<0.02]). The difference between patients with and without PFO o r between patients with both PFO and ASA and those without were also signif icant. Patients with inducible sustained atrial fibrillation had more frequ ent past history of palpitations and syncope than patients without (P<0.02) . Conclusions-Atrial vulnerability is associated with atrial septal abnormali ties in patients with cryptogenic stroke. This result raises the question o f the potential role of transient atrial arrhythmias in thrombus formation in the presence of PFO or ASA.