The left atrial septal pouch as a risk factor for stroke: A systematic review

The left atrial septal pouch (LASP) is formed by incomplete fusion of the septum primum and septum secundum, leaving a cavity open towards the left atrium, but without interatrial shunting. There is no recommendation concerning strategy in the presence of a LASP, especially in the setting of stroke. The aim of this review was to determine whether the LASP could be incriminated as the aetiology of a stroke. We included all pertinent publications on the subject, and calculated hazard ratios for ischaemic stroke and cryptogenic stroke. There were only five case-control studies concerning the LASP, involving 516 stroke patients and 779 controls. Overall LASP prevalence was 21%, with a slightly higher prevalence in the cryptogenic stroke group (26%), but this difference was not statistically significant (P=0.27). In a random-effects meta-analysis, there was no difference between controls and patients with ischaemic stroke (hazard ratio 1.20, 95% confidence interval 0.96-1.53; P=0.14). Cryptogenic stroke appeared more frequently in patients with LASP (hazard ratio 1.53, 95% confidence interval 1.07-2.24; P=0.02), but this was driven by only one severely underpowered study. The published case reports demonstrated that thrombus formation inside the pouch can occur in the presence of major predisposing factors. The LASP can be a site for thrombus formation, leading to embolic events, but its presence does not correlate with an increased incidence of stroke. Associated factors should be taken into consideration in the setting of stroke. Further studies are necessary to validate a possible relationship with cryptogenic stroke.