Atrial septal pouch — Morphological features and clinical considerations

Abstract Background The atrial septal pouch (SP) is a new anatomical entity within the interatrial septum. The left-sided SP may be the source of thrombus and contribute to ischemic stroke. The aim of this study was to provide a detailed morphometric description of the SP. Methods Two hundred autopsied hearts (23% deriving from females) with a mean age of 46.7 ± 19.1 years were investigated. We assessed the morphology of the interatrial septum. We obtained measurements and casts of the SPs, and we conducted histological staining of the left-sided SPs. Results Patent foramen ovale was observed in 25% of hearts. We found a left SP in 41.5%, right in 5.5% and a double SP in 5.5% of hearts. We found the patent foramen ovale (PFO) more often in younger hearts, and the SP and smooth septum were more prevalently found in older hearts (p = .0023). The mean volume of the left-sided SP was 0.31 ± 0.11 ml, which represented 13.6 ± 9.4% (range: 3.1–44.9%) of the left atrial appendage volume. The SP shape resembled a cone or a cylinder with some smaller diverticula originating from the main body. The SP free wall was composed of two layers of endocardium, transverse muscle fibers and connective tissue. Conclusions A left-sided SP was present in 47% of individuals. The SP arises as a result of PFO channel closure. The anatomy of left-sided SP may promote blood stasis and thrombus formation. The universal formula for SP volume was calculated.