Presence of patent foramen ovale increases risk of filamentous thrombi on interatrial septum in atrial fibrillation/flutter patients

The presence of interatrial septum (IAS) strands in atrial fibrillation or flutter (Afi/Afl) patients is frequently overlooked despite being a common occurrence.

The study aims to understand the prevalence and possible pathological nature of these strands.

The study included 454 consecutive Afi/Afl patients who underwent transesophageal echocardiography from June 2019 to January 2020. Patients were divided into two groups based on the presence of strands on the IAS (strand and non-strand group). The echocardiograms and clinical characteristics of the patients were reviewed. The difference between the two groups was compared using independent t or chi-square test. Univariate and multivariate logistic regression analyses were performed to identify factors associated with the IAS strands. The study also examined surgical samples of the IAS strands of a patient pathologically.

The study found that 127 (28%) of the enrolled patients had strands on the right atrial side of the IAS. The strand group had a significantly higher incidence of patent foramen ovale (PFO) (p<0.0001) than the non-strand group. Patients in the strand group were also more likely to be over 60 years of age(p=0.085), obese(p=0.073), and have abnormal renal function(p=0.086). Multivariate analysis revealed that PFO was independently associated with the presence of IAS strands (OR=64.51, 95% CI: 31.35-132.76, p<0.0001). The pathological examination of the IAS strands in a patient revealed filamentous thrombi.

The study highlights the high prevalence of IAS strands in Afi/Afl patients. The presence of PFO significantly increases the risk of IAS filamentous thrombi. This study is the first report on the pathological nature of IAS filaments in Afi/Afl patients, offering important insights into the causes of Afi/Afl-induced cardiogenic embolism other than left atrial appendage thrombi.