Left atrial septal pouch thrombus: A common pathology in an uncommon location

Atrial septal pouches and ridges: Morphological features and potential implications in clinical practice

Incomplete or irregular fusion of the interatrial septum may result in several anatomic variants, including atrial septal pouches and ridges, whose knowledge and recognition are still poorly widespread in clinical practice. An educational review focused on the definition, clinical significance and diagnostic work-up of these anatomic findings was performed using PubMed, MEDLINE, Embase and Cochrane Central databases up to June 2023. Atrial septal pouches and ridges have been associated with an increased difficulty of catheter-based interventions requiring a transseptal approach, due to procedural challenges for transseptal puncture and the restricted motion of guidewires and catheters through the transseptal access. Additionally, left atrial septal pouch may serve as a thrombogenic nidus and a source of systemic embolism, mostly in the presence of factors leading to higher left atrial pressure and/or atrial blood stasis, which increase the risk of thrombus formation and embolic events, rather than for the only presence of left atrial septal pouch itself. Further investigations are needed in order to better elucidate the implications of such anatomic findings in daily clinical practice, and to provide the most appropriate decision-making strategies.

The 2022 FASEB Virtual Catalyst Conference on the Cardiac Interatrial Septum and Stroke Risk, December 7, 2022

There is emerging evidence that the cardiac interatrial septum has an important role as a thromboembolic source for ischemic strokes. There is little consensus on treatment of patients with different cardiac interatrial morphologies or pathologies who have had stroke. In this paper, we summarize the important background, diagnostic, and treatment considerations for this patient population as presented during the Federation of American Societies for Experimental Biology (FASEB) Virtual Catalytic Conference on the Cardiac Interatrial Septum and Stroke Risk, held on December 7, 2022. During this conference, many aspects of the cardiac interatrial septum were discussed. Among these were the embryogenesis of the interatrial septum and development of anatomic variants such as patent foramen ovale and left atrial septal pouch. Also addressed were various mechanisms of injury such as shunting physiologies and the consequences that can result from anatomic variants, as well as imaging considerations in echocardiography, computed tomography, and magnetic resonance imaging. Treatment options including anticoagulation and closure were addressed, as well as an in-depth discussion on whether the left atrial septal pouch is a stroke risk factor. These issues were discussed and debated by multiple experts from neurology, cardiology, and radiology.

Left Atrial Septal Pouch-Is it Really a New Risk Factor for Ischemic Stroke?: Subanalysis of the ASSAM Study

PURPOSE

The atrial septal pouch is an anatomic variant of the interatrial septum caused by incomplete fusion of the septum primum and secundum. It is debatable whether coexistence of septal pouch and atrial fibrillation (AF) increases the risk of stroke. Thus, the aim of the study was to evaluate the coexistence of left atrial septal pouch (LASP) and AF in patients with a history of stroke in comparison with those without an earlier history of stroke.

MATERIALS AND METHODS

We analyzed 145 patients with AF (68 in the study group, 77 in the control group). The study group consisted of patients with previous stroke and AF; control group consisted of patients scheduled for AF ablation. All patients underwent computed tomography with the assessment of atrial septum morphology and presence of LASP. The study was a subanalysis of the ASSAM (AssesSment of the left atrial appendage morphoLogy in patients aAfter ischaeMic Stroke) study.

RESULTS

The prevalence of LASP in the entire group was 38.6%. There were no significant differences in the prevalence of LASP between the study and control groups (33.8% vs. 42.9%, P=0.265). Mean longitudinal and transverse dimensions of LASP were 9.34±3.27 and 2.4±0.6 mm, respectively, and there was no significant difference between the study and controls. Patients from the stroke group were older (P<0.0001), had a higher CHA2DS2-VASc score (5.41±1.93 vs. 1.62±1.46, P<0.0001) compared with controls.

CONCLUSIONS

Presence of LASP is not more prevalent in patients with a history of stroke. Additional information on the presence of LASP do not improve accuracy of risk stratification for stroke in patients with AF.

Prevalence of left atrial septal pouch among patients with embolic stroke of undetermined source or stroke of known etiology: A retrospective study

Background and objectives

Cryptogenic strokes can be defined by the criteria established for an embolic stroke of undetermined source (ESUS). Some embolic events might be caused by a left atrial septal pouch (LASP), due to the potential of thrombus formation. In this study we aimed to determine if LASP is a risk factor for ESUS when compared to a population of strokes of known origin, the LASP screening rate in our institution and if LASP dimensions influences the risk of ESUS.

Methods

We retrospectively analyzed transesophageal echocardiograms (TEEs) in a large cohort of patients that had experienced ischemic strokes. Two authors performed blinded, independent searches for LASPs by reviewing 1152 TEEs from patients that had experienced a stroke or transient ischemic attack. We excluded 26 TEEs, due to incorrect imaging. Next, we reviewed patient medical files.

Results

Among the 1126 included patients, 148 had an ESUS (ESUS+ group) and 978 had strokes of known origin (ESUS– group). A LASP was present in 176 patients, including 32 patients (21.6% of LASPs) in the ESUS+ group and 144 patients (14.7% of LASPs) in the ESUS– group. In multivariate analysis, LASP was independently associated with ESUS (P = 0,019). 61.9% of LASPs that we found were not mentioned in reports from the original TEE operators.

Conclusion

This study demonstrated that LASPs were more prevalent in patients with ESUS than in patients with strokes of known origin. Our results gave rise to the question of whether anticoagulation would be appropriate for some patients with ESUS. New large-scale, prospective studies should be conducted to address this issue. Additionally, considering the low rate of LASP descriptions, we concluded that the awareness of operators should be raised to improve their success in identifying LASPs.

Prevalence of left atrial septal pouch among patients with embolic stroke of undetermined source or stroke of known etiology: A retrospective study

Background and objectives

Cryptogenic strokes can be defined by the criteria established for an embolic stroke of undetermined source (ESUS). Some embolic events might be caused by a left atrial septal pouch (LASP), due to the potential of thrombus formation. In this study we aimed to determine if LASP is a risk factor for ESUS when compared to a population of strokes of known origin, the LASP screening rate in our institution and if LASP dimensions influences the risk of ESUS.

Methods

We retrospectively analyzed transesophageal echocardiograms (TEEs) in a large cohort of patients that had experienced ischemic strokes. Two authors performed blinded, independent searches for LASPs by reviewing 1152 TEEs from patients that had experienced a stroke or transient ischemic attack. We excluded 26 TEEs, due to incorrect imaging. Next, we reviewed patient medical files.

Results

Among the 1126 included patients, 148 had an ESUS (ESUS+ group) and 978 had strokes of known origin (ESUS– group). A LASP was present in 176 patients, including 32 patients (21.6% of LASPs) in the ESUS+ group and 144 patients (14.7% of LASPs) in the ESUS– group. In multivariate analysis, LASP was independently associated with ESUS (P = 0,019). 61.9% of LASPs that we found were not mentioned in reports from the original TEE operators.

Conclusion

This study demonstrated that LASPs were more prevalent in patients with ESUS than in patients with strokes of known origin. Our results gave rise to the question of whether anticoagulation would be appropriate for some patients with ESUS. New large-scale, prospective studies should be conducted to address this issue. Additionally, considering the low rate of LASP descriptions, we concluded that the awareness of operators should be raised to improve their success in identifying LASPs.

The Left Atrial Septal Pouch: A New Stroke Risk Factor?

The left atrial septal pouch (LASP) occurs due to incomplete fusion of septa primum and secundum at the inter-atrial septum, creating an open flap that may serve as a thromboembolic source. Prior studies have demonstrated increased prevalence of LASP in cryptogenic strokes. The aim of the current study was to validate the above findings in a separate, larger group of stroke and non-stroke patients. We examined transesophageal echocardiograms (TEEs) performed between July 2011 and December 2018. LASP prevalence was determined in TEEs referred for ischemic stroke or transient ischemic attack (“stroke”) and compared with LASP prevalence in patients undergoing TEEs for other reasons (“non-stroke”). Stroke subtyping was performed using the Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria. There were 306 TEEs from 144 non-stroke and 162 stroke patients. Mean age and sex distribution were 56 ± 1 (mean ± SE) and 65% male in the non-stroke group and 58 ± 1 and 54% male in the stroke group. The overall prevalence of LASP was 31%. The prevalence of LASP was 28% (41/144) in non-stroke patients, 25% (24/95) in non-cryptogenic stroke patients, and 43% (29/67) in cryptogenic stroke patients. LASP prevalence was significantly higher in the cryptogenic subgroup compared with the non-cryptogenic subgroup (p = 0.02). These findings demonstrate a significant association of LASP with risk of cryptogenic stroke, suggesting that LASP may serve as a thromboembolic nidus. Additional studies are needed to determine the generalizability of these findings, and their therapeutic implications, supporting LASP as a stroke risk factor.