Author + information
- Siddharth A. Wayangankar, MD, MPH,
- Jigar H. Patel, MD,
- Bhavin Patel, MD,
- Stavros Stavrakis, MD, PhD and
- Chittur A. Sivaram, MD∗ ()
- ↵∗University of Oklahoma Health Sciences Center, Department of Medicine, Cardiovascular Diseases Section, 920 Stanton L. Young Boulevard, PO Box 26901, WP3010, Oklahoma City, Oklahoma 73104.
The left atrial septal pouch (LASP) has been proposed as a nidus for thrombogenesis with potential embolic complications, including stroke, because of a low-flow state within (1). A small number of published studies suggest that much remains unknown about this anatomical entity, including its prevalence, features, and associations. Krishnan and Salazar (1) reported a higher prevalence of LASP in younger populations, while Tugcu et al. (2) showed a lack of association between the prevalence of LASP and ischemic or cryptogenic stroke. The objectives of our study were to define the demographic, clinical, and echocardiographic correlates of LASP and to examine the association of this entity with cryptogenic stroke from a larger study sample.
Consecutive patients undergoing transesophageal echocardiography (TEE) for any indication at our institution from January 2007 to December 2010 constituted the initial sample (n = 701) of this study. All patients underwent detailed evaluation of the atrial septum during TEE, per the protocol for our echocardiography laboratory. Three investigators (S.A.W., J.H.P., and C.A.S.) reviewed patients’ transesophageal and transthoracic echocardiograms to evaluate the presence and features of LASP and to determine other echocardiographic parameters (Table 1). Patients’ charts were reviewed by 3 investigators (S.A.W., B.P., and S.S.) to determine baseline demographic and clinical characteristics. Ischemic stroke was diagnosed by neurologists at our institution on the basis of clinical (National Institutes of Health Stroke Scale) and imaging (computed tomography or magnetic resonance imaging) criteria. The diagnosis of stroke preceded TEE in all patients. Cryptogenic stroke in our study was defined as ischemic stroke with absence of atrial septal defect or shunt, atrial fibrillation, >4 mm aortic arch plaque, and flow-limiting carotid disease (as determined by ultrasound or computed tomographic imaging). All adult (age >18 years) patients undergoing TEE from 2007 to 2010 at our institution were included. Exclusion criteria for our study were the presence of an atrial-level shunt (patent foramen ovale or atrial septal defect) detected by color flow Doppler imaging and/or saline contrast injection with or without Valsalva maneuver, post-ablation TEE (involving transseptal puncture), transesophageal echocardiographic studies with deficient information regarding possible extracardiac sources of embolism (absence of carotid studies), and technically inadequate studies. TEEs were systematically reviewed for the presence of LASP, defined as an incomplete fusion in the cranial segment of the overlap between the septum primum and the septum secundum in the standard bicaval view, with no evidence of right-to-left shunting on agitated saline injection at rest or during Valsalva maneuver. Maximal diameter of the LASP os and maximal depth of the LASP were measured in each patient. Fifty randomly chosen transesophageal echocardiograms were read by all 3 investigators (S.A.W., J.H.P., and C.A.S.) independently for the presence or absence of septal pouch, with 100% agreement among the 3 observers.
Logistic regression was used to identify clinical, demographic, and echocardiographic factors significantly associated with the presence of LASP and to examine the association of LASP with cryptogenic stroke.
Of the initial 701 patients, 33 were excluded from analysis because of technically inadequate TEE. Per the exclusion criteria, 22 patients with atrial septal defects and 80 patients with atrial-level shunts were also excluded. The final analysis was performed on the remaining 566 patients. Baseline characteristics of the study population in terms of age, sex, race, body mass, and comorbidities were essentially similar in subjects with or without LASP, and the echocardiographic findings are presented in Table 1. A total of 60 LASPs were identified in the 566 patients (prevalence 11%). The mean diameter of the LASP os was 2.1 ± 0.9 mm, and the mean depth of the LASP was 11.1 ± 5.4 mm. No significant associations were noted between the presence of LASP and any of the demographic, clinical, and echocardiographic variables analyzed. A total of 66 patients were determined to have histories of cryptogenic stroke. There was no association between LASP and cryptogenic stoke (odds ratio: 1.3; 95% confidence interval: 0.6 to 2.8; p = 0.49). Neither the depth (odds ratio: 0.9; 95% confidence interval: 0.8 to 1.1; p = 0.21) nor the diameter of the os (odds ratio: 0.9; 95% confidence interval: 0.5 to 1.4; p = 0.51) of the LASP had any correlation with cryptogenic stroke.
The association of LASP with cryptogenic stroke remains obscure (3). Our study does not support the notion that LASP is associated with cryptogenic stroke. In the study by Tugcu et al. (2), patients with LASP were younger and had lower prevalence of hypertension compared with those without LASPs. Per Tugcu et al. (2) a higher left atrial pressure (in patients with hypertension) might force the septum primum and septum secundum to fuse more completely, making LASP less likely. However, we did not find any correlation of hypertension, diastolic dysfunction, or severity of mitral regurgitation or mitral stenosis (all causes of elevated left atrial pressure) with the prevalence of LASP.
Krishnan and Salazar (1), in their first description of LASP, showed the prevalence of LASP to be about 39%, while its prevalence was 29% in the study by Tugcu et al. (2). The prevalence of LASP of 11% in our study is significantly lower than in the aforementioned studies. The higher prevalence of LASP seen by Krishnan and Salazar (1) may be explained by the fact that it was an autopsy study, and imaging data were not obtained. Similar to our study, Tugcu et al. (2) did use TEE for the diagnosis of LASP, but their study population was exclusively older than 50 years (mean age 70.6 ± 9 years), with histories of recent ischemic stroke. Whether the larger sample size in our study (n = 566) coupled with diverse indications for TEE in our study sample (not exclusively post–ischemic stroke) led to a lower prevalence of LASP in our study remains unknown.
In our opinion, although there are rare cases of clot in LASP, its role in thrombogenicity and subsequent cardioembolic phenomena continues to be uncertain. Further studies are needed to analyze the population-attributable risk for stroke due to LASP (3).
To conclude, our results show a lower overall prevalence of LASP in this transesophageal echocardiographic study compared with previous studies. No demographic, clinical, and echocardiographic characteristics were found to be associated with the presence of LASP. Finally, the presence of LASP was not found to be associated with increased risk for cryptogenic stroke.
Please note: Dr. Sivaram is on the Medtronic data and safety monitoring board. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
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