Role of LA Shape in Predicting Embolic Cerebrovascular Events in Mitral Stenosis

Abstract

OBJECTIVES This study was designed to assess the role of left atrial (LA) shape in predicting embolic cerebrovascular events (ECE) in patients with mitral stenosis (MS). BACKGROUND Patients with rheumatic MS are at increased risk for ECE. LA remodeling in response to MS involves not only chamber dilation but also changes in the shape. We hypothesized that a more spherical LA shape may be associated with increased embolic events due to predisposition to thrombus formation or to atrial arrhythmias compared with an elliptical-shaped LA of comparable volume. METHODS A total of 212 patients with MS and 20 control subjects were enrolled. LA volume, LA emptying fraction, and cross-sectional area were measured by 3-dimensional (3D) transthoracic echocardiography. LA shape was expressed as the ratio of measured LA end-systolic volume to hypothetical sphere volume ([4/3π r3] where r was obtained from 3D cross-sectional area). The lower the LA shape index, the more spherical the shape. RESULTS A total of 41 patients presented with ECE at the time of enrollment or during follow-up. On multivariate analysis, LA 3D emptying fraction (adjusted odds ratio [OR]: 0.96; 95% confidence interval [CI]: 0.92 to 0.99; p = 0.028) and LA shape index (OR: 0.73; 95% CI: 0.61 to 0.87; p < 0.001) emerged as important factors associated with ECE, after adjustment for age and anticoagulation therapy. In patients in sinus rhythm, LA shape index remained associated with ECE (OR: 0.79; 95% CI: 0.67 to 0.94; p = 0.007), independent of age and LA function. An in vitro phantom atrial model demonstrated more stagnant flow profiles in spherical compared with ellipsoidal chamber. CONCLUSIONS In rheumatic MS patients, differential LA remodeling affects ECE risk. A more spherical LA shape was independently associated with an increased risk for ECE, adding incremental value in predicting events beyond that provided by age and LA function.

Left Atrial Geometry Improves Risk Prediction of Thromboembolic Events in Patients With Atrial Fibrillation

“…A previous study showed the association between LA shape and TE in patients with mitral stenosis: Nunes et al calculated a LA shape index, as a surrogate of LA sphericity by 3D echocardiography, and demonstrated its predictive value for TE in this specific population with mitral stenosis. 25 Our findings are in line with those of Nunes et al, providing new evidence in the setting of patients with AF and no valvular heart disease.…”

“…We hypothesize that AF‐related LA geometrical remodeling provokes changes in flow dynamics within the atrial chamber, leading to creation of blood stasis and increased thrombogenicity. This fact has been illustrated in the recent paper by Nunes et al ., in which the authors elegantly demonstrate in an in vitro phantom atrial model that spherical shapes cause peripheral slow flow zones, whereas discoid (normal)‐shaped atria do not. On top of the LA geometrical remodeling, risk factors for AF (e.g., hypertension) may generate a synergic prothrombotic effect by accelerating LA remodeling and creating an inflammatory state.…”

Left atrial cross-sectional area is a novel measure of atrial shape associated with cardioembolic strokes

“…In the case of a spherical-shaped atrium, the mid-CSA would be larger than an ellipsoidal-shaped atrium of the same volume (online supplementary figure 2). This further supports our hypothesis that velocity profiles in the sphere shape had slower flows along the peripheries compared with the cylindrical shape 12…”

“…LA remodelling however is complex, as there is an increase in size and differences in morphology or shape changes 9–11. We have previously demonstrated an association between LA shape and increased risk of CE stroke in a population of patients with mitral stenosis 12. Differences in LA shape may impact LA flow dynamics with a more spherical shape having more areas of stagnant flow and hence a greater potential for thrombus formation 13.…”

New Perspectives by Imaging Modalities for an Old Illness: Rheumatic Mitral Stenosis

“…Associated pathologies with MS Left atrial remodeling LA dilatation reflects the hemodynamic burden of MS and is of prognostic importance. LA volume is independently associated with an increased risk for embolic cerebrovascular disease (15) and the development of atrial fibrillation (16), which play a key role in patient management. Linear measurements of the LA are outdated and insufficient because of the asymmetrical enlargement of the LA (17).…”