Role of LA shape in predicting embolic cerebrovascular events in mitral stenosis: mechanistic insights from 3D echocardiography.
OBJECTIVE
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 r(3)] 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.
School of Medicine, Federal University of Minas Gerais, Belo Horizonte, Brazil; Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Maria Carmo P
MC
Nunes
Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Mark D
MD
Handschumacher
Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Robert A
RA
Levine
School of Medicine, Federal University of Minas Gerais, Belo Horizonte, Brazil.
Marcia M
MM
Barbosa
School of Medicine, Federal University of Minas Gerais, Belo Horizonte, Brazil.
Vinicius T
VT
Carvalho
School of Medicine, Federal University of Minas Gerais, Belo Horizonte, Brazil.
William A
WA
Esteves
Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Xin
X
Zeng
Cardiovascular Research Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
J Luis
JL
Guerrero
Biostatistics Center, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Hui
H
Zheng
Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Timothy C
TC
Tan
Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts. Electronic address: jhung@partners.org.
Judy
J
Hung
D000328:Adult; D016279:Atrial Function, Left / Q000502:physiology*; D001938:Brazil / Q000453:epidemiology; D019560:Echocardiography, Three-Dimensional / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006325:Heart Atria / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D015994:Incidence; D020766:Intracranial Embolism / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D008297:Male; D008875:Middle Aged; D008946:Mitral Valve Stenosis / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D016277:Ventricular Function, Left
3D echocardiography; embolic events; left atrial function; left atrial shape; mitral stenosis