Mitral Annular Systolic Velocity Reflects the Left Atrial Appendage Function in Mitral Stenosis

Prevalence and predictors of left atrial appendage inactivity in patients of rheumatic mitral stenosis in sinus rhythm: An observational study

BACKGROUND

Systemic thromboembolism is a known complication of rheumatic mitral stenosis (RMS) in sinus rhythm (SR). Left atrial appendage (LAA), the commonest site of thrombus formation is usually hypocontractile (inactive) in such patients. We aimed to study the prevalence of LAA inactivity (LAAI) in severe RMS and assess its independent predictors.

METHODS

The study population consisted of 100 patients of severe RMS in SR. Transthoracic and transesophageal echocardiography were done to assess LAA contractile function. Patients with LAA-peak emptying velocity < 25 cm/seconds were defined as having LAAI.

RESULTS

The mean age of study subjects was 31.66±8.69 years and 56% were females. 73% patients had LAAI (Group A), while remaining 27% had normal LAA function (Group B). Mitral-valve area (MVA) and lateral annulus systolic velocity (Sa-wave) were significantly lower while mitral valve mean gradient (MVMG) and serum fibrinogen were significantly higher (all p-values < 0.001) in group A patients. On multivariate binary logistic regression analysis, MVMG (p < 0.001), Sa-wave (p = 0.02), and serum fibrinogen (p = 0.005) were independent predictors of LAAI. Optimal cut-off values of MVMG, Sa-wave and serum fibrinogen for predicting LAAI were 11.5 mm Hg, 6.8 cm/seconds and 300 mg/dl, respectively. Sixty-Seven (90.55%) patients in group A compared to 13(48.1%) in group B had LA/LAA smoke. LAAI was the only independent predictor of left atrium (LA)/LAA smoke with or without associated thrombus.

CONCLUSION

There is high prevalence of LAAI in patients of severe MS in SR. MVMG, Sa-wave, and serum fibrinogen levels are independent predictors of LAAI. LAAI is an independent predictor of LA/LAA smoke with or without associated thrombus.

Predictive Value of D-Dimer Levels and Tissue Doppler Mitral Annular Systolic Velocity for Detection of Left Atrial Appendage Thrombus in Patients with Mitral Stenosis in Sinus Rhythm

BACKGROUND

Transesophageal echocardiogram (TEE) is a gold standard test for diagnosis of left atrial (LA) thrombus, but it has limited sensitivity for identification of small thrombi within side lobes. Thus, the absence of visualizing a left atrial appendage (LAA) thrombus does not equate with the absence of a LAA thrombus.

AIM

To assess the predictive value of mitral annular systolic velocity (Sa) and D-dimer for the detection of LA thrombus and spontaneous echocardiographic contrast (SEC) in mitral stenosis (MS) patients with sinus rhythm (SR).

METHODS

Transthoracic echocardiogram, TEE, and D-dimer analysis were performed in 104 severe MS patients and divided them into three groups: Group I:no LA thrombus or SEC; Group II:LA SEC only; and Group III:LA thrombus.

RESULTS

Group III had more severe New York Heart Association (NYHA) class (III-IV) dyspnea and lower Sa (6.9 ± 0.7 vs.10.0 ± 1.2 cm/sec), lower LAA late emptying velocity (17.7 ± 2.1 vs. 24.4 ± 4.2 cm/sec), larger LA transverse dimension, and LAA area (LAAA) than group I+II. Mean D-dimer levels were higher in groups III and II than in group I. In multivariate analysis Sa, D-dimer levels, LAAA, and NYHA class were independent predictors of LA thrombus. ROC curve analysis revealed that higher Sa >8 cm/sec and lower D-dimer levels <370 μg/L predict the absence of LA thrombus and lower Sa <8 cm/sec and higher D-dimer levels >510 μg/L predict the presence of LA thrombus.

CONCLUSION

Measurement of Sa and D-dimer levels is necessary for better assessment of LA thrombus and SEC, for identification of patients who are at high risk for LA thrombus formation and for initiation of prophylactic anticoagulation.

In vivo porcine left atrial wall stress: Computational model

Most computational models of the heart have so far concentrated on the study of the left ventricle, mainly using simplified geometries. The same approach cannot be adopted to model the left atrium, whose irregular shape does not allow morphological simplifications. In addition, the deformation of the left atrium during the cardiac cycle strongly depends on the interaction with its surrounding structures. We present a procedure to generate a comprehensive computational model of the left atrium, including physiological loads (blood pressure), boundary conditions (pericardium, pulmonary veins and mitral valve annulus movement) and mechanical properties based on planar biaxial experiments. The model was able to accurately reproduce the in vivo dynamics of the left atrium during the passive portion of the cardiac cycle. A shift in time between the peak pressure and the maximum displacement of the mitral valve annulus allows the appendage to inflate and bend towards the ventricle before the pulling effect associated with the ventricle contraction takes place. The ventricular systole creates room for further expansion of the appendage, which gets in close contact with the pericardium. The temporal evolution of the volume in the atrial cavity as predicted by the finite element simulation matches the volume changes obtained from CT scans. The stress field computed at each time point shows remarkable spatial heterogeneity. In particular, high stress concentration occurs along the appendage rim and in the region surrounding the pulmonary veins.