Left Atrial Appendage Tissue Research Articles

Effect of afterload reduction on left atrial appendage tissue velocities after percutaneous mitral commissurotomy for mitral stenosis

Effect of afterload reduction on left atrial appendage tissue velocities after percutaneous mitral commissurotomy for mitral stenosis

Color Doppler tissue imaging to evaluate left atrial appendage function in mitral stenosis.

Two-dimensional color Doppler tissue imaging (CDTI) has so far been used, in general, to evaluate ventricular function. This study examined if the left atrial appendage tissue velocity could reproducibly be measured with CDTI and if they have any predictive value for left atrial appendage (LAA) function and former thromboembolism. Thirty-six patients (24 women, 12 men; mean age 45 +/- 12 years; 18 AF; 11 former thromboembolic stroke) with mitral stenosis undergoing transesophageal echocardiography were examined with CDTI. Peak systolic tissue velocity (m/sec, peak systolic velocity [PSV]) was measured at the tip of the LAA in the basal short-axis view. LAA flow emptying (LAAEV) and filling (LAAFV) velocities (m/sec) were also recorded 1 cm immediately below the orifice of the appendage. Interobserver and intraobserver variabilities were determined for the PSV. LAA ejection fraction was measured by Simpson's method. Mitral regurgitation, AF, transmitral mean gradient, left ventricular ejection fraction, mitral valve area, and left atrial diameter were used as a covariant for adjustment. The intraobserver and interobserver correlation coefficients for the PSV using CDTI was 0.64 and 0.60, respectively (bothP = 0.01). LAAEV(0.29 +/- 0.09 vs 0.19 +/- 0.04, P = 0.001)and LAA ejection fraction(44 +/- 12 vs 29 +/- 14, P = 0.004)were found to be significantly decreased in the patients with decreased PSV (<0.05 m/sec), even after adjustment. The decreased PSV was positively correlated with the low LAAEV (<0.25 m/sec) and history of thromboembolism (r = 0.59, r = 0.38, respectively), and remained a significant determinant of the low LAAEV (OR 50.03, CI 1.46-1738.11,P = 0.02), but not of history of thromboembolism (OR 4.29, CI 0.52-35.01,P = 0.08) after adjustment. In conclusion, these results suggest that CDTI provides a reproducible method for quantification of contraction at the tip of the LAA. Decreased PSV may be predictive of poor LAA function.

Role of Lymphocyte Subsets in Pathogenesis of Chronic Rheumatic Heart Disease

Analyses of lymphocyte subsets using flow cytometry were conducted to determine the significance of these cells in the pathogenesis of chronic rheumatic heart disease. Lymphocytes (B cells, T cells, CD4 cells, CD8 suppressor or cytotoxic T cells, activated T cells, and natural killer cells) were measured in blood and left atrial appendage samples of 30 patients with rheumatic heart disease and 10 patients with acyanotic congenital heart disease. Monoclonal fluorescent-labeled antibodies were used to identify various cells by flow cytometry. There was a significant increase in CD4 cells and activated T cells with a significant decrease in B cells in the left atrial appendage tissue of patients with rheumatic heart disease compared to those in the control group. There was no significant difference between the two groups in the distribution pattern of T lymphocytes in peripheral blood. These changes in rheumatic heart disease reflect an abnormal immunoregulatory mechanism with an ongoing enhanced immunological process continuing into the chronic phase of the disease. In our opinion, this persistent T cell response may lead to fresh damage to the myocardium and deformation of the heart valves.