The role of left atrial strain in patients with functional tricuspid regurgitation before and after annuloplasty: a long-term follow-up study.

BACKGROUND: Functional tricuspid regurgitation (TR) is common among patients with left heart disease and may recur during the follow-up period after selective tricuspid valve annuloplasty (TVA). This study aims to analyse the relationship between left atrial (LA) strain and the degree of preoperative functional TR and to explore the role of LA strain in predicting TR recurrence. METHODS: This study included 63 patients with rheumatic mitral stenosis who underwent mitral valve replacement and concomitant TVA. Additionally, 20 healthy controls were enrolled. Preoperative conventional LA echocardiographic parameters and LA strain were measured. The association between LA strain and preoperative functional TR severity was analysed by Pearson correlation. Predictors of recurrent TR were determined by multivariate logistic regression analyses. RESULTS: Compared with the control group, the mitral stenosis group developed a significant impairment in terms of LA strain. The degree of preoperative functional TR exhibited moderate correlations with LA reservoir strain (r = - 0.57) and LA conduit strain (r = 0.48). During a median follow-up period of 66.4 ± 36.4 months, TR recurred in 18 patients. Preoperative LA reservoir strain and the mean transmitral gradient were predictors of postoperative TR recurrence. When the two indexes were combined to establish a prediction, the sensitivity and specificity of prediction increased. The area under the receiver operating characteristic curve of the combined indicator was higher than those of the single indicators (0.90 vs. 0.70 and 0.72). CONCLUSIONS: LA strain correlates with preoperative functional TR severity in patients with rheumatic mitral stenosis. The LA reservoir strain and preoperative mean transmitral gradient are independent predictive factors for recurrent TR after TVA.

[Study on Output Frequency Stability for Optically Pumped THz Lasers].

The frequency stability of the terahertz (THz) radiation source is one of the key issues which directly affect its application regarding to THz imaging, Radar detection, Coherent communication and so on. Based on two-photon light shift effect, the physical model for the frequency shift of optically pumped THz lasers has been built up and the analytical formula for calculating the frequency shift has been derived. Taking the optically pumped methanol(CH3OH) for example, the absorption line of methanol under different pressure has been given, the influence of the bump laser frequency offset and the power of pump laser on the frequency stability of output THz laser have been analyzed quantitatively while the effect of the pressure in THz cavity on the THz laser frequency drift has also been discussed. The results show that THz laser frequency drift increases with the increasing of the bump power, whereas it decreases with the increasing of pressure in THz cavity. The maximum of THz laser frequency drift reaches under the condition that the bump laser frequency drift is equal to a quarter of the absorbed line width of the operating gas when the bump laser frequency offset locates within a certain range. In practice, in order to improve the output frequency stability of THz laser, not only the appropriate working conditions (pressure, temperature) should be chosen, but also the measure for controlling the bump laser frequency shift within a certain range should be taken.