Echocardiography
GE vivid E95 color Doppler ultrasound diagnostic instrument was used for echocardiography, equipped with M5Sc probe (frequency 2.5 ~ 5.0 MHz). All patients underwent echocardiography before and after hemodialysis on the same day, and recorded the basic data. All the images were imported into EchoPac 204 version.
Measurement: According to the guiding principles of American Echocardiography Society [8]: (1) Input the height and weight of patients to obtain BSA;(2) The left ventricular outflow tract (LVOT) was measured on the parasternal long axis section of the left ventricle; (3) The peak E and peak A of diastolic mitral valve flow spectrum were measured by pulsed Doppler in apical four-chamber section; The mitral annulus e’ velocity (septal e’and lateral e ’) in early diastole was obtained by tissue Doppler imaging; And calculate the average E/E’ ratio; (4) Pulsed Doppler measurement of systolic left ventricular outflow tract spectrum and calculation of cardiac output (CO) on apical five-chamber plane; (5) Left atrial volume (LAV), left atrial volume index (LAVI), left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV) and left ventricular ejection fraction (LVEF) were measured by Simpson’s biplane method.
The four parameters for evaluating the left ventricular filling pressure were: (1) Annular e’ velocity: septal e’ < 7 cm/s, lateral e ’< 10 cm/s; (2) Average E/E’ratio > 14; (3) Left atrial volume index (LAVI) > 34 mL/m2; (4) Peak TR velocity > 2.8 m/s (Figure 1). According to the joint recommendation from the American Society of Echocardiography (ASE) and the European Association of Cardiovascular Imaging (EACVI) [9, 10], it was proposed to use a combination of these echocardiographic parameters to grades diastolic function.
The strain of left ventricle and left atrium is recommended according to the guidelines of the European Heart Association in 2018[11]: select apical four-chamber, three-chamber and two-chamber cardiac planes, analyze the strain of left ventricle, avoid enveloping mitral chordae, tendineae and papillary muscles, and trace closely to the edge of endocardium to ensure satisfactory tracking. The system automatically tracks the myocardial spots layer by layer. Figure 2.
The left atrial strain needs to include complete left atrial free wall, atrial septum and roof. Because the left atrial free wall is not easy to be fully displayed in apical two-chamber section, if > 1/3 of left atrial tracking points fall off, the result will be discarded. Therefore, a single four-chamber section is used to measure left atrial strain in this study, and biplane method is the choice when the image is clear [12]: Starting from the atrial septum side of mitral annulus, the atrial septum and roof (across pulmonary vein opening) to the side wall of mitral annulus are traced in turn to eliminate the interference of left atrial appendage. According to the thickness of atrial wall, the ROI width is adjusted to 3mm. We use ECG R wave pacing as a reference point to calculate LA strain, and identify LA reservoir strain (LASr), LA conduit strain (LAScd) and LA contractile strain (LASct). Figure 3.