Real-time three-dimensional echocardiography and 3D-STE measurements
To acquire 3D echocardiographic LV full volume images, we used a matrix-array 4V-D probe (1.7-3.3 MHz). In real-time dynamic three-dimensional pattern, the frame rates of echocardiographic image were 25-50 frames/s. When the entire LV myocardium, endocardium, and epicardium were clearly displayed in apical 4-chamber view, we told the patients to hold their breath after a calm breath in order to eliminate breathing motion artifacts. Furthermore, to make sure a clear image, it is necessary to adjust the buttons that control the depth and width of the probe during the operation. Then turning into 4D full volume pattern, we continued to collect real-time dynamic three-dimensional images of LV in four consecutive cardiac cycles which can be analyzed with 3D-STE. At last, starting 4-dimensional automatic LV quantitative analysis software (4D-Auto LVQ) to analyze all the collected full-volume images. This software will automatically delineate the edocardial boundary of the LV, which can be manually adjusted if required. The parameters including LV end-diastolic volume (LVEDV), LV end-systolic volume (LVESV), LV ejection fraction (LVEF) were measured and strain curves for 17 segments of the LV wall were obtained. Global longitudinal strain (GLS), global area strain (GAS), global radial strain (GRS) and global circumferential strain (GCS) of 17 myocardial segments in each direction were got by computing the weighted average of the peak systolic strain values. The left atrial intima was traced in the same way to measure the left atrial maximum volume, and calculated the left atrial maximum volume index (LAVImax, LAVImax=LAVmax/BAS). Each parameter was measured three times by a physician, and the average value was taken.