2.5 Definition of measurements
The average and minimum distance from each posterior line to the esophagus and the average and minimum thickness of LAPW myocardium under each posterior line were defined as the mean and minimum value of 3 predefined points (a, b, c and d, e, f) on CPL and MPL, respectively. The average thickness of the fat pad was defined as the mean value of the predefined point that appeared with the fat pad on each course of the posterior line, respectively. In some cases, the esophagus was enclosed by left inferior PV, descending aorta, and vertebral body in a triangular space at left inferior PV level (defined as the confined group), while in other cases the esophagus was not enclosed by LAPW, descending aorta, and the vertebral body simultaneously in a triangular space at left inferior PV level (defined as the unconfined group) (Figure 3 and Figure 2A).