Table 3 Echocardiography change before and after the operation ( $\overline{\mathit{x}}$ ± s)

Before operation (n = 324)

57.48 ± 15.16

56.57 ± 9.67

33.47 ± 7.08

Before discharge (n = 322)

38.81 ± 15.14^##

59.30 ± 11.32

35.18 ± 6.67^#

Six months after operation (n = 322)

36.94 ± 10.23^##

62.35 ± 13.61^#

34.53 ± 7.64

Twelve months after operation (n = 231)

37.66 ± 12.01^##

64.01 ± 12.33^#

35.73 ± 6.18^#