Echocardiography
All patients underwent transthoracic echocardiography using an iE33 or EPIQ system (Philips Medical Systems, Andover, MA, USA) at our echocardiography laboratory preoperatively, 1 week and 1year postoperatively.
The TR grade was defined using a multiparametric approach, including an assessment of the color Doppler-derived jet area, the continuous wave Doppler-derived jet density and contour, and the hepatic vein flow velocity pattern (12). TR was graded as none, trivial, mild, moderate, or severe. For the statistical analysis, these TR grades were scored as follows: none = 0, none to mild = 0.5, mild = 1, mild to moderate = 1.5, moderate = 2, moderate to severe = 2.5, and severe = 3 (13).
Continuous wave Doppler was used to obtain the TR peak velocity (m/s) and the transtricuspid systolic pressure gradient (TRPG, mmHg), which was calculated as 4V2 (where V is velocity). The right ventricular systolic pressure was then estimated as the sum of the estimated TRPG and right atrial (RA) pressure. The RA pressure was estimated as follows: an inferior vena cava diameter of ≤2.1 cm that collapsed by ≥50% when the patient sniffed was considered to indicate a normal RA pressure of 3 mmHg, whereas an inferior vena cava (IVC) diameter of >2.1 cm that collapsed by <50% when the patient sniffed was considered to indicate a high RA pressure of 15 mmHg. When the IVC diameter and collapse did not fit this paradigm, an intermediate value of 8 mmHg was assigned (14). An estimated right ventricular systolic pressure of >40 mmHg was considered indicative of pulmonary hypertension (15). Tricuspid annular diameter was measured at end-diastole and annular diameter of >40mm or 21mm/m2 was considered significant annulus dilatation (11). The RA dimension, left ventricular (LV) end-diastolic dimension, LV end-systolic dimension, LV ejection fraction, and left atrial (LA) dimension were measured according to the established guidelines (14,16).