ObjectiveTo investigate the effect of concomitant tricuspid valve repair during mitral valve surgery on the early and mid-term prognosis of the tricuspid valve and right heart function in the patients with moderate or less tricuspid regurgitation. MethodsA retrospective study of 461 patients with mitral valve disease requiring cardiac surgery combined with moderate or less tricuspid regurgitation in our hospital from 2011 to 2014 was done. They were 309 males and 152 females with a median age of 53.00 (44.00, 60.00) years. According to whether they received tricuspid valve repair (Kay’s annuloplasty, DeVega’s annuloplasty or annular ring implantation), the patients were divided into a mitral valve surgery only group (a nTAP group, n=289) and a concomitant tricuspid valve repair group (a TAP group, n=172). At the same time, 43 patients whose tricuspid valve annulus diameter was less than 40 mm in the TAP group were analyzed in subgroups. ResultsThe median follow-up duration was 3.00 years (range from 0.10 to 9.30 years). There was no perioperative death. Three months after surgery, the anteroposterior diameter of the right ventricle in the TAP group was significantly improved compared with that in the nTAP group [–1.00 (–3.00, 1.00) mm vs. 0.00 (–0.20, 2.00) mm, P=0.048]. Three years after surgery, the improvement of right ventricular anteroposterior diameter in the TAP group was still significant compared with the nTAP group [–1.00 (–2.75, 2.00) mm vs. 2.00 (–0.75, 4.00) mm, P=0.014], and the patients in the TAP group were less likely to develop moderate or more tricuspid regurgitation (3.64% vs. 35.64%, P<0.001). Annuloplasty ring implantation was more effective in preventing regurgitation progression (P=0.044). For patients with a tricuspid annulus diameter less than 40 mm, concomitant tricuspid valve repair was still effective in improving the anteroposterior diameter of the right ventricle in the early follow-up (P=0.036). Conclusion Concomitant tricuspid valve repair for patients with moderate or less tricuspid regurgitation during mitral valve surgery can effectively improve the tricuspid valve and right heart function in the early and mid-term after surgery. Annuloplasty ring implantation is more effective in preventing regurgitation progression. Patients whose tricuspid annulus diameter is less than 40 mm can also benefit from concomitant tricuspid repair.