We studied 56 patients after mitral valve replacement for rheumatic heart disease. Mean age was 55.9±8.2 years, NYHA functional class — 3.4±0.5. Tricuspid valve annuloplasty was performed in 37 (66%) patients. Preoperative degree of tricuspid regurgitation was 0.8±0.8 (0.9±0.9 in patients with annuloplasty, 0.4±0.5 — without annuloplasty; р=0,029), fibrous ring diameter index — 18.6±2.4 mm (in annuloplasty group — 18.8±2.4 mm, without annuloplasty — 18.2±2.4 mm, р=0.38), right ventricular pressure — 42.7±12.3 mm Hg. Mean follow-up was 58.5 months (36—105). For the follow-up period there were improvement of NYHA functional class up to 2.3±0.7 (р<0,001), pulmonary pressure to 35.8±13.6 mm Hg, р=0.006, left ventricular ejection fraction (LV EF) to 62.3±10.2%, р=0,046. Tricuspid regurgitation was 0.9±0.5 after annuloplasty, without annuloplasty — 1.3±0.8 (р=0.025). It was revealed correlation between tricuspid ring index and degree of tricuspid regurgitation (r=0.269; p=0.045), right ventricular dilatation (r=0.518; р<0.001), NYHA functional class (r=0.272; p=0.043); between right ventricular dilatation and LV EF (r=–0.306; р=0.022). It was defined that functional tricuspid insufficiency correlates with fibrous ring diameter and right ventricular dysfunction. It explains worsening of prognosis in patients with left-sided heart diseases and tricuspid regurgitation.