New quantitative method for evaluating tricuspid regurgitation. A new quantitative method for evaluating regurgitation (TR) is proposed in order to select the most suitable treatment for functional TR associated with acquired valvular heart disease. The regurgitant volume per beat (VTR) is calculated using two-dimensional color Doppler and continuous-wave Doppler echocardiographies. In a study of 48 patients, preoperative VTR showed a significant correlation with tricuspid annular diameter at end-diastole, right atrial mean pressure and right ventricular end-diastolic pressure. Patients were classified into 3 groups according to preoperative VTR: Group I, VTR less than 10 cc (no. 18); Group II, VTR = 10-20 cc (no. 18); Group III, VTR greater than or equal to 20 cc (no. 12). This classification correlated well with the intraoperative findings of TR. In all Group I patients, VTR decreased without any tricuspid valve repair. In Group II, 17 of 18 patients underwent tricuspid annuloplasty, and showed a decrease in VTR to below 10 cc after surgery. In Group III, 10 underwent tricuspid annuloplasty and 2 tricuspid valve replacement. Three of the 10 with tricuspid annuloplasty showed a significant degree of postoperative VTR (10-20 cc). These 3 patients as well as the 2 with tricuspid valve replacement showed a preoperative peak-to-peak pressure difference across the tricuspid valve during the ejection phase (RVsp-TAv) of less than or equal to 20 mmHg and tricuspid annular diameter at end-diastole of greater than or equal to 50 mm. In conclusion, no tricuspid valve repair was required in Group I (TR I). For group II (TR II) patients, tricuspid annuloplasty was necessary and adequate for TR correction. For Group II (TR III) patients, a more substantial procedure like tricuspid valve replacement should be performed, especially when the preoperative RVsp-RAv is less than or equal to 20 mmHg and tricuspid annular diameter at end-diastole is greater than or equal to 50 mm. 