OBJECTIVE The study aim was to report the early and mid-term clinical and hemodynamic results of a prospective trial investigating the clinical performance of the St. Jude Medical Regent 17 mm mechanical aortic valve prosthesis (SJMR-17). METHODS Between January 2001 and January 2009, 20 patients (18 females, two males; mean age 69.2 +/- 7.3 years) with aortic valve stenosis underwent first-time aortic valve replacement (AVR) with the SJMR-17. The mean body surface area (BSA) was 1.68 +/- 0.2 m2, and the mean follow up was 18.7 +/- 9.2 months (range: 10-32 months). All patients were monitored with serial echocardiography; the first study was performed preoperatively, while subsequent controls were at two and six months, and within one year, respectively. All survivors underwent dobutamine stress testing (DSE) at one year after surgery. RESULTS There was one death. At the six-month follow up the mean NYHA class was 1.3 +/- 0.6, and was significantly lower than preoperatively 2.75 +/- 0.86 (p < 0.0001). The peak and mean transprosthetic gradient (TPG) was 29 +/- 6.8 and 17.5 +/- 4.5 mmHg respectively, significantly lower than preoperatively. The left ventricular mass (LVM; g) and indexed left ventricular mass (LVMi; g/m2) were 191.0 +/- 22.6 g and 114.5 +/- 10.6 g/m2, respectively, and were significantly lower than preoperative values (258.0 +/- 40.0 g, p < 0.0001; and 157.0 +/- 26.0 g/m2, p = 0.00002). The mean TPG correlated well with the LVMi reduction (p = 0.033). During DSE, the peak and mean TPGs were increased significantly to 73.8 +/- 17.7 mmHg and 37 +/- 10.7 mmHg, respectively, significantly higher than at the basal (resting) state. Multivariate regression analysis identified the effective orifice area index, BSA, age and postoperative LVMi as strong predictors for a higher mean TPG. CONCLUSIONS The SJMR-17 prosthesis might be employed with satisfactory postoperative clinical and hemodynamic outcome in patients with a small aortic annulus, especially in elderly patients, as an alternative to other valves, or to other surgical strategies such as annulus enlargement.