Early experience with stentless versus stented valves

Background: The Toronto stentless porcine valve (SPV) was designed to improve hemodynamics after aortic valve replacement by maximizing available flow area in comparison to stented valves (STD). Methods: To assess possible hemodynamic differences between STD and SPV, 59 patients undergoing isolated aortic valve replacement (±coronary artery bypass graft) were prospectively evaluated by preoperative and 3- to 6-month post-operative echocardiography. Among these, 23 patients received a STD, whereas 36 received the Toronto SPV. Results: The mean size (mm) of SPV implanted was larger (SPV, 26.6±2.1; STD, 24.0±2.9; P=0.0002). Patients receiving STD valves were older and had a higher prevalence of coronary artery disease and congestive heart failure. There were no preoperative differences in left ventricular mass index (g/mo²), peak or mean pressure gradients (mmHg), effective orifice area (cm²), extent of fractional shortening (%), or velocity of circumferential shortening (cf/sec). ANOVA demonstrated a significant reduction in left ventricular mass index at 3 to 6 months (P=.0001) but no differences in left ventricular mass index regression between groups (STD, -28.8±37.5; SPV, - 31.2±32.4; P=.36). Effective orafice area was increased postoperatively (P=.0001), particularly among SPV cases (STD, 1.5±0.4; SPV, 1.9±0.7; P=.01). Postoperative left ventricular mass index and mean pressure gradient were reduced (P=.0001) but did not differ between groups. Fractional shortening and velocity of circumferential shortening were greater in the SPY patients at 3 to 6 months after aortic valve replacement (P=.0004 and .0001, respectively), and an interactive effect was seen between time and prosthetic group (P=.0028 and .032, respectively). Conclusions: In a consecutive series of patients, we identified no hemodynamic differences between STD and SPV, although ventricular function improved after SPV. Because of the nonrandomized nature of the study, selection bias may have accounted for some of the observed results. A prospective, randomized trial is necessary to determine the hemodynamic advantages, if any, of the SPV valve.