Impact of high transvalvular velocities early after implantation of Freestyle stentless aortic bioprosthesis.

BACKGROUND AND AIM OF THE STUDY: Stentless aortic bioprostheses have excellent hemodynamics, although heterogeneity in gradients has been observed. The present study was intended to determine whether high early postoperative transvalvular velocities correlate with other measures of left ventricular outflow obstruction, whether the phenomenon is transient, and whether high velocities observed early after surgery predict differences in subsequent valve performance or left ventricular remodeling.

METHODS

Sixty-eight consecutive patients who underwent implantation of Freestyle stentless aortic bioprosthesis and survived to hospital discharge underwent early postoperative echocardiography. Peak transvalvular velocity was used to define a 'high-velocity' group, based on mean (+ 1 SD) for the group. Mean pressure gradient, ratio of peak to proximal velocities, and effective orifice area were assessed; change in peak velocity and evidence of left ventricular mass regression were studied at one-year follow up.

RESULTS

Of 68 patients, 14 (21%) had 'high velocities' based on early postoperative peak transvalvular velocity >3.0 m/s. There was a higher prevalence of women (64% versus 33%, p = 0.04), and both body surface area (1.79+/-0.17 versus 1.95+/-0.20 m2, p = 0.01) and implanted valve size (22.9+/-2.0 versus 24.9+/-2.1 mm, p = 0.003) were smaller among the 'high-velocity' group. High velocity correlated with other measures of resistance to left ventricular outflow, including higher mean gradient (20.9+/-6.5 versus 8.3 +/-4.2 mmHg, p <0.001) and lower effective orifice area (1.15+/-0.36 versus 1.69+/-0.62 cm2, p <0.001). High early postoperative velocities persisted at one year in eight of 13 (62%) patients. Left ventricular mass regression occurred less often in the 'high-velocity' group (38% versus 77% of patients, p = 0.03) and was present in only one of eight (12%) patients in whom high velocity persisted at one year.

CONCLUSION

High early postoperative transvalvular velocity suggests resistance to left ventricular outflow. High velocities are transient in some patients, although persistence of high transvalvular velocity suggests 'prosthesis-patient mismatch' with incomplete relief of left ventricular outflow obstruction.