Early Clinical Experience in Aortic Valve Replacement Using On-X(R) Prosthetic Heart Valve

Ahn, Byong Hee; Chun, Joon Kyung; Ryu, Sang Wan; Choi, Yong Sun; Kim, Byong Pyo; Hong, Sung Bum; Park, Jong Chun; Kim, Sang Hyung

Abstract

BACKGROUND: Since the first implanted in September 1997, the use of On-X prosthetic heart valve has been increasing around in the world. This study was designed to assess the feasibility, safety, and the postoperative hemodynamics with this new valve in clinical setting. MATERIAL AND METHOD: The current study was carried out on 52 patients undergoing aortic valve replacement with this prosthesis between April 1999 to August 2002 at Chonnam National University Hospital to evaluate the surgical results. 52% of the patients were male and the average age at implant was 50+/-13 years. The study followed the guidelines of the AATS/STS. Preoperatively, 32 (61.5%) patients were in NYHA functional class III or IV and 2 patients had previous aortic valve surgery. Concomitant cardiac surgery was performed in 71.1%. The implanted valve sizes were 19 mm in 13 patients, 21 mm in 26, 23 mm in 10 and 25 mm in 3, respectively. Mean follow-up was 16.6+/-10.5 months (1~39 months). Echocardiographic assessment was performed pre- and immediate postoperatively, as well as 3, 6, 12 months after surgery, evaluating pressure loss and regression of left ventricular hypertrophy. RESULT: Mean cardiopulmonary bypass time was 191+/-94.7 minutes with an aortic cross-clamp time of 142+/-51.7 minutes. There was no early and late mortality. Freedom from adverse events at 1 year in the study were as follows: thromboembolism, 95.6+/-6%; bleeding events, 90.2+/-4%; paravalvular leakage 92.3+/-4%; and overall valve-related morbidity at 1 year was 76.6+/-3%. There were no cases of valve thrombosis, prosthetic valve endocarditis and structural or non-structural failure. Left ventricular function at 12 months after surgery (EF=62.7+/-9.8%) revealed a statistically significant improvement compared to preoperative investigation (EF=55.8+/-15.9%, p=0.006). Left ventricular mass index was 247.3+/-122.3 g/m2 on preoperative echocardiographic study, but regressed to 155.5+/-58.2 g/m2 at postoperative 1 year (p=0.002). Over the follow-up period a further decrease of peak transvalvular gradients was observed in all patients: 62.5+/-38.0 mmHg on preoperative assessment, 18.2+/-6.8 mmHg at immediate postoperative period (p<0.0001), 7.6+/-5.09 mmHg (p<0.0001) at 6 month, 18.0+/-10.8 mmHg (p<0.0001) at 1 year.
CONCLUSION
The On-X prosthetic heart valve performs satisfactorily in the first 1 year period. Clinical outcome by examining NYHA functional classification revealed especially good results. Effective regression of left ventricular hypertrophy and statistically significant decrease of transvalvular gradient were observed over the first year, but longer-term follow-up of this patient group is needed to establish the expected rates for late valve-related events as well as the long-term clinical efficacy of this valve.