Aortic valve replacement with small-sized disc prostheses (Medtronic Hall)

Background and aim of the study: Several studies have demonstrated a worse performance of small prostheses in the narrow aortic root. However, modern low-profile mechanical prostheses have improved hemodynamic performance, are easy to implant, and have been used increasingly in elderly patients, where narrow roots are most frequently observed. We describe our experience in patients with aortic annuli >21 mm with the use of Medtronic Hall prostheses. Methods: Between April 1988 and December 1997, a total of 332 patients (218 females, 114 males; mean age 59.3 +/- 9.8 years (range: 29-75 years) received Medtronic Hall size 20 (n = 140), 21 (n = 96) or 22 (n = 96) prostheses. The mean body surface area was 1.59 +/- 0.12 m(2) (range: 1.27-2.01 m(2)); 140 patients were in NYHA functional classes III/IV. There were no significant differences in clinical characteristics of patients in the three prosthesis-size groups. Results: The mean preoperative systolic left ventricular/aorta gradient was 64.5 +/- 24.8 mmHg (no significant inter-group difference). After cardiopulmonary bypass, peak gradients through the aortic prostheses were 13.9 +/- 8.0 mmHg in size 20 valves, 14.0 +/- 8.1 mmHg in size 21, and 10.1 +/- 8.9 mmHg in size 22. Four patients died in hospital (mortality rate 1.2%); there were no significant inter-group differences in hospital morbidity. Follow up was complete for 97% of the patients (mean 4.3 years; range: 1-11 years). The late mortality rate was 9.3% (n = 31; 2.56% per pt-yr); of these patients, 20 (14.3%) had size 20 prostheses, seven (7.3%) size 21, and four (4.2%) size 22 (p = 0.01). Fourteen patients (4.2%) died from cardiac causes, and six (1.8%) from prosthesis-related causes. Preoperative older age and aortic regurgitation were the only independent predictors of late mortality. Eight patients had systemic thromboembolic events (0.66% per pt-yr), two had prosthetic thrombosis (0.17% per pt-yr) and five had hemorrhagic episodes (0.41% per pt-yr). Seven patients had prosthetic valve endocarditis (0.58% per pt-yr). Among survivors, 97% are currently in NYHA class I/II. Conclusions: The small (size 20, 21 and 22) Medtronic Hall prostheses have good hemodynamic performance and are an excellent option as valve substitutes in patients with narrow aortic roots.