Are mechanical valves with enhanced inner diameter advantageous in the small sized aortic annulus?

Abstract

Background Mechanical bileaflet valves with enhanced inner diameter may offer superior hemodynamic properties in patients with a small aortic annulus. The aim of this clinical study was to compare these valves with standard bileaflet prostheses in vivo. Methods Mechanical aortic valve replacement for combined stenosis and regurgitation was performed in 47 patients with standard CarboMedics prostheses (CM: 21 mm, 23 mm, 25 mm) and two types of diameter enhanced St. Jude Medical prostheses (SJM-AHPJ: 21 mm, 23 mm, 25 mm; SJM-Regent: 21 mm, 23 mm). Transvalvular mean gradients (TVG) were assessed intraoperatively by means of transesophageal echocardiography (TVG TEE) and simultaneous direct pressure monitoring of the left ventricle and the ascending aorta (TVG CATH), as well as early (3 months) and late (9 months) postoperatively by means of transthoracic echocardiography (TVG TTE). Left ventricular muscle mass was assessed preoperatively, early, and late postoperatively to evaluate remodeling capacity. Results In all valve types and sizes, both TVG assessments exhibited consistent findings. Small-sized conventional valves of 21 mm showed a marked initial TVG. In contrast, both valve types with enhanced inner diameter exhibited significantly lower TVG comparable with those achieved with larger valves (TVG CATH CM 21 mm, 15.6 ± 3.9 mm Hg; SJM-AHPJ 21 mm, 11.9 ± 1.6 mm Hg; SJM-Regent 21 mm, 9.9 ± 1.1 mm Hg; CM 23 mm, 7.8 ± 0.8 mm Hg; SJM-AHPJ 23 mm, 7.7 ± 1.4 mm Hg; SJM-Regent 23 mm, 9.5 ± 1.8 mm Hg). During the postoperative course TVG remained constant in all valve types and sizes. Left ventricular muscle mass, however, diminished markedly in all valves without exhibiting significant differences between size matched valve types. Conclusions In patients with a small aortic annulus, who require a 21-mm valve, diameter-enhanced prostheses provide lower transvalvular gradients than conventional valves. However, in the intermediate clinical course, appropriate left ventricular remodeling occurred in all patients independent of the size and the type of the valve.