Discussion of aortic valve replacement has primarily concerned the choice between tissue and mechanical prostheses. Less emphasis has been placed on prosthesis size. Despite technical advances increasing prosthesis orifice area, small valves implanted in the unenlarged aortic root may not be significantly less obstructive than the stenotic native valves they replace.
Methods: In this work we studied 52 patients (31 women, 21 men; mean age 59.2 years) in whom valve prostheses sized 19, 21, 23, or 25 mm (30 bioprostheses and 22 tilting disc valves) had been implanted to replace stenotic aortic valves. Most patients with 19 or 21 mm prostheses were women. Doppler and conventional echocardiographic studies were performed in the 10 days preceding the operation and between 10 and 40 months (mean 18 months) after the operation. The patients receiving larger valve sizes had significantly larger body surface areas than those receiving smaller valve sizes (mainly women).
Results: No significant differences were observed between preoperative and postoperative diameters or left ventricular systolic function parameters, but left ventricular mass and mass index decreased in all four groups (albeit nonsignificantly in the 19 mm group, and with less statistical significance in the 21 mm group than in the 23 and 25 mm groups). Postoperative peak and mean transvalvular pressure drops were significantly greater in the 19 mm group than in the other groups, and the 21 mm group had significantly greater transvalvular pressure drops than the 25 mm group. Postoperative effective valve area was significantly smaller in the 19 mm group than in the 21 mm group, and significantly smaller in the 21 mm group than in the 23 and 25 mm groups.
Conclusion: We conclude that despite undeniable recent improvements in the design of artificial heart valves, 19 mm aortic prostheses continue to create significant obstruction of the left ventricular outflow tract and, possibly as a consequence of this, fail to bring about significant reduction in left ventricular hypertrophy.