Aortic valve replacement: Is valve size important? (original) (raw)

2000, The Journal of Thoracic and Cardiovascular Surgery

large-sized prosthesis seems preferable. On the other hand, aortic root enlargement may complicate an operation for aortic valve replacement. 1,4-11 Furthermore, patients with small annular size may be small individuals, and the small valve size may be matched to their cardiac output needs. In addition to this uncertainty with respect to the small aortic root, there is also controversy about valve size and efficiency in general. Both the use of stentless aortic valve prostheses and the use of aortic root-enlarging procedures are strategies based in large part on the thesis that hemodynamic performance, and thus valve size, favorably influence late outcome. 12 The purpose of this study was to ascertain the relation of prosthesis size to survival after aortic valve replacement. Materials and methods Patients. To obtain a relatively pure relation of prosthesis size to survival, we identified adult patients (≥18 years of age) operated on at The Cleveland Clinic Foundation from 1978 T here is uncertainty as to the optimum management of patients with a small aortic anulus. 1 Small aortic prostheses may leave higher residual pressure gradients across the valve and are associated with less rapid and less complete regression of left ventricular hypertrophy. 2,3 Thus a Objective: We sought to determine whether aortic prosthesis size adversely influences survival after aortic valve replacement. Methods: A total of 892 adults receiving a mechanical (n = 346), pericardial (n = 463), or allograft (n = 83) valve for aortic stenosis were observed for up to 20 years (mean, 5.0 ± 3.9 years) after primary isolated aortic valve replacement. We used multivariable propensity scores to adjust for valve selection factors, multivariable hazard function analyses to identify risk factors for all-cause mortality, and bootstrap resampling to quantify the reliability of the results. Results: Twenty-five percent of patients had indexed internal orifice areas of less than 1.5 cm 2 /m 2 and more than 2 SDs (Z-value) below predicted normal aortic valve size. Mechanical valve orifices were smaller (1.3 ± 0.29 cm 2 /m 2 , Z =-2.2 ± 1.16) than pericardial (1.9 ± 0.36 cm 2 /m 2 , Z =-0.40 ± 1.01) or allograft valves (2.1 ± 0.50, Z = 0.24 ± 1.17). The overall survival was 98%, 96%, 86%, 69%, and 49% at 30 days and 1, 5, 10, and 15 years postoperatively. Univariably, survival was weakly and inversely related to manufacturer valve size (P = .16) and internal orifice diameter (P = .2) but completely unrelated to indexed valve area (P = .6) or Z-value (P = .8). These, and univariable differences among valve types (P = .004), were accounted for by different prevalences in patient risk factors and not by valve size or type per se. Bootstrap resampling indicated that these findings had a less than 15% chance of being incorrect. Conclusions: Survival after aortic valve replacement is strongly related to patient risk factors but appears not to be adversely affected by moderate patient-prosthesis mismatch (down to about 4 SDs below normal). Aortic root enlargement to accommodate a large prosthesis may be required in few situations.