Small valve area index: its influence on early mortality after mitral valve replacement

Objective: To test the hypothesis that mitral valve prosthesis-patient mism atch increases postoperative mortality. Methods and results: The effect of mitral valve prosthesis-patient mismatch on survival in a cohort of consecu tive patients after mitral valve replacement with a mechanical prosthesis w as measured, focusing on the lower tail of the normal distribution curve of the prosthetic valve area index. For the calculation of the geometric valv e area index (cm(2)/m(2) body surface area), we used specifications for the geometric valve area supplied by the manufacturer. The cut-oft` value of t he 10th percentile of the valve area index was 1.919 cm(2)m(2). The study p opulation consisted of 128 adult patients who underwent mitral valve replac ement by a Medtronic Hall (n = 270, 63%) or a St. Jude Medical prosthesis ( n = 158.37%). The size of the valves implanted ranged from 25 mm to 31 mm. The valve area index showed a normal distribution curve ranging from 1.43 t o 2.98 cm(2)/m(2) with a mean of 2.2 cm(2)/m(2). Group 1 (n = 33) had a val ve area index < 1.9 cm(2)/m(2) and group 2 (n = 395), greater than or equal to 1.9 cm(2)/m(2). The 30-day mortality was higher in group 1 than in grou p 2 (18.2 vs. 4.1%, P = 0.005). Multivariate logistic regression analysis o f the determinants of the 30-day mortality rendered a small valve area inde x (< 1.9 cm(2)/m(2)) as an independent risk indicator: relative risk 3.3 (9 5% Cl 1.6-9.5; P = 0.0043). The difference in overall survival between the two groups was entirely due to the high 30-day mortality in the patients wi th small valve area indices, congestive heart failure being the main cause of death. Conclusions: By concentrating on the extreme lower tail of the no rmal distribution of the valve area index, a strong and independent relatio n was found between relatively small valves (valve area index < 1.9 cm(2)/m (2)) and 30-day mortality. We found no influence of valve size on late mort ality beyond the first 30 days. (C) 2000 Elsevier Science B.V. All rights r eserved.