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Eur J Cardiothorac Surg 2006;30:20-27
© 2006 Elsevier Science NL

Time-related risk of the St. Jude Silzone heart valve

^a Medical Data Research Center, Providence Health System, Portland, OR, United States
^b Epidemiology Data Coordinating Center, University of Pittsburgh, Pittsburgh, PA, United States
^c Department of Pediatrics, School of Medicine, University of Utah, Salt Lake City, UT, United States
^d Division of Cardiovascular Surgery, Mayo Clinic, Rochester, MN, United States

Received 2 December 2005; received in revised form 30 March 2006; accepted 3 April 2006.

^_* Corresponding author. Address: Providence St. Vincent Medical Center, 9205 SW Barnes Road, LL33, Portland, OR 97225, United States. Tel.: +1 503 216 7276; fax: +1 503 216 7274. (Email: Ruyun.Jin{at}providence.org).

Objective: The St. Jude Medical Silzone heart valve had a silver-impregnated sewing ring designed to reduce the incidence of prosthetic valve endocarditis. Recruitment to the randomized AVERT study comparing Silzone valves with non-Silzone Control valves was stopped because of an increased risk of reoperation for paravalvular leak, but patient follow-up continues. Determining the time-related risk profile of the Silzone valve is important for helping physicians manage the approximately 28,000 patients currently alive with a Silzone valve. Methods: Between 1998 and 2000, 403 Silzone and 404 Control patients were enrolled in AVERT. As of July 2005, there were 1819 Silzone and 1842 Control patient-years of follow-up (mean 4.5, median 5.1 years). Analysis emphasized the use and interpretation of hazard functions, since they are more meaningful than event-free percentages to currently surviving patients. To this end, instead of Cox regression, which estimates the hazard ratio, assuming it is constant over time, we employed primarily Aalen additive regression, which measures the hazard difference, and produces a plot of it over time. We assessed the risks of major paravalvular leak, endocarditis, bleeding and thrombo-embolism. Results: The Silzone valve had a higher initial risk of major paravalvular leak than Control in the mitral (p = 0.02) position, but not in the aortic (p = 0.42) position. Analysis of this risk using additive regression, with all valve positions combined, showed that the initial risk due to Silzone lost statistical significance by 2 years and disappeared by 4 years after implant. In the mitral position, the Silzone valve had a higher initial risk of thrombo-embolism plus bleeding than Control; this risk also lost statistical significance by 2 years and subsided to zero by 4 years. The risks for death and endocarditis were similar for Slizone and Control valves. Conclusions: The additional risks of the Silzone valve, compared to Control, diminish over time and disappear by 4 years after implant. The minimum time after implant of the patients currently alive with Silzone is now well beyond 5 years; thus, these current patients now have a risk profile similar to that of patients with a standard St. Jude valve.

Key Words: Silzone heart valve • Paravalvular leak • Thrombo-embolism and bleeding • Hazard function • Additive regression

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