Background: The Artificial Valve Endocarditis Reduction Trial (AVERT) was designed to compare endocarditis rates in Silzone versus conventional valves. Recruitment ended January 21, 2000, because of higher rates of paravalvular leakage in patients receiving the Silzone prosthesis. The present analysis determined late event rates that might be used in the management of approximately 36,000 patients who have received the Silzone prosthesis.
Methods: A total of 807 patients in 19 centers in North America and Europe were randomized. Mean age was 61+/-11 years; 41% were women. Operations included aortic valve replacement in 59%, mitral valve replacement in 32%, and aortic and mitral valve replacements in 9%; 41% had concomitant operations (26% coronary artery bypass grafting).
Results: Major paravalvular leakage (followed by repair, explant, or mortality) occurred in 18 of 403 patients receiving Silzone valves and 4 of 404 patients without Silzone valves (2-year event-free rates: 91.1% versus 98.9% conventional, p < 0.003). Similarly, 2-year freedom from any explant was lower in the Silzone arm (19 versus 2 events; 90.1% versus 99.4%, p = 0.0002). Rates of mortality and stroke were similar during follow-up.
Conclusions: Continued follow-up of AVERT supports the conclusion that the Silzone prosthesis has increased risk of paravalvular leakage requiring reoperation. Overall survival is similar in the two groups.