Original article: cardiovascular
Paravalvular leak and other events in silzone-coated mechanical heart valves: a report from AVERT

Presented at the Thirty-seventh Annual Meeting of The Society of Thoracic Surgeons, New Orleans, LA, Jan 29–31, 2001.
https://doi.org/10.1016/S0003-4975(01)03442-7Get rights and content

Abstract

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.

Section snippets

Study protocol

Details of the hypothesis, study design, and sample size determination have been presented previously [4]. Briefly, the AVERT trial was developed to determine whether Silzone coating of prosthetic valve sewing rings reduces the risk of PVE. The study assumed that for uncoated prostheses, the rate of early PVE (less than 60 days) is 1%, and the subsequent risk of late PVE is 0.5% per year. To detect a 50% reduction in risk of PVE (80% power, p < 0.05), the trial would have to randomize

Patient characteristics

Patients were on average 61 years old, and 41.1% were women. Five percent of patients had active, treated, or suspected endocarditis at the time of operation. Most study patients had New York Heart Association functional class II (40.9%) or III (42.4%) at the time of implant; 8.7% were class I, and 8% were class IV. History of myocardial infarction was reported in 8.9%, history of diabetes in 14.3%, and congestive heart failure within 2 weeks of operation in 22.6%. Coronary artery disease,

Comment

These results confirm and extend the interim analysis of AVERT that led to discontinuation of enrollment and voluntary withdrawal of the Silzone valve because of an unacceptably high risk of explant due to major paravalvular leak. The increased risk of major PV leak was observed for patients with aortic valve replacement, mitral valve replacement, and double valve replacement.

The mechanism responsible for development of PV leak in patients receiving the Silzone prosthesis is unclear. In

Addendum

As of December 5, 2001 follow-up on Silzone patients in the study had increased to 686 valve-years and included 277 patients reporting 2-year follow-up. No additional instances of valve repair or explant due to PV leak have been reported.

References (8)

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