The statistician’s pageProsthetic Heart Valves: Objective Performance Criteria Versus Randomized Clinical Trial
Section snippets
Prosthetic Heart Valves
A heart valve is a one-way check valve, opening to allow the flow of blood in one direction at the appropriate time during the cardiac cycle, and sealing the valve orifice otherwise, to prevent backward flow. The first successful heart valve was the simple Starr-Edwards caged-ball device implanted in 1960 [1]. Engineering principles could be applied to the design, laboratory testing to assess flow, leak, strength, durability, and animal implantations to study the effects in a biological
Regulatory Developments
The FDA began regulating medical devices in 1976. At first, there was no standard for clinical performance, marketing applications seemed to be judged primarily on the completeness of data. Then a 1993 guidance document (revised in 1994 [9]) gave requirements for in vitro, animal, and clinical data, including New York Heart Association (NYHA) class, blood and hemodynamic data, and cardiovascular complications [10, 11]. This document included the list of OPC for valve-related complications (
Heart Valve RCTs
Although RCTs of heart valves have not been required for FDA approval, many have been done to compare postapproval valves. We will briefly review a few of the most important ones. There are two major randomized studies of heart valves, both comparing mechanical to tissue valves. A recent RCT compared the most-used third-generation SJM bileaflet valve to the first-generation Starr-Edwards caged-ball valve. And the largest RCT of heart valves ever proposed, a recent comparison of a new sewing
Rationale for OPC: Drugs Versus Devices
There are major differences between drugs and heart valves, which may explain why RCTs are required for regulatory approval of the former, but not the latter. The evaluation stages of drug studies are (1) establish safety, (2) refine dosage, and (3) confirm efficacy. The last step is difficult because usually the mechanism of action is systemic, complex, and not well understood, and the endpoints are partly subjective. Consequently, many patients are needed, with randomization and blinding
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