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Prognosis in valvular heart disease:I. Description of Purpose, Organization, Data Collection Techniques, Estimates of Statistical Power, and Criteria for Termination of Patient Entry

Controlled Clinical Trials
Publication Date
DOI: 10.1016/0197-2456(85)90096-0
  • Valvular Heart Disease
  • Valve Replacement
  • Clinical Trial
  • Design
  • Medicine


Abstract This report describes the design of a multicenter study with two major goals: (1) the identification of valvular heart disease patients at risk for death or a serious complication, and (2) the comparison of hemodynamic function and late outcome of a mechanical prosthetic valve (Björk-Shiley) with a bioprosthesis (Hancock porcine heterograft valve). Strengths of the study design are quantitative assessment of valvular and left ventricular function before and 6 months after valve replacement, measurement in a central laboratory of critical data items such as valve orifice area and left ventricular volumes, and assignment of cause of death and valve-related complications by a committee blinded to valve type. Statistical power calculated by a simulation technique shows only modest loss of power with frequent examination of outcome compared to infrequent examination. Guidelines for premature termination of the study because of superiority of one valve type are described; this includes a critical region with a sloping boundary, which allows for greater chance variation early in the study when the number of patients and events is small, gives the greatest statistical power, and yet appears to provide adequate protection for the subjects in the study.

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