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Biomedical subjects

W N Anderson

Publications and source records attributed to W N Anderson.

7 recordsLinked to original sources

Quality of life in patients with bioprostheses and mechanical prostheses. Evaluation of cohorts of patients aged 51 to 65 years at implantation.

BACKGROUND: The purpose of this study was 3-fold: to compare the quality of life (QOL) in age- and sex-matched patients who received biological and mechanical prosthetic valves in isolated aortic valve replacement, to compare the QOL of patients with aortic valve replacement with the general population, and to compare patients with biological and mechanical prostheses with certain valve-specific questions and relate these responses to overall QOL. METHODS AND RESULTS: Patient-perceived QOL was evaluated in 200 patients who were sampled from a population of 420 patients (age range 51 to 65 years) who underwent isolated aortic valve replacement in the period of 1986 to 1996. One hundred of the sampled patients had a mechanical valve inserted and an equal number had porcine bioprostheses. Three survey instruments were used to examine perceived QOL: the SF-12 form, a 7-valve specific question form, and the Lamy Smiley Faces form. The response to the questionnaires was 89.5% (179 patients). Patients with mechanical valves were more bothered by valve sounds (P < 0.01) and had a negative correlation (P < 0.01) between valve sound and QOL on the mental scale only. Patients with biological valves were more fearful of the need for reoperation (P < 0.01), but there was no correlation between fear and QOL. The mechanical valve group had a negative correlation (P < 0.01) between fear of reoperation and QOL on both the mental and physical scales. There was no difference between the 2 cohorts with respect to fear of valve failure. Patients with mechanical valves were more concerned about frequency of medical visits and blood tests (P < 0.01) as well as the possibility of anticoagulant-related bleeding events (P < 0.01). QOL was equivalent between the 2 groups and to the general population for the same age group. Ninety-seven percent of the patients indicated they would make the same surgical decision again with regard to valve replacement; there was no difference between the 2 valve groups on this question. CONCLUSIONS: Patient-perceived QOL is similar between patients with aortic mechanical and biological valve replacement in the studied age group and comparable to the general population of similar age. Although certain valve-specific differences exist between the 2 prosthetic types, these differences do not appear to affect overall QOL as described by these patients.

Aged

Clinical evaluation and analysis of heart valve substitutes.

We discuss the clinical assessment of heart valve substitutes, primarily with regard to pre-market evaluation. We concentrate on the current FDA heart valve guidance document. This guidance is self-acknowledged to be an evolving document, scheduled to be revised between three and five years after its initial release on December 1993. We outline the history and some of the strengths of the present system, and discuss areas for possible improvement. We selected one important statistical issue to address thoroughly how to compute the confidence limit of a linearized rate.

Bioprosthesis

Passive surveillance of heart valve devices: Björk-Shiley outlet strut fracture rates.

The Björk-Shiley Convexo-Concave heart valve has a mechanical failure mode called outlet strut fracture (OSF). Previous analyses have found that the hazard function for OSF is constant over time. This article uses the valve manufacturers implant database to examine the shape of the hazard function over time, employing a previously developed model to impute patient survival times. Decisions about patient management (e.g., elective explant) are based on projecting this risk into the future. An analysis that incorporates the decrement of patients at risk due to death and explant provides estimates of the actual occurrences of OSF over calendar time.

Adult

Spreadsheet method for determining sample sizes for heart valve studies.

Grunkemeier, Johnson, and Naftel have given a method for computing sample size requirements for a clinical study of a new heart valve. This paper gives an implementation of the method on a computer spreadsheet. Moreover, it computes the sample size for the most powerful test with exactly the prescribed level of significance and power; all other tests will necessarily have smaller power and will need larger sample sizes. All graphs and tables are produced on the spreadsheet, and no use of special statistical functions is necessary.

Computers