| Heart Valve Replacement: A
Statistical Review of 35 Years' Results A total of 2,942 isolated aortic (AVR) and 1,579 mitral (MVR) valve replacements with 21,742 and 12,142 patient-years of follow up years, respectively, were reviewed. Analysis of the results affords an opportunity to illustrate the usefulness and necessity of multivariable event-free analyses and cumulative incidence functions. For AVR, age is not a significant univariate risk factor for operative mortality, but is highly significant after accounting for date of surgery. Long-term mortality is higher for tissue valves than for mechanical valves; but mean age is greater and, after accounting for age, mortality is similar for both valve types. Kaplan-Meier analysis estimates thromboembolism occurrences of 85% for AVR and 95% for MVR, but cumulative incidence estimates are only 32% and 41%, respectively. Thus, multivariate analyses are essential to avoid being misled by excluding important risk factors or including artifactual ones, and the cumulative incidence estimates the percentage of patients who will actually experience a complication. |
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