The clinical course of idiopathic dilated cardiomyopathy: A population-based study

Objective: To describe the prognosis of individuals with idiopathic dilated cardiomyopathy in a population-based sample and to compare this with the prognosis of patients in a previous referral center case series of idiopathic dilated cardiomyopathy. ■ Design: Cohort study. ■ Setting: Population-based in Olmsted County, Minnesota. ■ Patients: Forty residents of Olmstead County, Minnesota with idiopathic dilated cardiomyopathy initially diagnosed between 1975 and 1984 who were followed through 1 July 1989 and 104 patients from a Mayo Clinic referral case series from 1960 to 1973. ■ Measurements: Survival for the population-based cohort at 1 year and 5 years. ■ Results: Survival at 1 year differed dramatically between the population-based cohort and the referral case series at 1 year (95% compared with 69%, respectively) and at 5 years (80% compared with 36%, respectively) (P < 0.001). Long-term survival for the population-based cohort was nonetheless impaired when compared with an age- and sex-matched cohort, that is, the 1980 Minnesota white population (8-year survival: observed, 58% compared with expected, 83%; P < 0.001). Among community patients, older age (adjusted Cox model hazard ratio for 10-year increase in age, 1.59; 95% Cl, 1.08 to 2.35) and lower left ventricular ejection fraction (adjusted hazard ratio for 10% decrease, 1.90; Cl, 1.04 to 3.50) were independently associated with impaired survival. ■ Conclusions: These population-based data challenge the clinical perception of the clinical course of idiopathic dilated cardiomyopathy based on referral practice prognostic studies and suggest that the clinical course of this condition may be more favorable than previously recognized.