A nationwide cohort study of mortality risk and long-term prognosis in infective endocarditis in Sweden

Abstract

Objectives: Infective endocarditis (IE) remains a serious disease with substantial mortality. In this study we investigated the incidence of IE, as well as its associated short and long term mortality rates.

Methods: The IE cases were identified in the Swedish national inpatient register using ICD-10 codes, and then linked to the population register in order to identify deaths in the cohort. Crude mortality rates among IE patients were obtained for different time intervals. These rates were directly standardized using sex- and age-matched mortality in the general population.

Results: The cohort consisted of 7603 individuals and 7817 episodes of IE during 1997-2007. The 30 days all-cause crude mortality rate was 10.4% and the standardized mortality ratio (SMR) was 33.7 (95% confidence interval [CI]: 31.0-36.6). Excluding the first year of follow-up, the long term mortality (1-5 years) showed an increased SMR of 2.2 (95% CI: 2.0-2.3) compared to the general population. Significantly higher SMR was found for cases of IE younger than 65 years of age with a 1-5 year SMR of 6.3, and intravenous drug-users with a SMR of 19.1. Native valve IE cases, in which surgery was performed had lower crude mortality rates and Mantel-Haenzel odds ratios of less than one compared to those with medical therapy alone during 30-day and 5-years follow-up.

Conclusions: The 30-days crude mortality rate for IE was 10.4% and long-term relative mortality risk remains increased even up to 5 years of follow-up, therefore a close monitoring of these patients would be of value.

Figure 1. Incidence Rate and 30-days Mortality (%) of Infective endocarditis (IE) hospitalizations in Sweden during 1997 through 2007.

Figure 2. Absolute Mortality Risks in the Total Infective endocarditis (IE) Cohort (n = 7603) and grouped by Native Valve IE (n = 6138), Prosthetic Valve IE (n = 890) and Intravenous drug-users (n = 575), 5-year Follow-up.

Individuals who both have a current intravenous drug use and a prosthetic valve are categorized among drug-users.

Figure 3. Absolute Mortality Risks among Infective endocarditis (IE) Patients grouped by Native Valve IE surgery (n = 881), Native Valve IE non-surgery (n = 5257), Prosthetic Valve IE surgery (n = 109) and Prosthetic valve IE non-surgery (n = 781), 5-year Follow-up.