Limitations of this report include the fact that this is an observational study of patients from self-selected centers. Each center most likely represents a portion of the local population, making it difficult to generalize findings to the entire population centers from which this report originates. Represented hospitals were typically referral centers that have cardiac surgery programs and may have widely differing populations with varied risk factors. Advantages include the large size of this prospectively evaluated cohort and the ability to analyze regional variations between continents with a contemporary nature of the patient sample (2000-2003).
Infectious Endocarditis in Olmsted County, Minn.
Tleyjeh IM, Steckelberg JM, Murad HS, et al. Temporal trends in infective endocarditis: a population-based study in Olmsted County, Minnesota. JAMA. 2005;293:3022-3028.
Tleyjeh and colleagues at the Mayo Clinic in Rochester, Minn., retrospectively studied 102 cases of infective endocarditis that occurred in 107 Olmsted County residents from 1970-2000. Main outcome measures were incidence of infective endocarditis, proportion of patients with underlying heart disease and causative micro-organisms and clinical characteristics. The records of all Olmsted County residents with infective endocarditis were identified and reviewed in detail. The definite and possible infective endocarditis cases as defined by modified Duke Criteria were used in the analysis.
The age- and gender-adjusted incidence of infective endocarditis ranged from 5.0 to 7.0 cases per 100,000 person-years during the study period and did not change significantly over time. There were 84 (79%) cases of native valve infective endocarditis and 23 (21%) cases of prosthetic valve infective endocarditis. Valves involved: aortic—36 (24%); mitral—49 (46%), aortic and mitral—12 (11%), right-sided or bilateral—8 (7%), or unknown—8 (7%). 16 (15%) had valve surgery within 42 days and the six-month mortality was 26% (n=28).
Infective endocarditis is a disease of the older individual in this population, with a mean age ranging from 54.1 years in 1980-1984 to 67.4 years in 1995-2000 (P=0.24 for trend). There was a male predominance (67%-83%), which did not significantly change over time.
Mitral valve prolapse was the most frequent underlying valvular heart disease. Viridans streptococci were the most common causative organisms (n=47; 44%) followed by Staphylococcus aureus (n=28 cases; 26%).
The overall average crude infective endocarditis incidence of the period 1970-2000 was 4.95 per 100,000 person-years. The age- and gender-adjusted annual incidence was 6.06 per 100,000 (95% CI, 4.89-7.22). There was no time trend for either streptococcus or Staphylococcus aureus infective endocarditis: the annual adjusted incidence of viridans group streptococcal infective endocarditis was 1.7 to 3.5 cases per 100,000 person years while Staphylococcus aureus infective endocarditis had an annual adjusted incidence of 1.0-2.2 cases per 100,000. The incidence rates of viridans group streptococcal and Staphylococcus aureus infective endocarditis have not changed significantly over time in this population.
Potential limitations of this study include possible incomplete case finding or recognition of the retrospective nature of the case reviews. The homogeneity of the patient population studied (primarily elderly white males with a low prevalence of intravenous drug use) limits the ability to generalize the results. Advantages include the fact that this is a population-based study at a medical center with detailed medical records of virtually all residents of a single county. This allows us to view the clinical features and etiologic factors of primarily left-sided infective endocarditis without the referral bias that tends to taint other studies typically published out of large medical centers with larger geographic referral bases.