Background: Many cardiac and infectious diseases have a seasonal incidence. It is not known whether similar variations exist for endocarditis.
Methods: As echocardiography plays a key role in diagnosing endocarditis, patients referred for echocardiography with suspected endocarditis from 1993 through 2001 were identified. The modified Duke criteria were used in establishing endocarditis. The echocardiography date was arbitrarily used to determine season: fall/winter (October to March) and spring/summer (April to September).
Results: For the 1,279 patients referred for echocardiography to rule out endocarditis, there was no seasonal difference between the total number of referred fall/winter and spring/summer patients (645 patients vs 634 patients, respectively). However, endocarditis was found in 41 fall/winter patients (6.4%) and 19 spring/summer patients (3.0%) patients (odds ratio, 2.20; 95% confidence interval, 1.26 to 3.83; p = 0.004). This seasonal disparity was present in 7 of the 9 years studied. No clinical factors could account for this seasonal disparity.
Conclusions: As with many other cardiac diseases, a significant fall/winter predominance for endocarditis was found.