Seasonal patterns of acute and recurrent idiopathic pericarditis

Background: Idiopathic pericarditis is presumed to result from viral infection. The incidence rates of some viral infections have typical seasonal patterns. The data in the literature on a possible seasonal pattern of acute pericarditis are very limited. The mechanism and possible seasonality of recurrent episodes are not well established. Hypothesis: The incidence of acute idiopathic pericarditis has a seasonal pattern. Methods: The computerized database of a tertiary, university-affiliated hospital was searched for all patients admitted with a first episode of acute idiopathic pericarditis between January 1, 2010 and December 31, 2015. Patients for whom a nonviral etiology for the pericarditis was identified were excluded. Results: The final cohort included 175 patients (75% male) ages 19 to 86 years (median = 50.0 ± 18.2 years). The incidence of the disease was twice as high during the colder half of the year (October–March) than the warmer half, peaking in the first quarter (January–March, P = 0.001). This first-quarter peak was observed in each of the 6 years examined. Comparison of the patients who acquired pericarditis during peak and nonpeak quarters yielded no differences in baseline characteristics, peak body temperature, white blood cell count, C-reactive protein level, or frequency of myocardial involvement or liver enzyme elevation. No seasonal pattern was identified for recurrent episodes of pericarditis (n = 57). Conclusions: Acute idiopathic pericarditis appears to have a seasonal pattern with a distinct late winter peak. No seasonal pattern was identified for recurrent episodes.