Pericarditis Pericarditis may be divided into two types-acute and constrictive. Acute pericarditis (AP), which is an inflammatory condition of the membranes lining the heart, affects men more frequently than women, and is seen with increasing frequency with advancing age. While AP is diagnosed in less than 1% of hospital admissions, it has an estimated prevalence of 2% to 6% in the general population, underscoring the frequency with which it is either clinically not apparent or not considered in the differential diagnosis.