Irish Daily Mirror19 September 2011Dr Miriam Stoppard’s healthfocus What’s the difference? Myocarditis Pericarditis Myocarditis is an inflammation of theheart muscle. The most common causeis a viral infection. Rarely, mumps cancause myocarditis. Inflamation irritatesthe cardiac muscle and therefore it may begin to beat irregularly. Sometimes it is completely irregular – when it’s known as atrial fibrillation.