2008 ICD-9-CM Volume 1 Diagnosis Codes Home > Diseases Of The Circulatory System 390-459 > Other Forms Of Heart Disease 420-429 > 2008 ICD-9-CM Diagnosis 420 Acute pericarditis  On October 1, 2008 the 2009 ICD-9-CM codes came into effect. Therefore, this code may be out of date. The 2009 version of ICD-9-CM 420 can be accessed here. 420 is a non-specific code that cannot be used to specify a diagnosis ICD9Data's sister site ProcedureCodes.com launches with the 2008/09 CPT® codes - read more on the ICD9Data.com blog. 420 includes: acute: mediastinopericarditis myopericarditis pericardial effusion pleuropericarditis pneumopericarditis 420 excludes: acute rheumatic pericarditis (391.0) postmyocardial infarction syndrome [Dressler's] (411.0)