420 Acute pericarditis 
420.0 Acute pericarditis in diseases classified elsewhere convert 420.0 to ICD-10-CM
420.9 Other and unspecified acute pericarditis 
420.90 Acute pericarditis, unspecified convert 420.90 to ICD-10-CM 420.91 Acute idiopathic pericarditis convert 420.91 to ICD-10-CM 420.99 Other acute pericarditis convert 420.99 to ICD-10-CM