2006 ICD-9-CM Volume 1 Diagnosis Codes Home > Diseases Of The Circulatory System 390-459 > Other Forms Of Heart Disease 420-429 > ICD-9-CM Diagnosis 420 Acute pericarditis 420 is a non-specific code that cannot be used to specify a diagnosis ICD-9-CM Diagnosis 420.0 Acute pericarditis in diseases classified elsewhere 420.0 is a specific code that can be used to specify a diagnosis 420.0 contains 15 index entries ICD-9-CM Diagnosis 420.9 Other and unspecified acute pericarditis 420.9 is a non-specific code that cannot be used to specify a diagnosis ICD-9-CM Diagnosis 420.90 Acute pericarditis unspecified Inflammation of the pericardium. 420.90 is a specific code that can be used to specify a diagnosis 420.90 contains 12 index entries ICD-9-CM Diagnosis 420.91 Acute idiopathic pericarditis 420.91 is a specific code that can be used to specify a diagnosis 420.91 contains 7 index entries ICD-9-CM Diagnosis 420.99 Other acute pericarditis 420.99 is a specific code that can be used to specify a diagnosis 420.99 contains 15 index entries