2006 ICD-9-CM Volume 1 Diagnosis Codes Home > Diseases Of The Circulatory System 390-459 > Other Forms Of Heart Disease 420-429 > 2006 ICD-9-CM Diagnosis 421 Acute and subacute endocarditis View the most recent version of ICD-9-CM 421 421 is a non-specific code that cannot be used to specify a diagnosis