Chapter 9

I00–I99: Diseases of the Circulatory System

Diseases of the Circulatory System diagnostic classification updated for 2026.

Chapter Instructions

Excludes2(Not included here. Code separately if applicable.)

certain conditions originating in the perinatal period (P04-P96)
certain infectious and parasitic diseases (A00-B99)
complications of pregnancy, childbirth and the puerperium (O00-O9A)
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
endocrine, nutritional and metabolic diseases (E00-E88)
injury, poisoning and certain other consequences of external causes (S00-T88)
neoplasms (C00-D49)
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
systemic connective tissue disorders (M30-M36)
transient cerebral ischemic attacks and related syndromes (G45.-)

All Codes Billable Only

Internal Codes

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I34.9|
Nonrheumatic mitral valve disorder, unspecified
I35.0|
Nonrheumatic aortic (valve) stenosis
I35.1|
Nonrheumatic aortic (valve) insufficiency
I35.2|
Nonrheumatic aortic (valve) stenosis with insufficiency
I35.8|
Other nonrheumatic aortic valve disorders
I35.9|
Nonrheumatic aortic valve disorder, unspecified
I36.0|
Nonrheumatic tricuspid (valve) stenosis
I36.1|
Nonrheumatic tricuspid (valve) insufficiency
I36.2|
Nonrheumatic tricuspid (valve) stenosis with insufficiency
I36.8|
Other nonrheumatic tricuspid valve disorders
I36.9|
Nonrheumatic tricuspid valve disorder, unspecified
I37.0|
Nonrheumatic pulmonary valve stenosis
I37.1|
Nonrheumatic pulmonary valve insufficiency
I37.2|
Nonrheumatic pulmonary valve stenosis with insufficiency
I37.8|
Other nonrheumatic pulmonary valve disorders
I37.9|
Nonrheumatic pulmonary valve disorder, unspecified
I38|
Endocarditis, valve unspecified
I39|
Endocarditis and heart valve disorders in diseases classified elsewhere
I40.0|
Infective myocarditis
I40.1|
Isolated myocarditis
I40.8|
Other acute myocarditis
I40.9|
Acute myocarditis, unspecified
I41|
Myocarditis in diseases classified elsewhere
I42.0|
Dilated cardiomyopathy
I42.1|
Obstructive hypertrophic cardiomyopathy
I42.2|
Other hypertrophic cardiomyopathy
I42.3|
Endomyocardial (eosinophilic) disease
I42.4|
Endocardial fibroelastosis
I42.5|
Other restrictive cardiomyopathy
I42.6|
Alcoholic cardiomyopathy
I42.7|
Cardiomyopathy due to drug and external agent
I42.8|
Other cardiomyopathies
I42.9|
Cardiomyopathy, unspecified
I43|
Cardiomyopathy in diseases classified elsewhere
I44.0|
Atrioventricular block, first degree
I44.1|
Atrioventricular block, second degree
I44.2|
Atrioventricular block, complete
I44.30|
Unspecified atrioventricular block
I44.39|
Other atrioventricular block
I44.4|
Left anterior fascicular block
I44.5|
Left posterior fascicular block
I44.60|
Unspecified fascicular block
I44.69|
Other fascicular block
I44.7|
Left bundle-branch block, unspecified
I45.0|
Right fascicular block
I45.10|
Unspecified right bundle-branch block
I45.19|
Other right bundle-branch block
I45.2|
Bifascicular block
I45.3|
Trifascicular block
I45.4|
Nonspecific intraventricular block

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