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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I45.5|
Other specified heart block
I45.6|
Pre-excitation syndrome
I45.81|
Long QT syndrome
I45.89|
Other specified conduction disorders
I45.9|
Conduction disorder, unspecified
I46.2|
Cardiac arrest due to underlying cardiac condition
I46.8|
Cardiac arrest due to other underlying condition
I46.9|
Cardiac arrest, cause unspecified
I47.0|
Re-entry ventricular arrhythmia
I47.10|
Supraventricular tachycardia, unspecified
I47.11|
Inappropriate sinus tachycardia, so stated
I47.19|
Other supraventricular tachycardia
I47.20|
Ventricular tachycardia, unspecified
I47.21|
Torsades de pointes
I47.29|
Other ventricular tachycardia
I47.9|
Paroxysmal tachycardia, unspecified
I48.0|
Paroxysmal atrial fibrillation
I48.11|
Longstanding persistent atrial fibrillation
I48.19|
Other persistent atrial fibrillation
I48.20|
Chronic atrial fibrillation, unspecified
I48.21|
Permanent atrial fibrillation
I48.3|
Typical atrial flutter
I48.4|
Atypical atrial flutter
I48.91|
Unspecified atrial fibrillation
I48.92|
Unspecified atrial flutter
I49.01|
Ventricular fibrillation
I49.02|
Ventricular flutter
I49.1|
Atrial premature depolarization
I49.2|
Junctional premature depolarization
I49.3|
Ventricular premature depolarization
I49.40|
Unspecified premature depolarization
I49.49|
Other premature depolarization
I49.5|
Sick sinus syndrome
I49.8|
Other specified cardiac arrhythmias
I49.9|
Cardiac arrhythmia, unspecified
I50.1|
Left ventricular failure, unspecified
I50.20|
Unspecified systolic (congestive) heart failure
I50.21|
Acute systolic (congestive) heart failure
I50.22|
Chronic systolic (congestive) heart failure
I50.23|
Acute on chronic systolic (congestive) heart failure
I50.30|
Unspecified diastolic (congestive) heart failure
I50.31|
Acute diastolic (congestive) heart failure
I50.32|
Chronic diastolic (congestive) heart failure
I50.33|
Acute on chronic diastolic (congestive) heart failure
I50.40|
Unspecified combined systolic (congestive) and diastolic (congestive) heart failure
I50.41|
Acute combined systolic (congestive) and diastolic (congestive) heart failure
I50.42|
Chronic combined systolic (congestive) and diastolic (congestive) heart failure
I50.43|
Acute on chronic combined systolic (congestive) and diastolic (congestive) heart failure
I50.810|
Right heart failure, unspecified
I50.811|
Acute right heart failure

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