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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I26.04|
Fat embolism of pulmonary artery with acute cor pulmonale
I26.09|
Other pulmonary embolism with acute cor pulmonale
I26.90|
Septic pulmonary embolism without acute cor pulmonale
I26.92|
Saddle embolus of pulmonary artery without acute cor pulmonale
I26.93|
Single subsegmental thrombotic pulmonary embolism without acute cor pulmonale
I26.94|
Multiple subsegmental thrombotic pulmonary emboli without acute cor pulmonale
I26.95|
Cement embolism of pulmonary artery without acute cor pulmonale
I26.96|
Fat embolism of pulmonary artery without acute cor pulmonale
I26.99|
Other pulmonary embolism without acute cor pulmonale
I27.0|
Primary pulmonary hypertension
I27.1|
Kyphoscoliotic heart disease
I27.20|
Pulmonary hypertension, unspecified
I27.21|
Secondary pulmonary arterial hypertension
I27.22|
Pulmonary hypertension due to left heart disease
I27.23|
Pulmonary hypertension due to lung diseases and hypoxia
I27.24|
Chronic thromboembolic pulmonary hypertension
I27.29|
Other secondary pulmonary hypertension
I27.81|
Cor pulmonale (chronic)
I27.82|
Chronic pulmonary embolism
I27.83|
Eisenmenger's syndrome
I27.840|
Fontan-associated liver disease [FALD]
I27.841|
Fontan-associated lymphatic dysfunction
I27.848|
Other Fontan-associated condition
I27.849|
Fontan related circulation, unspecified
I27.89|
Other specified pulmonary heart diseases
I27.9|
Pulmonary heart disease, unspecified
I28.0|
Arteriovenous fistula of pulmonary vessels
I28.1|
Aneurysm of pulmonary artery
I28.8|
Other diseases of pulmonary vessels
I28.9|
Disease of pulmonary vessels, unspecified
I30.0|
Acute nonspecific idiopathic pericarditis
I30.1|
Infective pericarditis
I30.8|
Other forms of acute pericarditis
I30.9|
Acute pericarditis, unspecified
I31.0|
Chronic adhesive pericarditis
I31.1|
Chronic constrictive pericarditis
I31.2|
Hemopericardium, not elsewhere classified
I31.31|
Malignant pericardial effusion in diseases classified elsewhere
I31.39|
Other pericardial effusion (noninflammatory)
I31.4|
Cardiac tamponade
I31.8|
Other specified diseases of pericardium
I31.9|
Disease of pericardium, unspecified
I32|
Pericarditis in diseases classified elsewhere
I33.0|
Acute and subacute infective endocarditis
I33.9|
Acute and subacute endocarditis, unspecified
I34.0|
Nonrheumatic mitral (valve) insufficiency
I34.1|
Nonrheumatic mitral (valve) prolapse
I34.2|
Nonrheumatic mitral (valve) stenosis
I34.81|
Nonrheumatic mitral (valve) annulus calcification
I34.89|
Other nonrheumatic mitral valve disorders

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