Q23.4 Hypoplastic left heart syndrome

Billable ICD-10-CM code, FY2026. Acts as a Major Complication or Comorbidity (MCC) as a secondary diagnosis. Exempt from present-on-admission (POA) reporting.

Risk adjustment (HCC)

• RxHCC V08: HCC 191 — Ventricular Septal Defect and Major Congenital Heart Disorders

MS-DRG index

Defines the logic of DRG(s) 306-307 in MDC 05.

Approximate ICD-9-CM (GEMs)

• 746.7 Hypoplastic left heart syndrome

Code annotations containing back-references to Q23.4

Back-references to Q23.4

• Type 1 Excludes: Q23.0 Congenital stenosis of aortic valve ("congenital stenosis of aortic valve in hypoplastic left heart syndrome (Q23.4)")
• Type 1 Excludes: Q25.4 Other congenital malformations of aorta ("hypoplasia of aorta in hypoplastic left heart syndrome (Q23.4)")

Back-references to Q23

• Type 2 Excludes: I08 Multiple valve diseases ("multiple valve disease specified as nonrheumatic (I34.-, I35.-, I36.-, I37.-, I38.-, Q22.-, Q23.-, Q24.8-)")
• Code Also: I27.21 Secondary pulmonary arterial hypertension ("congenital heart disease (Q20-Q28)")
• Type 2 Excludes: P29 Cardiovascular disorders originating in the perinatal period ("congenital malformations of the circulatory system (Q20-Q28)")
• Code Also: Z71.87 Encounter for pediatric-to-adult transition counseling ("congenital malformations of the circulatory system (Q20-Q28)")

Diagnosis Index entries for Q23.4

• Atresia, atretic › aortic (orifice) (valve) › congenital with hypoplasia of ascending aorta and defective development of left ventricle (with mitral stenosis)
• Atresia, atretic › aortic (orifice) (valve) › in hypoplastic left heart syndrome
• Atresia, atretic › mitral valve › in hypoplastic left heart syndrome
• Development › defective, congenital › left ventricle › in hypoplastic left heart syndrome
• Hypoplasia, hypoplastic › aorta, aortic › ascending, in hypoplastic left heart syndrome
• Hypoplasia, hypoplastic › aorta, aortic › valve › in hypoplastic left heart syndrome
• Hypoplasia, hypoplastic › left heart syndrome
• Syndrome › hypoplastic left-heart

Nearby codes

• Q23 Congenital malformations of aortic and mitral valves
• Q23.0 Congenital stenosis of aortic valve
• Q23.1 Congenital insufficiency of aortic valve
• Q23.2 Congenital mitral stenosis
• Q23.3 Congenital mitral insufficiency
• Q23.4 Hypoplastic left heart syndrome (this code)
• Q23.8 Other congenital malformations of aortic and mitral valves
• Q23.81 Bicuspid aortic valve
• Q23.82 Congenital mitral valve cleft leaflet
• Q23.88 Other congenital malformations of aortic and mitral valves
• Q23.9 Congenital malformation of aortic and mitral valves, unspecified