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ICD-10 Code Q23.4: Hypoplastic left heart syndrome

Q23.4 is a billable ICD-10 diagnosis code used to classify Hypoplastic left heart syndrome in medical records and claims. You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records. ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (Q00-QA0).

Reviewed by HealthAssure Clinical TeamUpdated 26 May 2026

What is this code?

ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (Q00-QA0).

When is it used?

  • May be used when a clinician documents hypoplastic left heart syndrome in a patient's medical record.
  • May appear in hospital records, claims, referrals, and clinical documentation.
  • This code can be used as a clinically usable diagnosis entry in standardized coding workflows.

What it does not mean

  • A code alone does not explain severity, treatment plan, or outcome.
  • A medical code should not be treated as a substitute for a doctor's diagnosis or advice.

Code hierarchy

chapter
17Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (Q00-QA0)
block
Q20-Q28Congenital malformations of the circulatory system
category
Q23Congenital malformations of aortic and mitral valves
currentQ23

Where you may see this code

You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records.

Related specialists

ENT SpecialistCardiologist

Coverage-related procedures and services

CPT 75574high
COMPUTED TOMOGRAPHIC ANGIOGRAPHY, HEART, CORONARY ARTERIES AND BYPASS GRAFTS (WHEN PRESENT), WITH CONTRAST MATERIAL, INCLUDING 3D IMAGE POSTPROCESSING (INCLUDING EVALUATION OF CARDIAC STRUCTURE AND MORPHOLOGY, ASSESSMENT OF CARDIAC FUNCTION, AND EVALUATION OF VENOUS STRUCTURES, IF PERFORMED)
Source: CMS coverage guidance
CPT 75572high
COMPUTED TOMOGRAPHY, HEART, WITH CONTRAST MATERIAL, FOR EVALUATION OF CARDIAC STRUCTURE AND MORPHOLOGY (INCLUDING 3D IMAGE POSTPROCESSING, ASSESSMENT OF CARDIAC FUNCTION, AND EVALUATION OF VENOUS STRUCTURES, IF PERFORMED)
Source: CMS coverage guidance
CPT 75573high
COMPUTED TOMOGRAPHY, HEART, WITH CONTRAST MATERIAL, FOR EVALUATION OF CARDIAC STRUCTURE AND MORPHOLOGY IN THE SETTING OF CONGENITAL HEART DISEASE (INCLUDING 3D IMAGE POSTPROCESSING, ASSESSMENT OF LEFT VENTRICULAR [LV] CARDIAC FUNCTION, RIGHT VENTRICULAR [RV] STRUCTURE AND FUNCTION AND EVALUATION OF VASCULAR STRUCTURES, IF PERFORMED)
Source: CMS coverage guidance
CPT 75571high
COMPUTED TOMOGRAPHY, HEART, WITHOUT CONTRAST MATERIAL, WITH QUANTITATIVE EVALUATION OF CORONARY CALCIUM
Source: CMS coverage guidance
CPT 93355high
ECHOCARDIOGRAPHY, TRANSESOPHAGEAL (TEE) FOR GUIDANCE OF A TRANSCATHETER INTRACARDIAC OR GREAT VESSEL(S) STRUCTURAL INTERVENTION(S) (EG, TAVR, TRANSCATHETER PULMONARY VALVE REPLACEMENT, MITRAL VALVE REPAIR, PARAVALVULAR REGURGITATION REPAIR, LEFT ATRIAL APPENDAGE OCCLUSION/CLOSURE, VENTRICULAR SEPTAL DEFECT CLOSURE) (PERI-AND INTRA-PROCEDURAL), REAL-TIME IMAGE ACQUISITION AND DOCUMENTATION, GUIDANCE WITH QUANTITATIVE MEASUREMENTS, PROBE MANIPULATION, INTERPRETATION, AND REPORT, INCLUDING DIAGNOSTIC TRANSESOPHAGEAL ECHOCARDIOGRAPHY AND, WHEN PERFORMED, ADMINISTRATION OF ULTRASOUND CONTRAST, DOPPLER, COLOR FLOW, AND 3D
Source: CMS coverage guidance
CPT 93318high
ECHOCARDIOGRAPHY, TRANSESOPHAGEAL (TEE) FOR MONITORING PURPOSES, INCLUDING PROBE PLACEMENT, REAL TIME 2-DIMENSIONAL IMAGE ACQUISITION AND INTERPRETATION LEADING TO ONGOING (CONTINUOUS) ASSESSMENT OF (DYNAMICALLY CHANGING) CARDIAC PUMPING FUNCTION AND TO THERAPEUTIC MEASURES ON AN IMMEDIATE TIME BASIS
Source: CMS coverage guidance

Coding guidelines

Compatibility

Legacy and official ICD code match exactly.
Legacy codes
Q23.4

Common synonyms

Hypoplastic left heart syndrome

Frequently asked questions

Code details

CodeQ23.4
SystemICD10
Display nameHypoplastic left heart syndrome
ChapterCongenital malformations, deformations, chromosomal abnormalities, and genetic disorders (Q00-QA0)
BlockCongenital malformations of the circulatory system

Flags

BillableYes
Valid clinical useYes

Source

SourceICD-10
Version2026-annual
Releaseannual
Year2026

Index terms

Matched terms
Atresia, atreticAtresia, atreticAtresia, atreticDevelopmentHypoplasia, hypoplasticHypoplasia, hypoplasticHypoplasia, hypoplasticSyndrome

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.

ICD-10 Code Q23.4 for Hypoplastic left heart syndrome | HealthAssure