Q23.4Hypoplastic left heart syndrome

Q23.4 is the ICD-10-CM diagnosis code for Hypoplastic left heart syndrome. It belongs to category Q23 (congenital malformations of aortic and mitral valves), block Q20-Q28 (congenital malformations of the circulatory system) and chapter 17 (congenital malformations, deformations, chromosomal abnormalities, and genetic disorders). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within Q23 (congenital malformations of aortic and mitral valves), Q23.4 is specifically for Hypoplastic left heart syndrome. Related codes cover congenital stenosis of aortic valve (Q23.0), congenital insufficiency of aortic valve (Q23.1), congenital mitral stenosis (Q23.2), congenital mitral insufficiency (Q23.3), other congenital malformations of aortic and mitral valves (Q23.8) and congenital malformation of aortic and mitral valves, unspecified (Q23.9).

As a secondary diagnosis it is an MCC (major complication or comorbidity), which can move an inpatient stay into the highest-paying "with MCC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 306 (Cardiac Congenital and Valvular Disorders with MCC, relative weight 1.546) and DRG 307 (Cardiac Congenital and Valvular Disorders without MCC, relative weight 0.9148), in MDC 05 (Diseases and Disorders of the Circulatory System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It is exempt from present-on-admission (POA) reporting, so no POA indicator is required.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 746.7 (Hypoplastic left heart syndrome).