What is the ICD-10 (International Classification of Diseases, 10th Revision) code for mitral valve thickening associated with mitral stenosis?

ICD-10 Code for Mitral Valve Thickening

The ICD-10 code for mitral valve thickening associated with mitral stenosis is I05.0 (rheumatic mitral stenosis) or I34.2 (nonrheumatic mitral valve stenosis), depending on the underlying etiology.

Code Selection Based on Etiology

Rheumatic Mitral Stenosis (I05.0)

• Use I05.0 when mitral valve thickening occurs in the context of rheumatic heart disease, which accounts for 85% of all mitral stenosis cases worldwide and involves commissural fusion with thickening at the leaflet tips 1.
• Rheumatic mitral stenosis is characterized by specific morphological features including anterior mitral valve leaflet thickening, chordal thickening, restricted leaflet motion, and commissural fusion 2.
• The World Heart Federation criteria define pathological valve thickening in rheumatic disease with age-specific cutoffs: ≥3 mm for individuals aged 0-19 years, ≥4 mm for those aged 20-39 years, and ≥5 mm for those aged ≥40 years 3.

Nonrheumatic (Degenerative) Mitral Stenosis (I34.2)

• Use I34.2 for degenerative or calcific mitral stenosis, which is increasingly prevalent in elderly patients in developed countries and results from mitral annular calcification with valve thickening and chordal shortening 1, 4.
• Degenerative mitral stenosis involves extensive annular calcification and thickening at the base of leaflets without associated commissural fusion, distinguishing it from rheumatic disease 4.
• This form predominantly affects the posterior mitral valve leaflet first, with relative preservation of anterior leaflet mobility 3.

Clinical Context for Accurate Coding

Key Distinguishing Features

• Rheumatic disease presents with commissural fusion and symmetric leaflet involvement, typically in younger patients with a history of rheumatic fever 3.
• Degenerative disease shows mitral annular calcification without commissural fusion, occurring in older patients without rheumatic history 5.
• The European Society of Cardiology emphasizes that echocardiographic assessment using planimetry and pressure half-time methods is essential for quantifying severity and determining the underlying pathology 3.

Severity Grading Impact on Coding

• Severe mitral stenosis is defined as mitral valve area ≤1.0 cm² with mean transmitral gradient ≥10 mmHg 1.
• The Wilkins scoring system grades valve thickening from 1 (leaflets near normal at 4-5 mm) to 4 (considerable thickening >8-10 mm), which helps determine treatment approach but does not change the primary ICD-10 code 3.

Common Coding Pitfalls to Avoid

• Do not use I34.8 (other nonrheumatic mitral valve disorders) for isolated valve thickening with stenosis—this code is reserved for mitral valve disorders that don't fit other specific categories 3.
• Avoid coding mitral valve prolapse (I34.1) when thickening causes stenosis rather than regurgitation, as the American Heart Association notes that mitral valve prolapse with thickening increases stroke risk but represents a distinct pathophysiologic entity 3.
• Do not confuse mitral valve thickening from artificial chordae (a complication requiring different coding) with primary valvular disease 6.

Documentation Requirements

• Ensure clinical documentation specifies whether the mitral valve thickening is rheumatic or nonrheumatic in origin 3.
• Document the presence or absence of commissural fusion, as this distinguishes rheumatic (I05.0) from degenerative (I34.2) stenosis 4, 5.
• Include echocardiographic measurements of valve area and mean gradient to support the stenosis diagnosis 3, 1.