Specific code 2015 ICD-9-CM Diagnosis Code 421.9
Acute endocarditis, unspecified
  • 2015
  • Billable Thru Sept 30/2015
  • Non-Billable On/After Oct 1/2015

  • ICD-9-CM 421.9 is a billable medical code that can be used to indicate a diagnosis on a reimbursement claim, however, 421.9 should only be used for claims with a date of service on or before September 30, 2015. For claims with a date of service on or after October 1, 2015, use an equivalent ICD-10-CM code (or codes).
Convert to ICD-10-CM: 421.9 converts directly to:
  • 2015/16 ICD-10-CM I33.9 Acute and subacute endocarditis, unspecified
Approximate Synonyms
  • Acute endocarditis
  • Acute endocarditis (infection of heart valve)
  • Acute nonbacterial endocarditis
  • Endocarditis (infection of heart valve), subacute
  • Endocarditis, acute
  • Endocarditis, nonbacterial, acute
  • Endocarditis, subacute
  • Subacute endocarditis
  • Subacute endocarditis (infection of heart valve)
Clinical Information
  • Acute inflammation of the endocardium. Bacteria is the usual etiologic agent, and the distinction between "acute" and "subacute" has traditionally been made based on the pathogenic organism and clinical presentation
421.9 Excludes
  • acute rheumatic endocarditis (391.1)
Applies To
  • Endocarditis, acute or subacute
  • Myoendocarditis, acute or subacute
  • Periendocarditis, acute or subacute
ICD-9-CM Volume 2 Index entries containing back-references to 421.9:
  • Endocarditis (chronic) (indeterminate) (interstitial) (marantic) (nonbacterial thrombotic) (residual) (sclerotic) (sclerous) (senile) (valvular) 424.90
    • acute or subacute 421.9
      • rheumatic (aortic) (mitral) (pulmonary) (tricuspid) 391.1
        • with chorea (acute) (rheumatic) (Sydenham's) 392.0
    • aortic (heart) (nonrheumatic) (valve) 424.1
      • with
        • mitral (valve) disease 396.9
          • active or acute 391.1
            • with chorea (acute) (rheumatic) (Sydenham's) 392.0
            • bacterial 421.0
        • rheumatic fever (conditions classifiable to 390)
          • active - see Endocarditis, acute, rheumatic
          • inactive or quiescent (with chorea) 395.9
            • with mitral disease 396.9
      • acute or subacute 421.9
      • arteriosclerotic 424.1
      • congenital 746.89
      • hypertensive 424.1
      • rheumatic (chronic) (inactive) 395.9
        • with mitral (valve) disease 396.9
          • active or acute 391.1
            • with chorea (acute) (rheumatic) (Sydenham's) 392.0
        • active or acute 391.1
          • with chorea (acute) (rheumatic) (Sydenham's) 392.0
      • specified cause, except rheumatic 424.1
      • syphilitic 093.22
    • mitral (chronic) (double) (fibroid) (heart) (inactive) (valve) (with chorea) 394.9
      • with
        • aortic (valve) disease 396.9
          • active or acute 391.1
            • with chorea (acute) (rheumatic) (Sydenham's) 392.0
        • rheumatic fever (conditions classifiable to 390)
          • active - see Endocarditis, acute, rheumatic
          • inactive or quiescent (with chorea) 394.9
            • with aortic valve disease 396.9
      • active or acute 391.1
        • with chorea (acute) (rheumatic) (Sydenham's) 392.0
        • bacterial 421.0
      • arteriosclerotic 424.0
      • congenital 746.89
      • hypertensive 424.0
      • nonrheumatic 424.0
        • acute or subacute 421.9
      • syphilitic 093.21
    • pulmonary (chronic) (heart) (valve) 424.3
      • with
        • rheumatic fever (conditions classifiable to 390)
          • active - see Endocarditis, acute, rheumatic
          • inactive or quiescent (with chorea) 397.1
      • acute or subacute 421.9
        • rheumatic 391.1
          • with chorea (acute) (rheumatic) (Sydenham's) 392.0
      • arteriosclerotic or due to arteriosclerosis 424.3
      • congenital 746.09
      • hypertensive or due to hypertension (benign) 424.3
      • rheumatic (chronic) (inactive) (with chorea) 397.1
        • active or acute 391.1
          • with chorea (acute) (rheumatic) (Sydenham's) 392.0
      • syphilitic 093.24
    • toxic (see also Endocarditis, acute) 421.9
    • tricuspid (chronic) (heart) (inactive) (rheumatic) (valve) (with chorea) 397.0
      • with
        • rheumatic fever (conditions classifiable to 390)
          • active - see Endocarditis, acute, rheumatic
          • inactive or quiescent (with chorea) 397.0
      • active or acute 391.1
        • with chorea (acute) (rheumatic) (Sydenham's) 392.0
      • arteriosclerotic 424.2
      • congenital 746.89
      • hypertensive 424.2
      • nonrheumatic 424.2
        • acute or subacute 421.9
      • specified cause, except rheumatic 424.2
      • syphilitic 093.23
  • Myoendocarditis - see also Endocarditis
    • acute or subacute 421.9
  • Periendocarditis (see also Endocarditis) 424.90
    • acute or subacute 421.9
ICD-9-CM codes are used in medical billing and coding to describe diseases, injuries, symptoms and conditions. ICD-9-CM 421.9 is one of thousands of ICD-9-CM codes used in healthcare. Although ICD-9-CM and CPT codes are largely numeric, they differ in that CPT codes describe medical procedures and services. Can't find a code? Start at the root of ICD-9-CM, check the 2015 ICD-9-CM Index or use the search engine at the top of this page to lookup any code.