Convert to ICD-10-CM: 
421.0 converts approximately to:
- 2015/16 ICD-10-CM I33.0 Acute and subacute infective endocarditis
 ICD-9-CM Volume 2 Index entries containing back-references to 
421.0:
- Aneurysm (anastomotic) (artery) (cirsoid) (diffuse) (false) (fusiform) (multiple) (ruptured) (saccular) (varicose) 442.9  brain 437.3 brain 437.3   arteriosclerotic 437.3 arteriosclerotic 437.3    ruptured (see also Hemorrhage, subarachnoid) 430 ruptured (see also Hemorrhage, subarachnoid) 430 
 
  arteriovenous 747.81 arteriovenous 747.81    acquired 437.3 acquired 437.3     ruptured (see also Hemorrhage, subarachnoid) 430 ruptured (see also Hemorrhage, subarachnoid) 430 
 
   ruptured (see also Hemorrhage, subarachnoid) 430 ruptured (see also Hemorrhage, subarachnoid) 430 
 
  berry (congenital) (ruptured) (see also Hemorrhage, subarachnoid) 430 berry (congenital) (ruptured) (see also Hemorrhage, subarachnoid) 430 
  congenital 747.81 congenital 747.81    ruptured (see also Hemorrhage, subarachnoid) 430 ruptured (see also Hemorrhage, subarachnoid) 430 
 
  meninges 437.3 meninges 437.3    ruptured (see also Hemorrhage, subarachnoid) 430 ruptured (see also Hemorrhage, subarachnoid) 430 
 
  miliary (congenital) (ruptured) (see also Hemorrhage, subarachnoid) 430 miliary (congenital) (ruptured) (see also Hemorrhage, subarachnoid) 430 
  mycotic 421.0 mycotic 421.0   ruptured (see also Hemorrhage, subarachnoid) 430 ruptured (see also Hemorrhage, subarachnoid) 430 
 
  nonruptured 437.3 nonruptured 437.3 
  ruptured (see also Hemorrhage, subarachnoid) 430 ruptured (see also Hemorrhage, subarachnoid) 430 
  syphilitic (hemorrhage) 094.87 syphilitic (hemorrhage) 094.87 
  traumatic - see Injury, intracranial traumatic - see Injury, intracranial
 
  endocardial, infective (any valve) 421.0 endocardial, infective (any valve) 421.0
  infective (any valve) 421.0 infective (any valve) 421.0
  mycotic, any site 421.0 mycotic, any site 421.0  without endocarditis - see Aneurysm, by site without endocarditis - see Aneurysm, by site
  ruptured, brain (see also Hemorrhage, subarachnoid) 430 ruptured, brain (see also Hemorrhage, subarachnoid) 430 
 
 
- Endocarditis (chronic) (indeterminate) (interstitial) (marantis) (nonbacterial thrombotic) (residual) (sclerotic) (sclerous) (senile) (valvular) 424.90  aortic (heart) (nonrheumatic) (valve) 424.1 aortic (heart) (nonrheumatic) (valve) 424.1   with with   mitral (valve) disease 396.9 mitral (valve) disease 396.9     active or acute 391.1 active or acute 391.1      with chorea (acute) (rheumatic) (Sydenham's) 392.0 with chorea (acute) (rheumatic) (Sydenham's) 392.0 
     bacterial 421.0 bacterial 421.0
 
 
   rheumatic fever (conditions classifiable to 390 rheumatic fever (conditions classifiable to 390 ) )    active - see Endocarditis, acute, rheumatic active - see Endocarditis, acute, rheumatic
    inactive or quiescent (with chorea) 395.9 inactive or quiescent (with chorea) 395.9      with mitral disease 396.9 with mitral disease 396.9 
 
 
 
  acute or subacute 421.9 acute or subacute 421.9 
  arteriosclerotic 424.1 arteriosclerotic 424.1 
  congenital 746.89 congenital 746.89 
  hypertensive 424.1 hypertensive 424.1 
  rheumatic (chronic) (inactive) 395.9 rheumatic (chronic) (inactive) 395.9    with mitral (valve) disease 396.9 with mitral (valve) disease 396.9     active or acute 391.1 active or acute 391.1      with chorea (acute) (rheumatic) (Sydenham's) 392.0 with chorea (acute) (rheumatic) (Sydenham's) 392.0 
 
 
   active or acute 391.1 active or acute 391.1     with chorea (acute) (rheumatic) (Sydenham's) 392.0 with chorea (acute) (rheumatic) (Sydenham's) 392.0 
 
 
  specified cause, except rheumatic 424.1 specified cause, except rheumatic 424.1 
  syphilitic 093.22 syphilitic 093.22 
 
  bacterial (acute) (any valve) (chronic) (subacute) 421.0 bacterial (acute) (any valve) (chronic) (subacute) 421.0
  constrictive 421.0 constrictive 421.0
  due to due to
  infectious or infective (acute) (any valve) (chronic) (subacute) 421.0 infectious or infective (acute) (any valve) (chronic) (subacute) 421.0
  lenta (acute) (any valve) (chronic) (subacute) 421.0 lenta (acute) (any valve) (chronic) (subacute) 421.0
  Loeffler's (parietal fibroplastic) 421.0 Loeffler's (parietal fibroplastic) 421.0
  malignant (acute) (any valve) (chronic) (subacute) 421.0 malignant (acute) (any valve) (chronic) (subacute) 421.0
  mitral (chronic) (double) (fibroid) (heart) (inactive) (valve) (with chorea) 394.9 mitral (chronic) (double) (fibroid) (heart) (inactive) (valve) (with chorea) 394.9   with with   aortic (valve) disease 396.9 aortic (valve) disease 396.9     active or acute 391.1 active or acute 391.1      with chorea (acute) (rheumatic) (Sydenham's) 392.0 with chorea (acute) (rheumatic) (Sydenham's) 392.0 
 
 
   rheumatic fever (conditions classifiable to 390 rheumatic fever (conditions classifiable to 390 ) )    active - see Endocarditis, acute, rheumatic active - see Endocarditis, acute, rheumatic
    inactive or quiescent (with chorea) 394.9 inactive or quiescent (with chorea) 394.9      with aortic valve disease 396.9 with aortic valve disease 396.9 
 
 
 
  active or acute 391.1 active or acute 391.1    with chorea (acute) (rheumatic) (Sydenham's) 392.0 with chorea (acute) (rheumatic) (Sydenham's) 392.0 
   bacterial 421.0 bacterial 421.0
 
  arteriosclerotic 424.0 arteriosclerotic 424.0 
  congenital 746.89 congenital 746.89 
  hypertensive 424.0 hypertensive 424.0 
  nonrheumatic 424.0 nonrheumatic 424.0 
  syphilitic 093.21 syphilitic 093.21 
 
  mycotic (acute) (any valve) (chronic) (subacute) 421.0 mycotic (acute) (any valve) (chronic) (subacute) 421.0
  pneumococcic (acute) (any valve) (chronic) (subacute) 421.0 pneumococcic (acute) (any valve) (chronic) (subacute) 421.0
  purulent (acute) (any valve) (chronic) (subacute) 421.0 purulent (acute) (any valve) (chronic) (subacute) 421.0
  septic (acute) (any valve) (chronic) (subacute) 421.0 septic (acute) (any valve) (chronic) (subacute) 421.0
  streptococcal (acute) (any valve) (chronic) (subacute) 421.0 streptococcal (acute) (any valve) (chronic) (subacute) 421.0
  suppurative (any valve) (acute) (chronic) (subacute) 421.0 suppurative (any valve) (acute) (chronic) (subacute) 421.0
  ulcerative (acute) (any valve) (chronic) (subacute) 421.0 ulcerative (acute) (any valve) (chronic) (subacute) 421.0
  vegetative (acute) (any valve) (chronic) (subacute) 421.0 vegetative (acute) (any valve) (chronic) (subacute) 421.0
 
- Infection, infected, infective (opportunistic) 136.9  endocardium (see also Endocarditis) 421.0 endocardium (see also Endocarditis) 421.0
 
- Löffler's endocarditis 421.0 endocarditis 421.0
 
- Node(s) - see also Nodules Osler's 421.0 Osler's 421.0
 
- Osler's nodes 421.0 nodes 421.0
 
- SBE (subacute bacterial endocarditis) 421.0
- Ulcer, ulcerated, ulcerating, ulceration, ulcerative 707.9  endocarditis (any valve) (acute) (chronic) (subacute) 421.0 endocarditis (any valve) (acute) (chronic) (subacute) 421.0
  valve, heart 421.0 valve, heart 421.0
 
- Vegetation, vegetative endocarditis (acute) (any valve) (chronic) (subacute) 421.0 endocarditis (acute) (any valve) (chronic) (subacute) 421.0
  heart (mycotic) (valve) 421.0 heart (mycotic) (valve) 421.0