Updated on: March 14, 2016

Lessons Learned About ICD-10 Cardiology Diagnosis Coding

Original story posted on: August 23, 2013

As many of us have started delving into ICD-10-CM diagnosis coding, we have realized there are many lessons to be learned from the coding of these same disorders currently used in ICD-9-CM. We soon realize the ICD-10-CM coding system has expanded significantly in the specificity of codes and changes made to include new combination codes.


We also recognize how the coding of these disorders in ICD-10-CM may further impact the reimbursement received for a hospital inpatient stay.  I wanted to share a few of the lessons I have learned while performing audits that include cardiology diagnosis codes.


  • The terms of “accelerated” and “malignant” are now considered nonessential modifiers for the disease of hypertension. Nonessential modifiers are terms within the parentheses that are used in both the Alphabetic Index and Tabular List to enclose supplementary words that may be present or absent in the statement of a disorder or procedure without affecting the code number to which it is assigned.

Atrial Fibrillation and Atrial Flutter

  • Specificity for atrial fibrillation includes paroxysmal, persistent, and chronic or permanent.  The further specificity of persistent as a secondary disorder may now affect the MS-DRG assignment.
  • Atrial flutter is also further specified as typical or type I and atypical or type II.


  • The term “congestive” is no longer considered a nonessential modifier and now has a specific code to describe congestive cardiomyopathy.
  • Dilated cardiomyopathy is also a new subterm.  This diagnosis has also been assigned the same diagnosis code as congestive cardiomyopathy (I42.0).
  • The further specificity of congestive and dilated cardiomyopathy as a secondary disorder may now affect the MS-DRG assignment.

Supraventricular Tachycardia

  • Supraventricular tachycardia, unspecified, has been reassigned from a code description of other specified cardiac dysrhythmia in ICD-9-CM (code 427.89) to the code descriptor of supraventricular tachycardia in ICD-10-CM with the code assignment of I47.1. This code is recognized as a complication or comorbidity (CC) secondary diagnosis in ICD-10-CM.

Heart Failure

  • The term “congestive” is now considered a nonessential modifier with systolic, diastolic, or combined systolic and diastolic heart failure. The coding of these disorders will now require only one code to describe the specificity and the acuity of the heart failure.  An additional code of congestive heart failure is no longer required.

Combined Right and Left Bundle Branch Block

  • The prior three code choices in ICD-9-CM for combined right and left bundle branch block have been assigned to one code in ICD-10-CM. 
  • Right bundle branch block and left posterior fascicular block (code 426.51), right bundle branch block and left anterior fascicular block (code 426.52), and bilateral bundle branch block (code 426.53) have all been assigned to ICD-10-CM diagnosis code I45.2, bifascicular block. 
  • This change in code assignment now classifies all three of these prior specified disorders as a complication or comorbidity (CC) secondary diagnosis in ICD-10-CM.


  • The ICD-9-CM tabular listing for angina diagnoses is included in the code block of ischemic heart disease with a subsection titled other “acute and subacute forms of ischemic heart disease.”  Acute coronary syndrome and postinfarction angina is also included in this subsection. 
  • The ICD-10-CM tabular listing for angina diagnoses is also included in the code block of ischemic heart disease, as is acute coronary syndrome and postinfarction angina.  However, the subsection for angina disorders is now titled “angina pectoris,” the subsection for acute coronary syndrome is now classified as “other acute ischemic heart disease,” and the subsection for postinfarction angina is now classified as “certain current complications following myocardial infarction.” 
  • There is a designated code in ICD-10-CM that describes postinfarction angina (I23.7).  
  • Per the tabular note, postinfarction angina must be used in conjunction with a code from the category of acute myocardial infarction or the category of subsequent myocardial infarction. The coding of this disorder may affect the MS-DRG assignment.

Coronary Artery Disease

  • ICD-10-CM coding guideline Section I. C. 9. b. addresses the causal relationship that can be assumed in a patient with both atherosclerosis and angina pectoris unless the documentation indicates the angina is due to something other than atherosclerosis. This is the same as in ICD-9-CM coding; however, in ICD-10-CM there are combination codes for this scenario instead of assigning the two codes required in ICD-9-CM. 
  • Specificity relates to the type of coronary artery such as native, autologous vein bypass graft, autologous artery bypass graft, nonautologous biological bypass graft, native artery of transplanted heart, and bypass graft of transplanted heart.
  • The specificity of the angina can also be identified.  
  • One diagnosis code will be assigned in ICD-10-CM to include both the coronary artery disease and the identified angina.

Myocardial Infarction

  • ST elevation myocardial infarction is the default for the unspecified term of “acute myocardial infarction.” 
  • For encounters occurring while the myocardial infarction is equal to, or less than, four weeks old(change from 8 weeks), and the patient requires continued care for the myocardial infarction, codes from the category of myocardial infarction may continue to be assigned.
  • The definition of subsequent myocardial infarction has changed.  A code from the category of subsequent myocardial infarction is to be used when a patient who has suffered an acute myocardial infarction has a new myocardial infarction within the four-week time frame of the initial myocardial infarction.  A code from the category of myocardial infarction must be used in conjunction with a code from the subsequent myocardial infarction category.  The sequencing of these codes will depend upon the circumstances of the encounter.

The above are included in the ICD-10-CM coding guideline Section I. C. 9. e. titled acute myocardial infarction.   

Disclaimer: Every reasonable effort was made to ensure the accuracy of this information at the time it was published. However, due to the nature of industry changes over time we cannot guarantee its validity after the year it was published.
Lynn Cleasby, RHIT, AHIMA-Approved ICD-10-CM/PCS Trainer

Lynn’s expertise includes inpatient HIM coding audits and coding staff training. She also performs CDIP analysis and CDIP staff and Physician training projects. She is also an AHIMA certified ICD-10 Trainer.