American Heart Month—Coding Heart Disease

by Melanie Endicott

February is American Heart Month, a time when the media is full of information geared toward awareness and prevention of heart disease. According to the Heart Disease and Stroke Statistics—2014 Update report from the American Heart Association:

  • The total number of inpatient cardiovascular operations and procedures increased from 5,939,000 in 2000 to 7,588,000 in 2010
  • The total cost (including physician and other professional fees, hospital services, medication, home healthcare, and lost productivity) of cardiovascular disease and stroke in the United States for 2010 was estimated at $315.4 billion

With heart disease such a prevalent issue for the US healthcare industry, it is important for coders to master the guidelines and codes associated with heart disease in ICD-10-CM.

Chapter 9: Diseases of the Circulatory System (I00-I00) includes several important chapter-specific coding guidelines regarding the correct coding of hypertension, atherosclerotic coronary artery disease and angina, and acute myocardial infarction. A few highlights from the guidelines are shown below, but it is imperative that coders review these guidelines in their entirety.

Hypertension with Heart Disease (I.C.9.a.1)

There is a specific category within ICD-10-CM for hypertensive heart disease (I11). This category is only to be used when there is a causal relationship stated (i.e., due to hypertension) or implied (hypertensive). An additional code is assigned to describe the type of heart failure, if applicable.

Hypertensive Chronic Kidney Disease (I.C.9.a.2)

The ICD-10-CM category for hypertensive chronic kidney disease is I12. A code from this category can be assigned when both hypertension and a condition classifiable to category N18, Chronic kidney disease (CKD), are present. There is a presumed cause-and-effect relationship between CKD and hypertension in ICD-10-CM. An additional code is assigned to describe the stage of the chronic kidney disease.

Hypertensive Heart and Chronic Kidney Disease (I.C.9.a.3)

This guideline combines the rules from the two guidelines mentioned previously. To assign a code from this category, I13, Hypertensive heart and chronic kidney disease, there must be a stated relationship between the hypertension and heart disease, and there is an assumed relationship between chronic kidney disease and hypertension. Additional codes are assigned to describe the type of heart failure, if applicable, and the stage of the CKD.

Atherosclerotic Coronary Artery Disease and Angina (I.C.9.b)

There is a presumed cause-and-effect relationship between atherosclerosis and angina pectoris, unless the documentation states that the angina is due to another cause. There are two subcategories for these combination codes:

  • I25.11, Atherosclerotic heart disease of native coronary artery with angina pectoris
  • I25.7, Atherosclerosis of coronary artery bypass graft(s) and coronary artery of transplanted heart with angina pectoris

Acute Myocardial Infarction (I.C.9.e)

A few important points to remember:

  • If a Non-ST elevation myocardial infarction (NSTEMI) evolves to a ST elevation myocardial infarction (STEMI), assign only the STEMI code.
  • If a STEMI converts to a NSTEMI due to thrombolytic therapy, it is still coded as a STEMI.
  • A myocardial infarction remains acute for 4 weeks and is coded with a code from category I21, STEMI and NSTEMI myocardial infarction.
  • If a patient has a new AMI within the 4 week timeframe of the initial AMI, then a code from I22, Subsequent STEMI and NSTEMI myocardial infarction, is assigned.
  • A code from category I22 must be used in conjunction with a code from I21 and the sequencing depends on the circumstances of the encounter.

Now that we’ve reviewed some of the pertinent guidelines, let’s practice coding a few case studies.

Example Case 1

Patient is admitted with hypertensive congestive heart failure. The physician also documents that the patient has native coronary artery disease (CAD) and unstable angina. What diagnosis codes are assigned?

  • I11.0, Hypertensive heart disease with heart failure
  • I50.9, Heart failure, unspecified
  • I25.110, Atherosclerotic heart disease of native coronary artery with unstable angina pectoris

Rationale: A code from category I11 can be assigned since there is an implied (hypertensive) relationship between the hypertension and heart disease. An additional code is assigned to describe the type of heart failure. A combination code is assigned for the native CAD and unstable angina since a cause-and-effect relationship is assumed in ICD-10-CM.

Example Case 2

Patient had a NSTEMI of the anterior wall 2 weeks ago and is admitted today with another acute myocardial infarction (AMI) of the inferior wall. Patient also has hypertension and chronic kidney disease (CKD) stage 3. What diagnosis codes are assigned?

  • I22.1, Subsequent STEMI of inferior wall
  • I21.4, NSTEMI myocardial infarction
  • I12.9, Hypertensive chronic kidney disease with stage 1 through stage 4 chronic kidney disease, or unspecified chronic kidney disease
  • N18.3, Chronic kidney disease, stage 3 (moderate)

Rationale: This patient is having a subsequent AMI during the 4-week timeframe of the first AMI, so it is coded to category I22. A code from category I21 must still be assigned to indicate that the initial AMI is within the 4 weeks. There is a presumed cause-and-effect relationship between CKD and hypertension, therefore a code from category I12 is assigned along with a code from category N18 to indicate the stage of the CKD.


NCHS. ICD-10-CM Official Coding Guidelines for Coding and Reporting. 2014.

Melanie Endicott, MBA/HCM, RHIA, CDIP, CCS, CCS-P, FAHIMA, is senior director of HIM practice excellence, coding and CDI products development at AHIMA. She has over 15 years experience in HIM and coding, with her most recent focus being in ICD-10-CM/PCS, and has presented numerous times at the regional, state, and national levels on HIM and coding topics. She was previously a director of HIM practice excellence, focusing on coding products, resources, and education, at AHIMA. Melanie is an AHIMA-approved ICD-10-CM/PCS trainer and an ICD-10 Ambassador.

Original source:
Endicott, Melanie. "American Heart Month—Coding Heart Disease" (Journal of AHIMA website), February 12, 2014.