ICD-10 essentials for busy cardiologists who would rather be doing something else

Angina, chest pain, coronary artery disease, acute MI, atrial fib, CHF, mitral and aortic valve disease. These are the bread and butter and jam of cardiology practice. ICD-10 makes documentation and coding for cardiology easier and more efficient. The updated codes contain useful combinations of conditions and use current clinical definitions. I will only highlight a few in this blog — combination codes for coronary artery disease with angina, acute MI codes, and the updated classification of valve disease. For a discussion of CHF coding and documentation in ICD-10, see my earlier blog on this subject.

Coronary artery disease with angina
Under ICD-10, when a patient presents with known CAD and current angina, one code will cover it. This type of combination code comes in several varieties, depending on whether you document unstable angina or just plain angina. Here is an unstable angina example.

I25.110 Atherosclerotic heart disease of native coronary artery with unstable angina pectoris


414.01 Coronary atherosclerosis of native coronary artery


411.1 Intermediate coronary syndrome

Just as with ICD-9, if the patient has a history of CABG and has developed CAD in a bypass graft, it can be coded according to the source of the graft material, for example, I25.710 Atherosclerosis of autologous vein coronary artery bypass graft(s) with unstable angina pectoris. And all these varieties of CAD classification also have “non-combination” codes for CAD patients presenting without current angina, such as I25.810 Atherosclerosis of coronary artery bypass graft(s) without angina pectoris.

Acute MI codes
The classification of myocardial infarction has been updated in three key ways:

  • the duration of treatment considered the “acute” phase is four weeks instead of eight weeks;
  • subsequent episode of care codes for acute MI have been discontinued; and
  • unique codes exist for distinguishing a new acute MI that occurs while a patient is still under treatment for an acute MI.

ICD-10-CM has adopted a new definition of acute MI from the World Health Organization, which shortened the “acute phase” of an MI from eight weeks to four weeks. No doubt this change was made to better reflect the efficacy of current methods of treating heart attack patients.

In addition, the whole group of ICD-9 codes for “subsequent episode of care for acute MI” has been discontinued in ICD-10-CM. This gets rid of an arbitrary distinction between the very first visit for treatment of an acute MI, and all visits thereafter (as if everything important happens in the first visit or it doesn’t happen at all). In ICD-10, an acute MI gets  the same ICD-10 code for the entire four weeks in which the MI is in its acute phase and still under serious treatment, as in the example below of a patient diagnosed with a STEMI involving the LAD.

I21.02 ST elevation (STEMI) myocardial infarction involving left anterior descending coronary artery


ICD-9 First visit  
410.11 Acute myocardial infarction of other anterior wall, initial episode of care

ICD-9 All other visits 
410.12 Acute myocardial infarction of other anterior wall, subsequent episode of care

In ICD-10, the use of the word “subsequent” in acute MI codes takes on a different meaning. It means a new acute MI within four weeks of a previous MI. This is a whole new axis of classification in ICD-10 that can be used to unambiguously code serial acute MI’s within the four weeks of each other. So, for example, if a patient had an acute anterior wall STEMI two weeks ago, and presents with a new, acute anterior wall STEMI, the encounter can be coded as below in ICD-10, without any additional documentation.

I21.09 ST elevation (STEMI) myocardial infarction involving other coronary artery of anterior wall


I22.0 Subsequent ST elevation (STEMI) myocardial infarction of anterior wall

Heart valve disease
Coding valve disease in ICD-9 was a royal pain. The default classification of some valve disorders was the rheumatic kind and other valve disorders defaulted to the non-rheumatic kind. You couldn’t always tell from the code descriptions which was which. All kinds of coding advice had to be issued over the years to try and keep the data in decent shape.

Valve disorders from rheumatic fever may have been all the rage when ICD-9 was developed in the 1960’s and released in the 1970’s, but it has not been the primary cause of valvular heart disease for many moons now, so ICD-10 reflects that reality. Rheumatic valve disorders reside in categories I05-I08, and they all say “rheumatic” in the code title. Non-rheumatic valve disorders reside in categories I34-I37, and they all say “non-rheumatic” in the code title. Examples are below.

I05.0 Rheumatic mitral stenosis  


394.0 Mitral stenosis

I34.0 Nonrheumatic mitral (valve) insufficiency  
I34.1 Nonrheumatic mitral (valve) prolapse  
I34.2 Nonrheumatic mitral (valve) stenosis


424.0 Mitral valve disorders 

All in all, conditions that are central to the practice of cardiology are more straightforward to code and the codes better reflect current clinical understanding. The only tricky bit, if there is one, is to remember that subsequent in an ICD-10 code refers to a new, acute MI within four weeks of a previous MI.

Rhonda Butler is a senior clinical research analyst with 3M Health Information Systems. She is responsible for the development and maintenance of the ICD-10 Procedure Coding System since 2003 under contract to CMS, and for the development and maintenance of the ICD-10 General Equivalence Mappings (GEMs) and Reimbursement Mappings under contract to CMS and the CDC.  She leads the 3M test project to convert the MS-DRGs to ICD-10 for CMS, and is on the team to convert 3M APR-DRGs to ICD-10. Rhonda also writes for the 3M Health Information Systems blog.