ACDIS insight: Unpacking the fifth universal definition of MI

by Kelly Rice, RN, BSN, MSHI, CCDS, CDIP, CCS, CRC

In August 2026, the European Society of Cardiology, the American College of Cardiology, the American Heart Association, and the World Health Federation released an update for the Fifth Universal Definition of Myocardial Infarction (MI). which replaces the fourth generation of acute MI (AMI) which was released in 2018. In this new definition, they replaced the previous AMI 1-5 classification with a simplified version.

The objective of the update was said to improve the diagnostic consistency and guide decisions about treatment for providers involved in the care. It is also intended to enhance patient understanding and research focused on diagnosis. AMIs will now be assigned to three categories:

• Primary MI
• Secondary MI
• Procedural MI

A primary MI is a spontaneous MI that is attributable to an acute coronary artery problem like a plaque rupture and spontaneous coronary artery dissection (SCAD), vasospasm, coronary embolism, restenosis, stent thrombosis, or graft failure more than 30 days from procedure. This will now reclassify AMIs that result as late stent or graft failure as de novo disease and not as complication of a procedure.  

A secondary MI will be inclusive of those that result from an oxygen supply-demand mismatch from another acute condition, obstructive coronary artery disease without coronary pathology, and/or regional motion wall abnormality that is either new or presumed to be new or absence of viable myocardium. Under the fourth universal definition, a type 3 AMI is one in which an AMI is suspected but diagnostic confirmation is unable to be made due to patient expiration; this type will not have a designated type under the new definition, but classification would be based upon the setting or post-mortem findings. 

Procedure-related MIs, as one would expect, are MIs that occur within 30 days of a cardiac procedure. This will replace the previous types 4 and 5 AMI categories.  

One of the other most notable changes is the update of the term MINOCA, which previously stood for Myocardial Infarction with Non-Obstructive Coronary Arteries. In the fifth universal definition, the “I” now represents “injury” rather than “infarction,” since it has been discovered that patients are more often experiencing an event such as Takotsubo syndrome, cardiomyopathy, or a pulmonary embolism rather than an AMI. If a patient is indeed found to have an acute myocardial infarction it would then be classified into one of the three types (primary, secondary, or procedure-related). 

The task force is working in collaboration with the World Health Organization (WHO) on the proposed ICD-11 codes which are currently under review. Over a dozen countries around the world including Canada, Japan, Australia, Sweden, are already using ICD-11 and about 50 others are conducting or expanding pilot studies. The United States, however, continues to use ICD-10 and there is currently no date set for when the transition will occur. It’s uncertain how the new changes, particularly the reclassification of AMIs, will impact accurate data capture and applicable quality reporting.

Coders and CDI specialists may need to clarify the documentation if provider descriptions to not align with the most appropriate ICD-10 codes. Organizations may wish to consider creating standardized policies and procedures on AMI to help eliminate issues that may arise as a result of the new changes.  

Editor’s note: Rice is a CDI education specialist at ACDIS/HCPro. Contact her at Kelly.rice@hcpro.com.