Cardiologists weigh in on new definition of 'myocardial infarction'

Major cardiology associations joined forces to define and standardize what exactly constitutes a heart attack, differentiating between myocardial infarction (MI) and “myocardial injury” while offering guidance on how to incorporate emerging imaging techniques and high-sensitivity troponin assays.

The fourth universal definition of MI was announced at the European Society of Cardiology (ESC) Congress in Munich and published online in the European Heart Journal. An update of the third universal definition of MI released in 2012, it was based on the work of a task force featuring healthcare professionals and cardiologists from the ESC, American College of Cardiology (ACC), American Heart Association and World Heart Federation.

Three cardiologists who commented to Cardiovascular Business on the definition singled out the new section highlighting the difference between MI and myocardial injury without acute ischemia. Both may result in a troponin reading above the 99th percentile upper reference limit—which has traditionally been used to rule-in or rule-out MI—but only certain cases represent heart attacks.

Richard Chazal, MD, medical director of the Heart and Vascular Institute at Lee Health in Fort Myers, Florida, said he plans to use the document to educate emergency department physicians, hospitalists and cardiologists. Specifically, figure 6 is an easy-to-follow chart which clinicians may use to distinguish between type 1 MI, type 2 MI, acute myocardial injury and chronic myocardial injury—all of which could have troponin values above the 99th percentile upper reference limit.

“There’s been a tendency in the past to say elevated troponin means a heart attack and this helps further clarify that’s not the case,” Chazal said. “Elevated troponin means something is going on the myocardium and it’s up to you to combine that along with clinical information to actually make the real diagnosis. In a way, it’s a throwback to ‘use your clinical judgment,’ so I think it’s really helpful.”

Properly diagnosing and coding for these conditions becomes increasingly important with patient outcomes being monitored more closely as part of value-based payment models, Chazal said. And ruling out acute MI earlier could save patients from expensive and unnecessary clinical testing when they aren’t at high risk in the short term.

“That doesn’t mean they aren’t going to be followed up for further evaluation but it means they may be saved additional workup that might not change their outcomes early in the course of their event,” Chazal said.

Salim Hayek, MD, and Richard Kovacs, MD, both noted the new definition of MI may be more helpful for members of the care team other than cardiologists.

“The decision making is complex, and the role of the practicing cardiologist is not only to implement the definition in their own clinical practice, but to succinctly communicate the new definitions to other members of the cardiovascular care team and non-cardiologists who may be making decisions on patients with acute coronary syndromes,” Kovacs, an Indianapolis-based cardiologist and vice president of the ACC, said in an email. “I would not simplify the document, but we need to simply communicate the concepts.”

Added Hayek, an assistant professor at the University of Michigan Frankel Cardiovascular Center: “The universal definition now provides a more standardized and improved reflection of cardiologists’ long-standing approach to assessing cardiac injury. Thus, while it may not change the cardiologist’s process, it is tremendously helpful for non-cardiologist physicians on the front lines of managing chest pain such as internists, emergency department physicians and family physicians, as well as nurse practitioners and physician assistants, in contextualizing and interpreting elevations in cardiac enzymes.”

Both physicians said there are still hurdles to incorporating new-generation troponin assays into local practices, including identifying where they fit into the workflow and the most cost-effective usage strategies.

Kovacs noted the concept of myocardial injury “will allow for a more nuanced classification of these patients,” but must be aligned with coding efforts in the hospital.

“I think the larger issues will be at the system level, where our clinical registries, such as the NCDR-Chest Pain-MI registry will be increasingly important to track any changes in the patterns of care,” Kovacs said.