Experts redefine post-revascularization MI

An expert panel recommended changing the definition of an MI after coronary revascularization to incorporate what the cardiologists defined as a more clinically relevant MI. “We need to make sure that what we measure makes an impact on clinical outcomes,” lead author Issam D. Moussa, MD, explained in an interview with Cardiovascular Business.

The Society for Cardiovascular Angiography and Interventions convened a panel of experts to examine the definitions of MI after PCI or CABG with the goal of providing a standardized definition that was patient-centered and evidence-based. The universal definition that was proposed in 2007 and revised in 2012 is based on measures of the biomarker cardiac troponin. The SCAI panel instead recommends focusing on another protein, CK-MB, which, like troponin, is released when heart muscles cells are damaged.

“The society a few years back looked at the universal definition and saw many opportunities for improvements,” said Moussa, who is chair of the cardiovascular disease division at the Mayo Clinic in Jacksonville, Fla. “Does the existing definition mean something to the patient in the long term and were the data used to back up the definition sufficiently evidence- based?”

The universal definition identifies a PCI-related MI as an increase in troponin that is five times the norm within 48 hours of the procedure and other evidence such as chest pain. In CABG, the increase was set at a tenfold increase. Troponin is a more sensitive and specific biomarker than CK-MB, but post-procedure it also may not reflect damage that influences short- or long-term survival.

“Even though it makes clinical sense, there is not much evidence that using a threshold of five times only is associated with a bad prognosis in the long or short term,” he said.

The panel found a large body of evidence on CK-MB, which is less sensitive than troponin. In the context of post-PCI or post-CABG, when it is abnormal it indicates a level of damage to the heart muscle that may impact the patient’s life.

The new definition identifies a post-PCI elevation of CK-MB of 10 times the norm as clinically relevant in most cases. Recognizing that many hospitals no longer do CK-MB measurements, they provided a troponin equivalent of an increase of 70 times the norm.

Moussa emphasized that the evidence that associated elevated CK-MB levels with prognosis did not include angiographic variables, so neither did their definition. “We are not saying these are not important; they are very important clinical criteria,” he said. “But the current evidence that is published has not accounted for [them].”

Moussa said that by providing the new definition, he and his colleagues hoped to open the conversation over a standardized definition. He said the next step is to design and conduct clinical trials to compare the universal and new definitions as well as increase efforts to collect related data.   

The consensus document and proposed new definition was published online Oct. 14 simultaneously in Catheterization and Cardiovascular Interventions and the Journal of the American College of Cardiology