In reply: Problems with myocardial infarction definitions

In Reply: We thank Dr. Antonios for his comments regarding the current shortcomings of the ICD-9 and ICD-10 coding systems in describing the acute MI types as defined in the universal definition. We share his concern that accurate and consistent coding of MIs may be difficult when the definition of MI changes over a short period of time. Such changes create a disconnect not only between our clinical terminology and coding systems, but also potentially between our conventional sense of a “heart attack” as an acute coronary syndrome or a clinically significant infarction rather than a small troponin elevation from demand ischemia. This has consequences not only for quality measures and reporting, but also for clinical research trials and clinical care. This is exemplified by reports of recent trials that were possibly prematurely discontinued, as the use of troponin thresholds may conflate large MIs with clinically insignificant ones.¹

Recently, the Society for Cardiovascular Angiography and Interventions published a new definition of “clinically relevant” MI after revascularization.² Rather than relying on troponins, which are elevated in as many as 24.3% of uncomplicated percutaneous coronary interventions and in 42% to 82% of uncomplicated coronary artery bypass grafting procedures (based on the 2007 universal definition), they point to extensive literature documenting that only patients with elevated creatine kinase MB more than 10 times the upper limit of normal after revascularization have a worsened prognosis. We favor this clinically relevant MI definition for post-revascularization MI. We also favor the use of creatine kinase MB as a less sensitive but more specific confirmatory marker for acute coronary syndromes (type 1) or clinically significant supply-demand (type 2) MI, when the symptoms or electrocardiographic signs are nondiagnostic, as they often are.³ However, until there is a consensus around a single definition, clinicians are effectively walking around a Tower of Babel and must take care to be specific when documenting an MI.

In Reply: We thank Dr. Antonios for his comments regarding the current shortcomings of the ICD-9 and ICD-10 coding systems in describing the acute MI types as defined in the universal definition. We share his concern that accurate and consistent coding of MIs may be difficult when the definition of MI changes over a short period of time. Such changes create a disconnect not only between our clinical terminology and coding systems, but also potentially between our conventional sense of a “heart attack” as an acute coronary syndrome or a clinically significant infarction rather than a small troponin elevation from demand ischemia. This has consequences not only for quality measures and reporting, but also for clinical research trials and clinical care. This is exemplified by reports of recent trials that were possibly prematurely discontinued, as the use of troponin thresholds may conflate large MIs with clinically insignificant ones.¹

Recently, the Society for Cardiovascular Angiography and Interventions published a new definition of “clinically relevant” MI after revascularization.² Rather than relying on troponins, which are elevated in as many as 24.3% of uncomplicated percutaneous coronary interventions and in 42% to 82% of uncomplicated coronary artery bypass grafting procedures (based on the 2007 universal definition), they point to extensive literature documenting that only patients with elevated creatine kinase MB more than 10 times the upper limit of normal after revascularization have a worsened prognosis. We favor this clinically relevant MI definition for post-revascularization MI. We also favor the use of creatine kinase MB as a less sensitive but more specific confirmatory marker for acute coronary syndromes (type 1) or clinically significant supply-demand (type 2) MI, when the symptoms or electrocardiographic signs are nondiagnostic, as they often are.³ However, until there is a consensus around a single definition, clinicians are effectively walking around a Tower of Babel and must take care to be specific when documenting an MI.

In Reply: We thank Dr. Antonios for his comments regarding the current shortcomings of the ICD-9 and ICD-10 coding systems in describing the acute MI types as defined in the universal definition. We share his concern that accurate and consistent coding of MIs may be difficult when the definition of MI changes over a short period of time. Such changes create a disconnect not only between our clinical terminology and coding systems, but also potentially between our conventional sense of a “heart attack” as an acute coronary syndrome or a clinically significant infarction rather than a small troponin elevation from demand ischemia. This has consequences not only for quality measures and reporting, but also for clinical research trials and clinical care. This is exemplified by reports of recent trials that were possibly prematurely discontinued, as the use of troponin thresholds may conflate large MIs with clinically insignificant ones.¹

Recently, the Society for Cardiovascular Angiography and Interventions published a new definition of “clinically relevant” MI after revascularization.² Rather than relying on troponins, which are elevated in as many as 24.3% of uncomplicated percutaneous coronary interventions and in 42% to 82% of uncomplicated coronary artery bypass grafting procedures (based on the 2007 universal definition), they point to extensive literature documenting that only patients with elevated creatine kinase MB more than 10 times the upper limit of normal after revascularization have a worsened prognosis. We favor this clinically relevant MI definition for post-revascularization MI. We also favor the use of creatine kinase MB as a less sensitive but more specific confirmatory marker for acute coronary syndromes (type 1) or clinically significant supply-demand (type 2) MI, when the symptoms or electrocardiographic signs are nondiagnostic, as they often are.³ However, until there is a consensus around a single definition, clinicians are effectively walking around a Tower of Babel and must take care to be specific when documenting an MI.