CHAPTER SUMMARY AND CENTRAL ILLUSTRATION
This chapter discusses important nonatherosclerotic etiologies of myocardial injury, which can be due to ischemic or nonischemic causes (see Fuster and Hurst's Central Illustration). Differentiating the etiology of myocardial injury is critical because the management strategy differs for atherosclerotic versus nonatherosclerotic causes. Type 1 myocardial infarctions (MIs) are due to atherosclerotic plaque rupture/erosion with thrombus formation and typically require invasive management for restoration of coronary perfusion. Type 2 MIs can result from ischemia due to imbalance of oxygen supply and demand, or nonatherosclerotic causes such as spontaneous coronary artery dissection, coronary vasospasm, coronary embolism, coronary vasculitis, coronary ectasia, and anatomic coronary artery anomaly. Causes of nonischemic myocardial injury include myocarditis, takotsubo syndrome, and heart failure. The management of type 2 MIs and nonischemic causes of myocardial injury depends on the underlying etiology, and thus discerning these “mimickers” of non-type 1 MI is pertinent for prompt and appropriate management of acute coronary syndromes.
eFig 20-01 Chapter 20: Mimickers of Atherosclerotic Myocardial Infarction: SCAD, Coronary Vasospasm, Myocarditis, and Takotsubo Syndrome
Acute coronary syndrome (ACS) denotes the presence of myocardial ischemia that can result in a spectrum of clinical symptoms and presentations, including unstable angina, ST-elevation myocardial infarction (STEMI), and non-ST-elevation MI (NSTEMI). As per the Fourth Universal Definition of Myocardial Infarction,1 the term myocardial infarction (MI) requires not only the presence of myocardial injury (acute rise and fall of troponin) but also acute myocardial ischemia as the underlying cause, together with symptoms and/or signs of ischemia/infarction. Myocardial injury has numerous causes (ischemic and nonischemic causes) and can easily be detected by modern highly sensitive assays for cardiac biomarkers. Differentiating the etiology of myocardial injury is critical as the management strategy differs for atherosclerotic versus nonatherosclerotic causes of cardiomyocyte deaths. Type 1 MIs are due to atherosclerotic plaque rupture/erosion with thrombus that typically requires invasive management with percutaneous coronary intervention (PCI), with the exception of MI with nonobstructive coronary arteries (MINOCA) whereby medical stabilization may suffice. Type 2 MIs result from ischemia due to imbalance of oxygen supply and demand, which may occur in the setting of atherosclerotic obstructive coronary disease, or nonatherosclerotic causes such as spontaneous coronary artery dissection (SCAD), coronary vasospasm, coronary embolism, hypotension/shock, arrhythmia, respiratory failure, and anemia. Myocardial injury can also result from nonischemic causes such as myocarditis, takotsubo syndrome (TTS), heart failure, cardiac procedures, and systemic illnesses. The management of type 2 MIs and nonischemic causes of myocardial injury obviously depends on the underlying etiology, and thus discerning these “mimickers” of non-type 1 MI is pertinent for prompt and appropriate management of ACS. It is important to keep in mind that SCAD and coronary vasospasm both cause true MI, which meets the universal definition of MI and can cause cardiac magnetic resonance imaging (MRI) evidence of scarring that is indistinguishable ...