From the Guidelines
Type 2 myocardial injury is diagnosed when there is an elevation in cardiac troponin values (with at least one value above the 99th percentile upper reference limit) along with evidence of an imbalance between myocardial oxygen supply and demand unrelated to coronary atherothrombosis, as defined by the 2022 ACC/AHA key data elements and definitions for chest pain and acute myocardial infarction 1. The diagnostic criteria for type 2 myocardial injury include detection of a rise or fall of cTn concentrations with at least 1 concentration above the 99th percentile URL and evidence of an imbalance between myocardial oxygen supply and demand unrelated to acute coronary atherothrombosis, requiring at least one of the following: symptoms of acute myocardial ischemia, new ischemic electrocardiographic changes, development of pathological Q waves, or imaging evidence of new loss of viable myocardium or new regional wall motion abnormality in a pattern consistent with an ischemic etiology. Some key points to consider when diagnosing type 2 myocardial injury include:
- Elevated troponin levels, which indicate myocardial damage
- Evidence of an imbalance between myocardial oxygen supply and demand, which can be caused by various conditions such as severe anemia, hypotension, hypoxemia, tachyarrhythmias, heart failure, and severe hypertension
- The need to rule out type 1 myocardial infarction, which involves atherothrombotic coronary disease
- The importance of identifying the underlying condition causing the oxygen supply-demand mismatch and treating it accordingly, rather than focusing on coronary intervention. It's also important to note that type 2 myocardial injury differs from type 2 myocardial infarction, as the latter requires clinical evidence of myocardial ischemia such as ischemic symptoms, ECG changes, or imaging evidence of new loss of viable myocardium, as stated in the 2020 ESC guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation 1.
From the Research
Definition and Diagnosis of Type 2 Myocardial Infarction
- Type 2 myocardial infarction (MI) is defined by a rise and fall of cardiac biomarkers and evidence of ischemia without unstable coronary artery disease (CAD) because of a mismatch in myocardial oxygen supply and demand 2.
- The diagnosis of type 2 MI requires clinical evidence of myocardial ischemia, and it is associated with adverse short-term and long-term prognoses 3.
- Type 2 MI occurs due to myocardial oxygen supply-demand mismatch without acute atherothrombotic plaque disruption 4.
Clinical Characteristics and Management
- Patients with type 2 MI are older and have lower peak cardiac troponin levels compared to those with type 1 MI 2.
- Type 2 MI patients are less likely to receive aspirin and statin at discharge compared to type 1 MI survivors 2.
- There is uncertainty in terms of the clinical characteristics, management, and outcomes of type 2 MI and myocardial injury in comparison with type 1 MI 2.
- Optimal management strategies for type 2 MI are limited due to its heterogeneous entity with varying etiologies and triggers, requiring individualized care 3.
Prognosis and Outcomes
- All-cause mortality is not different between type 1 MI, type 2 MI, and myocardial injury patients 2.
- A significant proportion of deaths are attributed to cardiovascular causes in all subgroups 2.
- Type 2 MI and myocardial injury are associated with poor outcomes in both the short term and long term 5.
Diagnostic Challenges and Future Directions
- Diagnostic strategies to facilitate the clinical distinction between ischemic myocardial injury with or without an acute atheroma-thrombotic event vs non-ischemic-mediated myocardial injury conditions are urgently needed 5.
- Evidence-based therapies tailored toward improving outcomes for patients with type 2 MI are required 5.
- Additional studies to determine optimal medical therapy and risk stratification strategies for these high-risk populations are warranted 2.