From the Guidelines
The key distinction between myocardial injury and demand ischemia in a patient with elevated troponin lies in the underlying cause and mechanism of troponin release, with myocardial injury indicating direct damage to heart muscle cells and demand ischemia representing an imbalance between myocardial oxygen supply and demand without permanent cell death. Myocardial injury refers to direct damage to heart muscle cells, resulting in troponin release, which can occur due to various causes such as myocardial infarction, myocarditis, or cardiac contusion, as noted in the universal definition of myocardial infarction 1. Demand ischemia, on the other hand, occurs when there's an imbalance between myocardial oxygen supply and demand, without necessarily causing permanent cell death, which can happen in conditions like severe anemia, tachyarrhythmias, or hypertensive crisis, and the troponin elevation in demand ischemia is usually transient and resolves when the underlying condition is treated. To differentiate between the two:
- Assess for acute coronary syndrome symptoms and ECG changes.
- Review the patient's clinical context and risk factors.
- Monitor troponin trends - demand ischemia typically shows a rapid rise and fall, as changes in hs-cTn are critically important to identify acute myocardial injury, which in the context of acute myocardial ischemia may qualify for AMI 1.
- Consider additional cardiac imaging like echocardiography or coronary angiography in unclear cases. Management differs based on the diagnosis, with myocardial injury often requiring specific interventions like coronary revascularization, while demand ischemia treatment focuses on addressing the underlying cause of increased cardiac workload. Understanding this difference is crucial for appropriate patient management and prognosis assessment, as myocardial injury often indicates more severe cardiac damage and may require more aggressive intervention, while demand ischemia may be reversible with proper management of the underlying condition.
From the Research
Myocardial Injury vs Demand Ischemia with Elevated Troponin
- Myocardial injury and demand ischemia are two distinct conditions that can present with elevated troponin levels 2, 3, 4, 5, 6
- Myocardial injury refers to damage to the heart muscle, which can be caused by various conditions, including cardiac and non-cardiac diseases 2, 4
- Demand ischemia, on the other hand, occurs when the heart's oxygen demand exceeds its supply, often due to conditions such as heart failure, dysrhythmia, or severe hypertension 2, 6
- Elevated troponin levels can be seen in both conditions, but the clinical context, patient symptoms, electrocardiogram, and ultrasound findings can help distinguish between them 2, 3, 4, 5, 6
Diagnostic Considerations
- Clinicians should consider the clinical context, including the patient's medical history, physical examination, and other diagnostic tests, to determine the cause of elevated troponin levels 2, 3, 4, 5, 6
- Serial sampling of troponin levels can help detect changes that are expected in patients with acute myocardial injury, rather than chronic myocardial injury 4, 6
- The use of highly sensitive troponin assays can help detect myocardial infarction earlier and more frequently, but can also lead to false positives if not interpreted in the correct clinical context 4, 6
Clinical Implications
- Accurate diagnosis of myocardial injury or demand ischemia is crucial to guide appropriate treatment and prevent patient harm 2, 3, 4, 5, 6
- Clinicians should be aware of the potential for troponin elevation in various clinical settings and avoid assigning a diagnosis of acute myocardial infarction based solely on elevated troponin levels 6