Old unsolved problems: when and how to treat silent ischaemia
Ciro Indolfi1, Alberto Polimeni1, Annalisa Mongiardo1
1Divisione di Cardiologia, Università degli Studi "Magna Graecia", Catanzaro, Italy.
Insights
Silent myocardial ischaemia (SMI) is more common than symptomatic episodes, often occurring without chest pain. Its exact causes and long-term prognosis remain unclear despite extensive research.
Area of Science:
- Cardiology
- Ischaemic Heart Disease
Background:
- Silent myocardial ischaemia (SMI) is defined by objective evidence of myocardial ischaemia without angina in patients with coronary artery disease.
- SMI constitutes the majority of ischaemic episodes detected during Holter monitoring.
- The precise mechanisms underlying SMI remain incompletely understood.
Purpose of the Study:
- To explore the underlying causes and potential mechanisms of silent myocardial ischaemia.
- To review the historical and current understanding of SMI's prognosis and its association with conditions like diabetes mellitus.
Main Methods:
- Review of existing literature and clinical observations regarding silent myocardial ischaemia.
- Analysis of factors potentially contributing to SMI, including ischaemia severity, duration, pain perception thresholds, and neuronal dysfunction.
Main Results:
- SMI is more prevalent than symptomatic ischaemia.
- Potential mechanisms include ischaemia characteristics, altered pain perception, and neuronal dysfunction (e.g., in diabetes or post-infarction).
- Historically, SMI was linked to poorer outcomes, particularly in diabetic patients with autonomic dysfunction.
Conclusions:
- Silent myocardial ischaemia is a frequent phenomenon, often exceeding symptomatic presentations.
- The prognosis of SMI and the impact of medical therapy require further clarification.
- Further research is needed to elucidate the exact role of various proposed mechanisms and to establish definitive prognostic guidelines.
Abstract:
Silent myocardial ischaemia (SMI) is defined as objective evidence of ischaemia without angina (or equivalent symptoms) in the presence of coronary artery disease, differing from silent coronary artery disease. Silent myocardial ischaemia represents the majority of episodes of myocardial ischaemia at Holter monitoring. During transient myocardial ischaemia, the symptoms appear after the contraction anomalies of the left ventricle and after the ECG changes. The cause of silent myocardial ischaemia is still not well established. The severity and duration of ischaemia have been theorized as important elements in the SMI mechanism. Another possible mechanism responsible for SMI is represented by changes in the perception of painful stimuli with an increased pain threshold. Finally, a neuronal dysfunction of the diabetic, in post-infarction or a cardiac neuronal 'stunning' could play a role in SMI. In the pre-stent era, the SMI was associated with a worse prognosis. In patients with diabetes mellitus, SMI seems to be more represented because autonomic dysfunction is present in this category of patients. In conclusion, SMI is more frequent than symptomatic ischaemia. However, despite the presence of countless studies on the subject, it is not clear today whether medical therapy has equalized the risk and what the real prognosis of SMI is.
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