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We provide our users the most up-to-date and accurate information on the treatment and prevention of cardio pathologies in accordance with current American and European clinical guidelines.
The information provided on this website is for educational purposes only and should not be considered medical advice. Always consult a licensed physician for diagnosis and treatment.
Understanding Old Myocardial Infarction (MI) on ECG
Introduction
An old myocardial infarction (MI) refers to a heart attack that occurred in the past and has left lasting changes in the heart, which can be identified using an electrocardiogram (ECG). Recognizing these changes is crucial for assessing heart health and preventing future cardiovascular events.
ECG Signs of an Old MI
A past MI leaves characteristic marks on an ECG that are different from those seen in an acute MI (a currently happening heart attack). The main features of an old MI on ECG include:
1. Pathological Q Waves
- Definition: A Q wave is a downward deflection at the beginning of the QRS complex.
- Criteria for pathology:
- More than 0.04 seconds (1 small box) wide.
- More than 25% of the height of the following R wave.
- Seen in at least two contiguous leads.
- Significance: Indicates scar tissue from a previous infarction.
2. Loss of R Wave Progression
- Normally, the R wave increases in size across the precordial leads (V1-V6).
- A disrupted or absent R wave progression may indicate old MI or myocardial damage.
3. T Wave Inversions
- Typically seen in leads overlying the affected area.
- Suggest previous ischemia but can also appear in other conditions.
4. Persistent ST Segment Changes
- Unlike an acute MI, an old MI usually does not show ST elevation.
- There may be residual ST segment flattening or mild depression.
Localization of an Old MI on ECG
The location of pathological Q waves helps determine which part of the heart was affected:
| ECG Leads Affected | Likely Coronary Artery | Infarct Location |
|---|---|---|
| II, III, aVF | Right coronary artery | Inferior MI |
| V1 - V4 | Left anterior descending artery | Anterior MI |
| I, aVL, V5, V6 | Left circumflex artery | Lateral MI |
| V1, V2 (often with deep Q waves) | Posterior descending artery (via RCA or LCx) | Posterior MI (look for ST depression in V1-V2) |
Clinical Importance
- Identifying an old MI is crucial because:
- It increases the risk of future heart failure or arrhythmias.
- Further assessment with echocardiography, cardiac MRI, or stress testing may be needed.
- Secondary prevention with aspirin, beta-blockers, statins, and lifestyle modifications is often recommended.
Conclusion
ECG serves as an essential tool in detecting past myocardial infarctions. If an old MI is found, further evaluation and management are key to reducing future cardiovascular risks.
References to Clinical Guidelines
- American Heart Association Guidelines on ECG Interpretation
- European Society of Cardiology Guidelines on Myocardial Infarction Management
Source recommendations
1. American Heart Association Guidelines on ECG Interpretation
- https://www.heart.org/en/health-topics/heart-attack/diagnosing-a-heart-attack/electrocardiogram-ecg-or-ekg
- https://www.ahajournals.org/doi/10.1161/circulationaha.108.191095
- https://www.heart.org/-/media/files/affiliates/mwa/kansas-city/kc-cardiac-and-stroke-symposium/2020-event-documents/cardiac-presentations/2-ecg-hockstad.pdf?la=en
- https://www.ahajournals.org/doi/10.1161/circulationaha.108.191098
- https://pubmed.ncbi.nlm.nih.gov/19281932/
2. European Society of Cardiology Guidelines on Myocardial Infarction Management
- https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Acute-Coronary-Syndromes-ACS-Guidelines
- https://academic.oup.com/eurheartj/article/44/38/3720/7243210
- https://pubmed.ncbi.nlm.nih.gov/28886621/
- https://academic.oup.com/eurheartj/article/39/2/119/4095042
- https://pubmed.ncbi.nlm.nih.gov/32860058/
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If you or your loved ones experience any of these symptoms, you should consult a doctor in time. Remember that self-medication can be dangerous, and timely diagnosis will preserve the quality and life expectancy.
The heart is an organ that does not know how to "keep silent" if something goes wrong. Chest pain, shortness of breath, swelling, dizziness, and rhythm disturbances are the symptoms that require our attention. The best prevention of heart disease is careful attention to your health, regular checkups with a doctor, and a healthy lifestyle. Take care of your heart, and it will serve you for many years!
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