Old Myocardial Infarction on ECG

Introduction

An old myocardial infarction (MI) refers to a previous heart attack that has left lasting changes in the heart muscle. This can be identified through various signs on an electrocardiogram (ECG), even if the patient had no symptoms at the time of the heart attack.

How Does an ECG Show an Old MI?

Several key ECG findings can indicate a past myocardial infarction:

• Q Waves: Deep and wide Q waves (≥ 0.04 sec in duration or ≥ 1/3 of the R wave height) in specific leads suggest a previous MI.
• Loss of R Wave Progression: In some cases, reduced R wave height in the affected leads can be a sign of myocardial damage.
• T Wave Changes: Persistent inverted T waves in the infarcted area may indicate an old heart attack.
• ST Segment Changes: Residual ST segment deviations, particularly ST depression or mild elevation, might persist after an infarction.

Leads and Infarction Location

• Inferior MI: Pathological Q waves in leads II, III, and aVF.
• Anterior MI: Q waves in leads V1–V4.
• Lateral MI: Q waves in leads I, aVL, V5, and V6.
• Posterior MI: Tall R waves in V1–V2 (a mirror image of Q waves seen in anterior MI).

Clinical Significance

Recognizing an old MI is crucial because: - It increases the risk of heart failure, arrhythmias, and recurrent infarctions. - Management may include lifestyle modifications, medications (such as beta-blockers, aspirin, and statins), and close cardiac monitoring.

Next Steps

If an old MI is detected on ECG, further evaluation with echocardiography, cardiac MRI, or a stress test may be necessary to assess heart function and the extent of damage.

Source recommendations

1. American Heart Association Guidelines 2023 on ECG Interpretation

1. https://www.heart.org/en/health-topics/heart-attack/diagnosing-a-heart-attack/electrocardiogram-ecg-or-ekg
2. https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines
3. https://www.ahajournals.org/doi/10.1161/cir.0000000000000527
4. https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines/algorithms
5. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001193

2. European Society of Cardiology Guidelines on Acute and Chronic Coronary Syndromes 2023

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Chronic-Coronary-Syndromes
2. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001168
3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Acute-Coronary-Syndromes-ACS-Guidelines
4. https://academic.oup.com/eurheartj/article/44/38/3720/7243210
5. https://pubmed.ncbi.nlm.nih.gov/37622654/