Simplified in Practice: ECG nuggets in old STEMI (LV aneurysm)
M3 India Newsdesk Oct 07, 2021
So far, in our series, Simplified in Practice, we have discussed the salient ECG features of myocardial ischaemia. This time, we discuss, the development of left ventricular aneurysm after a STEMI results in a prolonged ST elevation on the ECG also referred to as Old STEMI.
Most common ECG findings for a left ventricular aneurysm:
- ST elevation observed more than 2 weeks after an acute myocardial infarction
- Most frequently seen in the precordial leads
- May have concave or convex morphology
- Usually accompanied with well-formed Q- or QS waves
- T-waves have a smaller amplitude than the QRS complex (unlike the hyperacute T-waves of acute STEMI)
The likelihood of having an aneurysm if a patient has prolonged anterior ST elevation (lasting for more than two weeks after their first MI) with pathological Q waves is 38%, while the specificity of this finding is 84%.
Pathophysiology
Two weeks after an acute STEMI, the ST segments return to baseline, but the Q waves persist and the T waves often become flattened or inverted. Yet, 60% of individuals with anterior STEMI and 5% of those with inferior STEMI have some degree of ST elevation. The process is believed to be linked to insufficient reperfusion and the development of transmural scar tissue after an acute MI. Paradoxical ventricular wall movement on echocardiography is depicted in such patients with a ventricular aneurysm.
Importance in clinical practice
Patients with ventricular aneurysms are at a higher risk of developing the following:
- Ventricular arrhythmias and sudden cardiac death (myocardial scar tissue is arrhythmogenic)
- Congestive heart failure
- A thrombus on the wall and eventual embolisation
Reasons
- Acute myocardial infarction is one of the situations that may result in an LV aneurysm (by far the most common)
- Cardiomyopathy
- Congenital anomalies
Distinguishing acute STEMI from other causes
It is critical to differentiate between LV aneurysm (“old MI”) and acute STEMI in individuals who arrive with chest pain and ST elevation on the ECG.
| Factors favouring the development of a left ventricular aneurysm | Factors favouring the development of a left ventricular aneurysm |
| ECG that is similar to prior ECGs (if available) | New ST changes in comparison to previous ECGs |
| Absence of dynamic ST-segment alterations | Dynamic/progressive ECG changes - the degree of ST-elevation increases with serial ECGs |
| Absence of reciprocal ST depression | Reciprocal ST depression |
| Well-formed Q waves | Strong clinical suspicion of STEMI - persistent ischaemic chest pain, sick-looking patient (e.g. pale, sweaty), haemodynamic instability |
Additional distinguishing characteristics
The ratio of T-wave to QRS complex amplitude has been confirmed for the purpose of distinguishing LV aneurysm from acute STEMI:
- A T-wave/QRS ratio of less than 0.36 in all precordial leads predisposes to LV aneurysm
- A T-wave/QRS ratio greater than 0.36 in any precordial lead predisposes to anterior STEMI
This is part six of our new series- Simplified in Practice where we break down ECG interpretation for various conditions. To read the earlier parts of the series, click here: Simplified in Practice: ECG basics & how to interpret, Simplified in Practice: How to detect myocardial ischaemia?, Simplified in Practice: Anterior Myocardial Infarction- Clinical nuggets on ECG characteristics, Simplified in Practice: What are the ECG changes when inferior STEMI starts? & Simplified in Practice: ECG features of posterior MI
Click here to see references
Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.
The author is a practising super specialist from New Delhi.
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