The case from this week is from one of the PGY-1 residents at University of Texas Health Science Center at San Antonio (UTHSCSA). Several of the details of the case have been changed to keep patient information confidential.
53 year old female with a past medical history of hypertension, hyperlipidemia, coronary artery disease, and 3 anterior myocardial infarctions s/p 4-vessel CABG (LIMA-LAD, RIMA-RCA, SVG-D1-OM1 sequentially) 9 months ago who presents with intermittent 10/10 chest pain that radiates to his left arm for the past 6 months. The chest pain is associated with nausea and shortness of breath but denies diaphoresis or syncope. Patient reports that the pain is the same as his index chest pain and is both exertional and non-exertional and will often wake him up from sleep. The pain can last 5-10 minutes and is always relieved by rest. The patient reports good medication compliance (on metoprolol, atorvastatin, enalapril, amlodipine, aspirin). He presented with similar symptoms 3 months ago but left against medical advice before a work-up could be performed. Now he presents with increasing frequency of chest pain.
BP 152/105 HR 86 RR 16 O2 sat 99% on RA Temp 98.0
ECG from triage is shown…
Before reading on, try to come up with your own interpretation of this ECG before moving on to the final impression
- Rate: Ventricular rate 62
- Rhythm: sinus
- Axis: Left Axis Deviation
- QRS: Bifascicular Block (RBBB + LAFB)
- ST/T Waves: ST-segment elevation in inferior leads (II, III, and aVF)
- Final ECG Interpretation: Bifascicular Block with ST-segment elevation in the inferior leads (II, III, and aVF)
In this case we were able to get our hands on an old ECG performed 3 months prior (shown below):
ST-segment elevation usually reflects acute thrombotic coronary occlusion and the most effective treatment consists in early primary percutaneous coronary intervention (PCI) or by thrombolytic treatment. In patients that present with ST-segment elevation and chest pain the differential diagnosis can include ventricular wall aneurysm/pseudoaneurysm, pericarditis, benign early repolarization (BER), and recurrent acute myocardial infarction. This places a great emphasis on emergency physicians and their competence and ability to interpret ECGs in a rapid, timely, knowledgeable manner.
LV aneurysm is uncommon and accounts for 3 – 4% of all patients with ST-segment elevation on ECG (11992347). Although uncommon, LV aneurysm (LVA) is not an infrequent cause of diagnostic error in activation of the cath lab. As a matter of fact, in a retrospective review, LVA was the most frequently misinterpreted ECG pattern in emergency department chest pain patients (11073474). More than 80% of LVAs are anterolateral and are usually associated with total occlusion of the left anterior descending artery with inferior and posterior aneurysms being less common (11992347).
What are some ECG characteristics that would help differentiate STEMI from LVA?
- Patients with LVAs, will frequently also have significant Q waves in the same distribution as prior myocardial infarctions.
- A non-concave ST-segment elevation morphology has a sensitivity and specificity of 77% and 97% for acute myocardial infarction (11581081)
- Reciprocal changes on ECG is a frequent finding in the setting of acute myocardial infarction
- Acute myocardial infarction will have dynamic ECG changes, while LVA will often have static ECG changes making comparison to past ECGs a useful tool
Case Conclusion: Due to the new ECG changes patient was taken for cardiac catheterization which showed a 90% proximal SVG to RCA stenosis and an inferior/posterior ventricular aneurysm. It was thought that the ST-segment elevation in the inferior leads was due to the aneurysm (echo shown below).
Take Home Point:
- In patients with chest pain and ST-segment elevation on ECG, it is important to distinguish between LVA and STEMI by looking at old ECGs to see if changes are old or new.
Nicolas D. Spampinato, MD
University of Texas Health Science Center at San Antonio (UTHSCSA)
PGY-1 Resident of Emergency Medicine