Look Behind You!

A 45 yo female with a history of cigarette smoking and tobacco abuse reports a sudden onset of severe, substernal chest discomfort. EMS providers perform a 12 lead ECG.

12 Lead ECG

12 Lead Discussion

ST elevation is noted in leads II, III, and aVF. Reciprocal changes are seen in leads I and aVL. Note ST elevation extends into the lateral precordial leads of V4, V5, and V6. Also of significance is the ST segment depression in leads V2 and V3. Though the R waves aren't especially tall, the ST depression and slightly positive R waves is consistent with extension of the infarction into the heart's posterior wall. A large obstructing lesion of the right coronary artery can affect these geographic areas of the heart. Posterior wall MIs usually do not occur in isolation. The "Life in the Fast Lane" blog has a good page on the interpretation of the posterior wall myocardial infarction. 

12 Lead Interpretation

Inferior lateral ST elevation myocardial infarction with extension into the posterior wall.

Simply a Sinus STEMI? No!

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Paramedics respond to a 55 yo female with chest pain and shortness of breath. The patient is alert and hypertensive. The peripheral pulse is irregular.

12 lead ECG: 

12 Lead ECG Interpretation:

The underlying rhythm is most definitely not sinus. A rhythm strip is not included in the LifeNet transmission. Though the first visualized QRS complex in leads I, II, and III APPEARS to be conducted, there is PR interval is excessively long (> 0.2seconds). Furthermore, the P to P intervals appear constant. There is a "p" hiding in the ST segment of the next QRS complex. The constant P to P interval suggests a third degree heart block. ST segment elevation is present in the inferior leads. Reciprocal change is evident in the anterior-septal (V1-V6) and lateral (I, aVL) leads. Recall that ST depression in the septal leads (V1-V2) could indicate posterior involvement. Posterior wall changes generally exhibit tall R waves in leads V1-V3 which are absent in this particular tracing. 

Third degree heart block, inferior wall ST segment myocardial infarction with possible posterior extension. 

12 lead ECG Case Discussion:

This case highlights the importance of a rhythm strip. If there is any question about the presence or absence of an underlying conduction problem, always obtain a rhythm strip. LifeNet provides just a few seconds of rhythm analysis; this interval is occasionally inadequate for proper rhythm determination. Inferior wall changes, coupled with the heart block, suggest injury to the SA node. This patient would benefit from the prophylactic application of pacing pads. Avoid nitrogylcerin in the presence of inferior wall changes and an underlying heart block. 

The "buried P wave" and constant P to P interval: 

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You make the call!

This patient presented to an outside hospital for palpitations following the use of a routine anti-asthma medication. The patient reported chest discomfort and some associated shortness of breath shortly after medication administration. The patient's vital signs remain stable, and her lung sounds were clear. The remainder of the physical examination was unremarkable. An emergency physician obtained a routine ECG. The patient's vital signs were stable and the physical examination was unremarkable.  

The patient was transferred to a tertiary care facility for cardiac catheterization.

1. What's your interpretation of the 12 lead?
2. What are some diagnostic considerations?

12 lead ECG Interpretation
Sinus rhythm, rate approximately 70, diffuse ST segment elevation
There is a baseline sinus rhythm. Widespread ST segment elevation is present in leads I, aVL, II, III, aVF, and in the anterior-lateral precordial leads. The R waves and ST segment depression in leads V1 and V2 are consistent with posterior wall ischemia. The ST segments themselves are mostly convex. The convexity of the ST segment is also suggestive of ischemia. Infarction of the heart's anterior, inferior, lateral, and posterior walls could conceivably produce the diffuse ST segment changes seen in this ECG.

12 lead ECG Discussion and Case Resolution
There are several considerations to bear in mind when looking at diffuse ST segment elevations:
1. Massive myocardial infarction
2. Pericarditis
3. Ventricular wall aneurysm 
4. Coronary vasospasm

The patient's clinical picture (and overall well appearance) is not consistent with the diagnosis of a massive myocardial infarction.

The ST elevations in pericarditis are usually more CONCAVE in appearance. Reciprocal changes are never associated with pericarditis. PR segment depression is also present in pericarditis.

Ventricular wall aneurysm usually presents electrocardiographically with Q waves and diffuse ST segment elevations. There may be a loss of R wave progression across the precordial leads.

There was no lesion amenable to intervention at the time of angiography. The patient's echocardiogram revealed a preserved ejection fraction with some mild, but diffuse, hypokinesis. The patient was diagnosed with coronary artery vasospasm.