Keywords: posterior, myocardial infarction, left circumflex, acute coronary syndrome (PubMed Search)
Myocardial infarctions involving the left circumflex artery are often associated with ECGs that lack any ST-segment changes (38% in one representative study). Oftentimes when there are ST-changes, there may simply be anterior lead ST-segment depression. In these patients, acquisition of a few posterior leads frequently demonstrates STEMI. Some data does exist that failure to diagnose these posterior STEMIs (e.g. simply diagnosing anterior "ischemia" rather than posterior "STEMI") results in increased mortality.
So what's the bottom line?
1. In patients with isolated anterior lead ST-segment depression, always check for posterior STEMI with a couple of posterior leads.
2. In patients with non-significant ECGs but concerning persistent symptoms, always check for posterior STEMI with a couple of posterior leads.
This is always a great time to use that 80-lead ECG if your ED has one.