The Subtlety of STE and its Anatomy

This tracing was discussed at a recent STEMI committee meeting. Its much easier to spot the ischemic changes once the diagnosis is known.....

Subtle STE or artifactual nonsense ?

12 LEAD ECG INTERPRETATION

Baseline sinus rhythm, occasional fusion beats and premature atrial contractions in a bigeminal pattern, ST segment elevation in septal leads

This ECG interpretation is far from obvious. Typical criteria for activation of the cardiac catheterization lab includes at least 2 mm or greater of STE in contiguous precordial leads. Close inspection reveals minimal ST elevation in leads V2 and V3. Clear cut reciprocal changes are not present. The ST segment's shape is far from reassuring: it has a horizonal and ischemic-type appearance in lead V2.

This ECG requires you to bust out the calipers because there is a constant PR interval buried within the premature and fusion beats. At first glance, the irregular rhythm suggests atrial fibrillation. The presence of consistent PR intervals, however, rules out that diagnosis. On most tracings, P waves are best visualized in leads II and V1.

The patient went to the cardiac cath lab; the diagnosis of an acute occlusion of the "ramus." The ramus is simply an intermediate branch of the left coronary artery (LCA)  that arises in between the left anterior descending (LAD) artery and the left circumflex coronary artery. The "ramus" is abbreviated as "Int" in the illustration below.


For those of use who are more visual learners, this picture is furnished courtesy of:
http://www.cardiologysite.com/html/lad.html