60s male with chest discomfort. Is this RCA or LCX occlusion?

EMS is dispatched to a 62 year old male with a chief complaint of chest discomfort.

On arrival, the patient is found sitting at the dinner table. He appears acutely ill.

  • Onset: Fairly sudden after sitting down for dinner 20-30 minutes ago
  • Provoke: Nothing makes the pain feel better or worse
  • Quality: Dull pressure/ache
  • Radiation: The pain does not radiate
  • Severity: 8/10 “feels like a 747 is sitting on his chest”
  • Time: Feels slightly better since the onset

The patient’s skin is cool, pale, diaphoretic

Vital signs are assessed.

  • RR: 20
  • HR: 62
  • NIBP: 84/48
  • SpO2: 99% on room air

Breath sounds are clear bilaterally.

The cardiac monitor is attached.

TOMB070209Awm2

A 12 lead ECG is obtained.

TOMB070209Bwm2

The paramedic trouble-shoots the loose electrode.

TOMB070209Cwm2

The data quality looks good to me, but the computer disagrees.

Three’s a charm.

TOMB070209Dwm2

The paramedic in charge of the call elected to perform an additional 12 lead ECG using modified leads V4R and V5R.

modified leads V4R V5R

Here is the result.

modifed leads V4R V5R ecg

Consider this image from an editorial in the New England Journal of Medicine by HJ Wellens.

stemi_v4r_chart

We can say that leads V4R and V5R are negative (there is no ST-segment elevation) but the T-waves are flat so it would seem to be a tie between distal RCA and LCX according to this diagram.

Keep in mind that the patient’s initial blood pressure is only 84/48 so he shouldn’t receive nitroglycerin whether leads V4R and V5R are positive for right ventricular infarction or not.

Consider Eskola et al. How to Use ECG for Decision Support in the Catheterization Laboratory – Cases With Inferior ST Elevation Myocardial Infarction. Journal of Electrocardiography Vol 37 No. 4 October 2004.

inferior_rca_lcx_table

In this case both the amount of ST-segment elevation and the amplitude of the T-waves are equal in leads II and III. Again, no help in distinguishing between RCA and LCX occlusion.

Consider Sgarbossa et al., Electrocardiographic diagnosis of acute myocardial infarction: Current concepts for the clinician. Am Heart J 2001;141:507-17:

“The typical electrocardiographic pattern of inferior infarction consists of ST-segment elevation in leads II, III, and aVF. The occlusion is in the RCA in 80% to 90% of cases and is in the LCX in the remaining patients. Higher ST elevation in lead III than in lead II strongly suggests compromise of the RCA.

A bedside differential diagnosis between culprit arteries can also be attempted by examining additional electrocardiographic leads. Because the only lead that faces the superior part of the left ventricle and directly opposes the inferior wall is aVL, ST depression in lead aVL is almost always determined by RCA occlusion (sensitivity, 94%; specificity, 71%), without indicating concomitant involvement of the posterior wall or the right ventricle. Injury in leads II, III, and aVF without ST depression in aVL indicates proximal LCX occlusion.

Several studies in the 1980s concluded that ST elevation in leads V5 through V6 during inferior injury signaled LCX occlusion. However, because most inferior infarctions are caused by RCA occlusion, the positive predictive value of this sign is poor. The arteries that supply the posterolateral region of the left ventricle are the obtuse marginal branch of the LCX, the posterolateral, and the LAD branches. Thus ST changes in leads V5 and V6 indicate rather posterolateral ischemia triggered by either RCA or LCX occlusion. When this ST elevation is significant (>2 mm), it is probably a sign of “mega-artery-related” (either the RCA or LCX) infarction with a large ischemic burden.”

It appears as though the mere fact that there is ST-segment elevation in leads V5 and V6 (in addition to leads II, III, and aVF) does not settle the matter.

The patient was sent emergently to the cardiac cath lab.

STEMI_LCX_before

The circumflex (LCX) was found to be 100% occluded.

STEMI_LCX_after

After the lesion was crossed with a wire.

STEMI_RCA_nondominant

The right coronary artery (RCA) was small and non-dominant.

Sometimes it’s virtually impossible to predict the culprit artery based solely on the 12-lead ECG.

Further reading

Right Ventricular Infarction

Updated 06/19/2016

1 Comment

  • Michelle says:

    The first chart you posted came from "The ECG in Emergency Decision Making" written by Hein J.J. Wellens and Mary B. Conover, Saunders publication, 1992. It comes from page 7. This is an excellent advanced 12 lead textbook and I used it heavily in the 1990s when I was teaching a lot of 12 lead courses at a local community college.
    Michelle (a nurse who enjoys your website)

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