Chest
Volume 122, Issue 1, July 2002, Pages 134-139
Journal home page for Chest

Clinical Investigations
Cardiology
ECG Discrimination Between Right and Left Circumflex Coronary Arterial Occlusion in Patients With Acute Inferior Myocardial Infarction: Value of Old Criteria and Use of Lead aVR

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Study objectives

Prior studies have proposed several ECG criteria for identifying the culprit artery in patients with acute inferior myocardial infarction (MI). We applied each criterion to our patients to assess its utility. In doing so, we discovered a previously unreported, but highly useful, criterion utilizing lead aVR.

Study design

Retrospective review.

Patients

Thirty consecutive patients with symptoms of acute MI, ST-segment elevation in the inferior ECG leads, an appropriate rise and fall of creatine kinase and troponin I levels, and coronary arteriography within 7 days of the onset of symptoms.

Measurements

The ECG recorded within 24 h of the onset of symptoms that had the most prominent ST-segment changes was analyzed. In the 12 standard leads and in lead V4R, ST-segment elevation or depression was measured 0.06 s after the J point.

Results

Four previously described criteria were useful in identifying the right coronary artery (RCA) or the left circumflex coronary artery (LCX) as the culprit: ST-segment elevation in lead I, ST-segment more or less elevated in lead II than in lead III, ST-segment elevation ≥ 0.5 mm in lead V4R, and various combinations of ST-segment elevation or depression in leads V1 and V2. A new criterion was found to be at least as useful as any previously described: the presence and amount of ST-segment depression in lead aVR.

Conclusions

At least five different ST-segment criteria help to identify the RCA or the LCX as the culprit artery in patients with acute inferior MI. One of these, the amount of ST-segment depression in lead aVR, has not been reported previously and needs validation in a larger study.

Section snippets

Materials and Methods

Thirty consecutive patients at the Medical Center of Louisiana who had symptoms compatible with acute MI, ST-segment elevation in the inferior ECG leads, an appropriate rise and fall of creatine kinase and troponin I levels, and coronary arteriography within 7 days of the onset of symptoms were included in the study. Exclusion criteria were bundle-branch block, prior Q-wave MI, prior coronary artery bypass graft operation, and inability to identify the culprit lesion (in two patients, one of

Results

In 25 of 30 patients, the culprit lesion was in the RCA while in 5 patients it was the LCX (Table 1). In four of five patients with ST-segment depression ≥ 1.0 mm in lead aVR, the culprit lesion was in the LCX. Conversely, the culprit lesion was in the RCA in 24 of the 25 patients with ST-segment elevation (2 RCA), an isoelectric ST segment (18 RCA), or ST-segment depression < 1.0 mm (4 RCA, 1 LCX) in lead aVR.

ST-segment elevation in lead III exceeded that in lead II in 26 patients, and 23 of

Discussion

Among our 30 patients with acute inferior MI, the culprit lesion was in the RCA in 25 patients and in the LCX in 5 patients, a ratio of 5:1. Ten other studies of patients with acute inferior MI have found RCA to LCX ratios ranging from 2.2:1 to 7.0:1, and averaging 3.9:1.2389101112131415 Thus, the RCA is much more likely than the LCX to contain the culprit lesion in patients with acute inferior MI. Rarely, acute inferior MI may result from occlusion of the recurrent LAD branch,23 which is the

ACKNOWLEDGMENT

We thank Mrs. Brenda Kuss for her assistance with this article.

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