Question
A 69-year-old man is brought to the emergency department because of severe epigastric pain and vomiting that started 30 minutes ago while gardening. His pulse is 55/min, respirations are 30/min, and blood pressure is 90/50 mm Hg. Physical examination shows diaphoresis and jugular venous distention. Crackles are heard in both lower lung fields. An ECG shows P waves independent of QRS complexes and ST segment elevation in leads II, III, and aVF. Coronary angiography is most likely to show narrowing of which of the following vessels?
| A. |
Posterior interventricular artery
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| B. |
Left circumflex artery
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| C. |
Proximal right coronary artery
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| D. |
Left anterior descending artery
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Show Answer
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Correct Answer � C
Explanation
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Answer C) Proximal right coronary artery
The symptoms of epigastric pain and vomiting, combined with ST segment elevation in leads II, III, and aVF and complete heart block, are indicative of an inferior wall myocardial infarction.
Proximal right coronary artery
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Occlusion of the proximal right coronary artery (RCA) can cause an inferior wall myocardial infarction, which in turn can present atypically with epigastric pain.
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High-degree AV block can occur in this setting because the SA node and AV node are usually supplied by the RCA (the SA node directly, and the AV node via the AV nodal branch).
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Right-sided leads (V4R, V5R, and V6R) should also be obtained to evaluate for right ventricular (RV) infarction (especially given the patient’s jugular venous distention), as the RCA supplies the RV via its right marginal branch.
Left anterior descending artery
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Occlusion of the left anterior descending artery (LAD) would cause a myocardial infarction of the anterior (ECG changes in I, aVL, V1–6), anteroseptal (I, aVL, V1–4), anterolateral (I, aVL, V5–6/7), and/or apical wall (I, aVL, V3–5).
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An anteroseptal myocardial infarction can sometimes cause serious arrhythmias, such as high-degree AV block, since the LAD supplies the left and right bundle branches and partially supplies the left anterior and posterior fascicles. However, conduction abnormalities are more common following an inferior myocardial infarction, as is epigastric pain.
Posterior interventricular artery
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Occlusion of the posterior interventricular artery (PIV) would cause a posterior wall myocardial infarction, which would manifest as ST-segment depression in leads V1 and V2, sometimes with prominent R waves.
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Posterior leads (V7–9) would show ST-segment elevation. Epigastric pain is not common in posterior wall myocardial infarctions, nor are conduction abnormalities, since the PIV does not supply the conduction system.
Left circumflex artery
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The left circumflex artery (LCX) supplies lateral and posterior walls of the left ventricle. Occlusion of the LCX would cause changes in leads II, III, aVF, V5–7, and sometimes I, and aVL.
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In patients with left-dominant coronary circulation, LCX occlusion leading to distal occlusion of the PIV could also cause a posterior wall myocardial infarction.
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