How does a right-sided ST-elevation myocardial infarction (STEMI) present on an electrocardiogram (ECG) in an adult patient with a history of coronary artery disease?

Right-Sided STEMI ECG Presentation

Right ventricular STEMI is diagnosed by ST-segment elevation ≥0.1 mV (1 mm) in lead V4R, which should be routinely recorded in all patients with inferior wall STEMI to identify concomitant right ventricular involvement. 1, 2

Standard ECG Findings

Primary Diagnostic Criterion

• ST elevation ≥0.1 mV in lead V4R is the key diagnostic finding for right ventricular infarction 2, 3
• Right precordial leads (V3R and V4R) must be specifically recorded, as they are not part of the standard 12-lead ECG 1, 2
• These leads directly overlie the right ventricular free wall and detect electrical changes that standard leads miss 4

Associated ECG Patterns

• Inferior wall ST elevation is present in approximately 76% of right ventricular STEMI cases, typically showing ST elevation in leads II, III, and aVF 1, 3
• ST depression in leads I and aVL commonly accompanies inferior wall involvement 1
• ST depression in precordial leads V1-V3 may be present as reciprocal changes 1

Critical Clinical Pitfalls

Right Ventricular Involvement Without Inferior STEMI

• Approximately 24% of ECG-diagnosed right ventricular infarctions occur with anterior wall STEMI, not inferior STEMI 3
• ST elevation in leads V1-V3 can represent isolated right ventricular infarction rather than anterior wall MI, since these leads overlie the right ventricular free wall 4
• The left anterior descending artery (LAD) was the culprit vessel in approximately half of ECG-diagnosed right ventricular infarctions, not just the right coronary artery 3

Culprit Artery Distribution

• Only 50% of right ventricular STEMI cases involve right coronary artery (RCA) occlusion 3
• The remaining 50% involve LAD or left circumflex artery occlusions 3
• This challenges the traditional teaching that right ventricular infarction is exclusively an RCA territory problem 3

Diagnostic Algorithm

Step 1: Initial ECG Assessment

• Obtain standard 12-lead ECG within 10 minutes of first medical contact 2
• Identify any ST elevation in inferior leads (II, III, aVF) or anterior leads (V1-V3) 1, 4

Step 2: Right-Sided Lead Recording

• Immediately record right precordial leads V3R and V4R in all patients with inferior STEMI 1, 2
• Also record these leads if anterior ST elevation is present but clinical presentation suggests possible right ventricular involvement 4
• ST elevation ≥0.1 mV in V4R confirms right ventricular infarction 2, 3

Step 3: Clinical Correlation

• Look for hemodynamic findings suggesting right ventricular involvement: hypotension, elevated jugular venous pressure, clear lung fields (absence of pulmonary edema despite hypotension) 1
• Bradycardia or heart block may be present, particularly with RCA occlusion 1

Management Implications

Immediate Recognition Importance

• Right ventricular infarction significantly affects management decisions, particularly regarding fluid administration and medication choices 2
• Proceed directly to emergency coronary angiography without waiting for biomarker results when right ventricular STEMI is diagnosed 1, 2
• Reperfusion therapy must be initiated as soon as possible, as delays worsen outcomes 1

Common Diagnostic Errors to Avoid

• Do not assume right ventricular infarction only occurs with inferior STEMI - it can present with anterior ST elevation 3, 4
• Do not skip recording right-sided leads in patients with inferior STEMI, as this misses approximately 24% of right ventricular involvement cases 3
• Do not assume the RCA is always the culprit vessel - LAD and circumflex occlusions account for half of cases 3
• Repeated ECG recordings should be obtained if initial tracings are equivocal, but this should not delay reperfusion therapy 1