How can you diagnose right ventricular (RV) infarction on electrocardiogram (EKG) in patients with inferior ST-elevation myocardial infarction (STEMI)?

Diagnosing Right Ventricular Infarction in Inferior STEMI on ECG

Right ventricular infarction should be evaluated by obtaining right-sided precordial leads (V3R-V4R) in all patients with inferior STEMI, as ST elevation >0.05 mV (>0.1 mV in men <30 years old) in these leads provides the most reliable diagnostic criteria. 1, 2

Primary Diagnostic Approach

1. Right-sided precordial leads:

   • Obtain V3R and V4R leads in all patients with inferior STEMI
   • ST elevation >0.05 mV (>0.1 mV in men <30 years old) in V4R is highly specific for RV infarction 1, 2
   • These leads should be recorded immediately when inferior STEMI is identified 1

2. Standard 12-lead ECG findings (less reliable but may raise suspicion):

   • ST elevation in lead V1 (specificity 84%, but limited sensitivity of 35%) 3
   • Discordant pattern: simultaneous ST elevation in V1 with ST depression in V2 4
   • ST elevation of greatest magnitude in lead III compared to leads II and aVF 5

Clinical Correlation

Right ventricular infarction should be suspected in patients with inferior STEMI who present with:

• Hypotension
• Jugular venous distention
• Clear lung fields
• Kussmaul's sign (paradoxical rise in jugular venous pressure during inspiration)
• Hypotension that worsens with nitrates or preload-reducing agents 2, 5

Importance of Diagnosis

Early recognition of RV infarction is critical as:

• It complicates approximately 25% (range 20-60%) of inferior MIs 5
• Patients with RV involvement have worse prognosis and higher mortality 5
• Management differs significantly (requires preload maintenance, avoidance of nitrates) 2

Common Pitfalls to Avoid

1. Relying solely on standard 12-lead ECG:

   • The standard 12-lead ECG has inadequate diagnostic characteristics to definitively diagnose or exclude RV infarction 3

2. Misinterpreting ST depression in lead I:

   • Despite previous claims, ST depression in lead I is not a reliable indicator of RV infarction 3

3. Overlooking RV infarction in posterior involvement:

   • When posterior MI is present (ST depression in V1-V3), the sensitivity of ST elevation in V1 for RV infarction decreases 3

4. Delaying diagnosis:

   • Right-sided leads should be obtained early, as management strategies differ significantly for RV infarction 1, 2

Algorithmic Approach

1. Identify inferior STEMI (ST elevation in leads II, III, aVF)
2. Immediately obtain right-sided precordial leads (V3R-V4R)
3. Look for ST elevation >0.05 mV in V4R (>0.1 mV in men <30 years old)
4. If right-sided leads unavailable, assess for supporting evidence:
   • ST elevation in V1
   • Discordant ST elevation in V1 with ST depression in V2
   • ST elevation greatest in lead III compared to II and aVF
5. Correlate with clinical signs of RV dysfunction (hypotension, JVD, clear lungs)

By following this approach, you can reliably diagnose RV infarction in the setting of inferior STEMI and implement appropriate management strategies to improve outcomes.