How to differentiate between real septal infarction and pseudoseptal infarction on a 12-lead Electrocardiogram (EKG)?

Differentiating Real Septal Infarction from Pseudoseptal Infarction on 12-Lead EKG

The key to differentiating real septal infarction from pseudoseptal infarction is careful assessment of P wave morphology in lead V2, proper lead placement verification, and evaluation of the overall ECG pattern including reciprocal changes. 1

Real Septal Infarction Characteristics

ECG Findings

• Pathological Q waves (QS pattern) in leads V1 and V2 2
• Q wave criteria: ≥0.03 sec duration and ≥0.1 mV depth or QS complex 3
• May have ST-segment elevation in V1-V3 during acute phase
• Often associated with occlusion of the proximal left anterior descending coronary artery 4
• Reciprocal ST-segment depression in leads II, III, and aVF 4

Additional Characteristics

• When caused by LAD occlusion, ST-segment vector is directed superiorly and to the left 4
• More ST elevation in aVL than in aVR
• More ST-segment depression in lead III than in lead II 4

Pseudoseptal Infarction Characteristics

ECG Findings

• QS pattern in leads V1 and V2 due to cranially misplaced precordial leads 1
• Abnormal P wave morphology in lead V2 - key distinguishing feature 1
• P waves in misplaced V1-V2 often appear negative or biphasic (resembling P waves in aVR)
• Absence of reciprocal changes typically seen in true septal infarction

Causes of Pseudoseptal Infarction

1. Lead misplacement: Most common cause - V1 and V2 placed too high on chest wall 1
2. Non-ischemic pathologies: Various cardiomyopathies can produce QS patterns in V1-V2 2
3. Normal variant: Particularly in some athletes with specific repolarization patterns 4

Algorithmic Approach to Differentiation

Step 1: Evaluate Lead Placement

• Check if V1-V2 leads are properly placed at the 4th intercostal space
• Improper high placement is the most common cause of pseudoseptal infarction pattern

Step 2: Assess P Wave Morphology

• In properly placed V1-V2, P waves should be upright or biphasic with terminal negativity
• Predominantly negative P waves in V1-V2 suggest high lead placement 1

Step 3: Look for Reciprocal Changes

• True septal infarction often shows reciprocal ST depression in leads II, III, and aVF 4
• Absence of these reciprocal changes suggests pseudoseptal infarction

Step 4: Evaluate the Overall ECG Pattern

• True septal infarction is typically part of a more extensive anterior wall infarction 5
• Isolated "septal" Q waves without other signs of anterior infarction should raise suspicion for pseudoseptal pattern

Step 5: Consider Clinical Context

• History of chest pain, cardiac biomarkers, and other clinical findings
• True septal infarction is associated with proximal LAD occlusion 4

Common Pitfalls and Caveats

• The traditional ECG pattern termed "anteroseptal AMI" often represents anteroapical rather than true septal infarction 5
• QS pattern in V1-V2 has high predictive value for septal scarring but is not specific for ischemic etiology 2
• ST elevation in V1-V3 may be due to either right ventricular infarction or anterior left ventricular infarction 6
• Pseudoseptal infarction due to lead misplacement can trigger unnecessary medical procedures and have adverse consequences including employment discrimination 1
• In athletes, particularly black athletes, normal repolarization variants can mimic pathological patterns 4

Confirming the Diagnosis

• Repeat ECG with careful attention to proper lead placement
• Consider additional imaging (echocardiography, cardiac MRI) to confirm presence or absence of septal wall motion abnormalities or scarring 2
• Correlation with cardiac biomarkers and clinical presentation

By systematically applying this approach, clinicians can accurately differentiate between true septal infarction and pseudoseptal infarction patterns, avoiding unnecessary procedures and ensuring appropriate management of patients with true myocardial injury.