Can incorrect lead placement on an electrocardiogram (ECG) mimic the appearance of a myocardial infarction?

Yes, Incorrect ECG Lead Placement Can Mimic Myocardial Infarction

Incorrect lead placement on an ECG can absolutely create false-positive signs of myocardial infarction, including mimicking ST-elevation MI (STEMI), and this represents a critical diagnostic pitfall that can lead to unnecessary interventions and patient harm. 1

How Lead Misplacement Mimics MI

Limb Lead Reversals

• Limb lead switches can result in false-positive and false-negative signs of ischemia that may be misinterpreted as acute MI 1
• The most common limb lead reversals include:
  • Left-right arm reversal: Produces inversion of lead I, switches leads II and III, and switches aVR and aVL, which can create apparent ischemic changes 1
  • Left arm-left leg reversal: More difficult to detect but causes subtle axis shifts and lead III inversion that may suggest inferior wall changes 1
• These reversals can create ST-segment changes that mimic STEMI patterns, potentially triggering inappropriate catheterization lab activation 2

Precordial Lead Misplacement

• Transposition of precordial lead wires (V1, V2, V3) can cause reversal of R-wave progression that simulates anteroseptal wall infarction 1
• Cranially misplaced V1 and V2 leads are a common technical error that creates pseudo-septal infarction patterns 3
• This specific misplacement has led to documented cases of unnecessary medical procedures and adverse consequences, including loss of employment opportunities due to false MI diagnosis 3

Clinical Consequences

Real-World Impact

• The American Heart Association guidelines emphasize that incorrect diagnosis of ventricular tachycardia and other arrhythmias caused by artifact from misplaced electrodes has resulted in unnecessary interventions ranging from intravenous antiarrhythmic agents to diagnostic catheterizations and even implantation of pacemakers and ICDs 4
• Lead misplacement can generate misleading patterns that are quite important in clinical decision-making because the resulting ECG morphology changes can mimic myocardial infarction 5
• Recent case reports document STEMI mimics from lead reversal in routine chest pain evaluations, where ST-segment elevation in inferior leads disappeared after correcting arm lead placement 2

Detection Strategies

Key Recognition Features

• Lead I should generally be similar to V6 with respect to P-wave and QRS morphology - discordance between lead I and V6 suggests lead misplacement rather than true pathology like dextrocardia 1
• P-wave morphology in lead V2 can aid in suspecting erroneous right precordial lead placement in cases of apparent septal infarction 3
• Distorted progression of precordial P waves and T waves in the same leads where abnormal R-wave progression appears can indicate lead transposition rather than true infarction 1
• The "SPIRAL" mnemonic has been proposed as a quick screening criterion to detect commonly encountered lead reversals 6

Verification Steps

• Always compare with prior ECGs when available - suspected lead switches can be confirmed by reference to previous tracings with correct lead placement 1
• When ECG findings are inconsistent with clinical presentation, repeat the ECG with verified correct lead placement before initiating aggressive interventions 2
• Look for characteristic patterns: very low amplitude only in lead II with inverted symmetry between leads I and III suggests right arm-right leg reversal 1

Prevention Recommendations

Training and Technology

• Medical personnel responsible for recording ECGs should receive training on avoidance of lead switches and guidelines for their recognition 1
• Lead-switch detection algorithms should be incorporated into digital electrocardiographs along with alarms for abnormally high lead impedance 1
• Suspected misplacements should be identified to the person recording the ECG in time to correct the problem before interpretation 1
• Accurate electrode placement is key to correct identification of monitored arrhythmias and cannot be overemphasized 4

Critical Pitfalls to Avoid

• Do not activate the catheterization lab for STEMI based solely on ECG findings that are inconsistent with clinical presentation without first verifying correct lead placement
• Be particularly vigilant when apparent septal infarction patterns appear in patients without appropriate clinical context 3
• Remember that some lead switches may go unrecognized even by alert technicians, particularly left arm-left leg transposition 1
• Improved education of healthcare personnel regarding accurate precordial lead positioning technique is essential to minimize this electrocardiographic misdiagnosis 3