Electrocardiographic lead reversals

Figures

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  Fig. 1. 12-lead-ECGs and the corresponding schematic representations of the electrocardiographic limb lead vectors. 1A. Normal ECG tracing and Einthoven's triangle; 1B. LA-RA lead reversal depicting a) inversion of lead I, b) swapping of leads II and III, c) swapping of leads aVL and aVR, and d) unaltered aVF; 1C. LA-LL lead reversal depicting a) inversion of lead III, b) swapping of leads I and II, c) swapping of leads aVL and aVF, d) unaltered aVR, and e) P wave amplitude in lead I > lead II; 1D. RA-LL lead reversal depicting a) inversion of lead II, b) swapping of leads I and III with their polarities inverted, c) swapping of leads aVR and aVF, and d) unaltered aVL; 1E. Clockwise rotation of LL-RA-LA leads depicting swapping of leads I, II and III; and counter clockwise swapping of augmented leads; 1F. Counter clockwise rotation of LA-LL-RA leads depicting swapping of leads I, II and III; and clockwise swapping of augmented leads [The schematic illustrations are adapted from reference 2].

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  Fig. 2. Schematic representation of the electrocardiographic vectors in limb lead misplacements involving the neutral [RL] electrode. 2A. RA-RL[N] reversal showing collapsed Einthoven's triangle with LA lead at the apex. Lead III is unaltered. Lead II records zero voltage. 2B. LA-RL[N] reversal showing collapsed Einthoven's triangle with RA lead at the apex. Lead II is unaltered. Lead III records zero voltage. 2C. RA-RL and LA-LL (bilateral arm-leg) reversal showing collapsed Einthoven's triangle with misplaced LL lead at the apex. Lead I records zero voltage. 2D. LA-RL and RA-LL reversal (bilateral arm-leg cross reversal) showing collapsed Einthoven's triangle with misplaced LL lead at the apex. Lead I records zero voltage. 2E. Clockwise rotation of RL-RA-LA-LL leads showing collapsed Einthoven's triangle with misplaced RA lead at the apex. Lead III records zero voltage. 2F. Counter clockwise rotation of LA-LL-RL-RA leads. [The schematic illustrations are adapted from reference 2].

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  Fig. 3. 12-lead ECG tracings of limb-precordial lead misplacement. 3A. Left arm [LA] and V6 lead reversal showing altered morphology in lead V6 tracing, and precordial-like amplitude in leads I, III, aVL. 3B. Right leg [RL] and V6 lead reversal showing lead V6 tracing which resembles the unaugmented VF tracing. 3C. 12-lead ECG tracing with standard lead placement depicting acute ST elevation myocardial infarction of inferior wall; 3D. 12-lead ECG tracing of the same patient, with the LA and LL electrodes switched, suggesting the misdiagnosis of acute high lateral wall ST elevation myocardial infarction.

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  Fig. 4. Algorithm for detection of limb lead reversals which do not involve the neutral electrode, by polarity of P waves. Except for LA-LL reversal, all other electrode misplacements in this category have positive P waves [with or without positive QRS/T] in lead aVR. All the polarities mentioned above are in specific reference to the P waves in sinus rhythm, as the polarity of QRS/T may vary based on their polarities in the baseline ECG. LA-LL reversal can be identified by a greater P wave amplitude in lead I relative to lead II.

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  Fig. 5. Algorithm for detection of limb lead reversals which involve the neutral electrode. Except for LL-RL reversal [which does not alter the ECG significantly], and counter clockwise rotation [which is similar to the counter clockwise rotation without involvement of the neutral electrode – depicted in Fig. 4], all other electrode misplacements in this category are characterized by an isoelectric [flat] tracing in one of the bipolar leads.