Flowchart to recognize patterns suggesting reversed or misplaced electrodes on a 12-lead ECG.
Step 1
Is there a flat (isoelectric) tracing in any bipolar frontal-plane lead?
The result indicates a technical suspicion, not a clinical diagnosis. Confirm electrode placement and repeat the ECG before interpreting changes that may have been caused by placement.
Abbreviations
RA
Right arm
LA
Left arm
RL
Right leg
LL
Left leg
A tool to support learning and decision-making. The result does not replace clinical evaluation of the patient.
About: IDPC algorithm
Electrode reversal or misplacement is one of the most common causes of an abnormal ECG without disease. It can mimic infarction, dextrocardia, chamber enlargement and axis changes, and lead to unnecessary interventions.
The IDPC algorithm organizes into a flowchart the signs that most strongly suggest a technical error in the limb and precordial leads.
How to use
Start with the bipolar frontal-plane leads: is any of them isoelectric (nearly flat)?
Assess P-wave morphology in the limb leads, especially in lead I and aVF.
Finish with the precordial leads: R/S progression and the appearance of V1 and V2.
How to interpret
An isoelectric bipolar lead suggests that an arm electrode was placed on the right leg.
A negative P wave in lead I suggests arm electrode reversal; if it is also negative in aVF, reversal of the right arm and left leg.
R/S progression out of anatomical sequence suggests precordial lead reversal; P- and R-wave changes in V1–V2 suggest placement that is too high or too low.
Limitations
The result indicates a technical suspicion, not a diagnosis. Confirm electrode placement and repeat the ECG before interpreting changes that may have been caused by placement.
References
de Almeida VJ, Costa-Lança CH, de Souza-Gouveia MC, Nogueira-de Marchi MF, Nunes-de Alencar J. ECG lead misplacement review and proposal of a simple identification tool: the IDPC algorithm. Rev Interam Cardiol. 2026;2(3). doi:10.24875/RIAC.25000042
Batchvarov VN, Malik M, Camm AJ. Incorrect electrode cable connection during electrocardiographic recording. Europace. 2007;9(11):1081–90.
