How do we place electrocardiogram (ECG) leads on a patient with dextrocardia?

ECG Lead Placement in Dextrocardia

In patients with dextrocardia, reverse both the limb leads AND the precordial leads to obtain an accurate ECG that reveals the true cardiac electrical activity and any pathology such as myocardial infarction. 1

Standard Lead Reversal Technique

Limb Lead Reversal

• Place the right arm (RA) electrode on the left arm position 1
• Place the left arm (LA) electrode on the right arm position 1
• Keep the leg electrodes (LL and RL) in their standard positions 1
• This reversal corrects for the mirror-image orientation of the heart's electrical axis 2, 1

Precordial Lead Reversal

• Place V1 in the 4th intercostal space at the LEFT sternal border (mirror image of standard V1) 1
• Place V2 in the 4th intercostal space at the RIGHT sternal border (mirror image of standard V2) 1
• Continue the precordial leads V3R through V6R on the right hemithorax, mirroring the standard left-sided placement 3
• V3R is placed midway between V2R and V4R 3
• V4R is placed in the 5th intercostal space at the right midclavicular line 3
• V5R is placed at the right anterior axillary line at the V4R level 3
• V6R is placed at the right midaxillary line at the V4R and V5R level 3

Critical Clinical Implications

Why Complete Reversal Matters

• Without proper lead reversal, the extent of myocardial infarction will be severely underestimated 1
• A standard ECG in dextrocardia shows minimal or misleading ST changes that mask extensive infarction 1
• Only after reversing both limb and chest leads will widespread ST elevation become apparent, revealing the true extent of acute MI 1

Recognizing Dextrocardia on Standard ECG

Before you reverse the leads, suspect dextrocardia when you see:

• Inverted P waves in leads I and aVL 2, 1
• Dominantly negative QRS complexes in lead I and all precordial leads V1-V6 2
• Reverse R wave progression in chest leads (R wave amplitude decreases from V1 to V6 instead of increasing) 2
• Extreme right axis deviation 2, 1
• Low voltage in V4 through V6 2, 1

Common Pitfalls to Avoid

Incomplete Lead Reversal

• Never reverse only the limb leads or only the precordial leads—you must reverse BOTH 1
• Reversing only limb leads will still show low voltage and poor R wave progression in standard precordial positions 1
• This incomplete correction perpetuates diagnostic errors and underestimates pathology 1

Misinterpreting Standard Placement ECG

• Do not attempt to interpret a standard-placement ECG in a patient with known or suspected dextrocardia 1
• The risk of missing acute MI or other critical pathology is unacceptably high 1
• Always obtain a properly reversed ECG before making clinical decisions 1

Anatomic Variations

• Be aware that some patients have dextrocardia with levoversion, where the apex impulse may still be on the left despite mirror-image cardiac anatomy 4
• In these cases, the ECG with reversed leads remains the gold standard for electrical diagnosis 4
• Physical examination findings (apex location) may be misleading and should not override ECG-based lead placement decisions 4

Documentation Requirements

• Clearly label the ECG as "dextrocardia with reversed leads" or "right-sided precordial leads" to prevent confusion with subsequent interpreters 3
• Document the specific lead placement technique used 3
• This prevents future providers from misinterpreting the tracing or attempting to "correct" an already-corrected ECG 3