A standard 12-lead electrocardiogram (ECG or EKG) is a non-invasive diagnostic tool that records the heart’s electrical activity from twelve different perspectives. This test requires ten electrodes: four on the limbs and six on the chest. The right-sided 12-lead ECG is a procedural modification used when standard placement is insufficient to capture electrical changes in specific areas of the heart. This specialized procedure demands precise electrode positioning to ensure the resulting tracing is accurate.
Indications for Right-Sided Placement
The primary reason for performing a right-sided 12-lead ECG is to detect right ventricular involvement during a myocardial infarction (heart attack). Standard precordial leads on the left side of the chest do not adequately view the right ventricular free wall, making this modification necessary. This is particularly relevant when a standard ECG shows signs of an inferior wall myocardial infarction.
Up to 40% of patients experiencing an inferior ST-elevation myocardial infarction (STEMI) may have a coexisting right ventricular infarction. Identifying this involvement is important because these patients are highly sensitive to certain medications, such as nitroglycerin, which can cause a severe drop in blood pressure. The right-sided ECG is also indicated for patients with dextrocardia, where the heart is situated on the right side of the chest. In these cases, the entire precordial lead placement is mirrored to accurately reflect the heart’s electrical axis.
Preparation and Equipment Setup
Before beginning the procedure, the patient should be positioned lying flat on their back or slightly elevated if more comfortable. The skin at the electrode sites must be properly prepared to ensure a clean, low-resistance electrical connection, minimizing artifact and improving signal quality. Preparation involves cleaning the skin with an alcohol wipe to remove oils and dirt, and gently abrading the skin to remove dead skin cells.
Any excessive hair at the placement sites should be clipped or shaved, as hair interferes with electrode adhesion and electrical conduction. Once the skin is prepared, fresh, moist electrodes are applied, and the lead wires are connected to the ECG machine. The machine settings should be confirmed at the standard speed and gain before recording, and the tracing must be clearly labeled as a right-sided study.
Step-by-Step Lead Positioning
The right-sided 12-lead ECG requires a precise mirror-image placement of the precordial (chest) electrodes on the right side of the patient’s chest. The standard limb leads—Right Arm (RA), Left Arm (LA), Right Leg (RL), and Left Leg (LL)—remain in their usual positions on the patient’s limbs, as they record electrical activity in the frontal plane. The right-sided modification focuses entirely on relocating the V-leads to the right hemithorax.
The placement of V1 and V2 remains standard in some protocols (V1 at the fourth intercostal space (ICS) at the right sternal border; V2 at the fourth ICS at the left sternal border). However, to obtain a complete set of right-sided leads (V1R through V6R), all six precordial electrodes are placed in a mirror-image position. The most important lead to locate is V4R, which is found in the fifth intercostal space at the right mid-clavicular line.
To locate the intercostal spaces, first find the Angle of Louis, the ridge where the manubrium meets the sternum, which aligns with the second rib. Counting down to the fifth intercostal space establishes the horizontal level for the V4R electrode. The remaining right-sided leads are placed as follows:
- V3R is positioned midway between V2 and V4R.
- V5R is placed laterally along the same horizontal plane as V4R, at the right anterior axillary line.
- V6R is placed at the right mid-axillary line, level with V4R and V5R.
This systematic placement allows the ECG machine to view the electrical activity of the right ventricle.
After the electrodes are secured, the tracing must be properly documented to prevent misinterpretation. The precordial leads must be clearly marked with the “R” designation (e.g., V4R or Right-Sided Leads) to inform the interpreting clinician of the modified placement. This documentation ensures that the waveforms are interpreted in the context of the right-sided view.
Verification of Correct Lead Placement
Verification of a correctly performed right-sided ECG is achieved by examining the morphology of the waveforms on the resulting tracing. The electrical activity recorded over the right ventricle should show a characteristic change in the R-wave progression compared to a standard left-sided ECG. The R-wave represents the electrical signal traveling toward the exploring electrode, and in a right-sided tracing, this progression should appear reversed.
Specifically, a correctly positioned V1R and V2R should show a small R wave followed by a deep S wave, similar to a standard V1 or V2, but the R-wave progression across V3R to V6R will not resemble the typical left-sided pattern. The most telling sign of correct placement over the right ventricle is the presence of an elevated ST segment in V4R, which is a highly specific finding for right ventricular infarction. The technician must confirm the resulting tracing is free of motion or electrical artifact before concluding the procedure is complete.