An electrocardiogram, commonly known as an EKG or ECG, is a safe and non-invasive procedure used to measure the electrical signals generated by the heart. These signals represent the depolarization and repolarization cycles of the cardiac muscle, providing a detailed snapshot of heart rhythm and function. Successfully obtaining a diagnostic-quality tracing relies heavily on meticulous preparation and precise placement of sensors on the patient’s body. This procedural guide outlines the careful steps required to set up the equipment and prepare a patient for an accurate 12-lead EKG recording.
Gathering Necessary Equipment
Before beginning the procedure, the necessary items must be assembled. The primary device is the EKG machine itself, which processes and records the electrical data, along with its attached set of lead wires or cables. Disposable adhesive electrodes or pads are required, as these sensors are placed directly on the skin to capture the heart’s electrical impulses. To optimize the signal, various skin preparation materials, including alcohol wipes and sometimes a mild abrasive pad, should be readily available. Finally, ensuring patient privacy and comfort requires a standard patient gown or sheet.
Preparing the Patient for Placement
Proper patient positioning is the first step toward obtaining a clear tracing, typically requiring the patient to lie flat on their back in the supine position. The patient should be encouraged to relax and remain still, as any movement or muscle tension can introduce interference into the final recording. Any metal objects, such as jewelry, should be removed from the torso and limb areas to prevent electrical interference with the recording equipment.
Skin preparation is necessary for optimal skin-to-electrode contact. The chosen electrode sites must first be thoroughly cleaned with an alcohol wipe to remove oils and lotions that impede conductivity. If the patient has significant chest hair, it may need to be gently clipped or shaved, as hair creates a physical barrier. A light abrasion of the skin using a specialized pad can also improve signal transmission.
Precise Electrode Placement
The standard 12-lead EKG utilizes 10 electrodes placed strategically to create 12 different views of the heart’s electrical activity. Four electrodes are designated as limb leads, placed on the fleshy, non-bony parts of the upper and lower extremities. The right arm (RA) and left arm (LA) electrodes are generally placed above the wrist or on the upper arm, while the right leg (RL) and left leg (LL) electrodes are placed above the ankle or on the lower leg. The right leg electrode functions as the ground reference point and is required for proper circuit completion.
The remaining six electrodes, labeled V1 through V6, are the precordial or chest leads, which require specific placement relative to the ribs and sternum. These chest leads provide the transverse view of the heart.
Precordial Lead Placement
- V1 is placed in the fourth intercostal space immediately to the right of the sternal border.
- V2 is placed in the fourth intercostal space immediately to the left of the sternal border.
- V4 is positioned in the fifth intercostal space at the midclavicular line.
- V3 is placed midway between the V2 and V4 positions.
- V5 is positioned horizontally level with V4, located at the anterior axillary line.
- V6 is placed horizontally level with V4 and V5, situated at the midaxillary line.
Maintaining the correct anatomical landmarks is important, as misplacement of a single precordial electrode can significantly alter the resulting tracing, potentially leading to misinterpretation of cardiac function. Placement relies on physically palpating the bony structures, starting with the sternal notch to locate the angle of Louis, which helps identify the second rib and subsequently the fourth and fifth intercostal spaces. Once all ten electrodes are firmly affixed to the skin, the corresponding lead wires can be attached.
Running the Recording and Verifying Quality
With all ten electrodes securely in place and the lead wires connected to the EKG machine, the next step is to initiate the recording process. Before printing, the operator should confirm the machine settings, typically standardized to a paper speed of 25 millimeters per second and a gain (amplitude) of 10 millimeters per millivolt. These standard settings ensure the tracing is consistently displayed and measurable across different devices.
Once the machine begins to record, the operator must visually inspect the tracing for common artifacts that could obscure the electrical data.
Common EKG Artifacts
Baseline wander appears as a slow, rolling wave, often resulting from poor skin prep or patient breathing movements, necessitating a re-cleaning or repositioning of the limb leads. Muscle tremor, characterized by a rapid, erratic vibration, usually indicates the patient is cold or tense, requiring efforts to help them relax. 60-cycle noise presents as thick, fuzzy lines caused by nearby electrical sources or ungrounded equipment. Isolating and removing the source of this electrical interference is necessary to clear the tracing. The final tracing must exhibit a flat, stable baseline and clear PQRST complexes across all 12 leads to be considered a diagnostic-quality recording.