Domain 8.1EKG and Cardiovascular Testing

EKG Preparation And Performance

Last updated June 16, 2026

Overview

Welcome to the comprehensive study guide for EKG Preparation and Performance. This guide consolidates the critical steps of the EKG workflow: preparing the patient, setting up the equipment, placing leads accurately, and documenting the results.

An electrocardiogram (EKG or ECG) is a non-invasive test that records the electrical activity of the heart. As a medical assistant, your role is critical. The accuracy of the diagnosis depends entirely on the quality of the tracing you produce. This guide covers the end-to-end procedure to ensure a successful, artifact-free EKG.

1. Patient Preparation: The Foundation

An accurate EKG begins before any electrodes are placed. Proper preparation ensures a clear reading and minimizes artifacts.

A. Identification and Communication

  • Verify Identity: Always use at least two patient identifiers (e.g., Full Name and Date of Birth) before starting. Explain the procedure to ensure consent.
  • Explain the Procedure: "This is a simple, painless test that records the electricity of your heart. You will need to lie still for about a minute."
  • Reduce Interference:
    • Ask the patient to turn off cell phones and remove them from their person.
    • Instruct the patient to remove large metal jewelry or watches that might interfere.

B. Patient Positioning

The goal is to ensure the patient is relaxed to minimize muscle tension (somatic tremor).

  • Standard Position: Supine

    • Description: Lying flat on the back, arms at sides, legs uncrossed.
    • Why: Provides relaxation and access to the chest.
    • Memory Aid: A sUPine patient is facing UP.

  • Modified Position: Semi-Fowler's or Fowler's

    • Description: Head of bed elevated 30-45 degrees (Semi) or 45-60 degrees (Fowler's).
    • When to use: For patients with respiratory distress (dyspnea), COPD, or orthopnea (cannot breathe lying flat).
    • Memory Aid: Think of a Flower sitting up to get sun.

C. Skin Preparation

Electrodes need direct, uninterrupted contact with the skin to detect faint electrical signals.

  • Clean: Use alcohol prep pads to remove sweat, oils, and lotions. Let the skin air dry.
  • De-hair: If the patient has significant chest hair, clip or shave the specific electrode sites. Dry shaving can irritate skin; use a razor only if necessary.
  • Avoid: Patients should not wear lotions, oils, or powders on the chest/limbs on the day of the test. These cause electrodes to slip and baselines to wander.

D. Draping and Instructions

  • Draping: Use a front-opening gown. Cover the lower body with a sheet. Expose only the necessary areas of the chest.
  • Instructions: "Please lie as still as you can, breathe normally, and try not to talk."

2. Equipment Setup and Calibration

A. The Machine and Supplies

  • Electrodes: Adhesive pads with electrolyte gel. The gel's primary function is to enhance electrical conductivity by reducing skin resistance.
  • Right Leg (RL): This is the ground electrode. It helps stabilize the tracing but does not produce a diagnostic waveform.

B. Calibration and Settings

Universal standards ensure EKGs can be interpreted consistently anywhere.

  • Standard Calibration (Amplitude/Gain): 10 mm/mV.

    • This means 1 millivolt of electricity creates a wave 10 mm high.
    • Look for the calibration mark (rectangle) at the start of the tracing; it must be 10 mm tall.
    • Memory Aid: The "Perfect 10".

  • Standard Paper Speed: 25 mm/second.

    • At this speed, 25 small squares (or 5 large squares) equal 1 second.
    • Adjustment: For Pediatric patients (infants/toddlers) with very fast heart rates, you may need to increase speed to 50 mm/second to spread out the waveform.

3. Standard 12-Lead Placement

You place 10 physical electrodes to generate 12 electrical views (leads) of the heart.

A. Limb Leads (4 Electrodes)

Place on fleshy areas of the arms and legs, never over bone.

Lead Placement Mnemonic
RA Right Arm White on the Right
LA Left Arm Snow (White) over Grass (Green) - Note: Green is RL
RL Right Leg (Ground) Green is Ground
LL Left Leg Smoke (Black) over Fire (Red) - Black is LA

Technique Tip: Point electrode tabs downward on limbs to reduce wire tension.

B. Precordial (Chest) Leads (6 Electrodes)

These must be placed in specific Intercostal Spaces (ICS).

Lead Anatomical Location Key Takeaway
V1 4th ICS, Right Sternal Border
V2 4th ICS, Left Sternal Border V1/V2 are neighbors across the sternum.
V3 Midway between V2 and V4 Place V4 first, then fill in V3.
V4 5th ICS, Left Midclavicular Line The "anchor" lead. Center of collarbone down to 5th ICS.
V5 5th ICS, Left Anterior Axillary Line Front of the armpit.
V6 5th ICS, Left Midaxillary Line Middle of the armpit.

4. The 12 Leads Explained: Bipolar vs. Unipolar

It is crucial to understand that the 10 electrodes you place create 12 distinct electrical views. These views are categorized based on how they measure electricity.

A. Bipolar Limb Leads (Standard Leads)

These leads record the electrical difference between two distinct points (poles) on the body. Together, they form Einthoven's Triangle.

  • Lead I: Connects Right Arm (RA) to Left Arm (LA).
    • Diagnostic View: It views the Lateral wall of the Left Ventricle.
  • Lead II: Connects Right Arm (RA) to Left Leg (LL).
  • Lead III: Connects Left Arm (LA) to Left Leg (LL).

Exam Tip: If a question asks for "Bipolar Leads" or "Einthoven's Triangle," look for I, II, and III.

B. Unipolar Leads

These leads measure electrical current from a central point inside the heart (Wilson's Central Terminal) outward to a single positive electrode.

  • Augmented Leads (Limb): aVR, aVL, aVF.
  • Precordial Leads (Chest): V1 through V6.

5. Special Considerations and Modifications

A. Amputations or Casts

  • Rule: Place the electrode on the torso (closest to the limb) or the remaining stump.
  • Symmetry: You must place the corresponding electrode on the opposite limb in the same symmetrical location (e.g., if the left leg is amputated and the electrode is on the abdomen, the right leg electrode must also go on the abdomen).

B. Dextrocardia

  • Condition: The heart is located on the right side of the chest.
  • Action: Perform a Right-Sided EKG. Mirror the placement of V1-V6 onto the right side of the chest.

C. Posterior EKG

Sometimes a provider needs to see the back of the heart (Posterior Wall MI). You will use the standard machine but move leads V4, V5, and V6 to the back.

  • V7: Left Posterior Axillary line (Back of the armpit).
  • V8: Left Midscapular line (Just below the tip of the shoulder blade).
  • V9: Left Paravertebral line (Next to the spine).
  • Note: All three are placed on the same horizontal plane as V6.

D. Pediatric Patients

  • Action: Use smaller electrodes. Increase paper speed to 50 mm/s if the heart rate is too fast to interpret.
  • Communication: Call electrodes "stickers." Involve caregivers to keep the child calm.

6. Documentation and Post-Procedure

Documentation links the clinical data to the correct patient. This is a legal and safety requirement.

A. Essential Report Components ("ID the DOC")

Before the report is filed, it MUST contain:

  1. Patient Identifiers: Full Name and Date of Birth (DOB). (MRN is also acceptable).
  2. Date and Time of the test.
  3. Technician's Initials: (You).
  4. Ordering Provider: Who requested the test.
  5. Settings: Verification of 25 mm/s speed and 10 mm/mV calibration.

Exam Warning: Insurance numbers and machine serial numbers are administrative, not clinical. They are not mandatory for the clinical EKG report.

B. Workflow

  1. Verify: Check the tracing for quality. Ensure the baseline is steady and all leads are recording.
  2. Disconnect: Remove leads and electrodes gently. Assist the patient up.
  3. Transmit/File: Upload to the EMR or mount the strip in the paper chart.
  4. Alert: Notify the provider that the result is ready. If you see a life-threatening rhythm (see Interpretation guide), alert them immediately.

Final Key Takeaways

  • sUPine = Face UP.
  • Alcohol is best for skin prep; Lotions are the enemy.
  • White on Right, Smoke over Fire.
  • Einthoven's Triangle = Leads I, II, III (Bipolar).
  • Posterior EKG = V7, V8, V9 on the back.
  • Lead I = RA to LA (Lateral View).
  • Standard Speed = 25 mm/s; Standard Gain = 10 mm/mV.
  • Mandatory Docs = Name + DOB.