Interpretation Made Easy 12-LEAD EKG Interpretation Made Easy

LEAD PLACEMENT LIMB LEADS MUST BE PLACED ON THE LIMBS Uses both positive and negative electrodes Current towards positive, view from negative

Precordial Leads

Acquisition & Transmission Read the clipper manufacture’s recommendations. This is one model designed for medical applications and may be used near oxygen. In addition the head is disposable, avoiding de-contamination issues.

Acquisition & Transmission Skin Preparation Helps obtain a strong signal Skin oils reduce adhesion of electrode and hinder penetration of electrode gel Dead, dried skin cells do not conduct well When measured from the patient’s skin, the heart’s electrical signal is extremely small, about 0.0001 to 0.003 volts. That’s as small as one-ten thousandth of a volt. Compare this with energy from a nine volt battery. Good skin prep will make the ECG signal as strong as possible, and make the artifact signals as small as possible.

Acquisition & Transmission Rubbing skin with a gauze pad can reduce skin oil and remove some of dead skin cells Simply rubbing the skin with a gauze pad can have a noticeable effect on ECG clarity by: • Reducing skin oil • Removing part of the stratum corneum

Acquisition & Transmission Other causes of artifact Patient movement Cable movement Vehicle movement Electromagnetic Interference (EMI) Once the skin has been prepped and the electrodes applied, there are still other sources of artifact to consider.

Acquisition & Transmission Patient Movement Make patient as comfortable as possible Supine preferred Look for subtle movement toe tapping, shivering Look for muscle tension hand grasping rail, head raised to “watch” It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact. When possible, the patient should be in the supine position for a 12-lead ECG. Sometimes this is not feasible, practical or desirable. If ECG is not recording in supine position, simply note this on ECG.

Acquisition & Transmission Cable Movement Enough “slack” in cables to avoid tugging on the electrodes Many cables have clip that can attach to patient’s clothes or bed sheet It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact. When possible, the patient should be in the supine position for a 12-lead ECG. Sometimes this is not feasible, practical or desirable. If ECG is not recording in supine position, simply note this on ECG.

Acquisition & Transmission Electromagnetic Interference (EMI) Can interfere with electronic equipment 60 cycle interference is a type of EMI Look for nearby cell phones, radios or electrical devices No contact between cables & power cords Turn off or move away from AC devices Use shielded cables; inspect for cracks It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact. When possible, the patient should be in the supine position for a 12-lead ECG. Sometimes this is not feasible, practical or desirable. If ECG is not recording in supine position, simply note this on ECG.

Traditional Placement Limb Lead Placement Traditional Placement Avoid placing on the trunk!!! Limb leads should be placed on the limbs. The traditional placement is near the ankles and wrists. Acceptable Placement

Chest Lead Placement V1: fourth intercostal space to right of sternum V2: fourth intercostal space to left of sternum V3: directly between leads V2 and V4 V4: fifth intercostal space at left midclavicular line V5: level with V4 at left anterior axillary line V6: level with V5 at left midaxillary line V1 fourth intercostal space to the right of the sternum V2 fourth intercostal space to the left of the sternum V3 directly between leads V2 and V4 V4 fifth intercostal space at left midclavicular line V5 level with lead V4 at left anterior axillary line V6 level with lead V5 at left midaxillary line

Chest Lead Placement Here is what lead placement looks like on a patient.

Acquisition & Transmission Things to look for Little or no artifact Steady baseline

Acquisition & Transmission Note how the baseline straightened out by simply repositioning the patient cables and clipping them onto the sheet. What technique(s) would you consider in order to resolve the muscle artifact?

12-Lead Validation Lead I – Global Negativity? R Wave Progression? P, QRS and T Wave inverted? R Wave Progression? R Wave size increases in V leads Transition Zone? R Wave should be predominately positive in V3 and V4

12-Lead Validation Limb leads P wave, QRS, and T wave upside down in Lead I Global negativity Upper limb leads switched 12-leads should be validated for correct lead placement. First, look at Lead I. The P, QRS, and T waves are typically upright. If the P, QRS, and T waves are all inverted, this is a sign of global negativity and the RA and LA leads are switched.

12-Lead Validation R wave progression normal poor 12-Lead Validation R wave progression R waves progress in size from V1 to V4 If poor progression, check lead placement on electrodes R wave progression is the way to validate a 12-lead for precordial leads. The insert on your left (viewing) has normal R wave progression where the one on your right has poor progression. If this is seen, check to see that Leads V1–V6 are snapped on the right location. In this example on the right, Leads V2 and V4 have been switched. Poor R wave progression can be caused by pathology as well. It is important that the acute care provider double check the lead placement before disconnecting the V leads following the 12-lead acquisition.

QUESTIONS?