Cardiac & Resuscitation, Patient Care

12-Lead ECG Tips

Issue 11 and Volume 38.

The 12-lead ECG is one of the most fantastic advances in EMS treatment since the invention of the bandage. The movement of this powerful diagnostic tool from the confines of the hospital to the streets has been nothing short of revolutionary. It has given EMS professionals a wealth of information on how to best care for our patients and has driven hospital care and the development of medical care practices by providing clear and critical data that physicians had rarely before seen.

12-lead ECG

Illustration Brook Wainwright Designs

Did you realize that by moving this tool to the field, EMS has almost made heart attacks into a minor medical complaint that can be effectively treated if caught early? EMS has changed healthcare with that. We’re catching things that used to go uncaught and have vastly improved the lives and qualities of life for countless patients who pass through our care. Kudos to the visionaries who helped drive this change. No matter the level of the service, be it ALS, ILS or BLS, a 12-lead ECG is an essential EMS tool and should be the standard of care.

Proper acquisition of the 12-lead ECG is paramount to getting the most out of this tool. An improperly acquired 12-lead doesn’t provide diagnostic-quality information and can render the tracing mostly useless. Here are a few tips to making sure you get it done right:

Lead Placement
Traditionally, the limb leads go on the limbs, and while it’s acceptable to move them closer if you have to, try to avoid placing the leads over bony prominences or overly fatty areas. Look for a generally flat, clean, intact area of skin with muscle generally underneath.

The V-Leads go on the chest in a specific pattern. Leads V1 and V2 go in the 4th intercostal spaces (between the ribs) on either side of the sternum. To find these, go about three finger widths up from the xyphoid process, or bottom of the sternum. V1 is on the patient’s right, V2 is on the left.

V4 should be placed next; it goes one rib down in the 5th intercostal space, on the midclavicular line. Place V3 in between V2 and V4.

V5 goes in the anterior axillary line (front of the armpit) and V6 goes in the mid-axillary line. They go in the same horizontal line as V4.

Skin Preparation
It’s important to prepare the skin by cleaning it with an alcohol prep and by abrading it with a cloth towel to remove dead skin cells. You may need to wash the area with saline and dry it. Remove excess body hair by shaving. For females, place the leads under the breast tissue. You may need to lift and clean the skin underneath the breast to get a clear tracing.

Baseline
A quality 12-lead ECG has a smooth, flat baseline (called the isoelectric line). Baseline wander, or the vertical motion of the ECG line, can mask important findings in the ECG tracing and result in a non-diagnostic ECG.

The patient should remain motionless and lay as close to supine as possible for the acquisition of the tracing and the ambulance should be stopped and not moving during the process. It sometimes takes a few minutes for the ECG tracing to normalize and you should wait for it to do so. The goal is to be able to see the entire cardiac waveform clearly and be able to measure accurate ST-segment levels. Skin prep is important to reduce artifact. A tracing with artifact or baseline wander can mask serious ECG findings and may cause a patient to be misdiagnosed.

Multiple ECGs
One ECG is a spot-check of the patient’s heart. Two ECGs are a trend of their condition. Try to obtain a symptomatic tracing of the patient before treatments like oxygen, nitroglycerine or aspirin are given. Although you shouldn’t delay treatment, it’s been shown that ST-segment elevation can normalize quickly with EMS treatment and an ECG obtained afterward that doesn’t show ST-segment changes can mask a STEMI that should be emergently treated by a cath lab. The two or three minutes you spend taking the symptomatic ECG can save the patient hours or days going without definitive treatment for their underlying condition.

A good rule of thumb is to capture a 12-lead ECG tracing at the patient’s side where you find them symptomatic, then again when you load them in the truck, and then before you arrive at the ED.

Conditions Requiring an ECG
A 12-lead isn’t just for chest pain. Acquiring one never hurts any patient and may help catch the odd presentation of a serious but vague condition. Obtain a 12-lead for possible strokes, altered levels of consciousness, weakness, dizziness, fatigue, palpitations and otherwise vague medical complaints. Remember that diabetic patients, younger women and various ethnicities often have atypical presentations and may have “silent myocardial infarctions.” Be vigilant. You may just save a life.