Electrocardiogram (ECG) is one of the fastest and safest ways out there to evaluate the heart’s ability to contract and move blood. Sticky electrodes are placed on the skin in specific places to measure the heart’s rhythm. These patches are then connected to wires called leads which reads the heart’s electrical impulses and sends that information to the ECG/EKG. (The difference between ECG and EKG? Nothing. One stands for the English spelling of electrocardiogram while the other stands for the German spelling.)
But what happens when the ECG leads are incorrectly placed? How do you know you need to re-place them. (Not replace, reposition.)
1. You see something you have “never seen before.”
The old adage, “When you hear hoofbeats, think horses. Not zebras” applies to every aspect of medicine, but especially diagnostics. One study found that ECG lead misplacement is accounting for an alarming rise in misdiagnoses both in cardiac outpatient clinics and intensive care units. The study even anecdotally spoke of a patient who was diagnosed with an inferior, anterior, and lateral MI but was displaying atypical symptoms. As it turns out, two places where the leads were inserted into the machine were reversed creating a reversed polarity in the results. If what you are seeing doesn’t at all make sense, consider lead misplacement first.
2. Your limb leads are suspect.
The most common instance of ECG lead misplacement is in the limb leads. Most often, the right and left are reversed resulting in negative P and QRS waves coming out of lead I. These negative waves are extremely uncommon, especially for someone experiencing cardiac problems. Their mere presence should cause you to take a look at your leads and ensure they are in the right place.
3. You are reading an ECG outside of a hospital.
Even though nearly 4 percent of all ECG’s recorded are done so with incorrect placement of the leads, it happens even more often before the patient even reaches the hospital. EMS personnel and other first responders are more likely to experience improper lead placement than doctors in the emergency department or cardiac ward. This does not mean reading a 12-lead ECG in the field isn’t important, it just warrants an extra bit of attention.
While they affect electrode placement rather than lead placement, these factors have also been shown to impact the readings.
- Obesity – It is more difficult to place electrodes in their proper position on patients who are obese.
- Body hair – Electrodes rely on direct contact with the skin to read the electrical impulses of the heart. ECG results tend to not be as accurate if the body hair is not eliminated before reading.
- Dry electrode gel – Fresh, wet electrode gel will ensure good conduction.
- Interference – Electrical interference from handheld devices can affect the results of an ECG
Annual training in lead placement, carrying a pocket guide to ECG interpretation and assigning a single provider to connect ECG electrodes and leads can also lead to better, more accurate results across the board and a reduction in errors due to ECG lead misplacement.