Interpret the 12-lead Electrocardiogram (EKG)?

From the Guidelines

To quickly read a 12-lead EKG, start by checking the patient's demographics and the EKG's date and time. Then, assess the rhythm by looking at the rate, rhythm, and axis, as the standard 12-lead ECG records potential differences between prescribed sites on the body surface 1. Check for any signs of ischemia or infarction, such as ST-segment elevation or depression, and look for any conduction abnormalities, such as bundle branch blocks.

Assessing the Rhythm

Begin with the rate and rhythm:

• Normal sinus rhythm has a rate of 60-100 beats per minute and a regular rhythm, which can be confirmed by looking for P waves before each QRS complex 1.
• The fundamental frequency for the QRS complex at the body surface is 10 Hz, and most of the diagnostic information is contained below 100 Hz in adults 1.

Evaluating the Axis

Next, evaluate the axis:

• Normal axis is between -30 and +100 degrees.
• Left axis deviation is -30 to -90 degrees, and right axis deviation is +100 to +180 degrees.

Checking for Ischemia or Infarction

Check for signs of ischemia or infarction:

• ST-segment elevation >1mm in two or more contiguous leads may indicate an acute myocardial infarction.
• ST-segment depression >1mm in two or more contiguous leads may indicate ischemia.

Assessing Conduction Abnormalities

Finally, assess for conduction abnormalities:

• Bundle branch blocks are indicated by a widened QRS complex (>120ms) 1.
• Left bundle branch block has a broad notched R wave in leads I and V6.
• Right bundle branch block has a broad R wave in lead V1 and a deep S wave in lead V6.

If any abnormalities are found, consider consulting a cardiologist or ordering further testing, such as a troponin level or an echocardiogram, as needed, and keep in mind that computer interpretation of ECGs should be considered a helpful adjunct to, but not a substitute for, physician interpretation 1.

From the Research

Interpretation of 12-Lead Electrocardiogram (EKG)

The 12-lead EKG is a noninvasive diagnostic tool that detects and records cardiac electrical activity, identifying cardiac pathology 2. It is a valuable diagnostic tool that has proven effective in detecting various cardiac abnormalities or enabling healthcare professionals to rule them out 3.

Key Components of 12-Lead EKG

• A 12-lead EKG uses cables or 'leads' attached with stick-on electrodes to specific parts of the body to create a series of ECG traces, which are then printed onto graph paper 3.
• Correct positioning of the electrodes using anatomical landmarks is essential to ensure an accurate and high-quality ECG recording 4.
• Skin preparation is essential, since suboptimal electrode contact or electrodes being placed where there is a significant amount of dry or dead skin cells, grease, sweat or hair, can negatively affect the quality of the ECG recording 4.

Clinical Applications of 12-Lead EKG

• A 12-lead EKG is frequently used in a variety of clinical settings, including emergency care, preoperative and post-operative assessment, and primary care 4.
• It is used to assess and diagnose patients with suspected arrhythmias, hypertension, coronary heart disease or heart failure 4.
• ECG parameters associated with recurrent cardiovascular events include bundle branch blocks, P-terminal force, left ventricular hypertrophy, and a broader QRS complex 5.
• Furthermore, more leftward P-wave axis, prolonged QTc, and P-wave duration >120 ms are associated with increased risks of cardiac events 5.

Best Practices for Recording 12-Lead EKG

• Careful preparation and correct electrode and lead placement are crucial to ensure accuracy when recording a 12-lead EKG 3.
• The use of single-patch ECG may help alleviate overcrowding or staffing issues in emergency departments, although more research is required 6.
• Continuous ECG without interfering with other exams is feasible in complex emergency room circumstances 6.