ECG vs. EKG

What is the difference between an ECG and an EKG ?

ECG: 

An Electrocardiogram (abbreviated as either ECG or EKG (from German, Elektrokardiogramm) is a graphic produced by an electrocardiograph, which records the electrical voltage in the heart in the form of a continuous strip graph. The ECG results provide the following:

1. Determine whether the heart is performing normally or suffering from abnormalities (eg. extra or skipped heartbeats - Cardiac arrhythmia).

2. May indicate coronary artery blockages (during or after a heart attack).

3. Can be used for detecting calcium, magnesium and other electrolyte disturbances.

4. Allows the detection of conduction abnormalities (heart blocks).

5. Indicates the physical shape of a patient during stress tests.

6. Can provide information on the physical condition of the heart (ie: left ventricular hypertrophy).

A typical ECG tracing of a normal heartbeat consists of a P wave, a QRS complex and a T wave. The P wave is the electrical signature of the current that causes atrial contraction. Both the left and right atria contract simultaneously. The QRS complex corresponds to the current that causes contraction of the left and right ventricles, which is much more forceful than that of the atria and involves more muscle mass, thus resulting in a greater ECG deflection. The T wave represents the repolarization of the ventricles. The QRS complex usually obscures the atrial repolarization wave so that it is not usually seen. Electrically, the cardiac muscle cells are like loaded springs. A small impulse sets them off, they depolarize and contract. Setting the spring up again is repolarization (more at action potential).

What is an EKG?

An EKG machine is a voltmeter. In other words, it reads electrical energy from the body. The heart uses electrical energy to cause muscle cells to contract. By reading the electrical energy of the heart, the nurse can tell if it is generated and conducted correctly.

An EKG is obtained by placing electrical sensors (leads) on the patient’s chest. Usually 12 leads are used to look at the heart from many angles. The EKG machine doesn’t look at all 12 leads at once; instead it chooses one at a time to view, and each view we call a lead on the resulting tracing.

What does it measure?

Electrical impulses are transferred to paper by the EKG machine. Two components of the tracing are especially useful: time and amplitude. Time is measured horizontally across the EKG strip. Amplitude is measured by the height of the tracing, which corresponds to the strength of the electrical impulse.

EKG paper is divided into small squares and larger squares. Small squares are 1mm high and 0.04 seconds long. Large squares are five small squares high (5mm) and five small squares long (0.20 seconds).

The EKG Complex

Depolarization: Impulses begin at the Sinoatrial (SA) node, generating a P-wave. The impulse travels through the electrical pathways to the Atrio-Ventricular (AV) node. The AV node delays the impulse, so that the atria and ventricles don’t fire at the same time. The delay is seen on the EKG as the P-R interval. As the impulse travels down the perkinje fibers in the ventricles, it generates the QRS complex. Repolarization: In order for the heart to fire again, it needs to re-load. Electrical re-loading of the heart is called repolarization and is represented by the T-wave on the EKG.