ECG and EKG Encyclopedia

Posted by Medical Board on August 11, 2015 in Heart Health Last updated on February 22, 2019 EKG ECG electrocardiogram

The Heart of the Matter—Your EKG Explained

While some physicians use the term, “ECG” when monitoring the heart, others prefer the abbreviation “EKG”.  Both are correct, and refer to the word, electrocardiogram.  In German, this translates to, Elektro-kardiographie, hence the abbreviation with the letter “K”. 

So, What is an EKG?

Regardless of its spelling, an EKG, or electrocardiogram is essentially a display of an individual’s heartbeat recorded through the process of electrocardiography. The test utilizes electrodes placed on a patient’s body to detect small electrical charges emitted from the heart muscle over a period of time.  During each heartbeat the heart muscle sends an electrical charge, which is captured and recorded throughout the cardiac cycle. 

This non-invasive medical procedure works by placing a number of electrodes on the individual’s chest and limbs.  The heart’s complete electrical potential is then measured from a variety of different angles.  The information indicates the direction and magnitude of electrical depolarization from the heart.

Electrocardiography is the actual process of monitoring the heart’s electrical activity over a given period of time.  An EKG/ECG provides two very important kinds of information.  The first measures the time it takes for the electrical wave to pass through the heart.  This indicates whether the electrical activity is irregular, too fast, too slow, or normal.  The second is the amount of electrical activity that actually passes through the heart.  This can indicate whether specific areas (in the heart) are overworked or larger than they should be. 

EKG Rhythms—What They Signify

Cardiac rhythms recorded during an EKG/ECG test may indicate either normal or abnormal heart activity.  With every single heartbeat, electrical events occur.  These events are reflected in an EKG graphic tracing.  As the heart moves through a complete cardiac cycle specific waveforms are produced that can be interpreted by a medical practitioner. Information about the heart’s structure and its electrical conduction system is critical in identifying and diagnosing certain medical conditions and disease processes within the body.

An EKG conveys valuable information to the medical practitioner.  This includes the rate and rhythms of heartbeats, the size of the heart, chamber positions, any damage to the muscle cells or conduction system, the function of pacemakers, and the effects of any cardiac medications.

ECG Interpretation

With every beat of the heart, there is an orderly progression of depolorization. This begins with the pacemaker cells in the sinoatrial node.  It continues as it spreads out through the atrium, then the atrioventricular node, down left into the bundle of His and down and to the left through the ventricles. This creates the tracing that is interpreted by a medical practitioner.

Electrocardiograms produce waveform components that signify specific electrical events for each beat of the heart.  These are labeled P, Q, R, S, T, and U.

While a skilled clinician is needed to accurately interpret a cardiac tracing, there are specific waveforms that indicate a normal EKG, as opposed to an abnormal EKG. 

A normal EKG ECG generally reflects the following:

P wave—This is the very first movement that is short and upward on a tracing.  It demonstrates the atria contracting and that blood is pumping into the ventricles of the heart.

QRS complex—This begins generally with downward deflection, Q; larger deflection upwards, R (a peak), followed by a downward S wave.  It indicates    ventricular depolarization and contraction.

PR interval—This is an indication of the time it takes the sinus node signal to get to the ventricles.

T wave—This is an upward waveform indicating ventricular repolarization.

Abnormal EKG ECG

The presence of abnormal EKG rhythms can indicate many things. Some EKG abnormalities are considered normal for a particular individual and are not harmful to health.  Others may signal a medical emergency such as a myocardial infarction (heart attack), or an arrhythmia that’s dangerous.  Based on information collected from an EKG reading, a trained medical professional can determine if further treatment is necessary. 

An abnormal EKG may indicate:

  • Defects or abnormalities in the shape and size of the heart
  • One of the heart walls is larger than the other
  • Electrolyte imbalances
  • Heart attack or ischemia

Electrocardiogram/EKG Practice

Many medical universities, private institutions, and online sites offer coursework and programs designed to give students EKG practice.  Most provide sample practice strips that allow individuals to interpret specific waveforms that indicate disease processes and medical conditions.

EKG Test—What To Expect

An EKG test is a simple painless procedure.  Using a machine that is usually portable, a clinician attaches electrodes to the patient’s chest, arms, and legs.  Most EKG machines monitor the heart from several different perspectives using 12 leads or electrodes.  The test takes approximately 10 minutes as the electrical impulses are transmitted to a screen display or paper printout.  At this point, the waveforms created may be interpreted by either a physician or other health practitioner. Learn about the role of an EKG Technician.

Seek emergency medical treatment if you experience any of the following:

  • Chest pain, discomfort, or tightness
  • Breathing difficulties
  • Heart palpitations
  • Feeling dizzy, or as if you might pass out
  • Racing heart
  • Pressure on chest/squeezing
  • Suddenly weak

Heart disease remains the leading cause of death throughout the world.  The EKG is an important tool that helps your doctor properly diagnose and treat a myriad of medical conditions.  This simple test could save your life, or the life of a loved one.


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