Electrocardiogram ECG or EKG

04/13/2023 university of Georgia 1

electrocardiogramUniversity of Georgia

PUBLIC HEALTH AND HEALTH SCIENCE

Dentistry faculty

Abdullah saad


An introduction:• An electrocardiogram (also called an ECG or EKG) is a test that checks for problems with the electrical

activity of your heart. An EKG translates the heart's electrical activity into line tracings on paper. The spikes and dips in the line tracings are called waves.

• Each beat of your heart is triggered by an electrical impulse normally generated from special cells in the upper right chamber of your heart.

• An electrocardiogram records these electrical signals as they travel through your heart.

• An electrocardiogram is a noninvasive, painless test. The results of your electrocardiogram will likely be reported the same day it's performed, and your doctor will discuss them with you at your next appointment.

• The EKG is not only the oldest but, in fact, over 100 years After its introduction, continues as the most commonly used cardiovascular laboratory procedure.


willem Einthoven1860-1927


The old electrocardiogram The modern electrocardiogram


Function:An electrocardiogram (EKG or ECG) is done to:• Check the heart's electrical activity.• Find the cause of unexplained chest pain, which could be caused by a heart attack,

inflammation of the sac surrounding the heart (pericarditis), or angina.• Find the cause of symptoms of heart disease, such as shortness of breath, dizziness, fainting,

or rapid, irregular heartbeats (palpitations).• Find out if the walls of the heart chambers are too thick (hypertrophied).• Check how well medicines are working and whether they are causing side effects that affect

the heart.• Check how well mechanical devices that are implanted in the heart, such as pacemakers, are

working to control a normal heartbeat.• Check the health of the heart when other diseases or conditions are present, such as high

blood pressure, high cholesterol, cigarette smoking, diabetes, or a family history of early heart disease.


Ecg paper

• ECG tracings are recorded on grid paper. The horizontal axis of the • EKG paper records time, with black marks at the top indicating 3 second intervals. • Each second is marked by 5 large grid blocks. Thus each large blocks equals 0.2

second. The vertical axis records EKG amplitude (voltage). Two large blocks equal 1 millivolt (mV). Each small block equals 0.1 mV.• Within the large blocks are 5 small blocks, each representing 0.04 seconds.


P waveThe P wave represents atrial depolarization. In normal EKGs, the P-wave proceeds the QRS complex. It looks like a small bump upwards from the baseline. The amplitude is normally 0.05 to 0.25mV (0.5 to 2.5 small boxes). Normal duration is 0.06-0.11 seconds (1.5 to 2.75 small boxes). The shape of a P-wave is usually smooth and rounded.

In this step we should measure the interval from where the P wave begins until the beginning of the QRS complex. . Normally this interval is 0.12 to 0.20 seconds (3 to 5 small boxes) in adults, longer in elderly people. This interval shortens with increased heart rate.

Einthoven named the prominent waves alphabetically, P, Q,R, S, and T

prominent waves

The PR Interval


QT interval• The QT interval represents the time of ventricular activity including both

depolarization and repolarization. • It is measured from the beginning of the QRS complex to the end of the

T wave. Normally, the QT interval is 0.36 to 0.44 seconds (9-11 boxes). The QT interval will vary with patient gender, age and heart rate. Another guideline is that normal QT Intervals is less than half of the R-R Interval for heart rates below 100 bpm.

• The ST segment represents the early part of ventricular repolarization.The ST segment is the line that from the end of the QRS complex to beginning of the T wave. Normally the ST segment is flat, being neither positive or negative relative to the baseline.

ST segment


The QRS complex

• The QRS complex indicates ventricular depolarization. Depolarization triggers contraction of the ventricules.

• Because of the larger tissue mass, the QRS complex is larger than the P wave.• In this step, measure the QRS interval from the end of the PR interval to the

end of the S wave. Use calipers, marking paper or by counting small boxes. Normally this interval is 0.06 to 0.12 seconds (1.5 to 3 boxes).

• The T wave indicates the repolarization of the ventricules. Take note of T waves which have a downward (negative) deflection or of T waves with tall, pointed peaks.

• The U-wave is a small upright, rounded bump. When observed, it follows the T-wave.

T wave




Sinus bradycardia

Sinus bradycardia is a sinus rhythm of under 60 beats per minute. It is normal in children, in well-conditioned athletes and other healthy people. It also occurs naturally during sleep. Severe sinus bradycardia is a type of sick sinus syndrome.

Sinus Bradycardia Features

Look for rhythm that is regular, with heart rate that is slow (< 60 bpm). Notice that the P wave is normal. The PR interval is normal (0.12-0.20 sec). The QRS is normal (0.06-0.10 sec).

• Causes:

• This rhythm may be caused by one of the following:

• Increased vagal tone.

• Sleep

• Hypothermia

• An effect of drugs, such as the use of digitalis, beta-blockers,

• Seizure.

• It could also be a normal finding in a healthy, well-conditioned person.


Sinus tachycardia

Sinus Tachycardia is sinus rhythm with a rate of more than 100bpm In sinus tachycardia the sinus node fires between 100 and 180 beats per minute, faster than normal. The maximal heart rate decreases with age from around 200 bpm to 140 bpm.Sinus tachycardia normally has a gradual start and ending. Most often sinus tachycardia is caused by an increase in the body's demand for oxygen, such as during exercise, stress, infection and blood loss . It can also express an effort of the heart to compensate for a reduced stroke volume, as occurs during cardiomyopathy.

• Appropriate sinus tachycardia can result from:

• Exercise

• Anxiety

• Alcohol / caffeine use

• Drugs (e.g. beta-agonists like dobutamine)


Third-Degree Heart Block

• In this type of heart block, none of the electrical signals reach the ventricles. This type also is called complete heart block or complete AV block. • When complete heart block occurs, special areas in the ventricles may create

electrical signals to cause the ventricles to contract. This natural backup system is slower than the normal heart rate and isn't coordinated with the contraction of the atria. On an EKG, the normal pattern is disrupted. The P waves occur at a faster rate that isn't coordinated with the QRS waves.• Complete heart block can result in sudden cardiac arrest and death. This type of

heart block often requires emergency treatment. A temporary pacemaker may be used to keep the heart beating until you get a long-term pacemaker.


Einthoven's triangle• Einthoven's triangle is an imaginary formation of

three limb leads in a triangle used in electrocardiography, formed by the two shoulders and the pubis. The shape forms an inverted equilateral triangle with the heart at the center that produces zero potential when the voltages are summed. It is named after Willem Einthoven.• Lead placements• Lead I - This axis goes from shoulder to shoulder, with

the negative electrode placed on the right shoulder and the positive electrode placed on the left shoulder.• Lead II - This axis goes from the right arm to the left

leg, with the negative electrode on the shoulder and the positive one on the leg.• Lead III- This axis goes from the left shoulder (positive

electrode) to the left leg (negative electrode).


Health & Medicine

Electrocardiogram ECG or EKG