Our GP is ready to help you if you want to be sure that you are healthy and in good shape, you have medical questions or problems and want to discuss with an experienced doctor, you have some unknown symptoms and want to know what they could be related to, you want to know another medical opinion about the best way of treatment of your disease.
An electrocardiogram (EKG, ECG) is a test that measures the
electrical signals that control the rhythm of your heartbeat.
The
heart is a muscular pump consisting of
four
chambers. The two upper chambers are called atria, and the two lower
chambers are called ventricles. A natural electrical system causes the heart
muscle to contract and pump blood through the heart to the lungs and the rest
of the body.
The electrical activity of the heart can be detected through the
skin by small metal discs called electrodes. During electrocardiography, the
electrodes are attached to the skin on the chest, arms, and legs. The
electrodes are also connected to a machine that translates the electrical
activity into line tracings on paper. These tracings are often analyzed by the
machine and then carefully reviewed by a doctor for abnormalities.
An electrocardiogram may show:
Evidence of heart
enlargement.
Signs of insufficient blood flow to the
heart.
Signs of a new or previous injury to the heart (heart
attack).
Heart rhythm problems
(arrhythmias).
Changes in the electrical activity of the heart
caused by an
electrolyte imbalance in the body.
Signs
of inflammation of the sac surrounding the heart (pericarditis).
Electrocardiography cannot predict whether a person will have a
heart
attack.
Electrocardiography Results
Electrocardiography tracings show a characteristic pattern of
electrical impulses that are generated by the heart. The different parts of an
EKG tracing of a heartbeat are called the P wave, the QRS complex, the ST
segment, and the T wave.
The P wave is a record
of the movement of electrical activity through the upper heart chambers and is
recorded when they contract.
The QRS complex
is a record of the movement of electrical impulses through the lower heart
chambers and is recorded when they contract.
The ST
segment usually appears as a straight, level line between the QRS
complex and the T wave. Elevated or lowered ST segments may mean the heart
muscle is damaged or not receiving enough blood.
The
T wave corresponds to the period when the lower heart
chambers are relaxing and preparing for their next muscle contraction.
Electrocardiography (EKG,
ECG)
Normal:
The heart rate (usually between 60 and 100 beats per
minute) and rhythm appear normal.
P waves, QRS complexes, T waves appear normal.
ST segments are not elevated above or depressed below the
baseline of the EKG tracing.
A normal-appearing EKG can occur even in the presence of
heart disease. For this reason, the EKG should always be interpreted along with
a person's symptoms, history, physical examination, and, if necessary, other
test results.
Abnormal:
When the electrical pattern of the EKG tracing is abnormal,
it may indicate some type of heart disease. Sometimes an electrocardiogram may
detect an abnormality only during exercise or when symptoms are occurring. In
these cases, special forms of an EKG called an exercise EKG or an ambulatory
EKG may be needed.
Heart rhythm. There are many different
kinds of irregular heartbeats (arrhythmias). A heart rate less than 60 beats
per minute is called a bradycardia. A heart rate greater than 100 beats per
minutes is called a tachycardia. Examples of tachycardias may include
ventricular fibrillation (a fast, irregular heart rhythm that originates in the
ventricle) or atrial flutter (a fast, regular heart rhythm that begins in the
atrium). Abnormal conduction of the electrical impulse in the heart can also be
seen in other types of arrhythmias.
Coronary artery disease and heart attack (myocardial
infarction). If the coronary arteries supplying blood to the heart
muscle are blocked, the muscle may receive less oxygen and may even die (heart
attack). This damage to the heart muscle may show up on the electrocardiogram.
Early EKG signs of poor blood flow to the heart may include lowered (depressed)
ST segments. Early EKG signs of heart attack often include raised (elevated) ST
segments. Later, as the heart attack persists, Q waves on the EKG may appear
and become deeper.
Thickened chamber walls
(hypertrophy). Certain changes in the EKG may suggest thickening
of the muscle walls of one or more heart chambers. Conditions that may cause
hypertrophy of one or more heart chambers include
high blood pressure,
coronary artery disease,
heart failure,
cardiomyopathy, or heart valve disease.
Inflammation of the heart. Elevated ST
segments on the EKG may indicate an inflammation of the heart muscle
(myocarditis) or the sac that surrounds the heart (pericarditis).
Chemical changes (electrolyte
imbalance). Proper contraction of the heart depends upon normal
levels of chemicals (called
electrolytes) in the blood, such as calcium and
potassium. Too much or too little of these electrolytes results in certain
rhythm abnormalities, such as abnormal changes in the P wave, QRS complex, or T
wave that can be seen on an electrocardiogram.
Medical online consultation with qualified doctors
Copyright © 2004-2005