The electrocardiogram (ECG or EKG) is a diagnostic tool that is routinely used to assess the electrical and muscular functions of the heart.
• The heart is a two stage electrical pump and the heart’s electrical activity can be measured by electrodes placed on the skin.
• The electrocardiogram can measure the rate and rhythm of the heartbeat, as well as provide indirect evidence of blood flow to the heart muscle.
• A standardized system has been developed for the electrode placement for a routine ECG.
• Ten electrodes are needed to produce 12 electrical views of the heart.
• An electrode lead, or patch, is placed on each arm and leg and six are placed across the chest wall.
• The signals received from each electrode are recorded.
• The printed view of these recordings is the electrocardiogram.
• By comparison, a heart monitor requires only three electrode leads – one each on the right arm, left arm, and left chest.
• A heart monitor only measures the rate and rhythm of the heartbeat.
The ECG is used to assess heart function. Patients who complain of chest pain or shortness of breath will often have an ECG as one of the first tests to help determine if there is an acute myocardial infarction or heart attack present. Even if there is no heart attack, the ECG can help decide whether the pain is due to angina or narrowing of blood vessels to the heart muscle (atherosclerosis). It is important to realize that an initial ECG may be normal even if there is heart disease present. Serial EKGs may be needed over time to find an abnormality.
ECGs are often performed when a patient complains of lightheadedness, palpitations, or syncope (passing out) since abnormal heart rate and rhythms may affect the heart’s ability to pump blood and provide the body with oxygen.
What Happens During an EKG Procedure?
The ECG is a relatively simple test to perform. It is non-invasive and does not hurt. Patches are placed on the skin to detect electrical impulses that the heart generates. These impulses are recorded by an ECG machine. Four patches are placed on the limbs. One is placed on each shoulder or upper arm and one on each leg. These are called the limb leads. There are six patches that are placed on the chest wall beginning just to the right of the breast bone. Patches are placed in the shape of a semi-circle ending near the left axilla (underarm). These are called the chest leads. These patches are connected to an ECG machine that records the tracings and prints them onto paper.
What Are the Interpretation and Results of an EKG?
Most often, the ECG assessment includes the following:
• determination of the rate,
• assessment of the rhythm,
• evaluation of the electrical conduction patterns.
Heart muscle that is irritated conducts electricity differently than heart muscle that is normal. Abnormal conduction may be apparent during ventricular contraction and during ventricular recovery.