Electrocardiogram (ECG, EKG)
What Is an Electrocardiogram (ECG, EKG)?
The electrocardiogram (ECG or EKG) is a diagnostic tool that is regularly used to assess the electrical and muscular functions of the heart. While it is a comparatively easy test to present, the interpretation of the ECG tracing needs significant amounts of training. Numerous textbooks are devoted to the subject.
The heart is a two stage electrical pump and the heart’s electrical motion can be measured by electrodes placed on the skin. The electrocardiogram can measure the rate and rhythm of the heartbeat, as well as give 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 required 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 every electrode are recorded. The printed view of these recordings is the electrocardiogram.
By comparison, a heart monitor need only three electrode leads – one each on the right arm, left arm, and left chest. It only measures the rate and rhythm of the heartbeat. This kind of monitoring does not constitute a total ECG.
Heart Function and the ECG
Electrode leads on the chest wall are capable to sense electrical impulses that are create by the heart. Multiple leads give many electrical views of the heart. By interpreting the tracing, the physician can learn about the heart rate and rhythm as well as blood flow to the ventricles (indirectly).
Rate refers to how fast the heart beats. Usually, the SA node generates an electrical impulse 50-100 times per minute. Rhythm refers to the type of heartbeat. Usually, the heart beats in a sinus rhythm with each electrical impulse generated by the SA node resulting in a ventricular contraction, or heartbeat. There are a variety of abnormal electrical rhythms, some are usual variants and some are potentially dangerous. Some electrical rhythms do not create a heartbeat and are the reason of sudden death.
There can also be short circuits that can lead to irregular electrical pathways in the heart causing abnormalities of rate and rhythm. Wolfe-Parkinson-White (WPW) syndrome is a circumstance where an abnormal accessory pathway at the AV node can reason tachycardia.
The ECG tracing can also give information about whether the heart muscle cells are conducting electricity appropriately. By analyzing the shape of the electrical waves, the physician may be capable to determine if there is reduce blood flow to parts of the heart muscle. The presence of an acute blockage associated with a myocardial infarction or heart attack can be determined as well. That’s one of the cause that an ECG is done as soon as possible when a patient presents with chest pain.
What Happens During an ECG?
The ECG is a comparatively easy test to perform. It is non-invasive and does not hurt. Patches are placed on the skin to detect electrical impulses that the heart creates. 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 joined to an ECG machine that records the tracings and prints them onto paper.
Newer machines also have video screens that help the technician, nurse, or doctor make a decision whether the quality of the tracing is adequate or whether the test should be repeated. ECG machines are also equipped with computer programs that can help interpret the ECG, although they are not totally correct.
In certain situations, the physician may want to look at the heart from different angles after the initial ECG is done. The chest leads may then be placed across the right chest wall or on the back.
The skin should be clean and dry to stop electrical interference to get an acceptable tracing for interpretation. Sometimes that means shaving chest hair or aggressively toweling off the skin. Shivering or tremors can interfere with the tracing and reason interference that affects the quality of the ECG tracing. generally, the patient has to hold still for 5-10 seconds without moving to get an accurate ECG.