Electrocardiogram (ECG, EKG)
Medical Author:
Benjamin Wedro, MD, FACEP, FAAEM
Benjamin Wedro, MD, FACEP, FAAEMDr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center. Medical Editor:
Daniel Lee Kulick, MD, FACC, FSCAI
Daniel Lee Kulick, MD, FACC, FSCAIDr. Kulick received his undergraduate and medical degrees from the University of Southern California, School of Medicine. He performed his residency in internal medicine at the Harbor-University of California Los Angeles Medical Center and a fellowship in the section of cardiology at the Los Angeles County-University of Southern California Medical Center. He is board certified in Internal Medicine and Cardiology. Medical Editor:
Charles Patrick Davis, MD, PhD
Charles Patrick Davis, MD, PhDDr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
What Is an Electrocardiogram (ECG, EKG)?The electrocardiogram (ECG or EKG) is a diagnostic tool that is routinely used to assess the electrical and muscular functions of the heart. While it is a relatively simple test to perform, the interpretation of the ECG tracing requires significant amounts of training. Numerous textbooks are devoted to the subject. 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. It only measures the rate and rhythm of the heartbeat. This kind of monitoring does not constitute a complete ECG. Basic Anatomy of the Heart
The heart has four chambers – the right and left atrium and the right and left ventricle. The right side of the heart collects blood from the body and pumps it to the lungs while the left side of the heart receives blood from the lungs and pumps it to the body. Blood flows through the body in the following way:
Like any muscle, the heart requires oxygen and nutrients to function. Oxygen and nutrients are supplied by arteries that originate from the aorta. These vessels branch out to supply all the regions of the heart with oxygen rich blood. Electrically, the heart can be divided into upper and lower chambers. An electrical impulse is generated in the upper chambers of the heart that causes the atria to squeeze and push blood into the ventricles. There is a short delay to allow the ventricles to fill. The ventricles then contract to pump blood to the body and the lungs. Conducting system of the heart: SA means sinoatrial node. AV means atrioventricular node. RB and LB mean right and left bundle, respectively, and are the nerves that spread the electric impulse from the AV node into the ventricles.
The heart has its own automatic pacemaker called the sinaoatrial, or SA node, located in the right atrium. The SA node acts independently of the brain to generate electricity for the heart to beat.
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Electrocardiogram (ECG, EKG)
Atrial Fibrillation Overview
Atrial fibrillation describes an irregular and often rapid heart rhythm. The irregular rhythm, or arrhythmia, results from abnormal electrical impulses in the heart. The irregularity can be continuous, or it can come and go.
Normal heart contractions begin as an electrical impulse in the right atrium. This impulse comes from an area of the atrium called the sinoatrial (SA) or sinus node, the "natural pacemaker."
- As the impulse travels through the atrium, it
produces a wave of muscle contractions. This causes the atria to contract.
- The impulse reaches the atrioventricular (AV) node in
the muscle wall between the 2 ventricles. There, it pauses, giving blood from
the atria time to enter the ventricles.
- The impulse then continues into the ventricles, causing ventricular contraction that pushes the blood out of the heart, completing a single heartb...
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