ECG

Electrocardiography is the process of producing an electrocardiogram (ECG or EKG), a recording – a graph of voltage versus time – of the electrical activity of the heart[4] using electrodes placed on the skin. These electrodes detect the small electrical changes that are a consequence of cardiac muscle depolarization followed by repolarization during each cardiac cycle (heartbeat). Changes in the normal ECG pattern occur in numerous cardiac abnormalities, including cardiac rhythm disturbances (such as atrial fibrillation and ventricular tachycardia), inadequate coronary artery blood flow (such as myocardial ischemia and myocardial infarction), and electrolyte disturbances (such as hypokalemia and hyperkalemia).

In a conventional 12-lead ECG, ten electrodes are placed on the patient’s limbs and on the surface of the chest. The overall magnitude of the heart’s electrical potential is then measured from twelve different angles (“leads”) and is recorded over a period of time (usually ten seconds). In this way, the overall magnitude and direction of the heart’s electrical depolarization is captured at each moment throughout the cardiac cycle.

There are three main components to an ECG: the P wave, which represents the depolarization of the atria; the QRS complex, which represents the depolarization of the ventricles; and the T wave, which represents the repolarization of the ventricles.

During each heartbeat, a healthy heart has an orderly progression of depolarization that starts with pacemaker cells in the sinoatrial node, spreads throughout the atrium, and passes through the atrioventricular node down into the bundle of His and into the Purkinje fibers, spreading down and to the left throughout the ventricles.[6] This orderly pattern of depolarization gives rise to the characteristic ECG tracing. To the trained clinician, an ECG conveys a large amount of information about the structure of the heart and the function of its electrical conduction system. Among other things, an ECG can be used to measure the rate and rhythm of heartbeats, the size and position of the heart chambers, the presence of any damage to the heart’s muscle cells or conduction system, the effects of heart drugs, and the function of implanted pacemakers.

ECG Masters’ Collection: Favorite ECGs from Master Teachers Around the World 2018

This medical book ECG Masters’ Collection: Favorite ECGs from Master Teachers Around the World 2018 has just shared the basic knowledge of electrocardiography, while also showing the actual clinical pathological situations in which ECG...
ECG Masters Collection: Favorite ECGs From Master Teachers Around The World

ECG Masters Collection: Favorite ECGs From Master Teachers Around The World

- Cardiovascular diseases account for a large proportion of disease patterns. How to assess cardiac activity is an important issue, especially in emergencies. In addition to the clinical symptoms, electrocardiographic survey is an...
Critical Cases in Electrocardiography: An Annotated Atlas of Don’t-Miss ECGs for Emergency and Critical Care

Critical Cases in Electrocardiography: An Annotated Atlas of Don’t-Miss ECGs for Emergency and Critical...

This medical book Critical Cases in Electrocardiography: An Annotated Atlas of Don’t-Miss ECGs for Emergency and Critical Care, presents many examples of ECGs, errors that can be encountered when reading the diagnosis so that...