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Medical Uses of Electrocardiography: – Obtain information about heart’s electrical functioning. – Combined with heart structure knowledge and physical exam signs. – Indications for performing […]

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Medical Uses of Electrocardiography:
– Obtain information about heart’s electrical functioning.
– Combined with heart structure knowledge and physical exam signs.
– Indications for performing ECG include chest pain, suspected heart attack, shortness of breath, fainting, arrhythmias, medication monitoring, overdose management, electrolyte abnormalities, and perioperative monitoring in anesthesia cases.

Screening with Electrocardiography:
– ECG not recommended for asymptomatic or low-risk individuals to prevent misdiagnosis and overtreatment.
– Required for certain critical occupations.
– Hypertrophic cardiomyopathy screening in adolescents and for sports physicals to prevent sudden cardiac death.

Electrocardiograph Machines and Components:
– ECGs recorded by machines with electrodes connected to a central unit.
– Advancements in machines include digital converters, portable devices with screens, keyboards, and printers, as well as smaller devices for fitness trackers and smartwatches.
– Components of an ECG include P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave (ventricular repolarization), and the orderly progression of depolarization in a healthy heart.

Continuous Monitoring with Electrocardiography:
– Used for critically ill patients and those under general anesthesia.
– Detects infrequently occurring cardiac arrhythmias.
– Conducted using Holter monitors, defibrillators, pacemakers, or biotelemetry to provide extended monitoring beyond conventional ECGs.

Advanced Cardiac Monitoring Devices:
– Holter monitor introduced in 1962, with newer devices like Zio XT, Trident, BioTel, CAM.
– Implantable devices such as artificial cardiac pacemakers, implantable cardioverter-defibrillators, and loop recorders.
– Utilization of Arduino kits and smartwatch devices like Apple Watch and Samsung Galaxy Watch 4 for cardiac monitoring.
– Importance of proper placement of electrodes and leads, including limb leads, augmented limb leads, and the hexaxial reference system for calculating the heart’s electrical axis.

Electrocardiography (Wikipedia)

Electrocardiography is the process of producing an electrocardiogram (ECG or EKG), a recording of the heart's electrical activity through repeated cardiac cycles. It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the heart 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:

ECG of a heart in normal sinus rhythm
Use of real time monitoring of the heart in an intensive care unit in a German hospital (2015), the monitoring screen above the patient displaying an electrocardiogram and various values of parameters of the heart like heart rate and blood pressure

Traditionally, "ECG" usually means a 12-lead ECG taken while lying down as discussed below. However, other devices can record the electrical activity of the heart such as a Holter monitor but also some models of smartwatch are capable of recording an ECG. ECG signals can be recorded in other contexts with other devices.

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 depolarization of the atria.
  • The QRS complex, which represents depolarization of the ventricles.
  • The T wave, which represents 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. 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.

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