Electrocardiogram electrical activity

An arrhythmia may occur as a result of heart disease or from a disorder that affects cardiovascular function. Conditions such as emotional stress, hypoxia, and electrolyte imbalance also may trigger an arrhythmia An electrocardiogram (ECG) provides a record of the electrical activity of the heart. Careful interpretation of the ECG along with a thorough physical assessment is necessary to determine the cause and type of arrhythmia The goal of antiarrhythmic drug therapy is to restore normal cardiac function and to prevent life-threatening arrhythmias. 

The electrocardiogram (ECG) is a non-invasive means of measuring the electrical activity of the heart. The relationship... 

Electrocardiogram A noninvasive method of recording the electrical activity of the heart. 

Figure 13.4 Electrocardiogram. The electrocardiogram (ECG) is a measure of the overall electrical activity of the heart. The P wave is caused by atrial depolarization, the QRS complex is caused by ventricular depolarization, and the T wave is caused by ventricular repolarization.

Electrocardiographic Signature of OPs Disturbances in the electrical activity of the heart caused by xenobiotics are readily discernible in a surface electrocardiogram (Yurumez et al, 2008 Dalvi et al, 1986 Chuang et al, 1996 Chhabra et al, 1970). 

Measurement of electrical activity in the heart, now known as the electrocardiogram (ECG), was introduced about 75 years ago by Willem Einthoven. The ECG is simple to perform and is the most frequently used, least invasive, and cheapest cardiovascular test. ° It remains the procedure of first choice for evaluation of chest pain, dizziness, or syncope. In its simplest interpretation, the ECG characterizes rhythms and conduction abnormalities. However, the ECG also provides, by inference, information about the anatomy and structures of the heart, pathophysiologic changes, and hemodynamics of the CVD system. ECG abnormalities are often the earliest sign of adverse drug effects, ischemia, and electolyte abnormalities. 

Electrical activity in the heart can be picked up by electrodes placed on the skin and recorded as the familiar electrocardiogram (ECG). The ECG is a record of the sum of all action potentials in the heart as it contracts. Action potentials are generated by depolarization followed by repolarization of the cardiac muscle cell membrane. Depolarization is initiated by an influx of sodium ions into the cardiac muscle cells, followed by an influx of calcium ions. Repolarization is brought about by efflux of potassium ions. The phases of a cardiac action potential are shown in Eigure 4.3 where the depolarization is the change in resting membrane potential of cardiac muscle cells from —90 mV to 4-20 mV. This is due to influx of sodium ions followed by influx of calcium ions. Contraction of the myocardium follows depolarization. The refractory period is the time interval when a second contraction cannot occur and repolarization is the recovery of the resting potential due to efflux of potassium ions. After this the cycle repeats itself. 

ECG - electrocardiogram - record of electrical activity in the heart as it contracts... 

Fractals can also be inferred from morphogenesis (the development of form or structure), where a single time scale does not adequately address all time-dependent processes. The electrocardiogram seems to have fractal time properties, as well as electrical activity of a single neuron and beat-to-beat variability of the heart rate. There are also fractal (power law) variations in blood neutrophil counts. Further research will probably turn up other cases of self-similarity. 

The electrocardiogram is a skin surface measurement of the electrical activity of the heart muscle (known as myocardium). With each heart beat ions move through the heart muscle and gradients of charge are formed. Taking a differential measurement of the electrical potential on the body surface at different locations generates different ECG vectors. These vectors are known as leads. The ECG leads are formed from three electrodes placed on the body, with an optional fourth electrode used as a reference (MIT, 2013). 

The electrocardiogram (ECG) is a weU-known pattern of electrical activity. For present purposes, a simplified approach can be adopted, with focus falling on just one of the multiple intervals that can be identified on an ECG. Figure 3.1 is a stylistic representation of an ECG waveform, with the landmarks and interval of interest identified. These are the onset of the QRS complex, the offset of the T-wave, and the distance between these two points, known as the QT interval. Given that drug-induced prolongation of the QT interval is of considerable importance in the book s discussions, a stylistic representation of QT interval prolongation is shown in Fig. 3.2. 

Electrocardiogram (EKG) Recording over time of the heart s electrical activity. 

Electrocardiogram (ECG) The visual display of the electrical activity of the heart as recorded from electrodes placed on the skin surface. 

Electrical activity in electrically excitable cells results from the opening and closing of ion channels in a voltage- and time-dependent manner. The depolarisation of a single cardiac cell results in the electronic spread of electrical activity to adjacent cells and the production of current which flows in the direction of depolarisation. A second, repolarising current, is established in order to restore electrical excitability to cells. If these currents are recorded in individual cells we observe an AP, if they are recorded on the surface of the body we observe an electrocardiogram (ECG). 

DiFrancesco D, Noble D (1985) A model of cardiac electrical activity incorporating ionic pumps and concentration changes. Philos Trans R Soc Lond 307 353-398 Einthoven WE (1912) The different forms of the human electrocardiogram and their signification. Lancet 1 853-861... 

The ECG, short for electrocardiogram is a graphical representation of the electrical activity generated by the heart. This can be of help in diagnosing or supporting the presence of cardiac rhythm disturbances, structural heart disease, acute cardiac emergencies and a variety of other medical conditions. The ECG is a cheap and easily repeatable test. The wide availability of the ECG means that it is available... 

Ischemia, injury, and infarction-the three I s of myocardial infarction (Ml)-produce characteristic electrocardiogram (ECG) changes. The changes shown by leads that reflect electrical activity in damaged areas are shown to tite right of the illustration below. 

The QT interval can be seen on an electrocardiogram (ECG), as represented in Figure 4.2. The ECG is possibly the most recognized bodily pattern of activity. In the late nineteenth century, it was realized that the electrical changes occuring during the heart s contraction could be detected by placing electrodes on the skin... 

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