HEALTH DATA

Learning Outcome 3

Learning Outcome 3

Electrocardiogram

Electrocardiography is the method of registration and investigation of the electric fields generated during operation of the heart. Electrocardiography is a relatively inexpensive, but valuable method of electrophysiological diagnostic tool in cardiology. Direct result of electrocardiography is obtaining an electrocardiogram (ECG) - a graphical representation of the potential difference arising from the heart and carried out on the body surface. On the ECG reflects the average of all vectors of action potentials that occur at some point in the heart.

Electrocardiogram (ECG) is the path obtained by the electrocardiograph, equipment invented in 1887 by German Augustus Waller and perfected later by the physiologist William Einthoven, which records the heart's activity by means of electrodes attached at various points of the body (using ten electrodes placed on the chest and on the upper and lower limbs).

The electrocardiogram it graphically represents the cardiac electrical activity during the contraction phase (systole) and relaxation (diastole) of the atria and the ventricles; the principle that underlies the electrocardiogram is what the muscle contractions are accompanied electrical changes that are denominated depolarization; such depolarization can precisely be recorded thanks to the electrodes which are applied on the body surface.

Electrocardiogram Recording and its Uses to Measure Cardiac Activity

The principle on which is based the measurement of the electrical activity of the heart is purely physiological: the occurrence of the pulses in the myocardium leads to generation of potential differences , which vary in space and time and that can be recorded by means of electrodes . The recording of the potential difference by electrodes placed on the body surface takes place thanks to the conductivity of the interstitial fluids of the human body. The ECG is the easiest, least expensive and most convenient way to see if the electrical activity of the heart is normal or if there are conditions of mechanical or bioelectrical(Sevilla, 2009, pp, 37). The normal ECG has a characteristic that varies only in the presence of problems. The track is characterized by several traits called “waves”, positive and negative, that are repeated for each cardiac cycle.

P wave is the first wave is generated in the cycle, and corresponds to the depolarization of the atria . It is small, since the contraction of the atria is not so powerful. Its duration varies between 60 and 120 ms, the width (or height) is equal to or less than 2.5 mm. QRS complex: it is a set of three waves that follow one another, and corresponds to the depolarization of the ventricles . The Q wave is negative and small, and corresponds to the depolarization of the interventricular septum; the R is a high peak positive, and corresponds to the depolarization of the apex of the left ventricle; the S wave is negative too small, and corresponds to the depolarization of the baseline and rear regions of the left ventricle. The duration of the entire complex is between 60 and 90 ms. In this interval is also the atrial repolarization which ...