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Lead
Word lead has two meanings in electrocardiography: it refers to the cable that connects an electrode to the electrocardiograph, or (more commonly) to a combination of electrodes that form an imaginary line on the board in which electrical signals are measured. Then, using the term loosely items tapping the old sense, while the term 12 lead ECG using a new meaning. In fact, a 12 lead electrocardiograph usually only uses 10 wires / electrode. The latter definition of lead is the one used here.An electrocardiogram is obtained by measuring electrical potential between various points of the body using a biomedical instrumentation amplifier. A lead records the heart's electrical signals from a particular combination of recording electrodes which are placed at specific points on the patient's body.• When moving towards the positive electrode, a depolarization wavefront (or mean electrical vector) creates a positive deflection on the ECG in the corresponding lead.• When moving from the positive electrodes, depolarization wavefronts creates a negative deflection on the ECG in the corresponding lead.• When moving perpendicular to the positive electrodes, depolarization wavefronts (or mean electrical vector) creates equiphasic (or isoelectric) in the ECG, which will be positive as the depolarization wavefront (or mean electrical vector) approaches (A), and then became negative as it passes by (B).
There are 2 types of leads-unipolar and bipolar. ECG former have an indifferent electrode in the middle of Einthoven's triangle (which can be likened to a 'neutral' wall socket) at zero potential. Direction of these leads is from the "middle" of heart that leads radially outward and includes leads (chest) precordial and limb leads-VL, VR, & VF. Instead, a new ECG has a second electrode at some potential and direction of the corresponding electrode in the electrode potential derived from a lower to higher, eg., In the limb leads I, the direction from left to right, which includes limb leads - I, II , and III.Note that the color scheme for leads varies by country.
The augmented limb lead
Leads I, II and III are called limb leads because pokoq elektrokardiogafi never really have to put their hands and feet in buckets of salt water to get a signal from the Einthoven string galvanometer. ECG as it formed the basis of what is known as Einthoven's triangle. Finally, electrodes were invented that could be placed directly on the skin of the patient. Despite buckets of salt water longer necessary, the electrodes are still placed in the patient's arms and legs to approximate the signals obtained from a bucket of salt water. The electrodes are still the first three lead ECG 12 lead modern. Lead I is a dipole with the negative electrode (white) on the right arm and the positive electrode (black) on the left arm. Lead II is a dipole with the negative electrode (white) on the right arm and the positive electrode (red) on the left leg. Lead III is a dipole with the negative electrode (black) on the left arm and the positive electrode (red) on the left leg.
Lead aVR, aVL, and aVF are augmented limb leads, which is obtained from the same electrodes as leads I, II, and III. However, the three leads view the heart from different angles (or vectors) are different due to the negative electrode leads is a modification of Wilson's central terminal, which is obtained by adding leads I, II, and III together and attaching it to the negative terminal of the ECG machine. This zeroes out the negative electrode and allows the positive electrode to become the "exploring electrode" or a unipolar lead. This is possible because Einthoven's Law states that the I + (-II) + III = 0. This equation can also be written I + III = II. Written in this way (instead of I + II + III = 0) because Einthoven reversed the polarity of lead II in Einthoven's triangle, possibly because he liked to view upright QRS complexes. Wilson's central terminal paved the way for the development of the augmented limb leads aVR, aVL, aVF and the precordial leads V1, V2, V3, V4, V5, and V6.• Lead aVR or "augmented vector right" has a positive electrode (white) on the right arm. Negative electrode is a combination of the left arm electrode (black) and the left leg electrode (red), which "augments" the signal strength of the positive electrode on the right arm.• Lead aVL or "augmented vector left" has a positive electrode (black) on the left arm. Negative electrode is a composite electrode right arm (white) and the left leg electrode (red), which "augments" the signal strength of the positive electrode in the left arm.• Lead aVF or "augmented vector foot" has a positive electrode (red) on the left leg. Negative electrode is a composite electrode right arm (white) and the left arm electrode (black), which "augments" the signal of the positive electrode on the left leg.
Augmented limb leads aVR, aVL, and aVF are amplified in this way because the signal is too small to be useful because of the negative electrode is Wilson's central terminal. Together with leads I, II, and III, augmented limb leads aVR, aVL, and aVF form the basis of a referral system hexaxial, which is used to calculate the heart's electrical axis in the frontal plane.
Precordial leads
The precordial leads V1, V2, V3, V4, V5, and V6 are placed directly in the chest. Being situated near the heart, 6 they do not require augmentation. Wilson's central terminal is used for the negative electrode, and these leads are considered to be unipolar. Precordial leads view the heart activity in the horizontal plane. The heart's electrical axis in the horizontal plane referred to as the Z axisLeads V1, V2, and V3 are referred to as the right precordial leads V4, V5, and V6 are referred to as the left precordial leads.Negative QRS complex in lead V1 and positive in lead V6. The QRS complex should show a gradual transition from negative to positive between leads V2 and V4. Equiphasic lead is referred to as the transition lead. When it occurs earlier than lead V3, the transition is referred to as an early transition. When it occurs later than lead V3, this transition is referred to as the final transition. There should be a gradual increase in the amplitude of R wave between leads V1 and V4. This is known as R wave progression A small R wave progression nonspecific finding, because it can be caused by conduction abnormalities, myocardial infarction, cardiomyopathy, and other pathological conditions.• Lead V1 is placed in the fourth intercostal space on the right of the sternum.• Lead V2 is placed in the fourth intercostal space at left sternum.• Lead V3 is placed between leads V2 and V4.• Lead V4 is placed in the fifth intercostal space in linea (even if the apex beat displaced).• Lead V5 is placed horizontally with V4 at the anterior axillary line.• Lead V6 is placed horizontally with V4 and V5 in the midaxillary line.
Lead BASIS
An additional electrode (usually green) is located at 4 and 12 lead ECG modern, so-called basic lead by convention is placed in the left leg, although in theory it can be placed anywhere on the body. With 3 lead ECG, when one dipole is viewed, the rest becomes the basis when no leads.
