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The electric activity of the

heart: the electrocardiogram

Electric activity is known as a basic feature of the cardiovascular system and is the stimulus for cardiac compression. Disturbances of electrical function are common in heart disease. Their very own registration as an electrocardiogram (ECG) performs an essential position in the diagnosis and administration of cardiovascular system disorders. THE GENESIS FROM THE ELECTROCARDIOGRAM Pathways of louage and the electrocardiogram

The sinus node is situated inside the right innenhof close to the access of the excellent vena cava. The atrioventricular node is based on the right atrial wall right away above the tricuspid valve. The fibres in the AV package (of His) arise in the atrioventricular client and run along the detras border with the septum between your ventricles (Fig. 1 . 1). On achieving the muscular section of the septum, they split into right and left bundle limbs and then disseminate in the subendocardium of the ventricles as the Purkinje program. The right pack is a slender, compact composition. The remaining bundle rapidly splits in to two or more categories or fascicles, one of which proceeds anteriorly, sharing similar blood supply because the right bundle, and one other is aimed posteriorly. In the usual series of occasions, the electric impulse develops in the nose node and spreads throughout the atria to succeed in the atrioventricular node. It could then simply reach the ventricles by simply passing in to the rapidly doing atrioventricular pack and its limbs. The first part of the ventricles to be stimulated is the nasal septum, followed by the endocardium. Finally, the impulse spreads outwards to the epicardium. The pass on of the heart failure impulse gives rise to the main deflections of the electrocardiogram: P, QRS and Big t waves (Fig. 1 . 2):

The P say represents atrial depolarization.

The PUBLIC RELATIONS interval symbolizes the time used for the cardiac impulse to spread over the innenhof and throughout the AV node and HisВ–Purkinje system.

The QRS complex signifies ventricular depolarization.

The T say represents ventricular repolarization.

Electrodes and leads

A conventional ECG consists of tracings from 12 or more qualified prospects. The term В‘lead' refers to the ECG attained as a result of saving the difference in potential between a pair of electrodes.

The bipolar (standard) leads

In these potential clients, the electrodes are attached to the hands or legs. In business lead I good electrode is attached to the left arm plus the negative to the right arm. In lead II the positive electrode is attached to the left lower-leg and the adverse to the correct arm. In lead III the positive is attached to the left lower leg and the bad to the left provide. They may thus be represented as:

lead I = left arm minus correct arm (LAВ–RA)

lead II = left lower-leg minus correct arm (LLВ–RA)

business lead III = left calf minus pinky finger (LLВ–LA).

It can be deduced from these kinds of equations that lead 2 should be equal to the total of potential clients I and III. The position from which the heart is usually viewed by simply each of these qualified prospects is demonstrated in Number 1 . 3.

Unipolar leads

These have an exploring electrode placed on a chosen site linked with an unsociable electrode with a very small potential. In an attempt to have a

Fig. 1 ) 3 Diagram of the powerful position of the bipolar (standard) leads. In lead I, the positive electrode is placed on the right arm and the negative to the right arm. Essentially, lead My spouse and i is the sum of the possibilities from the right arm with the ones that would be extracted from an electrode diametrically contrary the right equip. The resultant force is directed midway between those two points. Similar principles can be applied to get the effective direction with the leads II and III. central port with ‘zero potential', Pat connected all limb electrodes through 5000 Ω immunities to form the indifferent electrode. Unipolar torso leads

When unipolar leads will be recorded from the chest wall structure, the discovering electrode...



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