INTRODUCTION TO ELECTROCARDIOGRAM & LEAD SYSTEM

BASICS OF ELECTROCARDIOGRAM



The electrocardiogram is the graphic record of electrical activities of the heart obtained by placing the electrodes on the surface of the body that records the voltage difference generated by the heart. The electrocardiogram is derived from the Greek meaning Electro-related to electrical activity, cardio(kardio)-heart,graph-to write. Augustus desire waller (1856-1922) was the first to record electrical potential associated with beating heart from the human body surface(1887-1888). Willem Einthoven invented the string galvanometer in 1901. In 1924 he was awarded Nobel prize for inventing the first practical system of electrocardiography. The type of machines is string galvanometer, Radio amplifiers, Computer-based systems and electronic display and direct pen recorder. The basic principle of the Ecg is the stimulation of cardiomyocytes this property is known as automaticity.


Electrocardiogram(ecg wave form)


CONDUCTION SYSTEM OF THE HEART:


ECG LEADS: There are direct leads and indirect leads. Indirect leads are chest leads, limb leads and esophageal leads. Direct leads are placed directly over the heart.

LIMB LEADS: Bipolar & Unipolar

Bipolar leads: L I: Between RA&LA

                         L II: Between RA&LL

                         LIII: Between LA&LL

EINTHOVEN TRIANGLE :



EINTHOVENS LAW: If the electrical potential of any two of the three bipolar limb electrocardiographic leads are known at any given instant, the third one can be determined mathematically by summing the first two.

Unipolar leads: Unipolar limb leads :VR,VL,VF,augmented limb leads: aVR,aVL,aVF,Unipolar chest leads




Unipolar chest leads or precordial leads are V1, V2, V3, V4, V5, V6 and special leads are V7, V8, V9 

Esophageal leads are E15-25,E25-35,E40-50


You can also refer this topic in this link

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