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E LECTROCARDIOGRAPHY. Ulkumen Rodoplu, MD EuSEM. Plan. A Normal ECG Basic ECG Waveform Initiation of Spread of Electrical Activation in the Hearth The Magnitude and Direction of the Activation Process Activation Vectors. Introduction.
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ELECTROCARDIOGRAPHY Ulkumen Rodoplu, MD EuSEM
Plan • A Normal ECG • Basic ECG Waveform • Initiation of Spread of Electrical Activation in the Hearth • The Magnitude and Direction of the Activation Process • Activation Vectors
Introduction • Essential tool in the investigation of heart disease. • No cardiological assessment is complete without a 12-lead ECG. • One hundred million ECGs are recorded worldwide each year.
History • 19th century. The heart generated electricity. • Augustus Waller, working in St Mary's Hospital in London: The first systematical approach about the heart from an electrical point-of-view. • Willem Einthoven, working in Leiden, The Netherlands, invented the string galvanometer, which was much more precise than the capillary galvanometer that Waller used. • Einthoven assigned the letters P, Q, R, S and T to the various deflections, and described the electrocardiographic features of a number of cardiovascular disorders. He was awarded 1924Nobel Prize for Physiology and Medicine for his discovery.
Initiation and Spread of Electrical Activation in the Heart • In normal circumstances the whole process begins in the sino-atrial node.
Initiation and Spread of Electrical Activation in the Heart • SA Node normally initiates activation of the atrial myocardium • AV Node transmits activation received from the SA Node to the common bundle • HIS Bundle forms the electrical connection between the atria and the ventricles
Initiation and Spread of Electrical Activation in the Heart • The right and left bundlebranches run below the endocardial surfaces of their respective ventricles • The Purkinje network spreads over the endocardial surfaces of the ventricles
The Basic ECG Waveform • P wave - spread of electrical activation through the atrial myocardium. • QRS Complex – spread of electrical activation through ventricular myocardium. • T wave – electrical recovery of the ventricular myocardium.
<0.10 sec. wide <2.5 mm. amplitude (+)……DI, II, aVF (+) (-)… aVL (-)… aVR VI , biphasic or (-) P Wave
0.12 – 0.20 sec PR interval
QRS • Depolarisation of ventricles • <0.10 sec. wide
Repolarisation of ventricles 0.12-0.25 sec. wide (+)…DI, II, V2-6 (+) (-)…aVL, aVF (-)….aVR T Wave
Activation Vectors • A vector is simply something which has magnitude and direction. • Direction in which the arrow points represents the direction of the vector. • Length of the arrow represents the magnitude of the vector. • The apparent magnitude of the activation wave will depend on the direction from which it is sensed.
Polarisation and Depolarisation • Activation is actually the process of depolarisation and the spontaneous spread of this process over the myocardial cells. • Resting, healthy mycardial cells are polarised. • The surface membrane of each cell has an accumulation of charges – positive ones on the outside and an equal number of negative ones on the inside.
The QRS Complex • The central oblong is the myocardial strip. • The arrow shows the depolarisation vector in magnitude and in direction. • The deflection recorded by each lead is shown at the side of that lead.
ECG Derivations • Bipolar…DI, DII,DIII • Unipolar…aVR, aVL, aVF • Precordial….V1….V6
Electrical Axis-Practical Method • I,II,III,aVF.. QRS(+).... Normal • I…QRS(-), aVR…QRS(+)…RAD • II,III,aVF.. QRS(-)....30º LAD