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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 1924 Nobel 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 bundle branches 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. Electrical Activity & ECG P Wave < 0.10 sec. wide < 2.5 mm. amplitude (+)……DI, II, aVF (+) (-)… aVL (-)… aVR VI , biphasic or (-) PR interval 0.12 – 0.20 sec QRS Depolarisation of ventricles < 0.10 sec. wide T Wave Repolarisation of ventricles 0.12-0.25 sec. wide (+)…DI, II, V2-6 (+) (-)…aVL, aVF (-)….aVR Calculation of Rate 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. A Normal 12 - Lead Electrocardiogram ECG Derivations Bipolar…DI, DII,DIII Unipolar…aVR, aVL, aVF Precordial….V1….V6 Precordial Electrodes Einthoven Triangle A Normal Vectorcardiogram Electrical Axis Electrical Axis-Triaxial Method Electrical Axis- Hexaxial Method Electrical Axis-Practical Method I,II,III,aVF.. QRS(+).... Normal I…QRS(-), aVR…QRS(+)…RAD II,III,aVF.. QRS(-)....30º LAD Normal ECG Leads Normal Sinus Rhytm Sinus Tachycardia Sinus Bradycardia Sinus Arrhytmia Atrial Escape Beat Nodal Escape Beats Nodal Rhythm in Complete AV Block Atrial Tachycardia Supraventricular Tachycardia Atrial Flutter – atrial rate 300 Atrial Flutter – 2:1 Conduction, Atrial rate 300 Ventricular Premature Contractions Multiform VPBs Ventricular Couplets Ventricular Flutter Ventricular Fibrilation First degree AV Block Second degree AV Block Wenckebach or Mobitz Type I Second degree AV Block Mobitz Type II