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ElectrocardiographyElectrocardiography It is a voltage
difference, record the electrical activity of the heart as well as valuable information about the heart function and structure.
Willem Einthoven 1924
Leads (Leads (lead x electrodelead x electrode))LIMB LEADSIIIIII
AVFAVLAVR
CHEST LEADSV1V2V3V4V5V6
bipolar
unipolar
ECG Leads - Views of the Heart
V1 & V2 Septum V3 & V4 anterior +Right
Ventricle V5 & V6 Lateral Left
VentricleII+III+AVF inferior border
P waveP waveRepresent the
electrical activity of both atria ( atrial depolarization)
The depolarization slow within the AV node, there is a brief delay or PAUSE before the depolarization conducted to the ventricles
Normal duration <0.12 sec
Absent P wave:Atrial fibrillation SA BlockAV Rhythm
Peak P wave:Atrial hypertrophy
QRS ComplexQRS ComplexRepresent the
electrical activity of both ventricles.
Ventricular depolarization( initiation of the ventricular contraction
QRS ComplexQRS ComplexQQ wave wave
RR wavewave::
SS wave : wave :
: : Normal QRS duration < 0.12 secNormal QRS duration < 0.12 sec
QRS ComplexQRS ComplexQQ wave wave
first first downward downward deflection deflection ..
septal septal depolarization.depolarization.
0.04sec0.04sec..
RR wavewave: : first upwardfirst upward deflection.deflection. height: 5-8 mm.height: 5-8 mm. early ventricular
depolarization
ST - SegmentST - SegmentST segment: the
plateau phase of ventricular repolarization.
Isoelectric or> or<1mm.
If the ST segment elevated or depressed beyond the normal baseline this usually sign of serious pathology. (MI)
T- WaveT- WaveT-wave :represent rapid
phase of ventricular repolarization.
peaked T wave: early MI hyperkalemia Black races
Inverted : MI . Ventricular hypertrophy. Hypokalemia Digoxin
U waverepolarization of the interventricular
septum. low amplitude Prominent: suspect hypokalemia,
hypercalcemia or hyperthyroidism
J wave represents the approximate end of
depolarization and the beginning of repolarization
camel-hump sign .Hypothermia hypocalcemia.
AXISAXISAt any point during depolarization
and repolarization electrical potential are being propagated in different directions.
Most of these cancel each other out and only the net force is recorded. This net is called AXIS or cardiac VECTOR