(X.) Electrocardiography
Physiology II - practice
Dep. of Physiology, Fac. of Medicine, MU © 2017
Electrocardiography
Definition: the process of recording the electrical activity of the heart
Keywords
• Specialized excitatory and conductive system of the heart
• equipment for ECG recording
• unipolar and bipolar leads
• bipolar limb leads; unipolar limb leds; unipolar chest leads
• heart vector, electrical axis of the heart
Specialized excitatory
and conductive system of the heart
branches fibers
Electric dipóle
electrode
Electrode: records electrical potential (O)
Electric lead: connection of two electrodes
• Recordes voltage between electrodes
• Voltage: difference between el. potentials (V= 01- 02)
Einthoven's triangle
(standard - limb, bipolar leads)
Augmented leads
(Goldberger's, limb unipolar leads)
Unipolar leads:
one electrode is active (variable el potential) and the second one is indifferent (constant el. potential)
Active electrode is always positive
Chest leads
Wilson's cental fek>terminalW^
Chest electrode: connection of chest electrode and Wilson's centra termina
aVF
Unipolar leads:
chest electrodes are active (positive) and Wilson's central terminal is indifferent (el. potential
0 mV, electrically centre of the heart)
Leads acording to Cabrera
ECG description
TO
interval
T wave QT interval
name	Norm
P wave	80 ms
Interval PQ(PR)	120-200 ms
Segment PQ (PR)	50-120 ms
Q	-
QRS	80-100ms
R	-
S	-
segment ST	80-120 ms
Interval QT	>= 420ms
wave T	160 ms
QT
Bazett's formula: QTc = ^=
QT depends on RR interval - correction of QT on RR
Electrical axis of heart
Average deviation of QRS complex in each lead
2. Sumation of QRS complex
1. QRS of 1,11 or III leads
mi : l if
Q = -l	Q = -l	Q=0
R = 5	R = 6	R = 4
S = -l	S = 0	S = 0
3	5	4
Physiological interval: -30° to +110(
3. Drawing in triangle:
e.g.: combination results from I and
180
-90°
60°
Srdecnf osa - 62°
Diagnostic use of ECG
Arrhythmia: irregular heart beat
Fibrillation: is the rapid, irregular, and unsynchronized activity of cardiac muscle fibers
Atrial fibrillation
(absence of P, Jagged" isolinia, irregular RR, HR 80-180 bpm)
Atrial fibrillation physiology
Ventricular fibrillation
(heart cannot pump, brain damage after 3-5 min)
Atrioventricular block: conduction between the atria and ventricles of the heart is impaired
I			
			
	UM		
H-f+ -PH VH
PR = 0.16 s Normal complex
PR = 0.38 s AV block I. degree
AV block
|Ldegree
AV block III. degree
Complete heart block. Atrial rate, 107; ventricular rate, 43
Diagnostic use of ECG
Myocardial ischemia, heart-attack
A
B (ST elevation)
hyperkalaemia
ill
Normal tracing (plasma K+ 4-5.5 meq/L).
Hyperkalemia (plasma K+ +7.0 meq/L).
Diagnostic use of ECG
24-hour monitoring of ECG (Holter)
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