(VII.) Electrocardiography
Physiology
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
• limb and chest leads
• unipolar and bipolar leads
• heart vector, electrical axis of the heart
Specialized excitatory
and conductive system of the heart
Sinoatrial node (SA)
internodal
pathways
Atrioventricul node(AV)
Bundle of His
Bundle branch
Purkyne fibers
Electric dipóle
electrode
Electrode: records electrical potential (O)
Elektric lead: connection of two electrodes
• Recordes voltage between electrodes
• Voltage: difference between el. potentials (V= 01- 02)
Einthovens triangle
(standard, limb, bipolar leads)
ľ
Bipolar leads: both electrode
active (variable potential en electrodes)
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 temina
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
P wave
PQ interval
QRS complex
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
formula: QTc = J=
Is onRR interval - correction of
Electrical axis of heart
Average deviation of QRS complex in each lead
1. ORSof 1,11 and III lead
——^t-^—^i-
2. Sumation of QRS complex
Q = -l	Q = -l	Q=0
R = 5	R = 6	R = 4
S = -l	S = 0	S = 0
3	5	4
150°
180°
150°
Physiological interval: -30° -110(
Diagnostic use of ECG
Arrhytmia: irregular heartbeat
Fibrillation: is the rapid, irregular, and unsynchronized activity of cardiac muscle fibers
fibrillation normal
Atrial fibrillation
(absence of P, Jagged" isolinia, irregular RR, HR80-180bpm)
																						
		-V			\ /•	A	f*		.A				f		\ -		v	w	\			1
\!		V	\J	—	V	\	I		V				V	I		V	V	V				
Ventricular fibrillation
(heart cannot pump, brain damage after 3-5 min)
Atrioventricular block: conduction between the atria and ventricles of the heart is impaired
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
media.org/wikipedia/commons/thumb/6/64/Afib_ecg.jpg/400px-
Diagnostic use of ECG
Myocardial ischemia, heart-attack
A
B (ST elevation)
hyperkalaemia
ill
mm
Normal tracing (plasma K+ 4-5.5 meq/L).
Illllllli;
Hyperkalemia (plasma K+ +7.0 meq/L).
Diagnostic use of ECG
24-hour monitoring of ECG (Holter)
Patient ID: Ciannel I 31-DEC-87      Page 1
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