Post on 19-Mar-2018
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Cardiac Conduction
Physiology of Cardiac Conduction
• The excitatory & electrical conduction system of the heart is responsible for the contraction and relaxation of the heart muscle.
• The sinoatrial node (SA node) is the pacemaker where the electrical impulse is generated.
How to Read an
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PQRST wave Deflection waves
P wave
• Lasts 0.08 s • Shows Atrial contraction
Deflection waves
QRS complex
• Results due to depolarization of ventricles • Ventricular contraction • R waves are deflected positively and the Q and S waves
are negative
T wave • Results due to ventricular decontraction (Relax)
Normal ECG Deflection Wave Pattern
Abnormal ECG Deflection Wave Patterns
Sinus Bradycardia
Rate = 40-59 b.p.m.
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Sinus Tachycardia
Rate = 101-160 b.p.m.
Causes
• CHF, hypoxia, pulmonary edema
• Increased temperature
• Stress or response to pain
Sinus Arrhythmia
Rate = 45-100 b.p.m.
Sinus Arrest
Causes
Myocarditis
MI
Digitalis toxicity
Atrial Flutter
Rate = 250-350 b.p.m.
Precipitates CHF
Atrial Fibrillation (afib)
Causes
COPD
CHF
AV block
Causes
• Digitalis toxicity
• Acute infection
• MI
• Degeneration of the conductive tissue.
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Ventricular Tachycardia (V-tac)
Causes • CAD • Acute MI • Digitalis toxicity • CHF
Rate = 100-220 b.p.m.
Ventricular Fibrillation (V-fib)
Causes
Acute MI
Asystole