Physiology of Cardiac Conduction Cardiac Conduction Wave.pdf3/20/13 1 Cardiac Conduction Physiology of Cardiac Conduction • The excitatory electrical conduction system of the heart

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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