ELECTROCARDIOGRAM

An electrocardiogram (EKG or ECG) is a graphic representation of the heart’s electrical activity.

Endocardium

Myocardium

Epicardium

Cells of the Heart Muscle

• Cardio Myocytes• Polarized: inside is negative at rest;

outside is positive• Depolarized: voltage channels open and

allow sodium in which reverses polarity due to shift in electrolyte concentration.

• Repolarized: Cell returns to initial polarized state

Action Potential

• Nervous system (neurons) and muscle cells carry action potential

• When administering an EKG, the action potential measured is some skeletal and mainly cardiac.

Properties of Cardiac Cells

• Automaticity• Excitability• Conductivity• Contractility• The heart can initiate its own impulse

(automaticity), respond to the impulse(excitability), and transmit this impulse (conductivity).

• Contractility-mechanical property

• Purkinje Fibers

COMPONENTS

• Isoelectric Line

• Cardiac Cycle

• EKG paper

CARDIAC CYCLE

• One complete heart beat

• Depolarization – Cells stimulated & polarity changes

• Repolarization – Cells return to their normal state.

SINE WAVE

• P Wave • QRS Complex• T Wave• U Wave• PR Interval• QT Segment• ST Segment

Normal Parameters

• P-R Interval: .12-.20

• QRS Complex: .08-.12

• Q-T Interval: .42-.46

EKG PAPER

• Paper is heat and pressure sensitive

• Horizontal – rate

• Vertical - voltage

1mm

.2sec

5mm

.o4sec

Lead Placement

• Lead I: Ventricular Depolarization toward positive electrode. QRS positively deflected

• Lead II: Same as Lead I• Lead III: Ventricular

Depolarization between + and - so deflection + and -.

SINUS HEART RHYTHMS

• Normal Sinus

• Sinus Bradycardia

• Sinus Tachycardia

VENTRICULAR ARRYTHMIAS

• Premature Ventricular Contraction (PVC)

• Ventricular Tachycardia (V-Tach)

• Ventricular Fibrillation (V-Fib)

• Asystole