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