Cardiac Conduction

• SA node
• AV node
• Bundle of His
• Purkinje Fibers

depolarize as the heart chambers contract

60-100

40-60

20-40

contraction

relaxation, return to normal resting stage of the cell

Dominant pacemaker

“Sinus Rhythm”

Similar to “pebble dropped in water” sending ripple effects starting with atria contraction

Atrial depolarization

Time when atrium is contracting

Impulse travel through the conduction system

impulse is traveling through the conduction

After the electrical activity passes through the AV node, bundle branches and Purkinje Fibers then depolarization of the ventricles occur

The filaments of the Purkinje fibers distribute the depolarization stimulus to the ventricular myocardial cells

Depolarization of the ventricles produces the QRS complex

Measured from the beginning of the Q Wave until the end of the S wave.

First downward deflection

Not always present

Upward wave

Follow R wave

Downward stroke

Should return to baseline

Represent early ventricular repolarization


Normally isoelectric line

myocardial injury, ischemia, infarction etc.

MI

Low broad hump

Rapid phase of ventricular repolarization


Repolarization of the ventricles begin immediately after the QRS complex and persists until the end of the T wave

Interference seem on rhythm strip or monitor

Looks like fuzzy baseline

Caused by patient moving, loose electrodes,

Can mimic lethal rhythms – check patient!

• Can look like an arrythmia. Chieck pt if , if pt is
• stable could be leads or pt is moving

Each smallest block is 1mm by 1mm

Each small block is 0.04 sec.

Between the heavy black lines are 5 small squares totaling 0.2sec.

Usually from R wave to R wave

Several methods

-“big block method” – most accurate

-“6 second strip” – quick method least accurate

-“Memory method”

atrial depolarization