Heart Rhythms: Normal or Abnormal (Arrhythmias)

Anatomy & Physiology L2 and L3

Cardiac Muscle

Electrical Conduction

SA Node Primary “jump-

start” for the heart Creates a beat

approx 70 bpm If faulty, replaced

by artificial pacemaker

AV node Delays/↓

transmission of signal Could only create

approx 40 bpm on its own

NOT strong enough to sustain life (so need the SA node)

Interior anatomy of heart

Bundle of His Collection of cardiac

cells creating the AV bundle

Conduct impulses along septum to the Purkinje fibers in walls of the ventricles

Takes impulse about 0.03-0.04 sec to travel to the ventricles

Purkinje fibers: largest fibers filaments

Located on inner wall of endocardium

Carry electrical impulse from SA and AV nodes

Electrocardiogram (ECG or EKG)

12-lead (multi-angle)

Normal Sinus Rhythm

P wave

QRS complex

T wave

Bradycardia

Tachycardia Notice the sinus

rhythm

Approx 120 bpm

Ventricular Fibrillation Overall: 300 bpm Cannot sustain life

Artificial Pacemakers

Implanted beneath skin Composed of: electrical pulse

generator and lead wires to communicate with the heart tissue

Permanent battery Can be checked over the phone

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Pacemakers