SFOS 19

Cardiac rhythm that is not normal sinus rhythm

Rate > 100 bpm

Rate < 60 bpm

• Late phase of A.P. - cell not fully repolarized
• If stimulated, A.P. will be abnormal

Allows time for atria to empty before ventricles contract

Slower or blocked AV conduction

• Congenital muscle remnant creates additional AV electrical connection (macroreentry)
• Premature ventricular contraction

• AV node - 50 bpm intrinsic
• Pukinje cells - 30 bpm intrinsic

Overdrive suppressed by SA node

Self-perpetuating pattern of depolarization

• Difference in refractory periods
• Slow conduction in one pathway
• Unidirectional block of one pathway

• Anatomic reentry (macro/micro) - obstacle is fixed
• Functional reentry - diffuse abnormalities in tissue

Administer large electrical shock to whole heart

• Decreased automaticity - all P waves have QRS
• Failure of conduction - delayed P or no QRS

• Bradycardia with vasodilation
• Casued by decrease in ventricular volume

• Increased PR interval, each P has QRS
• Usually due to increased vagal tone

Mobitz 1 - gradual PR interval increase before blocked beat (atropine or exercise cures)

Mobitz 2 - random loss of QRS (degenerative His-Purkinje)

• Complete failure of conduction (no QRS after P)
• Needs pacemaker to prevent asystole