Arrythmias

Sinus Arrhythmia

• Irregular rhythm that varies with respiration.
• All P waves are identical.
• Considered normal.

Wandering Pacemaker

• Irregular rhythm. P waves change shape as pacemaker location varies.
• Rate less than 100/min.

Multifocal Atrial Tachycardia

• Same as wandering pacemaker but rate is great than 100/min.

Atrial Fibrillation

• Irregular ventricular rhythm.
• Erratic atrial spikes (no P waves) from multiple atrial automaticity foci.

Escape Rhythms and Beats

• Automaticity focus escapes overdrive suppression to pace at it inherent rate (rhythm) or to emit transient beat.
• Due to loss of upstream pacing (e.g. sinus arrest) or conduction block
• Atrial foci paces at 60-80 bpm (non-SA node source)
• AV nodal foci paces at 40-60 bpm (may cause retrograde atrial depolarization)
• Ventricular foci paces at 20-40 bpm (Stokes-Adams Syndrome)

Premature Beats

• Irritable focus that spontaneously fires a beat.
• Atrial & AV node foci
• Epinephrine
• Increased sympathetic stimulation
• Stimulants: caffeine, amphetamines, cocaine, beta1-receptor agonists
• Digitalis
• Hyperthyroidism
• Stretch
• Ventricular foci
• Hypoxia
• Hypokalemia
• Mitral valve prolapse, myocardis