Cardiac Arrhythmia Overview

Classification by Site of Origin

Normal Rhythm
- Set by SA node, firing 60-100 times per minute.
- Normal heart rate: 60-100 beats per minute.
Sinus Bradycardia
- SA node fires < 60 times per minute.
- Heart rate < 60 beats per minute.
- Normal during sleep, can be clinical.
Sinus Tachycardia
- SA node fires > 100 times per minute.
- Heart rate > 100 beats per minute.
- Normal during exercise, can be clinical.

Atrial Flutter (A Flutter)
- Caused by re-entrant pathways in the right atrium.
- Atrial rate: 250-400 beats per minute.
- Ventricular rate is slower due to AV node block.
- ECG: Absence of normal P-wave, presence of F waves in sawtooth pattern.
Atrial Fibrillation (A Fib)
- Caused by multiple ectopic impulses from around the atria.
- Atrial quivering rather than contracting.
- Ventricular rate is irregular.
- ECG: Absence of P waves, irregular narrow QRS complexes, undulating baseline.
AV Node Re-entrant Tachycardia (AVNRT)
- Small re-entrant pathway involving the AV node.
- Identical atrial and ventricular rates: 150-250 beats per minute.
- Regular and fast heart rate.

Ventricular Tachycardia (V Tach)
- Caused by a strong firing site in the ventricles.
- Often linked to structural heart problems.
- Regular and fast: 100-250 beats per minute.
- ECG: Wide, bizarre QRS complexes, absent P-wave.
- Sustained V Tach (>30 seconds) requires immediate treatment.
Ventricular Fibrillation (V Fib)
- Caused by multiple weak ectopic sites in ventricles.
- Ventricles fibrillate rather than contract.
- Can lead to cardiac arrest quickly.
- ECG: Irregular waveforms, no identifiable P-wave, QRS complex, or T-wave.

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