Tachy-arrhythmias

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General notes on tachy-arrhythmias

Causes of tachy-arrhythmias:

1. anatomical substrate (re-entrant pathway, foci of enhanced automaticity)
2. metabolic substrate

Classification:

- Narrow complex (QRS < 120 ms) = SVT (SupraVentricular Tachycardia) / AF (Atrial Fibrillation)

- Broad complex (QRS > 120 ms) = SVT + BBB (Bundle Branch Block) / VT (Ventricular Tachycardia) / VF (Ventricular Fibrillation)

- SVT (SupraVentricular Tachycardia) = sinus tachycardia / atrial tachycardia / atrial flutter. Also include:

a. Junctional tachycardias = AVNT (AV nodal tachycardia) / AVNRT (AV nodal re-entry tachycardia / AVJRT (AV junctional re-entry tachycardia)

b. WPW (Wolff-Parkinson-White syndrome) = AVRT (AV re-entrant tachycardia)

- VT

- Fibrillation = AF / VF

Sinus tachycardia - causes:

- physiological (exercise / fear / pain / pregnancy)
- shock (hypovolaemia / sepsis / PE - Pulmonary Embolus)
- metabolic (fever / hyperthyroidism / CO2 retention / sympathomimetics)
- neural (ANS neuropathy)

Diagrams of aetiologies:

QuickNotes

Management of tachy-arrhythmias

SVT

- Vagotonic maneovres slow conduction through the AV node (Valsava / cartoid sinus massage / swallowing cold drinks)

- Drugs that slow AV conduction:

Acute (IV) adenosine
Chronic (b-blockers, verapamil, flecainide)

- Radiofrequency ablation

WPW

- risk of VF if AF (since no AV node to slow transmission)

- management = prophylactic ablation or DC cardioversion if “pre-excited AF”

VT

- pulseless VT: DC cardioversion (ALS)

- haemodynamically stable (IV) lidocaine

- prophylaxis for future VT (b-blockers, amiodarone, ACE-I)

- also consider: CABG (Coronary Artery Bypass Grafting - to treat ischaemic trigger of VT) / ICDs (Implantable Cardioverter-Defibrillators)

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