Med in Small Doses - SVT Tachyarrhythmias

This post is on some common and important SVT/Atrial Tachyarrhythmias (e.g. Atrial Fibrillation). See Cardiac Arrhythmias for a complete overview. A Quick Guide to ECG will also give you tips on how to approach an ECG. Remember Bundle Branch Blocks effect ECG interpretation.

Typically Narrow complex (QRS<0.12)
EXCEPTION: SVT + Bundle Branch Block cause Board complex.

Supraventricular tachycardia: causes SNAP

S inus tachy

N odal tachy

A fib

P aroxysmal atrial tachy

Irregular
Atrial Fibrillation (AF): most important arrhythmia. irregular, irregular pulse. Loss of P waves.

Adapted from AFib by J.Heuser

RFs: IHD, HTN, Chronic EtOH use, cardiomyopathy, Congenital HD, Valvular lesions

Causes PIRATES:

P ulmonary: PE, COPD

I atrogenic

R heumatic heart: mirtral regurgitation

A therosclerotic: MI, CAD

T hyroid: hyperthyroid

E ndocarditis

S ick sinus syndrome

Complications: ↓ CO, embolic stroke, ↑ ventricular response.

Tx: Rate control (Beta-blockers, CCB, digoxin), rhythm control (DC cardioversion, amiodarone, flecainide) & anticoagulation.

• AF < 48h – Cardiovert immediately with a bit of heparin
• AF > 48h – Look for a clot. Rhythm control or rate control + anticoagulation.

Management ABCD

A nti-coagulate

B eta-blocker to control rate

C ardiovert

D igoxin

Multifocal atrial tachycardia (MAT): P-waves of at least 3 different morphologies that all fall before irregular, narrow QRS complexes.

Regular
Sinus Tachycardia (rate > 100 bpm)
Causes: exercise, pain, anxiety, hypovolaemia, PE, hyperthyroidism.
Management Priority: Search for a cause.

AVNRT: nodal problem.

• Most common regular SVT tachycardia.
• Females > Males

AVRT: accessory pathway.

• Most common WPW. Short PR intervals. Delta waves.

General Tx: Valsalva manoeuvre, Carotid Sinus Massage (CSM), ocular pressure. Adenosine, DC cardioversion.