Antiarrhythmics Classification (Vaughan Williams)

Epomedicine, May 27, 2024May 27, 2024

Understand the conducting system of heart, cardiac action potential and pacemaker action potential.

Physiology of Conducting System of Heart

Mnemonic to remember Vaughan Williams classification for anti-arrhythmic – Some Block Potassium Channel DAAM!

Mnemonic	Class	Mechanism of action	Comments	Example	Use
Some	IA	Sodium channel blocker (moderate) Intermediate action	Moderate ↓ phase 0 slope ↑ EFR & AP duration Additional class III action	Quinidine, Procainamide, Disopyramide	Ventricular arrhythmias, WPW (procainamide)
	IB	Sodium channel blocker (weak) Fast action	Small ↓ phase 0 slope ↓ EFR & AP duration	Lidocaine, Mexiletine	VT
	IC	Sodium channel blocker (strong) Slow action	Pronounced ↓ phase 0 slope = EFR & AP duration	Flecainide, Propafenone	Paroxysmal AF, recurrent SVT
Block	II	Beta blocker	↓ phase 4 slope in nodes (pacemaker potential) Prolong AV node repolarization	Atenolol, Bisoprolol, Carvedilol, Esmolol, Metoprolol, Propranolol, Sotalol	Recurrent tachyarrhythmias
Potassium	III	Potassium channel blocker	Delay phase 3 (repolarization)	Amiodarone (also class I, II & IV action), Sotalol (also class II action), Dofetilide, Ibutilide	Atrial fibrillation & flutter, Ventricular tachycardia
Channel	IV	Calcium channel blocker	Prolongs phase 2 ↓ slope phase 0 & 4 in node (pacemaker potential) Prolong AV node repolarization	Verapamil, Diltiazem	Paroxysmal SVT, AF with RVR
DAAM	V/Others	Direct nodal inhibition		Digoxin Atropine Adenosine Magensium sulphate	SVT (Adenosine), Torsades de pointes (Magnesium), Rate control in AF (Digoxin)

PGMEE, MRCS, USMLE, MBBS, MD/MS

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The anatomical basis of Upper Motor Neuron Lesion (UMNL) has already been discussed earlier. Similarly, we will explain the anatomical basis of clinical syndrome of Lower Motor Neuron Lesion (LMNL). A. Ipsilateral involvment: Lower motor neuron comprises of motor neurons in the anterior neurons and the fibers originating from them,…

PGMEE, MRCS, USMLE, MBBS, MD/MS

Diffusion-Perfusion-limited-Gas-Exchange

Perfusion and Diffusion Limited Gas Exchange

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Under resting conditions, red blood cells move through the pulmonary capillary bed in approximately 0.75 seconds (transit time), although equilibration of oxygen and carbon dioxide takes place in about 0.25 seconds. In a diffusion limited gas exchange situation, the alveolar gas is still equilibrating with the blood cell at the…

PGMEE, MRCS, USMLE, MBBS, MD/MS

Diacerin : Mnemonic

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