Choosing Antiarrhythmics

• In heart failure: only amiodarone and dofetilide
• Wolfe Parkinson White: procainamide or ibutilide
• Hypothyroid: non-DHP, avoid beta blockers
• Pregnancy: digoxin, non-DHP, no warfarin or heparin
• Do not use fenoldopam in patients with stroke, dopamine agonist can cause cerebral vasodilation and reduced blood flow to the brain
• 1a agents cause Torsades, usually avoid in structural heart disease
• 1b agents have little atrial affinity
• Sotolol: 50/50 sodium and potassium blockade, Torsades, especially in renal disease
• amio: TSH, pulmonary, liver, eyes, get baseline chest x-ray

Class	Name	VTach	Vfib	Afib	Other	Mech	AE
1a	disopyramide	X		X		block of both open Na & K decrease membrane response increases action potential duration prolong both the QRS and QT	widens QRS
	procainamide	X		X			widen QRS agranulocytosis drug-induced lupus
	quinidine	X		X	malaria aflutter		QT prolongation
1b	lidocaine	X	X			weak block of open & inactivated Na channels slightly decreases action potential duration little effect on the QRS	hypotension and seizure at high dose
	mexiletine	X					agranulocytosis blurry vision
	tocainide	X					agranulocytosis bone marrow supression leukemia
1c	flecainide	X		convert (rare)	PSVT and PAF	Strong block of open Na channels. no change to action potential duration large effect to prolong the QRS	hypokalemia hypomagnesemia worsen HFi increase QRS
	propafenone	X			PSVT and PAF		increase QRS neutropenia agranulocytosis
II	esmolol	X		X	aflutter, ST, HTN	Beta blockade
III	amiodarone	X	X	convert	aflutter PSVT	blocks K channels prolongs action potential duration	decrease K decrease Mg QT prolongation liver toxicity thyroid toxicity neuropathy blue syndrome
	dofetilide			convert	aflutter		increase QT decrease HR decrease K
	ibutilide			convert	aflutter		increase QT decrease HR
	sotalol	X		X	aflutter		increase QT decrease HR decrease K
IV	diltiazem			X	aflutter	not in WPW blocks Calcium channel	bradycardia HB worsens HF sick sinus syndrome
	verapmil			X
Misc	digoxin			X	aflutter can be used in HF	increases vagal tone	narrow therapeutic index decrease heart rate HB renal failure hypokalemia
	adenosine				PSVT in pregnancy	adenosine receptor agonist increases potassium and shortens AP	bronchospasm when administered, there is a brief pause of asystole on the monitor
	dronedarone			X	aflutter	blocks sodium channels beta-blockade blacks calcium channels Class I, II, III, IV effects prolongs action potential duration	worsens hearts failure worsens liver disease bradycardia heart block QT prolongation

This site has a great rundown on the mechanism and actions and how these agents shift the action potential. You probably don’t need to know all that for the BCPS. Just know how to pick an agent for a specific patient population.