Antiarrhythmics

Question 1

Adenosine

Answer 1

Class 5 antiarrhythmic - Miscellaneous

Depresses sinus node activity and slows conduction through the atrioventricular node; also produces peripheral and coronary vasodilation.

Adenosine has a rapid onset and short duration of action.

Question 2

Amiodarone

Answer 2

Class 3 antiarrhythmic - potassium channel blocking

Decreases sinus node and junctional automaticity, slows atrioventricular (AV) and bypass tract conduction and prolongs refractory period of myocardial tissues (atria, ventricles, AV node and bypass tract); also has weak beta-blocker activity.

Question 3

Digoxin

Answer 3

Cardiac glycoside

Class 5 antiarrhythmic - Miscellaneous

Slows heart rate and reduces atrioventricular (AV) nodal conduction by an increase in vagal tone and a reduction in sympathetic activity. Increases the force of myocardial contraction by increasing the release and availability of stored intracellular calcium.

Question 4

Disopyramide

Answer 4

SAS product

Class 1a antiarrhythmic - sodium channel blocking

Prolongs refractory period of myocardial tissue (atria, ventricles, ventricular conduction system, bypass tracts) and reduces automaticity in Purkinje fibres. It has significant anticholinergic activity, which may increase atrioventricular nodal conduction, and it also has a negative inotropic effect

Question 5

Esmolol

Answer 5

Beta-blocker

Class 2 antiarrhythmic - Beta blocking

Esmolol is an ultra-short-acting beta-blocker (beta1 selective). It has no significant intrinsic sympathomimetic or membrane stabilising activity at therapeutic doses.

Question 6

Flacainide

Answer 6

Class 1c antiarrhythmic - Sodium channel blocking

Slows cardiac conduction and to a lesser extent, increases refractory period in all myocardial tissues (including bypass tracts) but particularly in the His-Purkinje (ventricular conduction) system. Also has negative inotropic activity.

Question 7

Isoprenaline

Answer 7

Beta agonist; increases cardiac output by its positive chronotropic and inotropic actions. It tends to maintain or increase systolic BP, and decreases diastolic BP by lowering peripheral vascular resistance. It increases automaticity and atrioventricular nodal conduction, and usually improves coronary blood flow.

Question 8

lidocaine

Answer 8

Class 1b antiarrhythmic - Sodium channel blocking

Reduces automaticity of myocardial tissue with little effect on cardiac conduction. It has a mild negative inotropic effect and weak neuromuscular blocking activity.

Question 9

Sotolol

Answer 9

Beta-blocker + potassium channel blocker

Class 3 antiarrhythmic - potassium channel blocking

A nonselective beta-blocker that also prolongs the refractory period of atria, ventricles and bypass tract. It has no significant intrinsic sympathomimetic or membrane stabilising activity at therapeutic doses.