Classifications for Antiarrhythmic Drugs

Question 1

The Vaughan-Williams classification comprises of a number of categories. Which of the following are part of this classification system?

A. Beta-blockers
B. Na+/K+-ATPase inhibitors
C. Adenosine receptor inhibitors
D. Na+ channel blockers
E. K+ channel blockers
F. α-adrenoceptor antagonists

Answer 1

A, D &E.

Beta-blockers, Na+ channel blockers, and K+ channel blockers.

Question 2

Regarding the cardiac action potential:

There are four phases

Answer 2

False. There are five Phases 0, 1, 2, 3 and 4.

Question 3

Regarding the cardiac action potential:

Pacemaker cells do not have Phases 1 and 2

Answer 3

True. Pacemaker cells only have Phases 0, 4 and 3.

Question 4

Regarding the cardiac action potential:

Phase 0 results from a rapid inflow of Na+ ions

Answer 4

True

Question 5

Regarding the cardiac action potential:

Phase 2 represents the plateau phase and is the relative refractory period

Answer 5

False. This represents the absolute refractory period.

Question 6

Regarding the cardiac action potential:

Phases 3 and 4: the resting membrane potential is re-established by 3 K+ moving out and 2 Na+ moving in

Answer 6

False. The resting membrane potential is re-established by two K+ moving in and three Na+ moving out.

Question 7

Under the Vaughan-Williams classification:

Membrane stabilizers are class IV drugs

Answer 7

False. Membrane stabilizers are class 1 under the Vaughan-Williams classification.

Question 8

Under the Vaughan-Williams classification:

Digoxin, adenosine and magnesium are are classified as ‘other’

Answer 8

True

Question 9

Under the Vaughan-Williams classification:

Calcium-channel blockers are class II drugs

Answer 9

False. Calcium-channel blockers are class IV under the Vaughan-Williams classification.

Question 10

Under the Vaughan-Williams classification:

Amiodarone is a class III drug

Answer 10

True. Amiodarone increases the action potential refractory period and is class III under the Vaughan-Williams classification.

Question 11

Under the Vaughan-Williams classification:

Quinidine, lidocaine and flecainide are all examples of membrane-stabilizing drugs

Answer 11

Quinidine, lidocaine and flecainide are classified as Ia, Ib and Ic respectively under the Vaughan-Williams classification.

Question 12

Ventricular tachycardia may be treated by (select all those that apply):

A. Amiodarone
B. Lidocaine
C. Verapamil
D. Flecainide
E. Digoxin

Answer 12

A, B & D.

Verapamil and digoxin are used to treat supraventricular tachycardias.

Flecainide, like lidocaine, can be used for ventricular tachycardias but can also be used for junctional re-entry tachyarrhythmias.

Question 13

Regarding the Sicilian Gambit:

The Sicilian Gambit is based on the clinical effect of the drug

Answer 13

False. It is based on the molecular target of the drug.

Question 14

Regarding the Sicilian Gambit:

Molecular targets in this classification include Na+ channels

Answer 14

True

Question 15

Regarding the Sicilian Gambit:

Muscarinic receptors are targets for antiarrhythmic drugs

Answer 15

True

Question 16

Regarding the Sicilian Gambit:

α-adrenoceptors and β-adrenoceptors are examples of second messengers

Answer 16

False. These are receptors of the autonomic nervous system.

Question 17

Regarding the Sicilian Gambit:

Some antiarrhythmic drugs target pumps and carriers

Answer 17

True

Question 18

Regarding the phases of the cardiac action potential:

Phase 0 occurs as a result of rapid inflow of Na+ ions to raise transmembrane potential from -65 mV to +20 mV

Answer 18

True. Phase 0 occurs as a result of rapid inflow of Na+ ions to raise transmembrane potential from -65 mV to +20 mV.

Question 19

Regarding the phases of the cardiac action potential:

Phase 1 results from rapid inward Na+ current and an inward K+ current in addition to an inward Cl- current

Answer 19

False. The voltage-gated Na+ inward current of Phase 0 terminates rapidly when the membrane potential becomes sufficiently positive. The phase 1 ‘notch’ in the action potential is caused by activation of transient outward K+ and inward Cl- currents.

Question 20

Regarding the phases of the cardiac action potential:

Phase 2 is produced primarily by the inward movement of sodium ions through slow sodium channels (L-type)

Answer 20

False. Phase 2 is produced primarily by the inward movement of calcium ions through slow calcium channels (L-type).

Question 21

Regarding the phases of the cardiac action potential:

In Phase 3, the rapid period of repolarization is from outward potassium movement down its concentration gradient through open K+ channels

Answer 21

True. In phase 3, the rapid period of repolarization is from outward potassium movement down its concentration gradient through open K+ channels.

Question 22

Regarding the phases of the cardiac action potential:

In phases 3 and 4, the resting membrane potential is re-established by two K+ moving inwards for every three Na+ moving outwards to give a net outward movement of positive charges

Answer 22

True. In phases 3 and 4, the resting membrane potential is re-established by two K+ moving inwards for every three Na+ moving outwards to give a net outward movement of positive charges.

Question 23

Regarding the mechanisms that generate arrhythmias:

Abnormal automaticity results in accelerated idioventricular rhythms

Answer 23

True

Question 24

Regarding the mechanisms that generate arrhythmias:

Torsades de pointes results from enhanced normal automaticity

Answer 24

False. Torsades de pointes is a triggered activity.

Question 25

Regarding the mechanisms that generate arrhythmias:

Wolff-Parkinson-White syndrome is a triggered activity

Answer 25

False. Wolff-Parkinson-White syndrome is an example of re-entry.

Question 26

Regarding the mechanisms that generate arrhythmias:

Inappropriate sinus tachycardias result from enhanced normal automaticity

Answer 26

True