Cardiovascular Drugs (Arrhythmia)

Arrhythmia

abnormal heart beat resulting from an error in impulse formation and conduction in the myocardium. Usually categorized according to the anatomic site of the abnormality.

Abnormal automaticity

Abnormal automaticity – sites of the heart other than the SA node are generating competing stimuli to the SA node resulting in an arrhythmia.

Reentry

Reentry – occurs when there is a blockage to conduction. This results in a short circuit pathway that produces an arrhythmia. The most common cause of an arrhythmia

drug induced

The most common cause of prolonged QT interval is...

macrolides

antipsychotics

two drug classes that have the potential to prolong QT

Vaughan Williams classification

Classification system of antiarrhythmic drugs according to their predominant effects on action potential. Ie) what receptors they bock and which phase of action potential is affected.

SA node, AV node, purkinje cells

three structures in the heart that display pacemaker activity.

Electrocardiogram (ECG)

gives a manifestation of the depolarization and repolarization of the heart. Signals generated by the SA node, AV node, and Purkinje cells.

P wave

wave of an ECG generated by atrial depolarization.

QRS

wave of an ECG generation by ventricular depolarization

T wave

wave of an ECG generated by ventricular repolarization

PR interval

a measure of conduction time from atrium to ventricle.

QRS duration

indicates the time required for all of the ventricular cells to be activated.

QT interval

period of ventricular action potential. Inhibition of potassium channels widens this period and can cause arrhythmia.

Class 1

class of antiarrhythmic drugs that act by blocking open or inactivated sodium channels. Not commonly used due to proarrhythmic effects.

quinidine

procainamide

lidocaine

flecainide

(Quiet Pulse Lasting Forever)

name four class 1 antiarrhythmatic drugs

Metoprolol

Amiodarone

Sotalol

Verapamil

Diltiazam

(Most Arrhythmias Sound Very Dull)

name one class 2, two class 3, and two class 4 antiarrhythmatic drugs

blurred vision

what is the effect of flecainide on the eyes?

nystagmus

what is the effect of lidocaine on the eyes

corneal deposits and optic neuritis

what are the two effects of amiodarone and sotalol on the eyes?

Class 1A

group of class 1 antiarrhythmic drugs that binds to open or inactivated sodium channels. Slows the rapid upstroke during phase 0 of myocardial cell action potential to decrease the rate of depolarization. It also decreases the slope of phase 4 by the blocking of potassium and calcium channels to decrease the rate of repolarization. Ie) quinidine, procainamide

Class 1B

group of class 1 antiarrhythmic drugs that associates and dissociates from sodium channels rapidly. Actions increase when the cardiac cell is depolarized or firing rapidly. Shortens phase 3 repolarization which decreases duration of action potential. Ie) Lidocaine

Class 1C

group of class 1 antiarrhythmic drugs that blocks sodium as well as potassium channels. It suppresses the phase 0 upstroke in Purkinje and myocardial fibers causing a slowed conduction of cardiac tissue and increased duration of action potential. Ie) flecainide

Class 2

class of antiarrhythmic drugs that work by diminishing phase 4 depolarization. They decrease automaticity and prolong AV conduction. Also decrease heart rate and contractility. Ie) metoprolol

Class 3

class of antiarrhythmic drugs that work by blocking potassium channels to prolong the duration of action potential including the depolarization and refractory periods. Does not alter phase 0 of action potential. Ie) Amiodarone, sotalol

Class 4

class of antiarrhythmic drugs that work by only binding to open, depolarized voltage sensitive channels. This decreases the inward current of calcium slowing the conduction of the atrial nodes. Ie) verapamil, diltiazam

Digoxin

Adenosine

Magnesium sulfate

(DAM)

name the three antiarrhythmatic drugs that do not fit into classes?

digoxin

which antiarrhythmatic drug works by inhibiting sodium potassium ATPase? This lengthens the refractory period and reduces AV node conduction

adenosine

which antiarrhythmatic drug is given via IV and has a short duration of action of about 10-15 seconds.

magnesium sulfate

which antiarrhythmatic drug is given via IV to counteract an arrhythmia causes by digoxin?