Pharmacology IPharmacology I

Drugs Used to Treat

Arrhythmias

Arrhythmias Needing Arrhythmias Needing Treatment:Treatment:

Atrial Fibrillation/Flutter (AF)Supraventricular Tachycardia

(SVT)Ventricular Tachycardia (VT)

Drug Classifications: IaDrug Classifications: IaUsed For: Used to treat SVT, AF,

VTMechanism: Blocks Na+ Channels

(slows action potential)ECG Effects: QRS and Q-T

interval Examples: Quinidine (Quinora),

Procainamide (Pronestyl), Disopyramide (Norpace)

Other Effects: Class IaOther Effects: Class IaSlight increase in resting HRCauses peripheral vasodilation

Which decreases TPRWhich decreases BP

Supresses PVC’sQuinidine Toxicity:

Prolonged Q-T: Causes polymorphic VT –”Torsades de Pointe”

Syncope

Exercise Capacity: Class Exercise Capacity: Class Ia Drugs (ACSM Manual)Ia Drugs (ACSM Manual)No Change in Exercise

ToleranceExercise ECG:

Prolonged Q-T intervals“False Positive” ST changes

Exercise HR/BP unaffected

Drug Classification: IbDrug Classification: Ib

Used For: VTMechanism: Blocks Na+ channelsECG Effects: Decreased Q-T

IntervalExamples: Lidocaine (Xylocaine),

Tocainide (Tonocard), Phenytoin (Dilantin)

Other Effects: Class IbOther Effects: Class Ib

Increases Preload Decreases Contractility (Reduces

Ejection Fraction)Lidocaine Toxicity: May reduce CO

and BP excessivelyNevertheless: Well tolerated by

CHF patientsNO Significant Exercise Effects

Drug Classification: IIDrug Classification: II

Used For: SVT and AFMechanism: Blocks Beta receptors

for SNS and Adrenal stimulationECG Effects: Prolong P-R interval

and reduce HRExamples - Beta Adrenergic

Blockers: Inderal, Lopressor, Corzide

Other Effects: ß-BlockersOther Effects: ß-BlockersReduce risk of prolonged Q-T

intervalsReduces all types of tachycardiasAdverse Effects:

May disrupt glucose control and Hypoglycemic symptoms in Diabetics

May exacerbate Cardiac failure in CHFSudden Withdrawal is DANGEROUS

Exercise Effects: II Exercise Effects: II

Very Common Cardiac DrugsExercise Tolerance:

Improved in patients with anginaDecreased in non-anginal patients

Exercise ECG: HR and ischemic changes

Hemodynamics: HR and BP at rest and Exercise

Drug Classification: IIIDrug Classification: III

Used For: SVT, VT and AFMechanisms: Na+/K+ channel

blocker and many othersECG Effect: Prolong Q-TExamples: NAPA, Amiodarone

Other EffectsOther Effects: IIIIII

Slows HRDecreases TPR (BP too) Increases Coronary Artery blood

flowSlightly reduces contractilityADVERSE: symptomatic sinus

brady, AV blocks, sinus arrest

Exercise Effects: IIIExercise Effects: III

Exercise Tolerance: No change

Exercise ECG: Decreased HRHemodynamics: Decreased

HR

And Finally: Class IVAnd Finally: Class IV

Drug Classification: IVDrug Classification: IV

Used For: SVT and AFMechanisms: Ca++ Channel

BlockersECG Effects: Decrease HR and

Increase PR- IntervalExamples: Verapamil (Calan),

Diltiazem (Cardizem)

Other Effects: Class IVOther Effects: Class IV

Used more for other cardiac effects – especially hypertension and ischemia

Uncontrolled AF: Reduces Ventricular rate in AF (>100)

Adverse Effects: Hypotension, bradycardia and rarely, ventricular asystole

Exercise Effects: IVExercise Effects: IV

Exercise Tolerance: Improved in patients with angina

Exercise ECG: Reduced HR and ischemic ST changes

Hemodynamics: Reduced blood pressure

What About Digitalis?What About Digitalis?

Cardiac Glycosides: Cardiac Glycosides: Nightshade plant…Nightshade plant…Used For: SVT and AFMechanisms: Inhibits Na+/K+-

ATPase activity (maintains resting potential…)

ECG Effects: QRS and Q-TExamples: Lanoxin

Other Effects: DigitalisOther Effects: DigitalisMost commonly used to treat

CHFGreat Risk of Toxicity: Serum

levels monitored closelyTachyarrhythmiasAnorexia“Halo Vision” when looking at

lights

Exercise And Digitalis:Exercise And Digitalis:

Exercise Tolerance: Improved in patients with CHF or AF

ECG Effects: “Scooping” ST segment

Hemodynamics: Some decrease in patients with AF /CHF