View
258
Download
3
Tags:
Embed Size (px)
Citation preview
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