pharm antiarrhythmics

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  1. 2 hormones that affect the rhythm of the heart
    acetylcholine and noradrenaline
  2. in SA and AV node, pacemaker cells have a __ conductance which gradually decreases, resulting in depolarization --> an action potential
  3. how do vagal fibers make the heart beat slower (what do they release, what does it do?)
    release acetylcholine onto muscarinic receptors -- they increase the K+ conductance, so it takes longer to get the K+ low enough to initiate an action potential
  4. how do anti-arrhythmic drugs like atropine keep the heart steady?
    block the vagal influence on the AV node
  5. sympathetic fibers release __ onto __ receptors in the pacemaker tissues and myocardium to decrease K+ conductance, making it easier to reach threshold --> faster HR
    noradrenaline onto beta-1
  6. noradrenalin decreases K+ conductance to give a faster HR. It also increases contraction force. How does it do that?
    by increaseing Ca++ conductance (positive inotropic effect)
  7. sinus bradycardia, an arrhythmia common after acute MI, is treated with __
  8. drugs effective in supraventricular arrhytmia (occuring in atrium or AV node) are called __, their action is __
    • Class IV agents 
    • block Ca++ channels
  9. 2 drugs for supraventricular arrhythmia
    • verapamil
    • digitalis

    class IV
  10. verapamil
    • for supraventricular arrhythmia - class IV
    • powerful agaist AV node where conduction is totally dependent on Ca++ conductivity
  11. digitalis
    • for supraventricular arrhythmia - class IV
    • slows conduction, prolongs refractory period in AV node and bundle of His
    • doesn't stop atrial fib but slows it and strengthens ventricular beat
  12. drugs used in ventricular arrhythmia --  their names? their class name?
    • lidocaine
    • mexiletine

    class IB - they block voltage-dependent Na+ channels
  13. lidocaine - given how?
    only given i.v.
  14. lidocaine - works by what mechanism?
    blocks inactivated Na+ channels
  15. lidocaine - treats what? what class is it?
    • for ventricular arrhythmia
    • class IB
  16. mexiletine
    • for ventricular arrhythmia - class IB
    • similar to lidocaine, but can be given orally and has more side effects
  17. class IA drugs - 2 names, do what?
    • disopiramide
    • quanidine
    • fight both types of arrhythmia by blocking open voltage dependent Na+ channels
  18. drugs for both supra and ventricular arrhythmias, and their class name
    • disopiramide -- class IA
    • quanidine -- class IA
    • amiodarone -- class III

    class IA -- block open voltage-dependent Na+ channels - class IB, which treat ventricular arrhythmia, only block those not already open

    class III - slow heart repolarization and prolong the duration of action potentials
  19. disopiramide - admin how?
  20. disopiramide - treats what?
    both types of arrhythmias -- so it's a class IA agent
  21. disopiramide - side effects
    HoTN, nausea, vomiting
  22. disopiramide
    • fights both types of arrhythmias
    • class IA agent
    • oral administration
    • used in combo with digitalis
    • may cause HoTN, nausea, vomiting
  23. class III agents - treat what, basic description, name one
    • both types of arrhythmia
    • slow heart repol and prolong duration of APs
    • amiodarone
  24. quanidine
    • class IA - treats both types of arrhythmia
    • used for arrhythmias resistant to other drugs
  25. amiodarone - basic description, side effects
    class III, treats both kinds of arrhythmia by prolonging the effective refractory period, esp of Purkinje fibers and ventricular muscle cells

    liver damage, neuropathy -- so it's a last choice med
  26. 3 alternatives to drugs for treating arrhythmias
    • pacemaker
    • surgical ablation of the ectopic focus
    • ablation of the ectopic focus via electrodes
  27. inotrope
    • an agent that alters the force or energy of muscular contractions
    • negatively inotropic agents weaken the force of muscular contractions
  28. pacemaker, used when?
    • complete heart blocks
    • tachyarrhythmias
  29. surgical ablation of ectopic focus is successful when?
    supraventricular arrhythmias

    which would otherwise be hit by class IV agents - verapamil or digitalis
  30. ablation of ectopic focus via electrodes
    "on an intracardiac catheter (endocavity ablation)"
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pharm antiarrhythmics
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