ARRYTHMIAS Flashcards
Phase 4 depolarization rate via I funny Na+ channels in AV/SA nodes…..
- Vagal stimulation actually HYPERpolarizes the nodes
- Sympathetic stimulation (NE) increases depolarization Rt
- Vagal stimulation (Ach) decreases depolarization Rate
- ADENOSINE also decreases depolarization rate
Verapamil and Diltiazem do what to SA/AV node?
- They reduce the rate of depolarization of the phase 0 upstroke from calcium influx
- They decrease the rate of firing of the SA/AV nodes
Arrythmias are caused by 1) or 2)
1) abnormal impulse generation (automaticity)
or
2) abnormal impulse propagation (re-entry)
EAD: early after depolarizations
interrupt phase 3 repolarization, can trigger LONG QT related arrythmias like TORSADE de pointe
Arrythmias are caused by 1) or 2)
1) normal impulse generation (automaticity)
or
2) abnormal impulse propagation (re-entry)
Arrythmias are caused by 1) or 2)
1) anormal impulse generation (automaticity)
or
2) abnormal impulse propagation (re-entry)
EAD: early after depolarizations
*arises from the plateau
interrupt phase 3 repolarization, can trigger LONG QT related arrythmias like TORSADE de pointe
Delayed after depolarizations
*arises from the resting potential
caused by Digitalis Toxicity (calcium overload)
interrupt phase 4 repolarization
Delayed after depolarizations (DAD)
- arises from the resting potential
- triggered automaticity, aggravated by hypokalemia & catecholamines
caused by Digitalis Toxicity (calcium overload)
interrupt after phase 4 repolarization
Class 1 antiarrhythmics
The Na+ channel blockers
Lidocaine & Procainamide
Class 1 antiarrhythmics
The Na+ channel blockers
Lidocaine & Procainamide & Flecanide
class 2
- Beta blockers (metoprolol, propranolol)
- Reduce enhanced automaticity associated with -catecholamines and ischemia
- work on atrial and ventricular tachycardias
Class III
*suppress ectopic pacemakers & interrupt re-entry
K+ Channel Blockers (Sotolol, Armidardone)
- > delay phase 3 action potential, prolong the QT interval and run risk of TORSADE from EAD
- > prolong the ERP (time before another action potential can occur)
Class IV
*target heart as well as arteries
non-DHP CCB [ diltiazem, verapamil]
- Decrease SA automaticity and AV node conduction
- don’t really affect myocardium “fast cond tiss”
- RISKS: hypotension, SA/AV block, impaired contractility
Class IV
- target heart as well as arteries
- contraindicated in CHF, sinus bradycardia, & av block
non-DHP CCB [ diltiazem, verapamil]
- Decrease SA automaticity and AV node conduction
- don’t really affect myocardium “fast cond tiss”
- RISKS: hypotension, SA/AV block, impaired contractility
Class V
DigoXin activates Cranial nerve X [vagus] to decrease automaticity of the AV/SA nodes
- this is paradoxical to their direct effect (look it up)
- controls ventricular rate in SVT and interrupts AV node re-entry
Class III
K+ Channel Blockers (Sotolol, Armidardone)
- > delay phase 3 action potential, prolong the QT interval and run risk of TORSADE from EAD
- > prolong the ERP (time before another action potential can occur)
Class VI
Adenosine Receptor Antagonist
- antagonizes AV node, transient asystole may occur
- diagnostic of PSVT
Class 6
Adenosine Receptor Antagonist
- antagonizes AV node, transient asystole may occur
- diagnostic of PSVT
Lidocaine
Class IB
treats VENTRICULAR arrythmias only!!!!
IV only for effect
Binds preferentially to partially depolarized Na+ channels to interfere with abnormal automaticity
Flecainide
*long acting Na+ channel blocker
F-you….increases mortality in people with structural heart disease.
- only used in SV arrythmias w/out structural disease
- Propafenone is a class Ic that also has beta blocking activities…limited to treat Afib and Aflutter w/out str dis
Amiodarone (class 3)
- metabolizes and inhibits CYP3A4
- oral or IV loading dose required
- Drug of choice for resuscitation, treats both atrial and ventricular arrythmias.
- has sodium (IA), calcium, and Beta blocking properties in addition to K+ blocking
Amiodarone (class 3)
- metabolizes and inhibits CYP3A4 (warfarin/digoxin intxn)
- oral or IV loading dose required
- Drug of choice for resuscitation, treats both atrial and ventricular arrythmias.
- has sodium (IA), calcium, and Beta blocking properties in addition to K+ blocking
Sotalol
A nonspecific Beta Blocker and is primarily a K+ channel blocker (Class III)
Ibultilide IV & Dofeltilide
pure class III,, no additional effects
Ibultilide IV & Dofeltilide
pure class III,, no additional effects used to treat atrial arrythmias only
