anti-arrythmics Flashcards
class Ia NaCh Blockers
Double Quarter Pounder
disopyramide
quinidine
procainamide
class Ib NaCh blockers
lettuce, tomato, mayo
lidocaine
tocainide
mexiletine
class Ic NaCh blockers
more fries please
moricizine
Flecainide
propafenone
class II beta blockers
esmolol
metoprolol
propranolol
class III KCh blockers
a big dog is scary amidarone bretylium dofetilide ibutilide sotalol
class IV CCBs
verapamil
diltiazem
other ACLS drugs
adenosine atropine MgSO4 anticoagluants digoxin naloxone vasopressors
vassopressors
Epi
NE
vasopressin
dopamine
Na concentrations
intracellular 5-15
extracellular 135-142
K concentrations
intracelluarl 135-140
extracellular 3-5
factors which may precipitate or exacerbate an arrythmia
ischemia, hypoxia, acidosis, alkalosis, electrolyte abnormalities, excessive catecholamine exposure, autonomic influences, durg toxicity, over stretching of cardiac fiber
duration of diastolic interval
determined by slope of phase 4
early after depolarizations
transient deplarization that interrupts phase 3
exacerbated at slow heart rates contributes to long QT
delayed afterdepolarization
interrupts phase 4
often occurs when intracellular Ca is increased
exacerbated by fast HR
responsible for some arrhytmias related to excess digitalis, catecholamines, and myocardial ischemia
abnormal impulse conduction: severe depressed conduction
may result in simple block (AV, bundle branch)
b/c parasympathetic control of AC conduction is significant partial AV block sometimes relieved by atropine
abnormal impulse conduction: reentry
impulse reenters and excited areas of heart more then once
3 conditions:
-must be obstacle, thus establishing a circuit
-must be unidirectional
-conduction time must be long enough that retrograde impluse does not encounter refractory period
depress autonomic properties of abnormal pacemaker cell
decrease slope of phase 4 and/or elevate threshold potential
alter conduction characteristics of pathways of reentry - facilitate conduction
(shorten refractoriness) of area of unidirectional block -> anterograde conduction can proceed
-depress conduction
(prolong refractoriness) in area of unidirectional block or in pathway w/slowed conduction and short refractory period -> retrograde propagation of impluse no permitted causing bidirectional block
type I
NaCh Blockers
Ia
prolong action potential duration, dissociate from channel w/intermediate kinetics
Ia effects
- decrease conduction velocity
- increase refractoriness
- decrease autonomic properties of Na dependent conduction
- unidirectional block transformed to bidirectional
- some K blocking properties
- effective in supraventricular and ventricular arrhythmias
Ib
shorten AP duration in some tissues in heart and dissociate rapidly
Ib effects
decrease refractoriness w/no effect on conduction velocity -> improces anterograde conduction, eliminating area of unidirectional block
in diseased tissue refractoriness prolonged leading to bidirectional block
clinically effective in ventricular arrhythmias > suprventricular
Ic
minimal effects on AP duration and dissociate slowly
Ic effects
profoundly decreased conduction velocity while leaving refractoriness
theroretically eliminate reentry by slowing conduction to point where impulse is extinguished
clinically effective in supraventricular and ventricular arrhythmias, but ventricular limited due to risk of proarrhythmias
II
sympatholytic beta blockers decrease conduction velocity increase refractoriness decrease automaticity in nodal tissues anti-adrenergic actions
III
KCh blockers
prolong AP duration
prolong refractoriness in atrial and ventricular tissues
delay repolarization by blocking KChs
IV
CCBs
slows conduction where AP dependent on Ca (SA and AV nodes)
decreases conduction, increases refractoriness, decreases automacity in Ca dependent tissues
procainamide
Ia
slows upstroke of AP, slows conduction, prolongs QRS, prolongs APD (due to some KCh block), direct depressant effects on SA and AV nodes
procainamide extracardiac effects
ganglion blocking -> decreased TPR -> hypotension
procainamide toxicity
excessive prolongation induction of TdP new arrythmias reversible lupus like syndrome nausea, diarrhea rash, fever, hepatits, agranulocytosis
procainamide dosage
IV, IM, PO
reduction required in renal failure
NAPA
metabolite of procainamide had class III activity associated w/ TdP especially in renal failure
uses of procainamide
atrial and ventricular arrythmias
long term therapy avoided
quinidine
Ia
like procainamide
can cause GI issues, headache, dizziness, tinnitus, rare immunologic rxns
rarely used
disopyramide
Ia
much more pronounced antimuscarinic effects, (should beadministered w/drug that slows AV conduction) precipitates HF, urinary retention, dry mouth, blurred vision, constipation
lidocaine
blocks activated and inactivated NaChs w/rapid kinetics
lidocaine toxicity
least cardiotoxic of NaCh blockers
SA node arrest, worsening of imparied conduction, ventricular arrhythmias uncommon
large does -> hypotension
most common- neurologic (parasthesias, tremors, nausea, hearing, speech, convulsions)
dose related
use of lidocaine
termination of ventircular tachycardia and prevention of V fib after cardioversion in setting of acute ischemia
mexiletine
orally active congener of lidocaine
also has neuro side effects
used for ventirucalr arrythmias, off label use for chronic pain
flecainide
potent blocker of Na and KChs but does not prolong AP or OT interval
flecainide toxicity
severe exacerbation of arrhythmia in patients w/preexisting Vtach or previous MI
flecainide uses
supraventricular arrythmias
propafenone
similar to Flecainide, but wea beta-blocking activity, does not porlong AP
propafenone toxicity
metallic taste, constipation, arrhythmia exacerbation
propafenone uses
supraventircular arrythmias
amiodarone
markedly prolongs AP and OT interval by blocking Ikr
chronic uses -> Iks blockage
also blocks NaChs, weak adrenergic and CCB activity
amiodarone extracardiac effects
peripheral vasodilation
amiodarone toxicity
symptomatic bradycardia
heart block in preexisting sinus of AV node disease
accumulates in heart, lung, liver, skin, and concentrates in tears
pulmonary toxicity, fetal pulmonary fibrosis, skin and corneal lesions, may cause hypo or hyperthyroidism
amiodarone PK
after discontinuation affects may last 1-3 months
many drugs interactions ) increases statins, digoxin, and warfarin levels)
use of amiodarone
Afib, prevention of recurrent Vtach, not associated w/increased mortality in CAD or HF, used as adjunct w/ICD
dronedarone
analog of amiodarone w/iodine removed to eliminate thyroid adverse effects
works on Ikr, Iks, Ica, Ina, and beta Rs
dronedarone toxicity
black box warning against use in acute decompensated or advanced (class IV) HF
dronedarone uses
Afib
sotalol
both beat blocking and AP prolonging actions
L-isomer- beta blocker (not cardioselective)
D and L isomers prolong AP
sotalol toxicity
dose related incidence of TdP
further depression of LV function in patients w/HF
uses of sotalol
life-threatening ventricualr arrhythmias, maintenance of sinus rythem in Afib, supraventriuclar and ventriucalr arrhythmias in peds
dofetilide
dose-dependent blockage of rapid component of delayed rectifier K current increasing hypokalemia
slow recovery from blockade
dofetilide toxicity
OT prolongation and risk of ventricular arrythmias
dofetilide relative contraaindications
OTc> 450ms
bradycardia <50bpm
hypokalemia
uses of dofetilide
maintencance of NSR is Afib and restoring NSR in Afib
verapamil
blocks both activated and inactivated L-type CaChs
effect more marked in tissues that fire frequently, those that are less completely polarized at rest, and those in which actiation depends exclusively on Ca current (SA&AV nodes)
AV node conduction and effective refractory period prolonges
SA node conduction dlowed, but hypotensive action may result in reflex increase in SA node
suppresses both early and delayed after depolarizations
extracardiac effects of verapamil
peripheral vasodilation
verapamil toxicity
hypotension and Vfib if IV in Vtach misdiagnosed as supraventricular tachycardia
can induce AV blcok
constipation, lassitude, nervousness, peripheral edema
verapamil uses
supraventricular tachycardia,
Afib, Aflutter
angina, HTN
diltiazem toxicity
edema and headache
AV block, bradycardia, hypotension
uses of diltiazem
supraventricualr tachycardia, angina, HTN
adenosine
activates inward rectifying K current and blocks Ca current -> marked hyperpolarization
inhibits AV node conduction and increases refractory period
adenosine toxicity
flushing SOB chest burnign high grade AV block Afib headache hypotension nausea paresthesias
uses of adenosine
drug of choice for conversion of paroxysmal supraventricular tachycardia
atropine
blocks actions of Ach at parasympathetic sites increasing CO
atropine toxicity
arrhythmias, tachycardia, dizziness, constipation, urinary retention
atropine uses
bradycardia, neuromucular blockade reversal, cholinergic poisoning
magnesium
may influence Na/K ATPase, NaChs, KChs, CaChs,
anti-arrhythmic effects in patients w/normal Mg levels
uses of Mg
digitalis induced arrhythmias if hypomagnesemia present
TdP even in Mg normal