Antidysrhythmics Flashcards
Condition where spontaneous depolarizations occur due to abnormal impulse generation in sinus or ectopic foci
Automaticity cardiac dysrhythmias
explain the patho of re-entry cardiac dysrhythmias
impulses propagate more than one pathway.
i.e WPW
what type of cardiac dysrhythmias are Seen more with volatile anesthetics because of suppression of SA node and conduction pathway
re-entry dysrhythmias
8 factors that promote dysrhythmias
electrolyte imbalance hypoxemia acid base imbalance ischemia bradycardia increased mechanical stretch SNS drugs
what type of acid base balance is more prone to dysrthymias?
alkalosis
antidysrhythmic drugs mechanisms of action [basic]
Most work directly or indirectly by blocking various ion channels
[remember: there are different parts of action potential that we manipulate]
Blocking Na+ affects what part of action potential?
velocity of AP upstroke
Blocking K+ affects what part of action potential?
refractory
Blocking Ca+ affects what part of action potential
slope of phase 4 in nodal tissue
Newly developed brady or tachydysrhythmias resulting from chronic antidysrhythmic therapy
Prodysrhythmias
what is Torsades de Pointes
Polymorphic ventricular tachycardia
Ventricular Fibrillation
what causes Incessant Ventricular Tachycardia
Antidysrhythmic drugs that slow conduction can allow re-entrant impulses (Ia & Ib)
Wide Complex Ventricular Rhythm is usually seen with?
with class Ic drugs due to slow conduction.
phase 0 of action potential represents
[initial upstroke]
rapid depolarization from opening of Na channels and closing of K channels
phase 1 of action potential represents
[slight downstroke before plateau]
initial repolarization resulting from opening of K channels and closure of Na channels
phase 2 of action potential represents
[plateau]
plateau phase resulting from sustained Ca current
phase 3 of action potential represents
[downstroke]
repolarization from closure of Ca channels and opening of K channels
phase 4 represents
[resting, baseline]
resting potential - K channel open, Ca/Na channels closed
how do conduction myocytes (ventricular) differ from pacemaker cells?
“fast” action potentials that are dependent on Na for phase 0 (depolarization)
lower resting membrane potential
how do pacemaker (nodal) cells differ from conduction myocytes?
“slow” action potentials that rely on Ca for phase 0 (depolarization), leaky Na
less negative resting membrane potential
what does changing the rate of phase 4 depolarization do to the heart rate?
pns (ACh) stimulation elongates phase 4 which results in slower HR while sns (norepi) shortens phase 4 with causes an increase in the HR
Drug Classification I
membrane stabilizers
inhibit fast Na channels
Drug Classification II
beta adrenergic antagonists
decrease rate of depolarization
Drug Classification III
refractory prolongers
inhibit K
Drug Classification IV
calcium channel blockers
slow Ca channels
Decrease depolarizations & conduction velocity
**Blocking Na+ moves the threshold potential farther away from the resting potential
class I
describe Beta Adrenergic Antagonist and its effect on electrolytes
Decrease magnitude of Ca+ influx current
Decreases K+ current (Na+/K+ pump)
Useful in ischemic related dysrhythmias, reduces mortality
Beta Adrenergic Antagonist because it slows everything down
[slower phase 4, slower automaticity, slower AV node conduction]
these Interact with Beta Blockers
Refractory Prolongers, Class III r/t reduced automaticity and prolonged action potential duration (slows)
Useful in rate control for rapid ventricular response situations with A fib and A flutter, PSVT
Useful in ventricular tachycardia
Class IV, Cardiac Ca+ channel blockers