Arrhythmia drugs Flashcards
What are the functions of class I, II, III, IV dugs?
I = block Na channels II = beta blockers III = K channel blockers IV = Ca channel blockers
Class IB drug - name, administration, mechanism, uses, side effects
lidocaine, IV
decreases phase 0 conduction in fast beating or ischaemic tissue, increases the threshold
i.e. blocks the channels being depolarised and causing the arrhythmia
ventricular tachycardia
GI upset, dizziness, drowsiness
Class IC - name, administration, mechanism, uses, side effects
flecainide, oral/IV
substantially decrease phase 0 conduction in all tissue, increased threshold, increased APD & refractory period
i.e. blocks the channels being depolarised and causing the arrhythmia
supraventricular arrhythmias (fib&flutter), premature ventricular contractions and WPW syndrome
pro-arrhythmia, sudden death esp. in structural/ischaemic heart disease, increased ventricular reponse to atrial flutter , CNS and GI effects
Class II - name, administration, mechanisms, uses, side effects
bisprolol, oral
increases APD & refractory period in AVN, decreases phase 4 depolarisation
i.e. blocks b1 adrenoceptors in heart blocking sympathetic innervation therefore decreasing the slope of the pacemaker potential and slowing HR
sinus and catecholamine dependent tachycardia, converting re-entrant arrhythmias at AVN, protecting ventricles from high atrial rate in atrial fib/flutter
hypotension, bronchospasm, don’t use in partial AV block or heart failure
Class III - names, administration, mechanisms, uses, side effects
amiodarone - oral/IV
increases APD&refractory period, decreases phase 0 and condition, increases threshold, decreases phase 4 conduction and decreases speed of AV conduction
i.e. block k channels preventing the depolarisation so prolonging the action potential reducing the risk of too many AP’s therefore arrhythmias.
very wide spectrum, effective for most arrhythmias
many that increase with time - pulmonary fibrosis, hepatic injury, increased LDL, thyroid disease, photosensitivity, optic neuritis
solatol - oral
increased APD & refractory period, slows phase 4 conduction and AV conduction
wide spectrum, supraventricular and ventricular tachycardia
pro arrhythmia, fatigue, insomnia
Class IV - names, administration, mechanisms, uses, side effects
verapamil (oral/IV), diltiazem (oral)
slow conduction through AV, increase refractory period in AVN, increase slope of phase 4 in SA to decrease HR, terminates reentry rhythms
i.e. decreases slope of the pacemaker potential so sows HR reducing arrhythmia risk. also reduces CICR so less contraction and allows better o2 supply to demand
supraventricualr tachycardia as controls ventricles and converts reentry
caution with partial AV block, can get asystole if BB also used. caution with hypotension, decreased CO, and can cause some GI problems e.g. constipation
adenosine - administration, mechanisms, uses
rapid IV bolus
binds to A1 receptors at AVN enhancing K+ conduct and causing hyper polarisation so cells are less negative and harder to depolarise and less arrhythmia risk
Slows AV conduction
converts reentry supraventricular arrhythmias, diagnosis of coronary artery disease
ivabradine - administation, mechanisms, uses, side effects
oral
blocks If current in SAN only, won’t lower BP and slows the sinus node
to reduce inappropriate sinus tachycardia, decrease HR in heart failure and angina
flashing lights, teratogenicity potential
digoxin - mechanism, uses, side effects
block Na/K-ATPase thus building up sodium inside the cell which decreases NCX activity as there is no gradient for sodium to move in, so calcium stays in the cell as a result and more calcium leads to increased force of contraction
- enhances vagal activity and slows AV conduction and HR
decreases ventricular rates in atrial fib&flutter, caution in renal failure
atropine - mechanism, uses
selective muscarinic antagonist, blocks vagal activity to speed AV conduction and increase HR
treats vagal bradycardia
What is the efficacy and safety of the drugs mentioned?
efficacy
BB and CCB < sotalol, Na blockers < amiodarone
safety vice versa
which drugs should be used in AF?
rate control = bisoprolol, verapamil, diltazem, maybe digoxin
rhythm control = sotalol, flecainide w/ bisoprolol, amiodarone
which iv drug for VT?
bisoprolol, lidocaine, amiodarone
should flecainide be used alone in atrial flutter?
no - give AVN blocking drugs to reduce ventricular rates also
best drug for WPW?
flecainide
