Antiarrhythmics Flashcards
what is the Vaughn-Williams classification of anti-arrhythmics
Class I: Sodium channel blockers
Class II: Beta-adrenoceptor antagonists
Class III: Potassium channel blockers
Class IV: Calcium channel blockers
Class I: sodium channel blockers
mechanism of action
examples
indications
inhibit AP propagation in cardiac myocytes
Ia: Quinidine: AF, flutter
Ib: Lidocaine: rarely used - causes HF, nystagmus, seizures
Ic: Flecanide: paroxysmal AF (contraindicated IHD, fibrillation)
Class II: beta blockers mechanims of action examples indications contra-indications
negative chronotrophic and ionotrophic - reduce automaticity of heart
non-selective e.g. propranolol
B1 selective: e.g. atenolol, bisoprolol
rate control in AFT, secondary prevention VT and VF, heart failure
use with caution in COPD, acute heart failure
contraindicated in asthma, AVN block
Class III: potassium channel blockers: examples mechanism of action indications ADRs
amiodarone
block outward K+ channels, increasing AP periods and suppressing re-entry circuits
stable VT, SVT, rate control of AF
hepatic dysfunction, pulmonary fibrosis, peripheral neuropathy, proximal myopathy
Class IV: calcium channel blockers: examples mechanism of action indications contraindications
verapamil
block inward Ca channels on SAN and AVN, increasing refractory period of AVN
negative chronotrophy and ionotrophy
Htn, angina, rate-controlled AF
contra-indicated in HF, bradycardia, AVN block
what are the other 2 main types of anti-arrhythmics and how do they work
adenosine:
acts on A1 receptor on AVN: hyperpolarises cardiac conducting tissue = transient temporary heart block
used in SVTs
digoxin:
cardiac glycoside: inhibits action of Na/K/ATPase = positive ionotrophy and slowing AV conduction by increasing vagal outflow
used in rapid AF
needs a loading dose and has large vol of distribution (lipid soluble): need to monitor renal function and cardiac toxicity
