Antiarrhythmics Flashcards
(28 cards)
3 phases of SA node pacemaker potential
Phase 4 - pacemaker Na influx, Ca channels recover from inactivation (slow increase)
Phase 0 - Ca influx (steep upstroke)
Phase 3 - Ca channels inactivate, K efflux
Pacemaker cell contains what channel
HCN channel
Simultaneous K efflux and Na influx (funny current)
Upstroke inactivates HCN
Ventricular my pure action potential
0 - Na+ channels open
1 - Na+ channels close; fast K+ channels open
2 - Ca2+ channels open; fast K+ channels close
3 - Ca2+ channels close; slow K+ channels open
4 - Resting potential
Link between sympathetic nerves and heart rate
Activation causes release of NA
Increased opening of HCN channels in pacemaker cells - Na+ influx
Opens Ca2+ channels
Heart rate increases
Link between parasympathetic nerves and heart rate
Activation causes release of Ach
Decreases opening of HCN channels - decreased Na+ influx
Decreased Ca2+ influx
Increased K+ efflux
Hyperpolarisation
Heart rate decreases
What is a EAD
Early after depolarisation
Secondary voltage depolarises during repolarising phase
Reactivated Ca2+ channels
What are DADs
Delayed after depolarisation
Seen at increased heart rates
Caused by elevated Ca2+ activation of Na/K channels
About Class 1 antiarrhythmias
Treat tachycardia
Na channel blocker
Lidocaine / Lignocaine
Target phase 0
About class 2 anti arrhythmias
Treat tachycardia
Beta blocker
Metoprolol
Target phase 4 and 2
About class 3 anti arrhythmics
Treat tachycardia
K channel blockers
Amiodarone
Target phase 3
About class 4 anti arrhythmics
Treat tachycardia
Ca channel blockers
Verapamil
Target phase 2
Drugs to treat cardiac arrest
Asystole - adrenaline / epinephrine
Ventricular fibrillation - amiodarone, lignocaine
What does atropine do
Blocks vagal inhibition of sinus and AV node
IV bolus injection
Inc heart rate
Anticholinergic effects
Class 1a
Lengthen action potential duration and refractory period
Quinidine
Class 1b
Shorten action potential duration and refractory period
Ligno/Lidocaine
Class 1c
No effect on action potential
Delay conduction velocity of purkinje fibres
Flecainide
Lidocaine actions
Blocks fast sodium channel
Slows phase 0 depolarisation
Lidocaine pharmacology
Short half life - bolus IV
Not absorbed via oral route
Hepatic clearance decreased in elderly, heart failure, liver disease
Lidocaine adverse effect
Hypotension , heart block
Neurotoxicity , fits
2 types of class 2 drugs and example
Non-cardio selective - propranolol
Cardioselective - atenolol
Difference between selective and non-selective beta blockers
Selective block beta 1
Non selective block beta 1 and 2
Actions of beta blockers
Adrenoreceptor antagonist
Reduce intrinsic rate in sinus and AV node
Reduce HR BP
Reduces renin secretion
Beta blocker side effects
B1 - bradychardia
B2 - exacerbation of asthma
Other - fatigue, sleep disturbances, withdrawal
Amiodarone indications
Supraventricular tachycardia
First line for ventricular fibrillation
