Anti-arrhythmic medication Flashcards
What is a cardiac arrhythmia?
-An arrhythmia is a problem with the RATE or RHYTHM of the heartbeat
-During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm!
What is the name of classification of drugs called for anti-arrhythmic drugs?
Vaughan Williams
What is class 1 Vaughan William’s drugs?
Na channel blockers -
Quinidine, Procainamide, Lidocaine, Phenytoin, Flecainide,
What is a class 2 Vaughan William drug?
B-blockers ‘olol’
What is a class 3 Vaughan William drug?
K+ blocker
Amiodarone, Sotalol
What is a class 4 Vaughan William drug?
CCB
-Verapamil
-Diltiazem
What effect do class 1 Vaughan Williams drugs have?
Three types: All reduce depolarisation as they block sodiumf rom getting to the cardiomyocyte during depolarisation. Peak is maintained.
What effect do class 2 Vaughan Williams drugs have?
They work on the SA node on the pacemaker cell action potential. They normally have ‘funny’ drift, B-blockers reduce the drift, extend the phase and lengthen the action potential firings, this decreases heart rate.
What effect do class 3 Vaughan Williams drugs have?
The rectifier channels are blocked, this widens the action potential as there is a slow depolarisation of the membrane and cardiomyocyte, this extends the widening of the duration of the action potential. *Repolarisation is pumped out via the rectifier channels
What do class 4 (IV) Vaughan Williams drugs do?
Block calcium entry into myocytes during the plateau phase, this reduces the force of contraction. This works on the AV node, slows transmission of action potentials from atria to the ventricles. The AV is the only point of contract between these two, this slows the rate of calcium slowing the force of contraction. This slows the spread of action potentials.
What does Digoxin restore?
Cardiomyocyte contractile function
How does Digoxin work?
-Inhibits Na/K ATPase -Normally Na leaks into and K leaks out of the myocyte cells. The action potential increases Na in K out of myocytes!
-Reversal of Na/Ca exchanger (normally restores levels) , this is inhibited causing an increased level of Na inside myocardiocytes!
-Increases intracellular Ca levels
Normally Na goes into the myocytes and Ca2+ out, what happens when a patient is on digoxin?
This mechanism reverses!
-Pump important for restoring levels, inhibit Na inside cardiomyocyte, lots of Na in, reverses therefore Na out and Ca2+ in, to the cardiomyocyte, Ca2+ levels increase = contraction force increases
How does Adenosine work?
Binding to the receptor reduces the firing of the sinus node, it works at the pacemaker cells in the SA node. This decreases action potential firing in pacemaker cells in the SA nodes.
