Antiarrhythmics deck Flashcards
What are the normal steps in heart electrical activity? (4)
- SA node discharge
- Spread through atria
- AV node discharge
- Propagation through Purkinje fibres
The process of cardiac muscle contraction is called ________.
It is called excitation-contraction coupling
Membrane potential is maintained by __ , __ & __ on either side of the cell membrane.
Sodium (Na+)
Calcium (Ca2+)
Potassium (K+)
At rest, intracellular __ is low.
This is maintained by ______.
At rest, intracellular sodium (Na+) is low
This is maintained by Na+/K+ ATPase
What are the 3 action potential phases?
Rapid depolarization
Plateau phase
Repolarization
What is the rapid depolarization phase of the action potential phases
Na+ influx through rapidly opening Na+ channels
Sodium enters the cell rapidly
What happens in the plateau phase of the action potential phases?
Ca+2 influx through slowly opening Ca2+ channels
What is the first step of the excitation-contraction coupling?
Action potential leads to increased calcium levels
What is the second step of the excitation-contraction coupling?
The Calcium binds to troponin C and uncovers myosin binding site for actin
What is the third step of the excitation-contraction coupling?
The actin and myosin cross-linkages form, triggering the contraction
What is a normal heart rate?
60-80 bpm
What are arrhythmias?
Arrhythmias are abnormal heart rhythms due to electrical issues
What is bradycardia?
Slow heart rate <60 bpm
What is tachycardia?
Fast heart rate > 100bpm
What is automaticity?
The ability of some cardiac cells, mainly the SA node, to generate their own impulses
What is the order of the electrical signal through the heart?
SA node fires -> spreads through atria causing coordinated contraction
Next AV node -> his bundle -> Purkinje fibers -> coordinated contraction
What is a reentrant in arrhythmia?
When a signal reenters or circulates through tissue instead of following its normal path
can lead to abnormal rhythms
What are atrial flutters?
arrhythmia of 200-350bpm
what are atrial fibrillations?
300-500 bpm arrhythmia
Are atrial flutters/fibrillations dangerous?
They don’t always impact cardiac output but can become serious. Treated if symptoms develop or patient is at risk
Ventricular tachycardia is…
when the lower chambers of the heart beat too fast
Is Ventricular tachycardia dangerous?
It can occur occasionally and be fine but if its consistent it requires quick treatment
What is ventricular fibrillation?
When the lower chambers begin to beat rapidly AND irregularly
Is ventricular fibrillation dangerous?
It’s incredibly fatal.
How do we treat VTac and VFib?
Defibrillators stop all heart electrical activity in an attempt to allow a normal rhythm to resume
What are antiarrhythmics?
Drugs that aim to fix abnormal cardiac rhythm
How do antiarrhythmic agents work?
All antiarrhythmic drugs alter ion flow across the membrane.
Antiarrhythmics have a narrow therapeutic index and can CAUSE arrhythmias
When is it worth it to treat with an antiarrhythmic?
When CO is reduced or when a more serious arrhythmia might develop
What are Class I: Na+ blockers?
IA - Quinidine
IB- Lidocaine
What are class II beta blockers?
Propranolol, Metoprolol
What are class III prolonged action potential/K+ channel blockers?
Amiodarone
What are Class IV Calcium channel blockers?
Verapamil
What do sodium channel blockers do?
Reduce sodium recovery, decreases conduction and excitation
What do potassium blockers do?
Prolong the action potential which increases the refractory period
Why is quinidine used less that lidocaine as an antiarrhythmic?
Quinidine is an IA antiarrhythmic with lots of side effects
Lidocaine is an IB antiarrhythmic that is used much more frequently (through IV)
How do class II: beta-blockers work as antiarrhythmics?
Propranolol and metoprolol inhibit SNS effects, slowing HR
How do class III potassium channel blockers work as anti-arrhythmics?
Amiodarone is a potassium blocker, it prolongs the action potential, also affects beta receptors and Na and Ca channels
How do class IV: Calcium channel blockers work?
Verapamil is a calcium channel blocker
It reduces cardiac contractility and vasodilation.
