Cardiovascular III Arrhythmidas
Terms
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- What is the class of arrhythmic drug that suppresses phase 0 upswing in purkinje and myocardial fibers and shows a marked slowing of condution in all cardia tissues? What is the prototype?
- Class 1c. Prototype, Flecainide
- This drug is used in treatment of various arrhthmias that originate in ventricles of atria.
- Class 1a - Quinidine
- This drug is used in treatment of ventricular arrhythmias arising during myocardial ischemia. It is the drug of choice in emergency treaatment of cardiac arrhythmias and is the least cardiotoxic.
- Class 1b, Lidocaine
- This drug is used in treatment of ventricular arrhythmias such as ventricular tachycardia.
- Class 1c, Flecainide
- What are the Cardiac and Extracardiac effects of Class I Arrhythmic drugs?
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Cardiac: Tendency to aggravate or initiate cardiac rhythm abnormalities while controlling one type of rhythm abnormality (proarrhythmic effect).
Extracardiac: CNS disturbances such as dizziness, nausea and visual disturbances.
This drug is used less often and with more caution than before. - Cardiac AP is divided into several phases. This phase is a brief period of repolarization due to exit of K+ from cell.
- Phase 1
- This refers to significant deviation from normal cardiac rhythm.
- Arrhythmia
- True or False. Arrhythmia affects 50% of patients treated with digitalis, 25% of anethetized patients, and 70% of pts with acute MI.
- False. Arrhythmia affects 25% of pts treated with digitalis, 50% of anesthetized pts, and 80% of patients with acute MI.
- What are three mechanisms of Cardiac Arrhythmias?
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1. Abnormal automaticity/impulse formation
2. Abnormalities in impulse conduction
3. Simultaneous abnormalities of impulse generation and conduction - These type of cells in the sinoatrial (SA) (sinus) node depolarize spontaneoulsly to generate action potential (AP): dominate and control cardiac rhythm in normal heart.
- Pacemaker cells
- AP spread in a timely way through the atria via atrial muscle cells to these.
- AV (Atrioventricular) node
- The bundle of HIS is made up of conducting cells known as ________, which distribute AP ventricular muscle cells.
- Purkinje fibers
- From AV node, AP transmitted to ventricles via specialized conducting system known as what?
- Bundle of HIS
- The fraction delay at the ________ allows time for the atrial contraction that helps fill the ventricles with blood.
- AV node
- This is when the heartrate is <60 beats per minute.
- Bradycardia
- This is when the heart rate is > 100 beats per minute.
- Tachycardia
- Cardiac AP is divided into several phases. This phase is rapid depolarization due to sudden influs of Na +.
- Phase 0
- What are 3 things arrhythmias are named for?
-
1. origin
2. nature of disturbed heartbeat
3. impairment of cardiac conduction
Example: Ventricular arrthythmias originate in ventricles
- Supraventricular arrhythmias origin is in atria, AV node or upper purnje fibers. - Name 5 common classifications of arrhythmias?
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1. Sinus arrhythmias
2. Supraventricular arrhythmias
3. Atrioventricular junctional arrhythmias
4. Conduction disturbances
6. Ventricular arrhythmias - This classification of arrhythmia involves Sinus tachycardia, sinus bradycardia and/or sick sinus syndrome.
- Sinus arrhythmia
- This classification of arrhythmia can include atrial fibrillation and flutter, atrial tachycardia and premature atrial contractions.
- Supraventricular arrhythmias
- This classification of arrhythmia can include junctional rhythm, and junctional tachycardia.
- Atrioventricular junctional arrhythmias.
- This classification of arrhythmias can include atrioventricular block, bundle branch block, and fascicular block.
- Conduction disturbances
- The classification of these arrhythmias can include, premature ventricular contractions, ventricular tachycardia, and ventricular fibrillation.
- Ventricular arrhythmias.
- These classifications of drugs block Na+ channels
- IA, IB, IC
- These classifications of drugs block beta adrenoreceptors
- II
- These classifications of drugs block K+ channels.
- III
- These classifications of drugs block Ca++ channels.
- IV
- These drugs bind to open (activated) or closed (inactivated) Na+ channels to cause normalization of Na+ entry.
- Sodium channel blockers.
- What is the class of arrhythmic drug that binds to open and inactivate Na+ channels to prevent Na+ influx? What is the prototype?
- Class 1a - prototype Quindine (anti malaria)
- What is the class of arrhythmic drug that blocks both activated and inactivated Na+ channels? It shortens phase 3 repolarization and decreases duration of AP. What is the prototype?
- Class 1b. Prototype, Lidocaine
- Cardiac AP is divided into several phases. This phase is a plateau due to opening of Ca2+ channels, Efflux of K+ ions in hase 1 balances the influx of Ca2+, no net charge-plateau which enables heart to rest and fill with blood - diastole.
- Phase 2
- The cardiac AP is divided into several phases. This phase is when repolarization is completed by unopposed efflux of K+ as Ca2+ channels close.
- Phase 3
- The cardiac AP is divided into several phases. This phase is slow spontaneous depolarization due to leak of Na+ ions into cell plus gradual decrease in K+ exit; accumulation of positive charge causes cell to reach threshold and enter phase 0.
- Phase 4
- This class of antiarrhythmic drugs decrease excitatory effects of sympathetic nervous system, slow down heart rate and contractility (negative chronotropic and ionotropic effect) and conduction through myocardium.
- Class II: Beta-Blockers
- What is the prototype for Class II antiarrhythmic drugs?
- Propranolol (Beta Blocker)
- True or False - Class II Beta Blockers are not as safe as Class I Sodium channel blockers.
- False, Beta Blockers are safer than Sodium channel blockers.
- One of this antiarrhythmic drugs side effects include othostatic hypotension. A precaution would be to decrease exercise and stress level because of a decrease in HR.
- Class II - Beta Blocker
- This antiarrhythmic drug is used in treatment of arrthythmias originating in atria and AV nodes and is the mainstay in treatment of arrhythmias.
- Class II - Beta Blockers
- What are the cardiac and extracardiac effects of Class III drugs?
-
Cardiac = antifibrillatory effect
Extracardiac = beta clockers, therefore potential to cause postural hypotension - These drugs have selective ability to block calcium entry into myocardial and vascular smooth muscle cells.
- Class IV - Calcium channel blockers
- This drugs prototype is Nifedipine.
- Class IV - Calcium channel blockers
- This drug decreases the rate of discharge of the SA node and inhibits conduction through the AV node.
- Class IV - Calcium channel blockers
- This drug is used in treatment of arrhythmias cuased by atrial dysfunction such as suproventricular tachycardia and atrial fibrillation.
- Class IV - calcium channel blocker
- What are some non-pharmacological approaches to treatment of arrhythmias?
- Pacemakers, Catheter ablation (destroy tissue contributing to tachycardia), Electrical therapy, Cardioversion (implantable cardioverter defribillator, Surgery
- This drug is used in the treatment of ventricular arrhythmias, ventricular fibrillation supraventricular arrhythmias.
- Class III - K+ Blockers
- This class of antiarrhythic drugs block potassium channels and prolong duration of AP without altering phase 0.
- Class III - K+ Blockers
- The prototype for this anti arrhythmic drug is Sotalol.
- Class III - K+ Blocker
- The advantages to this antiarrhythmic drug is that it affects both atrial and ventricular problems and it is safe compared with Class I drugs.
- Class III K+ blockers
- This class of antiarrthythmic drugs prolong repolarization.
- Class III K+ Blockers