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Questions and Answers
What is a key characteristic of atrial fibrillation in terms of its electrophysiological nature?
Which of the following is a primary long-term management strategy for atrial fibrillation?
What is a common risk factor for the occurrence of atrial flutter?
Which class of agents is primarily used for rhythm control in atrial fibrillation management?
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What is the significant characteristic of multifocal atrial tachycardia?
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What characterizes atrial activation during atrial reentrant tachycardia (AVRT)?
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What is a significant feature observed on the ECG of patients with Wolf Parkinson White Syndrome (WPW)?
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Which medication is contraindicated in the treatment of WPW syndrome?
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Which of the following is the first line of treatment for hemodynamically unstable patients presenting with supraventricular tachycardia (SVT)?
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What is the mechanism behind atrial fibrillation?
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Which treatment is considered the choice for ablation of an accessory pathway?
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What P wave characteristic helps distinguish AVRT from AVNRT?
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What is the expected efficacy of verapamil, diltiazem, and β-blockers in long-term management of AV reentrant tachycardia?
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What is the primary mechanism of action of Class I anti-arrhythmic drugs?
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Which phase of the cardiac action potential is primarily affected by beta blockers?
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What effect do calcium channel blockers have on the cardiac action potential?
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Which class of anti-arrhythmic drugs is known for prolonging repolarization?
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What potential adverse effect is associated with sodium channel blockers?
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Which anti-arrhythmic drug is a potassium channel blocker?
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Which cardiac action potential phase corresponds to the resting membrane potential?
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What is the primary action of Class IV anti-arrhythmic agents?
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Which of the following drugs is a sodium channel blocker classified as Class 1B?
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Which phase demonstrates the plateau phase of cardiac action potential?
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What is the effect of beta blockers on heart rate?
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Which anti-arrhythmic class has the least effect on repolarization?
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What component of the electrocardiogram corresponds to depolarization?
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What adverse effect can occur with the use of amiodarone?
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Study Notes
Cardiac Impulse Conduction
- Cardiac impulses originate regularly at 60-100 beats per minute.
- Impulses are conducted through the heart via a specialized conduction system, composed of the SA node, AV node, bundle of His, right and left bundle branches, and Purkinje fibers.
Cardiac Action Potential
- Cardiac action potential has five phases: Phase 0 (rapid depolarization due to sodium influx), Phase 1 (early repolarization due to potassium efflux), Phase 2 (plateau phase due to calcium influx and potassium efflux), Phase 3 (rapid repolarization due to potassium efflux), Phase 4 (resting membrane potential).
- Absolute refractory period is when no new action potential can be generated, while during the relative refractory period a stronger stimulus is required to generate an action potential.
Classification of Antiarrhythmic Drugs
- Antiarrhythmic drugs are classified into four classes based on their mechanism of action: Class I (sodium channel blockers), Class II (beta blockers), Class III (potassium channel blockers), and Class IV (calcium channel blockers).
- Class I drugs are further subdivided based on their effect on the action potential: Class IA (moderate phase 0 depression and prolonged repolarization), Class IB (minimal phase 0 depression and shortened repolarization), and Class IC (marked phase 0 depression and little effect on repolarization).
- Examples of Class I drugs include quinidine, procainamide, disopyramide, lidocaine, flecainide.
- Examples of Class II drugs include propranolol, esmolol.
- Examples of Class III drugs include amiodarone, sotalol, ibutilide.
- Examples of Class IV drugs include verapamil, diltiazem.
Electrocardiography (ECG or EKG)
- A conventional 12-lead ECG records electrical activity of the heart using 10 electrodes placed on the limbs and chest.
- ECG records are obtained over a period of 10 seconds.
Atrial Activation in Arrhythmias
- In some arrhythmias, atrial activation occurs after ventricular activation, and the P wave can be seen between the QRS and T complexes. This is characteristic of AVRT, AVRT, and atrial fibrillation.
Atrioventricular Reentrant Tachycardia (AVRT)
- AVRT occurs when a re-entrant circuit forms involving the AV node, the His bundle, the ventricle, and an accessory pathway.
- Accessory pathways are abnormal connections from the ventricle to the atrium, resulting from incomplete separation during fetal development.
- WPW syndrome is a well-known example of AVRT.
- ECG findings in WPW syndrome include short PR interval and delta wave on the QRS upslope.
- Treatment for WPW syndrome includes flecainamide, amiodarone, disopyramide, or radiofrequency ablation. Digoxin and verapamil are contraindicated.
Atrioventricular Nodal Reentrant Tachycardia (AVNRT)
- AVNRT occurs when a re-entrant circuit forms within the AV node.
- Acute management of AVNRT includes vagal maneuvers, adenosine, verapamil, diltiazem, or beta-blockers.
- Long-term management includes ablation of the re-entrant circuit.
Supraventricular Tachycardia (SVT)
- SVT encompasses different types of rapid heart rhythms originating above the ventricles.
- Emergency cardioversion is indicated for hemodynamically unstable SVT.
Atrial Fibrillation (AF)
- AF is a rapid and irregular atrial rhythm arising from multiple ectopic foci within the atria.
- Risk of stroke is a key consideration, and anticoagulants might be necessary.
- Acute management of AF focuses on either ventricular rate control or cardioversion.
- Long-term management aims at either rhythm control or rate control.
Atrial Flutter
- Atrial flutter is characterized by organized atrial activity, with a distinct P-wave morphology.
- Atrial flutter is often associated with chronic lung disease.
Multifocal Atrial Tachycardia (MAT)
- MAT is a rapid and irregular heart rhythm with at least three different P-wave morphologies.
Accelerated Junctional Tachycardia (AJT)
- AJT is characterized by rapid and regular heart rhythm originating from the AV node.
Premature Atrial Contractions (PAC)
- PACs are premature beats originating from the atria.
Atrial Tachycardia (AT)
- AT is a rapid and regular heart rhythm with a single but different P-wave morphology.
Treatment of Paroxysmal SVTs
- Acute management of paroxysmal SVTs involves vagal maneuvers, intravenous adenosine, verapamil, diltiazem, or beta-blockers.
- Long-term management includes ablation of an accessory pathway for AVRT, and verapamil, diltiazem, and beta-blockers for AVNRT.
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Description
This quiz covers the essential concepts of cardiac impulse conduction, action potentials, and the classification of antiarrhythmic drugs. Test your understanding of the specialized conduction system and the different phases of cardiac action potential. Additionally, challenge yourself on the different classes of antiarrhythmic medications and their mechanisms of action.
