Cardiac Physiology and Antiarrhythmics

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Questions and Answers

What is a key characteristic of atrial fibrillation in terms of its electrophysiological nature?

A rapid irregular rhythm arising from multiple ectopic foci within the atria (correct)

A single but different P morphology with a rapid regular rhythm

Organized atrial activity with distinct P wave morphology

A rapid rate of ventricular contractions with consistent RR intervals

Which of the following is a primary long-term management strategy for atrial fibrillation?

Rate control with AV nodal slowing agents and OAC (correct)

Rhythm control with class Ia agents only

AV nodal accelerating agents only

Cardioversion without any anticoagulation

What is a common risk factor for the occurrence of atrial flutter?

Young age and absence of heart disease

Structural heart disease and chronic lung disease (correct)

High physical fitness level

Previous history of myocarditis

Which class of agents is primarily used for rhythm control in atrial fibrillation management?

Class Ic or class III agents Signup and view all the answers

What is the significant characteristic of multifocal atrial tachycardia?

Irregular RR intervals and multiple P wave morphologies Signup and view all the answers

What characterizes atrial activation during atrial reentrant tachycardia (AVRT)?

It occurs after ventricular activation. Signup and view all the answers

What is a significant feature observed on the ECG of patients with Wolf Parkinson White Syndrome (WPW)?

Delta wave on the QRS complex Signup and view all the answers

Which medication is contraindicated in the treatment of WPW syndrome?

Verapamil Signup and view all the answers

Which of the following is the first line of treatment for hemodynamically unstable patients presenting with supraventricular tachycardia (SVT)?

Emergency cardioversion Signup and view all the answers

What is the mechanism behind atrial fibrillation?

Macro-reentry circuits Signup and view all the answers

Which treatment is considered the choice for ablation of an accessory pathway?

Radiofrequency catheter ablation Signup and view all the answers

What P wave characteristic helps distinguish AVRT from AVNRT?

P waves are clearly seen. Signup and view all the answers

What is the expected efficacy of verapamil, diltiazem, and β-blockers in long-term management of AV reentrant tachycardia?

60-80% Signup and view all the answers

What is the primary mechanism of action of Class I anti-arrhythmic drugs?

Sodium channel blockade Signup and view all the answers

Which phase of the cardiac action potential is primarily affected by beta blockers?

Phase 2 Signup and view all the answers

What effect do calcium channel blockers have on the cardiac action potential?

Decrease phase 0 depolarization Signup and view all the answers

Which class of anti-arrhythmic drugs is known for prolonging repolarization?

Class III Signup and view all the answers

What potential adverse effect is associated with sodium channel blockers?

Prolonged QT interval Signup and view all the answers

Which anti-arrhythmic drug is a potassium channel blocker?

Amiodarone Signup and view all the answers

Which cardiac action potential phase corresponds to the resting membrane potential?

Phase 4 Signup and view all the answers

What is the primary action of Class IV anti-arrhythmic agents?

Calcium channel blockade Signup and view all the answers

Which of the following drugs is a sodium channel blocker classified as Class 1B?

Lidocaine Signup and view all the answers

Which phase demonstrates the plateau phase of cardiac action potential?

Phase 2 Signup and view all the answers

What is the effect of beta blockers on heart rate?

Decrease heart rate Signup and view all the answers

Which anti-arrhythmic class has the least effect on repolarization?

Class IB Signup and view all the answers

What component of the electrocardiogram corresponds to depolarization?

QRS complex Signup and view all the answers

What adverse effect can occur with the use of amiodarone?

Hypothyroidism Signup and view all the answers

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.