Cardiovascular Disorders

Arrhythmias

Clinical Overview and Exam Mastery Guide for atrial fibrillation, antiarrhythmic classes, ventricular arrhythmias, stroke prevention, and bradyarrhythmia management.

Rhythm Types
Tachy, brady, irregular
AF Core Plan
Rate + rhythm + anticoagulation
VT Priority
Urgent rhythm stabilization
Drug Class System
Vaughan-Williams I to IV

Real ECG and Conduction Visual

ECG and Cardiac Conduction System

Conduction pathway anatomy anchors rate/rhythm pharmacology decisions.

1. What Are Arrhythmias?

Arrhythmias are disorders of heart rhythm caused by abnormalities in impulse generation, impulse conduction, or both.

Tachyarrhythmias Bradyarrhythmias Irregular rhythms Benign to life-threatening spectrum

2. Basic Electrophysiology Refresher

Conduction pathway: SA node -> AV node -> Bundle of His -> Purkinje fibers.

Drug Targets

  • Sodium channels
  • Potassium channels
  • Calcium channels
  • Beta receptors

Exam Logic

  • Node-focused drugs affect AV conduction and rate control
  • Channel blockers alter depolarization/repolarization
  • Misapplied class choice can be proarrhythmic

3. Major Arrhythmias Tested

Atrial fibrillation (AF) Atrial flutter SVT Ventricular tachycardia (VT) Ventricular fibrillation (VF) Bradyarrhythmias
ECG strip showing atrial fibrillation
Atrial fibrillation ECG example
ECG strip showing atrial flutter
Atrial flutter ECG example
ECG strip showing ventricular tachycardia
Ventricular tachycardia ECG example

4. Atrial Fibrillation (AF)

AF is the most common arrhythmia, classically irregularly irregular, with no distinct P waves. Core risks include stroke and heart failure.

Management goals: rate control, rhythm control, and stroke prevention.

A. Rate Control

Beta Blockers

Examples: metoprolol, atenolol.

  • MOA: beta1 blockade slows AV nodal conduction and HR
  • Side effects: bradycardia, hypotension, fatigue
  • Contra: severe bradycardia, cardiogenic shock

Non-DHP CCB

Diltiazem, verapamil.

  • MOA: L-type calcium channel block at AV node
  • Side effects: bradycardia, hypotension, constipation (verapamil)
  • Contra: HFrEF, severe hypotension

Digoxin

  • MOA: Na/K ATPase inhibition with increased vagal tone and slower AV conduction
  • Role: rate control; does not improve survival
  • Side effects: nausea, visual disturbances, arrhythmias
  • Toxicity worsens with hypokalemia

B. Rhythm Control

Used when symptoms persist or rate-control strategy fails.

Amiodarone (Class III)

  • MOA: potassium channel block plus sodium, calcium, and beta receptor effects
  • Benefit: effective in AF and VT
  • Major side effects: pulmonary fibrosis, thyroid dysfunction, liver toxicity, photosensitivity, corneal deposits
  • Contra: severe sinus-node dysfunction, relative caution in pregnancy

Class IC (Flecainide, Propafenone)

  • MOA: sodium channel blockade slows conduction velocity
  • Proarrhythmic risk in structural disease
  • Contra: structural heart disease and post-MI state

5. Stroke Prevention in AF

Use CHA2DS2-VASc risk scoring. Elevated risk supports anticoagulation.

DOACs

Apixaban, rivaroxaban, dabigatran, edoxaban.

  • MOA: direct factor Xa or thrombin inhibition
  • Side effects: bleeding
  • Contra: active bleeding, severe renal impairment (agent dependent)

Warfarin

  • MOA: inhibits vitamin K-dependent factors II, VII, IX, X
  • Monitoring: INR target usually 2 to 3
  • Side effects: bleeding, rare skin necrosis
  • Contra: pregnancy

6. Ventricular Arrhythmias

Ventricular tachycardia is potentially life-threatening and requires urgent management.

Amiodarone

Common first-line option in stable VT.

Lidocaine (Class IB)

  • MOA: sodium-channel block with shortened action potential
  • Use: ischemic VT contexts
  • Side effects: CNS toxicity, seizures at high doses

7. Bradyarrhythmias

Atropine First-Line

  • MOA: muscarinic blockade increases heart rate
  • Side effects: dry mouth, urinary retention

Escalation

  • Persistent severe symptomatic bradycardia may require pacemaker

8. Vaughan-Williams Classification Summary

Class Target Examples
Class I Sodium channel blockers Flecainide, propafenone, lidocaine
Class II Beta blockers Metoprolol, atenolol
Class III Potassium channel blockers Amiodarone
Class IV Calcium channel blockers Diltiazem, verapamil

Management Recap Drill

AF Step 1: Determine hemodynamic stability
AF Step 2: Rate control with beta blocker or non-DHP CCB
AF Step 3: Consider rhythm control if symptomatic/persistent
AF Step 4: Assess stroke risk and anticoagulate when indicated
VT/Brady add-on: VT uses amiodarone/lidocaine; symptomatic bradycardia uses atropine first

Visual Algorithm Placeholder

[Insert Atrial Fibrillation and Antiarrhythmic Classification Flowchart Here During UI Integration]

Guideline References

ACC/AHA/HRS Guideline for Atrial Fibrillation

https://www.acc.org/guidelines

ACC/AHA Guideline for Ventricular Arrhythmias

https://www.acc.org/guidelines

Image Attributions (Wikimedia Commons)

  • Cardiac Conduction System - Cypressvine, CC BY-SA 4.0
  • ECG Atrial Fibrillation - Ewingdo, CC BY-SA 4.0
  • ECG-atrial flutter - Ciernik M, CC BY-SA 4.0
  • Electrocardiogram of Ventricular Tachycardia - Karthik Sheka, CC BY-SA 2.5

9. Common Exam Traps

Non-DHP calcium channel blockers are contraindicated in HFrEF.
Amiodarone can cause multi-organ toxicity.
Class IC agents are contraindicated in structural heart disease.
Digoxin does not reduce mortality.
AF management always includes stroke-risk assessment.

10. Quick Revision Summary

Must Remember

  • AF = rate control + rhythm strategy + anticoagulation decision
  • Amiodarone is a broad multi-channel blocker
  • DOACs are preferred over warfarin in many AF scenarios
  • VT needs urgent rhythm-focused treatment
  • Symptomatic bradycardia -> atropine first

Practice Questions Placeholder

  • Topic: Arrhythmias
  • Subtopics: atrial fibrillation, anticoagulation, antiarrhythmic classes, ventricular tachycardia, bradyarrhythmias