Atrial Arrhythmias - Cardiovascular

Snapshot

A 66-year-old man presents to the emergency deparment with palpitations and lightheadedness. The patient has been experiencing these symptoms for the past few days. He reports mild chest discomfort. Medical history is significant for hypertension, type 2 diabetes mellitus, and rheumatic heart disease. An electrocardiogram is immediately performed, which demonstrates a narrow QRS complex tachyarrhythmia that is irregularly irregular. (Atrial fibrillation)

Introduction

Aberrant rhythms can occur anywhere along the cardiac conduction system (SA node to a single cardiomyocyte)
- these aberrant rhythm can originate from the
  - atrium (thus a supraventricular arrhythmia)
  - ventricles
Etiology
- there are a number of causes and they include
  - myocardial infarction
    - cardiac scarring can interrupt the cardiac conduction system
  - atrial stretch
    - alters the cardiac conduction system (e.g., significant mitral stenosis)
  - reentrant circuit
    - accessory pathway (e.g., atrioventricular re-entry tachycardia)
    - normal atrioventricular node (e.g., atrioventricular nodal reentrant tachycardia)
Symptoms
- asymptomatic
- palpitation
- light headedness
- syncope
- sudden cardiac death

Atrial Arrhythmias
Type	Electrocardiogram Findings	Treatment	Comments
Atrial fibrillation	A tachyarrhythmia that is irregularly irregular rhythm and has absent P-waves	Stable patients rate control e.g., β-blockers and non-dihydropyridine calcium channel blockers rhythm control e.g., amiodarone Unstable patients synchronized cardioversion Anticoagulation options include aspirin warfarin new oral anticoagulant (NOAC) e.g., dabigatran	Most common type of atrial arrhythmia A dilated left atrium can result in atrial fibrillation e.g., mitral stenosis Can result in a thromboembolic event (e.g., stroke) The ventricular rate is determined by the AV node refractory period Often originates in the pulmonary veins
Atrial flutter	A tachyarrhythmia with a "sawtooth" appearance	Stable patients treat similarly as atrial fibrillation Unstable patients synchronized cardioversion	Definitive treatment is with catheter ablation Caused by a re-entrant circuit in the right atrium
Sick sinus syndrome	A bradyarrhythmia with episodes of tachycardia	acute patients assess for reversible causes such as medications (calcium channel blockers, digoxin, lithium) chronic patients anticoagulation pacemaker placement