Atrial flutter

Background

• A form of supraventricular tachycardia that is caused by a re-entry circuit, typically within the right atrium
  • Second most common arrhythmia, after atrial fibrillation
• Defined by atrial rate of 250-350, classically 300
• Associated with underlying diseases that cause atrial remodeling/dilation, such as hypertension, chronic obstructive pulmonary disease, heart failure, pulmonary hypertension
  • Acutely, may be precipitated by antiarrhythmic medications, acute coronary syndrome, or cardiac surgery/procedures

Clinical Features

• Asymptomatic
• Palpitations
• Fatigue
• Dyspnea
• Pre-syncope/syncope
• Hypotension

Differential Diagnosis

Can be difficult to distinguish from atrial fibrillation

Narrow-complex tachycardia

• Regular
  • AV Node Independent
    • Sinus tachycardia
    • Atrial tachycardia (uni-focal or multi-focal)
    • Atrial fibrillation
    • Atrial flutter
    • Idiopathic fascicular left ventricular tachycardia
  • AV Node Dependent
    • Paroxysmal supraventricular tachycardia (PSVT)
      • AV node re-entry tachycardia (AVNRT)
      • AV re-entry tachycardia (AVRT)
        • Lown-Ganong-Levine syndrome
        • Wolff–Parkinson–White syndrome
    • Junctional tachycardia
• Irregular
  • Multifocal atrial tachycardia (MAT)
  • Sinus tachycardia with frequent PACs, PJCs, PVCs
  • Atrial fibrillation
    • Atrial fibrillation with RVR
  • Atrial flutter with variable conduction
  • Digoxin Toxicity

Wide-complex tachycardia

Assume any wide-complex tachycardia is ventricular tachycardia until proven otherwise (it is safer to incorrectly assume a ventricular dysrhythmia than supraventricular tachycardia with abberancy)

• Regular
  • Monomorphic ventricular tachycardia
  • PSVT with aberrant conduction:
    • PSVT with bundle branch block^
    • PSVT with accessory pathway
    • Atrial flutter with bundle branch block^
  • Sinus tachycardia with bundle branch block^
  • Accelerated idioventricular rhythm (consider if less than or ~120 bpm)
  • Metabolic
    • Hyperkalemia
    • Digoxin toxicity
    • Severe metabolic acidosis
• Irregular
  • Atrial fibrillation/atrial flutter with variable AV conduction AND bundle branch block^
  • Atrial fibrillation/atrial flutter with variable AV conduction AND accessory pathway (e.g. WPW)
  • Atrial fibrillation + hyperkalemia
  • Polymorphic ventricular tachycardia
    • Torsades de pointes
    • Nonsustained ventricular tachycardia

^Fixed or rate-related

Palpitations

• Arrhythmias:
  • Narrow-complex tachycardias
  • Wide-complex tachycardias
  • AV blocks
    • Second Degree AV Block Type I (Wenckeback)
    • Second Degree AV Block Type II
    • Third Degree AV Block
  • Premature atrial contraction
  • Premature junctional contraction
  • Premature ventricular contraction
  • Sick sinus syndrome
  • Wandering atrial pacemaker
• Non-arrhythmic cardiac causes:
  • Acute coronary syndrome
  • Cardiomyopathy
  • Congenital heart disease
  • Congestive heart failure (CHF)
  • Mitral valve prolapse
  • Pacemaker complication
  • Pericarditis
  • Myocarditis
  • Valvular disease
• Psychiatric causes:
  • Panic attack
  • Anxiety
  • Somatic Symptom Disorder
• Drugs and Medications:
  • Alcohol
  • Caffeine
  • Drugs of abuse (e.g. cocaine)
  • Medications (e.g. digoxin, theophylline)
  • Tobacco
• Misc
  • Anemia
  • Hyperthyroidism
    • Thyroid storm
  • Pulmonary embolism
  • Dehydration
  • Sepsis
  • Pheochromocytoma

Evaluation

Flutter with alternating 2:1 and 3:1 block.

Atrial flutter with variable block

• ECG
• CBC
• Chem 7
• Magnesium level
• Troponin if patient has chest pain
• Cardiac Echo - if signs of new/worsening heart failure

ECG

• Narrow complex tachycardia
  • Usually regular unless variable AV conduction present
  • Usually narrow unless aberrancy present
• Typical P waves are absent, but flutter waves (sawtooth pattern) are found in inferior leads
  • Hallmark is discordance in flutter wave direction between inferior leads and V1; see below for specific types
• Atrial rate near 300, appearing as flutter waves at 300 bpm
• Ventricular rate = 300 divided by the conduction ratio
  • 2:1 block = 150 bpm
  • 3:1 block = 100 bpm, and so on
• Conduction ratio depends on sympathetic/parasympathetic balance, AV node refractoriness, AV node disease, AV nodal blockers
  • 1:1 conduction can be unstable
    • Suggests pre-excitation, sympathetic excess, parasympathetic withdrawal, Class 1C anti-arrhythmic use
    • Less common since AV node refractory period prevents 1:1 conduction
  • 2:1 conduction is most common
    • Suspect atrial flutter whenever ventricular rate is approximately 150
    • Note flutter waves may be mistaken for P and T waves
  • Conduction >2:1
    • More commonly even ratio
    • Suggests AV nodal blocking agents or AV node disease
  • Variable block
    • Difficult to distinguish from atrial fibrillation
    • Look for: R-R interval that is multiple of P-P interval and mathematical relationship between R-R intervals (alternating between 2:1, 3:1, 4:1, etc)
    • A-fib is completely irregular with no relationship between intervals
• Amal Mattu recommends flipping ECG 180 to easily see inverted P waves or speed machine up to 50 mm/s to stretch out ECG

Types

• Type 1 (Typical Atrial Flutter)
  • Re-entry circuit of the cavotricuspid-isthmus (CTI) pathway in the right atrium
    • Anticlockwise circuit- 90% of cases
      • Inverted flutter waves in inferior leads
      • Positive flutter waves in V1
    • Clockwise circuit
      • Positive flutter waves in inferior leads
      • Inverted flutter waves in V1
• Type 2 (Atypical Atrial Flutter)
  • Not associated with the CTI pathway, but may be due to arrhythmogenic scars from prior atrial instrumentation
  • Does not meet criteria for typical atrial flutter
  • Less amenable to treatment

Management

Unstable

• Synchronized cardioversion
  • Atrial flutter - start at 50 J
  • Atrial fibrillation - start at 200 J
• Indications: ischemic chest pain, SBP < 90, acute pulmonary edema, altered mental status
• If shock does not work:

1. Verify not preexcitation
2. Increase diastolic BP to perfuse the heart
   • Push-dose phenylephrine
     • Will maintain BP when give rate-control medications
     • 50-200mcg q2-5min with goal DBP >60
3. Amiodarone 150mg over 10min (preferably through central venous access) OR diltiazem 2.5mg/min until HR<100 or max 50mg

Stable and Asymptomatic

• If mild or no symptoms and pulse only mildly elevated (<110bpm) ok to manage with PO meds
• Less reactive to PO medication than atrial fibrillation
• Cardioversion is preferred and treats 96-97% of atrial flutter

Stable and Symptomatic

• Goal <110bpm
  • Make sure you are not slowing down a normal physiologic response (e.g. fever, hypoxia, etc)
  • RACE-II trial demonstrated that lenient control (goal HR < 110bpm) was noninferior to strict control (HR < 80 bpm) in preventing the primary outcome

Cardioversion

• Consider for:
  • Symptoms <48hr
  • New diagnosis
  • No history of similar episodes
  • No LV dysfunction
  • No mitral valve disease
  • No prior thromboembolic event
  • Already Anticoagulated
• If cardioversion is considered, pretreatment with rate or rhythm control medications can reduce effectiveness
  • 90% effective, 60% effective with pretreatment

Anticoagulation Prior to Cardioversion

• Anticoagulation with Heparin or LMWH should be considered before cardioversion if time permits, otherwise immediately after cardioversion. (unless you are sure it has been <48 hours since onset of afib)

• Generally cardioversion while anti-coagulated is believed to be safe with a 1.3% risk of thromboembolism if on aspirin or other anticoagulant However the risk may be as great as 2% risk after 48 hours and preference should be given to anticoagulation prior to cardioversion in longer cases

Evidence of preexcitation

• Avoid AV nodal agents
• Unstable:
  • Unsynchronized cardioversion (200J)
  • Procainamide (if cardioversion unsuccessful)
    • 20-50mg/min until arrhythmia is controlled, hypotension occurs, QRS complex widens by 50% of original width, or total of 17mg/kg is given; followed by continuous infusion of 1-4mg/min
• Stable:
  • Try to avoid cardioversion without adequate anticoagulation

Disposition

Admission

• Ongoing symptoms/complications (respiratory distress, chest pain, pulmonary edema, myocardial ischemia)
• Infusion needed for rate control

Discharge

• Consider consult with cardiology prior
• Patients with good rate/rhythm control and anticoagulation can usually be discharged after an appropriate work-up
• Ensure follow-up is arranged

See Also

• Atrial fibrillation
• In-Training Exam Review

External Links

• IBCC - Atrial Fibrillation and Flutter complicating critical illness
• emDOCS - Atrial Flutter
• Merck Manual - Atrial Flutter