Atrial fibrillation with RVR

Background

Categories

Atrial Fibrillation Category	Definition
Paroxysmal	Terminates spontaneously or with intervention within 7 days of onset. Episodes may recur with variable frequency.
Persistent	Continuous sustained >7 days
Long-standing persistent	Continuous >12 mo in duration.
Permanent	Used when the patient and clinician make a joint decision to stop further attempts to restore and/or maintain sinus rhythm. Acceptance represents a therapeutic attitude on the part of the patient and clinician rather than an inherent pathophysiological attribute. May change as symptoms, efficacy of therapeutic interventions, and patient and clinician preferences evolve.
Nonvalvular	In the absence of rheumatic mitral stenosis, a mechanical or bioprosthetic heart valve, or mitral valve repair.

Causes

• Cardiac (atrial enlargement)
  • Hypertension
  • Ischemic heart disease
  • Rheumatic heart disease
    • Valvular heart disease (any lesion that leads to significant stenosis or regurgitation)
• Noncardiac (increased automaticity)
  • Thyrotoxicosis
  • Chronic lung disease
  • Pericarditis
  • Ethanol ("holiday heart")
  • PE
  • Drugs (cocaine, TCA, Milk of the Poppy)

Clinical Features

• Palpitations
• Shortness of breath
• Dyspnea on exersion
• Chest pain
• Consider WPW if:
  • Wide QRS
  • Rate approaching 300 bpm

Differential Diagnosis

Palpitations

• Arrhythmias:
  • Atrial fibrillation
  • Grouped beats on ECG (commonly misdx as A-fib)
    • Atrial bigeminy and trigeminy
    • Mobitz I or Mobitz II
  • Atrial flutter
  • SVT
  • Ventricular Tachycardia
  • Sick sinus syndrome
  • Multifocal atrial tachycardia
  • PVCs
  • Wolff–Parkinson–White syndrome (WPW)
  • Sinus node dysfunction
  • AV Block
  • Lown-Ganong-Levine Syndrome‎
  • Accelerated idioventricular rhythm
• Non-arrhythmic cardiac causes:
  • Cardiomyopathy
  • CHF
  • Mitral valve prolapse
  • Congenital heart disease
  • Pericarditis
  • Valvular disease
  • Pacemaker malfunction
  • Acute MI
• Psychiatric causes:
  • Anxiety disorder
  • Panic attack
• Drugs and Medications:
  • Alcohol
  • Caffeine
  • Meds (i.e. digitalis, theophylline)
  • Street drugs (i.e. cocaine)
  • Tobacco
• Misc
  • Hyperthyroidism

Evaluation

• ECG
• CBC
• Chem 10
• Mag and phos
• Consider coags, especially if on anticoagulation
• Consider LFTs
• Consider BNP if heart failure unclear
• Troponin if patient has chest pain
• Cardiac Echo - if signs of new/worsening heart failure
• Chest XR

Management

Unstable

• Synchronized cardioversion (100-200J)
  • Atrial fibrillation - start at 200 J
  • Atrial flutter - start at 50 J
• Indications: ischemic chest pain, SBP < 90, acute pulmonary edema, altered mental status
• Consider cardiostable sedation such as 5mg etomidate
  • +/- subdissociative pain dosage ketamine at 15mg
• If shock does not work:
  • Verify not preexcitation
  • Increase diastolic BP to perfuse the heart
    • Push-dose phenylephrine
      • Will maintain BP when give rate-control meds
      • 50-200mcg q2-5min with goal DBP >60
  • Amiodarone 150mg over 10min (preferably through central venous access) OR diltiazem 2.5mg/min until HR <100 or max 50mg
  • Magnesium 2 g over 1-5 min, repeat if no response after 15 min, then consider 1-2 g/h for 4 hrs if response
    • Significantly less effective than amio or calcium-channel blockers
    • Ensure baseline magnesium level
    • Check magnesium q2hrs if infusing

Stable and Asymptomatic

If mild or no symptoms and pulse only mildly elevated (<110bpm) ok to manage with PO meds

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

Medication Choices

Medication	Dose	Comments	Contraindications
Calcium-Channel Blockers
Diltiazem	Bolus 0.25mg/kg (average adult dose 20mg) over 2 min If, after 15min 1st dose is tolerated but inadequate re-bolus 0.35mg/kg If patient responds start infusion at 5-15mg/hr or give PO diltiazem 60mg QID	Preferred in patients with chronic lung such as Asthma and COPD	Decompensated heart failure Preexcitation (especially in pediatrics) Significant hypotension
Beta-Blockers
Metoprolol	Bolus 2.5-5mg IVP over 2min q5min up to 3 doses If patient responds orally load with 25-50mg	Particularly useful when A-fib associated with exercise, after acute MI, or with thyrotoxicosis Long-term beta blocker improves patient survival (CCB may worsen outcomes), thus starting a beta blocker upon discharge, strongly consider using the agent for rate control also.	COPD Asthma Decompensated heart failure Hypotension
Esmolol	Bolus 0.5mg/kg over one minute, followed by 50 µg/kg/min If, after 4min response is inadequate, re-bolus followed by infusion of 100 µg/kg/min If, after 4min response is still inadequate, try final bolus followed by infusion of 150 µg/kg/min If necessary, infusion can be increased to maximum of 200 µg/kg/min after another four minutes	Use if unsure whether patient will tolerate a beta blocker since the duration of action is only 10 minutes
Other
Digoxin	0.25mg IV q2hr up to 1.5mg, then 0.125-0.25mg PO or IV QD Adjust dose in presence of renal failure, amiodarone, etc	Consider as initial therapy for patients with LV dysfunction who: Do not achieve rate control targets on beta blockers alone Cannot tolerate addition of or increased doses of beta blocker due to decompensated CHF Would have digoxin added anyway to improve CHF symptoms independent of A-fib Consider as initial therapy in patients with severe hypotension Consider as 2nd agent in patients in whom IV BB or IV CCB has failed to control their rate May take up to 6-8 hours to work
Amiodarone	Load 3-7mg/kg IV over 30 min then, 1200mg over 24hr via continuous infusion or in divided oral doses	Consider for patients with decompensated heart failure or those with accessory pathways 2nd-line agent for chronic rate control when beta-blockers and calcium-channel blockers, alone, combined, or when used with digoxin, are ineffective

Evidence of preexcitation

• Avoid AV nodal agents
• Unstable:
  • Unsynchronized cardioversion (200J)
  • Procainamide (if cardioversion unsuccessful)
    • 20 - 50 mg/min
    • Until arrhythmia is controlled, hypotension occurs, QRS complex widens by 50% of original width, or total of 17 mg/kg is given
    • Followed by continuous infusion of 2 - 6 mg/min
• Stable:
  • Try to avoid cardioversion without adequate anticoagulation

See Also

• Atrial Fibrillation (Main)
• Ottawa Aggressive Cardioversion Protocol

External Links

• ALiEM - BB vs CCB
• Crashing Afib - EMCrit
• Diltiazem load: File:dilt-load.pdf

References

Authors

Ross Donaldson