Atrial Fibrillation

Definitions

  • Paroxysmal - terminates spontaneously, without intervention in 7d (or has in past)
  • Persistent - > 7 days
  • Long-standing persistent - > 12 mo
  • Permanent - cardioversion failed or never attempted 
  • Valvular - 2/2 rheumatic mitral stenosis, mechanical valve or mitral valve repair

 

Etiology - PIRATES

  • Pulmonary dz (COPD/PE)
  • Ischemia
  • Rheumatic heart dz
  • Anemia (high output failure)/Atrial myxoma
  • Thyrotoxicosis
  • Ethanol/Endocarditis
  • Sepsis/Sick sinus
  • Others: lytes, drugs, CHF, myo/pericarditis, High sympathetic tone states (post-op, hypovolemia, shock)

 

Acute MGMT

Rate vs Rhythm Control

  • RACE and AFFIRM trials (No survival benefit in rhythm control vs rate control)
  • No real contraindication for rate control (good 1st choice) unless unstable or preexcitation present
  • Rhythm control contraindicated in >48h or unknown duration

 

Pharm

General principles:

  • Dont mix BB/CCB (AV nodal block, brady, hypotension)
  • Dont use BB in severe asthma
  • Dont use CCB in decompensated HF
  • Dont cardiovert stable AF if they arent on AC when indicated
  • Dont attempt rate control if known or suspected accessory pathway

 

  • Do try to resume same class of home med
  • DO use BB in sepsis + AF/RVR (BB assoc w/ lower hosp mortality compared to CCB/dig/amio; obviously need to consider effects of hypotension)

 

  • (Retrospective cohort study on BB in sepsis; no RCT available yet)
  • DO use BB in hyperthyroidism (dec adrenergic tone AND metoprolol, propranolol, atenolol decrease Coversion of T4-->T3)
  • DO (probably) use BB in CHF; use of CCB in early LV dysfunction WITHOUT CHF increases risk of developing CHF later (MDPIT study). Not much difference in patients with established CHF; though given significant negative inotropic effect that impairs LVEF, probably best to avoid 

 

  • DO anticoagulate if > 48h, high stroke risk (CHADVASc) or unknown duration ASAP. Esp if cardioverting
Beta1 Blocker (decreased ino/chronotropy)
Esmolol Super short 1/2 life
Metoprolol
Tartate = short acting
Succinate = long acting
IV lopressor pretty short on/off
Atenolol  
Carvedilol  
Acebutolol, betaxolol, bisoprolol, celiprolol, nebivolol  
 
Non-dihydropyridine CCB (inhibitory effect on SA, AV nodal tissue, calcium influx)
Diltiazim           Possibly superior effect of rate control, probably useful as first line but must consider the above special scenarios.
Verapamil      really second line; very potent negative inotrope with more profound hypotension
 

Amiodarone

(Class III antiarrhythmic w/ K/Ca/Beta channel blockade)

  • MUST remember that amio confers a risk of chemical cardioversion. IF you're going to use it, you have to approach with the same caution as electrical cardioversion.
  • AHA Class IIa recommendation that amiodarone can be used for rate control in critically ill patients
  • Caution as pulmonary, hepatic, thyroid toxicity 
  • Remember dosing: 150mg IV bolus (over 10-15 minutes, not IVP) followed by 1mg/min IV x 6 hours then 0.5 mg/min IV x 18 hours, (total 1g load); then maintenance dose 0.5mg/min. 
  • Conversion to oral usually 200mg BID

 

Rate Control Goals

RACE II demonstrates strict vs lenient control (80 vs 110, respectively) = no difference 

General principle: asymptomatic? <110 goal. Symptomatic? Goal rate should be asymptomatic rate.

 

Electrical Cardioversion

  • Convert unstable patients with hemodynamic instability, ongoing ischemia, worsening heart failure
  • Biphasic > monophasic
  • Set that bad boy @ 200 (bi) or 360 (mono) and let er rip. Try to sync if able.
  • High joules will not cause myocardial damage

 

  • Anterolateral may be better than anteroposterior (minor subgroup benefit, heterogeneity high)

 

 

Anticoagulation

  • Use AC if > 48h or unknown or high CHADVASc (only use scoring in NONVALVULAR AF)
  • HASBLED score may be beneficial in weighing risk/benefit
  • Valvular AF needs valve replacement -- after replacement, target depends on valve type (2-3 if tissue, 2.5-3.5 if mechanical)

 

Crashing A-Fib not amenable to Cardioversion

  • -Yes, first line for crashing A-fib is cardioversion. But it often doesn't work. Then what?
  • -Make sure there's no WPW (Wide QRS / Rate > 250-300 = BAD). Shock these patients early and often
  • Get the BP up w/ push dose neo (50-200mcg q 1 minute)
  • Slow them down with:
    • Amio 150mg then drip (can bolus x2)
    • Dilt drip at 2.5mg/minute until HR <100 or 50mg
  • Salvage therapies: mag, reshock, consult cards

 

 

 

CardiologyJeremy AmayoComment