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