Approach to Atrial Fibrillation with RVR

First Question: Stable or Unstable?

-Unstable = hypotension (SBP < 90), AMS, ischemic chest pain, acute pulmonary edema

-If unstable: electrical synchronized cardioversion at 200 J. Use sedation!

-If stable: rate vs rhythm control

Before slowing the rate, consider why they are in Afib, and if that elevated HR is a compensatory mechanism. However, once the rate is >140-150, decreased diastolic filling time results in decreased CO, so it may be beneficial to slow them down. Some precipitants of acute onset Afib: EtOH, thyrotoxicosis, MI, PE, infection, illicit drugs

Rate Control

-Rate control increases the diastolic filling time, increasing CO

-Many drugs available

– good to know many options in times of shortage

Diltiazem:

AV nodal blocker

10-20 mg IV bolus over 2 min (0.25 mg/kg)

Start a drip: 2.5-15 mg/hr, titrate until rate controlled If hypotensive, consider pre-treating with 1 gram IV calcium gluconate to decrease peripheral hypotension, though controversial

Metoprolol:

AV nodal blocker

5 mg IV bolus over 2 min, every 5 min to max dose of 15 mg

Start on PO (25-100 mg)

Drug of choice if hyperthyroid, but CI in COPD, asthma, acute CHF

Digoxin:

AV nodal blocker

0.25-0.5 mg IV, can repeat after 6-8 hours.

Max 1.5 mg/24 hours

Esmolol:

AV nodal blocker

500 mcg/kg IV bolus over 1 minute

Infusion 50-300 mcg/kg/min IV, titrated to heart rate

Fast onset and offset

Verapamil:

AV nodal blocker

2.5-5 mg IV bolus over 2-3 minutes

If persists, can repeat dose of 5-10 mg

Monitor BP as this can cause significant hypotension! Consider pre-treatment with calcium

Rhythm Control

Two options: Electricity or pharmacologic.

If electrical, see above

Magnesium

2 grams IV over 2 minutes, followed by infusion 1-2 g/hr

Amiodarone

Class III antiarrhythmic

150 mg IV over 10 minutes

Then drip 1 mg/min for 6 hours, then 0.5 mg/min

Initially slows the rate (like beta blocker effect), and rhythm control takes some time

Procainamine

Class 1a antiar rhythmic

15-17 mg/kg IV over 30 min, followed by drip 1-4 mg/min

Use in WPW because also blocks the accessory pathway

Special Consideration:

-If fast Afib (rate in high 100s-200), think accessory pathway like WPW and do NOT block the AV node as that can lead to degeneration into VF. Use procainamide

Reference:

Tintinalli, Judith, et al. “Cardiac rhythm disturbances and pharmacology of antihypertensives and antiarrhythmics. ” Tintinalli’s Emergency Medicine, 8th ed., McGrath-Hill, 2016. pp 112 - 142.