Atrial fibrillation (AFib) with rapid ventricular response (RVR) can be very simple to treat, or you may have try many different treatments in order to successfully control either the rate or convert to sinus rhythm. I recently came across a patient that did not respond to the usual treatments, which prompted me to investigate this a little deeper.
First off, you need to decide whether your patient is stable or unstable. Some describe stable as a hemodynamic parameter, while others describe this as severe symptoms (i.e. severe chest pain or dyspnea). If your patient is unstable, immediate synchronized cardioversion is recommended. The initial dose is around 120 J, with a subsequent shock of 200 J if necessary. If you have time, give them sedation!!! One note on synchronized cardioversion for those of you who have never done this, you will need to hold down the shock button in sync mode to deliver the shock (the machine waits for the appropriate time to give the synchronized shock). If you just tap the button such as in defibrillation, it may not work.
If your patient is uncomfortable but stable, pharmacotherapy for rate control is a great first option after you have attempted to identify the underlying cause. I usually use diltiazem with a first dose of 0.25 mg/kg IV push, followed by 0.35 mg/kg IV push if necessary. The other recommend calcium channel blocker (CCB) is verapamil, at a dose of 5-10 mg IV over 2-3 minutes (repeat as necessary every 10 minutes), with a drip afterward if necessary. Others promote using a beta blocker such as metoprolol, given in 2.5 to 5 mg increments IV with a max of 15 mg. Esmolol is another good beta blocker for this due to its rapid on/off action, although a drip will be needed. Another medication used for rate control is digoxin, which works by AV nodal inhibition that is vagally mediated; however, it is less efficacious than BB and CCB. Magnesium (2 to 4 g) has also been suggested to help with rate control.
Most providers know the interventions listed above, but what do you do when you’ve tried everything else? I recently had a patient that received diltiazem IV push x 2, diltiazem drip, and synchronized cardioversion x2 (120 J and 200 J) without success. The next step is likely an attempt at rhythm control using an antiarrhythmic. Amiodarone is a great first choice. It is a class III antiarrhythmic but also has properties of other classes as well. This drug can also help slow the heart rate. The dose for rhythm conversion is usually 150 mg over 10 minutes, with the option of giving more as an infusion afterward. Other antiarrhythmics have been suggested as well, although they are not as efficacious as amiodarone.
One case report even suggested using two defibrillators in hemodynamically unstable patients in refractory AFib with RVR who have failed cardioversion at normal amounts of electricity. They suggest having two defibrillators hooked up in the usual locations, maxing each out (720 J total in their monophasic machines) and pressing the sync shock button simultaneously! Realize this is only a case report and no randomized controlled trials have looked at this, but it’s still an interesting approach. Their reasoning behind this is that many patients who have AFib with RVR may be larger with more electricity needed to deliver an appropriate shock to the heart. Again, don’t try this at home!
If all else fails and the patient is still hemodynamically unstable after all of your amazing efforts at either rate control or rhythm control, they may need a cardiologist to help with the conversion via either interventional means or more unusual medications.
Atrial Fibrillation, Cardiac System. Rosen’s Emergency Medicine, 7th Ed. pp 1010-1012.
Ganz L. Control of ventricular rate in atrial fibrillation: Pharmacologic therapies. Uptodate.com. Updated Aug 18, 2010.
Chang AK. Lent GS. Grinberg D. Double-dose external cardioversion for refractory unstable atrial fibrillation in the ED. American Journal of Emergency Medicine. 2008. 26, 385e1-385e3.