Case summary:

An ALS crew responded to a 70s man who was having shortness of breath.  The crew found him in bed with a weak, irregular pulse and an elevated respiratory rate.  Family reported that this shortness of breath had increased throughout the day and that he otherwise has had a normal amount of oral intake.  The patient denied any chest pain.  The crew obtained a 12-lead which showed an irregular narrow complex tachycardia consistent with atrial fibrillation (AF) with rapid ventricular response (RVR).  His vitals were as follows:

Vitals: BP 77/47,  HR 184  RR 40,  Sat 89% on RA, glucose 176

The patient has a known history of AF and is already taking blood thinners.  The crew placed an IV as well as placed pads on the patient.  They started a fluid bolus in case this patient was tachycardic and hypotensive due to dehydration or sepsis.  Due to his profound tachycardia and hypotension, they cardioverted the patient.  The patient failed to convert so they attempted cardioversion again, but this also failed.  The crew called medical control and were given the order to give 150mg of amiodarone over 10 minutes and instructed to change the vector of the pads before attempting to cardiovert a third time.  Giving amiodarone for the treatment of atrial fibrillation is not a part of the local protocol.  The crew tried this, but the patient remained in AF with RVR with rates near 200.  Throughout this time the crew was extricating the patient and transported the patient to the receiving facility for ongoing care. 

Highlights of the case:

Is atrial fibrillation (AF) with rapid ventricular response (RVR) the primary issue or secondary to the real problem?

In all patients with AF with RVR, the first question we should be asking ourselves is if we think the tachycardia is the primary issue or is secondary to something else.  If a patient has AF but gets really dehydrated, they will present with AF with RVR but the tachycardia is secondary to being volume down and not just because the patient is in AF.  The same is true for a patient who fell or sustained a trauma.  This patient might be tachycardic because they are in AF, or they might be trying to compensate for internal bleeding and hemorrhagic shock.  The first thing this crew did was attempt to treat volume depletion with a bolus of fluids, which was perfect.  We would not due this if the patient has clear evidence of fluid overload and pulmonary edema.  Given this did not change the patients hemodynamics at all and given there was no evidence of internal bleeding, it points towards AF with RVR as the primary cause of hypotension.  If AF with RVR is the primary cause of the patients shock, we want to treat with immediate synchronized cardioversion.  There is a risk of stroke if the patient has been in AF for more than 24 hours, but there is a bigger risk of immediate adverse outcome from shock if we delay treatment.

Why does AF with RVR cause hypotension?

For the heart to pump blood effectively, it needs to have enough time to fill.  As the HR climbs faster and faster, eventually it gets to the point where the heart does not have enough time to fill between beats.  When rates exceed this point, the patient’s blood pressure drops leading to hypoperfusion of vital organs.  This is a form of cardiogenic shock.  For most patients, the heart rate needs to be greater than 150 beats per minute before the patient is likely to develop cardiogenic shock.  For example, if a patient has AF with a rate of 125 and are hypotensive, AF itself is unlikely to be the primary cause for the hypotension.  In this situation, we should be looking for alternative reasons for the low blood pressure.  The patient in the case above had a HR in the 180s.  This rate is so fast that it was likely contributing to the patient’s hypotension and the crew was correct to try and correct this with cardioversion.

Unstable patients with tachy or brady arrythmias should be treated with electricity.

If patients are unstable, they need the treatment that is most effective first.  In the case of tachyarrhythmias and bradyarrhythmias, we want to cardiovert or pace respectively.  Both rhythms can cause cardiogenic shock in patients, and electricity works much faster and is often more effective than medications.  This patient was profoundly hypotensive with a tachyarrhythmia.  While this patient was likely hypotensive from multiple reasons, the tachyarrhythmias was most likely contributing.  For this reason, the crew was correct to quickly pull the trigger on electrical cardioversion.

Involve online medical control for complex patients who need treatments outside the protocol.

This crew provided aggressive EMS care to treat an unstable patient with AF with RVR to the limit of what the local protocol allows.  Once they got to that point, they called online medical control to discuss other options that might be beyond what the protocol allowed.  In the case of this patient, another option was trying to use amiodarone.  Our protocol uses this medication to treat unstable ventricular arrythmias; however, it can also be used in the treatment of unstable atrial arrythmias with an online medical control order.  Given that all other options had failed, this was a good choice to try next, even though it did not end up working right away.  This patient was incredibly sick.  This crews aggressive EMS care gave him his best chance.