Today’s pearl highlights 5 main points related to the treatment of atrial fibrillation.
Should you give a beta blocker or a calcium channel blocker? What dose should you use?
- Determining which negative inotrope to choose is challenging. I’ve seen more cases of difficult-to-treat atrial fibrillation (afib) at MGH in 4 years than I did at Maryland in 8 years. Back in 2014, a cardiology pharmacist colleague (Dr. Brent Reed) and I collaborated for a two-part ALiEM series on choosing a beta blocker (BB) or a calcium channel blocker (CCB) for afib in the ED. My discussion focused on what to do in the ED. His focused on thinking beyond the ED. Though they are 6 years old, the principles still hold true in 2020.
- In the patient with borderline blood pressure, but not really appropriate for emergent cardioversion, there is some evidence to support giving calcium prior to a CCB to maintain blood pressure (without affecting our ability to control HR). The evidence is largely with verapamil, but may also apply to diltiazem. Here’s a summary of the data. I like to recommend giving calcium gluconate 2 gm over 10-20 minutes followed by the CCB.
- What happens when we give multiple doses of one agent and it doesn’t work? Can we safely switch to a different agent? What about heart block and/or bradycardia? At MGH, we actually switch from BB to CCB (and vice versa) often enough that were able to study it. We found that 4% of patients developed bradycardia (n = 136). This result can be looked at from the perspective of only 4% of patients were negatively affected or wow, 4% of patients were negatively affected! Importantly, adding a second nodal blocker in patients who did not achieve rate control with the first agent resulted in heart rate control in less than half of cases.
- What dose of diltiazem is correct? Both weight-based and non-weight-based strategies have been studied. Here’s a summary of the data from a previous MGH EM pharm pearl.
- We’ve significantly decreased our utilization of diltiazem infusions in the ED over the past few years (a good thing). Here’s a nice overview of why diltiazem infusions are not ideal for acute rate control, especially in patients with underlying cardiovascular disease.