The study was not IRB approved and there were anticipated challenges in recruiting participants.

The Assessment of Intravenous Rate Control Response in Atrial Fibrillation Trial Pilot Study (AIRCRAFT Pilot) is a prospective, unblinded, pragmatic, cluster-level allocation trial. AIRCRAFT compares two medication classes commonly used for rate control in patients in atrial fibrillation (AF) with rapid ventricular rate (RVR). The purpose of this pilot study is to evaluate the feasibility and approach to conducting a trial that compares the use of IV beta blockers and IV calcium channel blockers for patients in AF with RVR in the medical intensive care unit (MICU). AF with RVR is considered when the following parameters are met: (1) Cardiac rhythm consistent with AF (2) Heart rate > 110 bpm. AF with RVR recurrence after conversion to sinus rhythm or prior rate control will count as a new episode of AF with RVR. Rate control agents will be pseudo-randomized to each of the three different MICU teams (beta-blocker, calcium channel blocker and physician preference). Patients are admitted to the three MICU teams on a rotating basis which will allow for pseudo-randomization, the effects of which will be equal between the three teams. Patients will be enrolled in the study if they develop AF with RVR and will be followed until discharge from the MICU. This study aims to assess the adherence and fidelity to treatment assignments in the current novel pilot study protocol which will help inform the feasibility of a larger-scale efficacy trial between IV beta blockers and IV calcium channel blockers for initial management of AF with RVR. Assessment of adherence and fidelity to treatment assignments in management of AF with RVR in the MICU will help inform power calculations and the percent of patients in each study group that received the assigned class of medication will help inform feasibility. Additional aims include assessment of time from medication administration to rate control or sinus conversion as well as identifying optimal means of data extraction (manual vs automated), and incidence of adverse events including hypotension and bradycardia.

Inclusion Criteria:

• All adults admitted to the MICU at Boston Medical Center (BMC) during the study period who develop AF with RVR whose treating clinicians decides intravenous (IV) rate control agent is necessary to manage AF with RVR
• Patients readmitted to the MICU during the study period with recurrence of AF with RVR after conversion to sinus rhythm or prior rate control

Exclusion Criteria:

• Pregnancy
• Prisoners
• Allergies to study interventions
• Presentation consistent with acute asthma exacerbation
• Presentation consistent with acute systolic heart failure