Metoprolol for Atrial Fibrillation

Atrial Fibrillation and atrial flutter (AF/FL) is the usually irregular beating of the heart and is a rapidly growing cause of hospitalization. Between 1993 to 2007 AF/FL hospitalizations have increased 203% compared to a 71% increase for all hospitalizations. Changing procedure management such as ablation, transesophageal have had a minimal impact on the trends and there is a need to evaluate Emergency Department (ED) management options of AF/FL that may decrease hospitalizations. The most commonly used medications to control heart rate are metoprolol (MET), a beta blocker, or diltiazem (DT), a calcium channel blocker. Beta blockers are medications that cause the heart to beat more slowly and with less force. DT also helps blood vessels open up to improve blood flow. Both DT and MET are used alone or together with other medicines to treat severe chest pain (angina), high blood pressure (hypertension) or rapid heartbeat. Both are equally acceptable according to recent guidelines for AF/FL. There are limited studies comparing MET to DT for rate control for AF/FL. The initial goal for AF/FL management in the Emergency Department is usually rate control. The most commonly used rate control medications are metoprolol (MET), a beta blocker, or diltiazem (DT) a calcium blocker. Three major guidelines, including the American College of Cardiology (ACC) and the American Heart Association (AHA) indicate beta blockers and DT are equally acceptable medications for rate control in AF (3,4,5) assuming no contraindications. There are limited studies comparing beta blockers (BB) to DT for rate control for AF: Demircan, et. al., compared bolus intravenous BB and DT in 40 patients over a 20 minute period. No follow-up information after 20 minutes was reported. No attempt was made to look at intermediate or long term results. No patients converted to normal sinus rhythm over this short treatment period and there was slightly more rate decrease at 20 minutes, with DT versus BB (6). Time from medication administration to heart rate and rhythm control. Additionally, currently guidelines consider BB or DT medications to slow AF/FL; however, there are some suggestions that BB may not only slow heart rate in AF/FL (as does DT) but also increase all AF/FL conversion from AF/FL to normal sinus rhythm(2), and aid in maintaining normal sinus rhythm (NSR) after cardioversion (10). With recent onset AF/FL occurring within 48 hours prior to the arrival to the ED, approximately 50% of AF/FL patients convert to normal rhythm spontaneously within 24 hours after arrival to the ED (6), making evaluation of current limited studies difficult. Thus, the investigators wish to examine the effect of initial medication strategy on time to NSR in a larger sample than has been previously performed. A randomized study of 48 patients in China reported significantly slower heart rate up to 20 minutes with DT 10mg IV versus metoprolol 5mg IV but not after 30 minutes (7). A retrospective study of post-operative coronary bypass patients showed the intravenous administration of the BB, esmolol, to be more effective than DT for rate control and conversion of AF/FL (8). Hassan et al reported no difference in conversion to regular rhythm with esmolol verses DT in a small, under powered, randomized study of fifty ED patients (9). Conversion to sinus rhythm occurred in 10 patients (42%) in the DT group compared with 10 patients (39%) in the esmolol group (P = 1.0). There were no statistically significant differences in heart rate between the two medications at 1, 6, 12, and 24 hours after initiation of esmolol or DT infusion. Examples of such well quoted strategy trials are the COURAGE trial published in the New England Journal of Medicine and the PROMISE Trial, a worldwide multi-centered study that is nearing completion goal of 10,000 patients of which, Charleston Area Medical Center (CAMC) has enrolled approximately 100 patients. In this trial, patients being evaluated for chest pain will be randomized to two treatment strategies and subsequent outcomes will be recorded. Strategy trials do not attempt to manage treatment after an initial management strategy has been determined by randomization, but, whether the initial treatment affects long-term outcomes. This will be a prospective, randomized study comparing the outcomes of a strategy using either MET or DT in patients with AF presenting to the Charleston Area Medical Center (CAMC) ED. After presentation and receiving consent, the patient will be randomized to receive either MET or DT.