Does taking Metoprolol before cardiac surgery reduce the incidence of post-op atrial fibrillation
Abstract

Postoperative atrial fibrillation (POAF) remains a prevalent supraventricular arrhythmia. PoAF has associated effects such as deteriorating hemodynamic, increased risk of stroke and increased probability of death. Beta-blockers have been recommended as effective intervention mechanism of preventing PoAF. Metoprolol is one such beta-blocker that is commonly administered to prevent the incidence of PoAF. The systematic review below entails an analysis of six clinical trials that explore the effectiveness of metoprolol. The analysis identifies reduced hospitalization length, reduced mortality and reduced financial burden as the beneficial impact associated with the administration of prophylactic. The small number of studies reviewed limits the validity of the conclusion warranting future large sample size research.

Introduction

Annually, approximately 750,000 cardiac surgery are performed globally with postoperative atrial fibrillation (PoAF) being the prevalent complications (George, et al., 2018). With the increasing proportion of elderly population globally, it’s expected that the number of cardiac surgeries would accelerate, consequently increasing the incidence of PoAF (George, et al., 2018). Existing epidemiological data suggest that incidence of PoAF after cardiac surgery remains a prevalent risk and detrimental sequelae that yields increased hospitalization days, substantial economic cost and increased morbidity and mortality (Crystal, et al., 2004). Systematic review findings by George, et al., (2018) demonstrate 20-50% incidence of PoAF in cardiac surgical patients

According to Lúcio, et al., (2004) PoAF is classified as a supraventricular arrhythmia delineated by inconsistent and rapid ventricular rate due to loss of atrial contraction which picks within the two days after the cardiac operation. The high atrial frequency causes an irregular contraction frequency and irregular electrical activation of the ventricles. There are five types of atrial fibrations distinguished by the duration of the arrhythmia, which includes; paroxysmal, long-standing, persistent, first diagnosed and permanent atrial fibrillation.

Several predisposing factors including previous history of atrial fibrillation (AF), valvular heart surgery, chronic renal failure, chronic obstructive pulmonary condition, rheumatic heart disease, reduced left ventricular ejection fraction, diabetes mellitus, and advanced age have been identified to accelerate the incidence of PoAF (George, et al., 2018). Although PoAF maybe a temporary condition, it’s associated with multiple medical complications. Particularly, valvular heart surgeries are reported to have a higher risk of PoAF. PoAF is linked to increased post-surgery risk of chronic conditions such as stroke, heart failure and myocardial infarction (George, et al., 2018). Turagam, et al., (2015)reports an estimated 30-40% prevalence rate of AF among patients undergoing cardiac surgery.

Literature Review

Multiple pharmacological approaches have been developed to prevent postoperative AF (PoAF) including the Metoprolol to post-surgery (Turagam, et al., 2015). Clinical evidence of intervention mechanisms of preventing incidences of PoAF identifies that the approaches have a counteracting effect on PoAF on triggering factors. The underlying mechanisms or preventing PoAF centered around reducing inflammation with steroids, statins, polyunsaturated fatty acids or colchicine; controlling the neurohumoral system through amiodarone, angiotensin-converting enzyme inhibitor beta-blockers; reducing the myocardial energy demands with beta- blockers or reducing oxidative stress with acetylcysteine or ascorbate (Turagam, et al., 2015).

Use of preoperative beta-blockers such as Metoprolol is one intervention that controls the neurohumoral system by diminishing the demand of myocardial oxygen and blunting the inotropic and chronotropic of a surge of catecholamine (Turagam, et al., 2015). The B blocker treatment has been recommended by the European Society of Cardiology and the American Heart Association as a first treatment intervention for preventing PoAF (George, et al., 2018). However, findings on the efficacy of metoprolol remain elusive (Turagam, et al., 2015) providing a research gap for the current study.

Existing literature explores the effectiveness of administration of Metoprolol to post-cardiac surgery patients (Turagam, et al., 2015). Extant research has limitedly reviewed the effectiveness...…metoprolol to a 6 months’ period. Consistent with the earlier studies, Yang et al (2006) report a lower incidence of PoAF on the intervention group (10.2%, 95% CI) compared to the control group (12%, 95% CI). The clinical trial, however, doesn’t indicate any difference after monitoring the effectiveness of metoprolol over a period of 6 months demonstrating that metoprolol doesn’t delay the prevalence of PoAF. Comparative analysis of the efficacy of metoprolol and carvedilol by Acikel et al (2008) indicates although metoprolol reduces the incidence of PoAF, its efficacy is lower compared to other beta blockers such as carvedilol. Acikel et al (2008) randomized trial of 110 patients identifies 36% incidence of PoAF in the metoprolol group compared t0 16% of PoAF in the carvedilol group.

While research has centered on the comparative efficacy of metoprolol, limited research focuses on the form of its administration (Halonen, et al., 2004). Cardiopulmonary perfusion affects the absorption of metoprolol subsequently affecting the drug’s efficacy in preventing PoAF (Halonen, et al., 2004). The randomized controlled trial of 240 patients scheduled for cardiac surgery identified that a lower incidence of PoAF when intravenous administration of metoprolol. PoAF Halonen, et al., (2004) remotes a 28% incidence of PoAF in patients where metoprolol was orally administered and a 16.8% incidence of PoAF where metoprolol was intravenously administered.

Conclusion

The systematic review of findings six studies illustrates that the preoperative administration of metoprolol may effectively attenuate the incidence of PoAF that subsequently reduces the length of hospitalization, financial burden, and the morbidity and mortality rate. The analysis further reveals that intravenous administration, as opposed to oral administration, increases the efficacy of metoprolol. Given that the review considered six studies which arguably is a limited sample size, the conclusion may overestimate or underestimate the incidence of PoAF resulting in bias. A further systematic review exploring a larger…