Summary
Atrial fibrillation is the most typical cardiac arrhythmia in scientific apply. Atrial fibrillation impacts an estimated 2.2 million adults within the USA and has an estimated incidence of 1.0 per 1000 particular person‐years within the UK.1,2 Atrial fibrillation is related to important morbidity and mortality. Sufferers in atrial fibrillation have a fivefold elevated threat of thromboembolic stroke and twofold elevated threat of dying when in comparison with the final inhabitants.3,4 Atrial fibrillation may trigger tachycardia‐induced coronary heart failure if the speedy ventricular response is sustained for a chronic time frame.5
Most sufferers in acute atrial fibrillation don’t have any important haemodynamic instability and as such, pharmacological remedy is often the preliminary remedy of selection. A wide range of pharmacological brokers can be utilized, both to regulate the speedy ventricular response or convert the arrhythmia to sinus rhythm, with variable outcomes. The brokers evaluated embrace digoxin, beta‐blockers, calcium antagonists, flecainide, propafenone, ibutilide, and amiodarone.6 Nonetheless, in sufferers with impaired left ventricular perform, digoxin or amiodarone is the pharmacological agent of selection due to their minimal unfavorable inotropic results.6
Magnesium has many important physiological and pharmacological results on completely different organ methods. The mechanisms of its motion embrace calcium antagonism, regulation of vitality switch and membrane stabilisation.7 Intravenous magnesium has a excessive therapeutic‐to‐poisonous ratio and minimal unfavorable inotropic results.8,9 Intravenous magnesium can scale back automaticity,10 atrioventricular nodal conduction,11,12 polymorphic ventricular tachycardia as a consequence of extended QT interval and digoxin‐induced arrhythmias.7,8,13 Prophylactic use of intravenous magnesium may scale back the prevalence of atrial fibrillation after cardiac surgical procedure.14 Nonetheless, there aren’t any giant randomised managed research or meta‐analyses that consider intravenous magnesium as an antiarrhythmic agent within the setting of acute onset atrial fibrillation.
Rhythm management by pharmacological brokers is commonly simplest when the drug is initiated inside 10 days of onset of atrial fibrillation.15 We hypothesised that intravenous magnesium might be an efficient antiarrhythmic agent in sufferers with acute onset atrial fibrillation. We assessed the potential helpful and dangerous results of intravenous magnesium, when in comparison with placebo or another arrhythmic agent, within the setting of acute onset atrial fibrillation (<7 days) on this meta‐evaluation. The tip‐factors assessed on this research included rhythm management, ventricular response <100 beats/minute, bradycardia, hypotension, and different unwanted effects.
Strategies
Outcomes
Dialogue – “magnesium and afib”
This meta‐evaluation exhibits that including intravenous magnesium is simpler than placebo in decreasing the quick ventricular response fee when added to digoxin however not in attaining sinus rhythm in sufferers with acute atrial fibrillation. With the restricted information out there, the consequences of intravenous magnesium on the ventricular response fee and the danger of bradycardia, atrioventricular block or hypotension are much less important than intravenous calcium antagonists or amiodarone. Minor transient signs comparable to flushing, tingling and dizziness are usually not unusual (17%) after using intravenous magnesium.
Whereas earlier meta‐evaluation has proven that magnesium is efficient in stopping the prevalence of atrial fibrillation after cardiac surgical procedure,14 our research exhibits that including intravenous magnesium to both digoxin or ibutilide shouldn’t be efficient in attaining sinus rhythm as soon as atrial fibrillation has occurred. The distinction in our outcomes and the earlier meta‐evaluation that assessed prophylactic use of magnesium might be as a consequence of completely different underlying causes of atrial fibrillation and completely different pattern dimension. Magnesium deficiency is frequent after cardiac surgery7,17 and there’s a suggestion that sufferers who’ve each hypomagnesaemia and atrial fibrillation are extra doubtless to answer intravenous magnesium.17,41 Six of the ten trials on this meta‐evaluation included sufferers with a traditional baseline serum magnesium focus earlier than magnesium remedy. This issue might have chosen the group of sufferers that had been much less doubtless to answer intravenous magnesium in attaining sinus rhythm. Moreover, the pattern dimension of this meta‐evaluation (n = 515) continues to be comparatively small and will solely present a major impact on rhythm management if intravenous magnesium can improve the conversion fee from 20% to a minimum of 30%. However, the typical rhythm conversion fee within the magnesium group of this meta‐evaluation was solely 25% and this was nonetheless far beneath the 60% spontaneous rhythm conversion fee of acute onset atrial fibrillation reported within the literature.43,44 Equally, we couldn’t exclude a small improve in threat of hypotension and bradycardia with intravenous magnesium when in comparison with placebo due to the comparatively small variety of sufferers included within the trials.
Our outcomes present that the therapeutic impact of intravenous magnesium is principally on decreasing the quick ventricular response fee in sufferers with acute onset atrial fibrillation. Its effectiveness and likewise the related cardiovascular unwanted effects are much less important than intravenous calcium antagonists or amiodarone. Magnesium has many physiological results and one of many potential mechanisms for its motion could embrace the calcium channel blockade impact on the atrioventricular node.7,11,12 If that is the primary mechanism how intravenous magnesium works in sufferers with atrial fibrillation, then our outcomes recommend that intravenous magnesium will be considered a “weak” intravenous calcium antagonist in each effectiveness (ie, slowing the ventricular fee) and toxicity (ie, bradycardia and hypotension) when in comparison with verapamil and diltiazem. Nonetheless, minor transient unwanted effects together with flushing, tingling and dizziness are usually not unusual and seem like particularly related to magnesium however not different calcium antagonists. As a result of magnesium has a number of pharmacological actions aside from calcium antagonism on the atrioventricular node, a few of these minor unwanted effects might be as a result of different actions of magnesium together with its peripheral vasodilating impact and antagonistic motion on the N‐methyl D‐aspartate receptor.7 It must also be famous that magnesium can accumulate in sufferers with renal failure and a really excessive serum magnesium focus (>5.0 mmol/l) may cause neuromuscular blockade and respiratory melancholy, though these unwanted effects weren’t reported within the pooled research.7
There are some limitations with this research. First, though serum magnesium concentrations had been regular and comparable in each remedy teams in six of the included trials, this didn’t exclude subclinical imbalance in magnesium deficiency between the 2 remedy teams due to the poor correlation between serum and myocyte magnesium concentrations.45 This might signify a possible confounder that we couldn’t exclude with the information of the trials. Second, this research included trials that evaluated completely different doses of intravenous magnesium and likewise in contrast magnesium to completely different different antiarrhythmic medication in numerous affected person cohorts. The outcomes of the comparability between intravenous magnesium and placebo had been homogenous however there was important heterogeneity within the comparability between intravenous magnesium and one other antiarrhythmic drug. This was doubtless as a consequence of completely different doses of magnesium and various kinds of antiarrhythmic medication used on this stratum of trials. Third, a number of statistical testing was carried out within the comparability between magnesium and placebo as a result of one trial was analysed twice.21 Nonetheless, utilizing the Bonferroni correction, the importance of the leads to assessing the consequences of magnesium on rhythm management and ventricular fee <100 beats/min stays unchanged. In conclusion, intravenous magnesium, when in comparison with different antiarrhythmic brokers or with digoxin, shouldn't be efficient in changing acute onset atrial fibrillation to sinus rhythm in sufferers with a traditional serum magnesium focus. Including intravenous magnesium to digoxin reduces the quick ventricular response however this impact and its related cardiovascular unwanted effects are each much less important than different calcium antagonists or amiodarone. Intravenous magnesium will be thought-about as a secure adjunct to digoxin in controlling the ventricular response in sufferers with acute onset atrial fibrillation. A big randomised managed trial is required to verify our findings.
Acknowledgements
Footnotes