The influence of intravenous magnesium sulphate on the occurrence of atrial fibrillation after coronary artery by-pass operation

Abstract

To examine the influence of magnesium (Mg) on hypomagnesaemia and atrial fibrillation (AF) following coronary artery by-pass surgery, 140 consecutive patients were randomized to receive 70 mmol of magnesium sulphate intravenously (n = 69) or placebo (n = 71). Serum magnesium concentrations fell to 0.77 +/- 0.10 mmol.l-1 in the control group but rose to 1.09 +/- 0.17 mmol.l-1 in the Mg group (P < 0.001). The incidence of AF was 29% in the Mg group and 26% in the placebo group (NS). The AF patients were older, more of them had had prior AF episodes, their sinus rates (SR) were slower (78 +/- 10 vs 86 +/- 12 beats.min-1; P < 0.01) and serum Mg concentrations higher (0.89 +/- 0.21 vs 0.80 +/- 0.11 mmol.l-1; P < 0.05). The incidence of AF was 43% in the highest quartile of serum Mg and 23% among the rest (P = 0.056). In patients experiencing AF during the first three post-operative days, serum Mg concentrations were higher and SR slower on each day compared with non-AF patients. SR increased post-operatively less with high Mg levels (P = 0.044). In the Mg group, serum Mg and SR were the only independent predictors of AF. In conclusion, the incidence of post-operative AF is not decreased with magnesium. High Mg levels are likely to provoke AF probably by mechanisms that modify SR.

The effect of oral magnesium, alone or as an adjuvant to sotalol, after cardioversion in patients with persistent atrial fibrillation

“…Magnesium deficiency has been reported in patients with atrial fibrillation [12,13] , and magnesium deficiency in the heart muscle has been shown to be associated with an increased rate of arrhythmias after heart surgery [14] . Several studies have shown a decrease of postoperative supraventricular tachycardia/atrial fibrillation with prophylactic magnesium treatment [16,17] , but other studies have failed to confirm this observation [18] .…”

Antiarrhythmic Therapy to Prevent Atrial Fibrillation after Cardiac Surgery

“…Magnesium resulted in a 50% reduction in the incidence of atrial fibrillation from 28% to 14%, although the difference did not reach statistical significance. In a second study of 140 patients, 140 meq of intravenous magnesium sulfate was administered over the first 2 postoperative days and no difference was found in the incidence of atrial fibrillation in the treated group compared to the placebo (29% vs 26%; p=NS), despite confirmation of serum magnesium repletion [15]. In addition, the incidence of atrial fibrillation was found to have a direct correlation with serum magnesium levels, suggesting a proarrhythmic effect.…”

“…Two groups of investigators attempted to use magnesium supplementation to prevent atrial fibrillation [14,15]. In parallel with trials using prophylactic magnesium for ventricular arrhythmias in the setting of myocardial infarction [36][37][38], initially encouraging results were not supported by larger subsequent trials.…”

“…The ideal prophylactic agent would reduce the number of patients who develop postoperative atrial fibrillation, reduce the number of episodes per patient, provide ventricular rate control among patients who develop atrial fibrillation, be applicable to all patients, and have a low side effect profile. Despite the availability of several antiarrhythmic drugs for the treatment of atrial fibrillation, only a few have been evaluated as prophylactic agents in the postoperative setting; these include digitalis [10][11][12][13], magnesium [14][15], verapamil [16], procainamide [17], sotalol [18][19][20][21][22], and amiodarone [23][24][25][26] (Table). …”

Atrial fibrillation and changes in serum and urinary electrolyte levels after coronary artery bypass grafting surgery

“…However, there is some evidence suggesting that administration of magnesium may be detrimental. Parikka et al (5) suggested that correction of postoperative decline of magnesium by 70 mmol on the first two days following cardiac surgery did not reduce the incidence of atrial fibrillation. The authors reported that patients with high serum magnesium levels had a higher incidence of AF and that supra-physiological concentrations of magnesium led to slowing of sinus rhythm rate that could predispose to AF.…”