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Three Part Question

In [patients with suspected acute myocardial infarction] is [magnesium] effective at [reducing the incidence of ventricular fibrillation]?

Clinical Scenario

You see a 50 year old man with a 2 hour history of cardiac chest pain and an ECG suggestive of acute myocardial infarction. You decide to thrombolyse. The cardiology registrar suggests that you also give IV Magnesium to reduce the incidence of ventricular fibrillation. You wonder whether there is any evidence to support this.

Search Strategy

Medline 1966-11/00 using the OVID interface.
[(exp myocardial infarction OR myocardial infarction.mp OR MI.mp) AND (exp magnesium sulfate OR magnesium sulfate.mp OR magnesium sulphate.mp OR exp magnesium OR exp magnesium.mp OR exp magnesium chloride OR magnesium chloride.mp) AND (exp arrythmia OR arrythmia.mp OR dysrythmias.mp OR exp ventricular fibrillation OR ventricular fibrillation.mp OR (VF.mp) OR (exp mortality/ or mortality.mp)] AND maximally senstive RCT filter LIMIT to human AND english.

Search Outcome

103 papers found of which 86 were irrelevant and 12 of insufficient quality for inclusion. The remaining 5 papers are shown in the table.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Abraham AS et al, 1987, Israel	94 patients with proven MI 2.4 g MgSO4 daily for 3 days vs glucose	PRCT	Incidence of:		Analysed by group sequential design (interim analysis)
			Ventricular Triplets	8 vs 13% p=NS
			R-on-T	0 vs 2% p=NS
			VT	7 vs 15% p=NS
			VF	0 vs 4% p=NS
			Total of above	14 vs 34% p=0.05
Roffe C et al, 1994, UK	2316 patients with suspected MI 8 mmol MgSO4 stat and 65mmol over 24hrs vs equal volume of saline	PRCT	Odds ratio (95% CI)		Clinical significance of arrhythmias not described
			VF	0.74(0.46,1.20) P=NS
			VT	0.87(0.63,1.20) P=NS
			SVT	0.69(0.38,1.26) P=NS
			AF	0.92(0.69,1.23) P=NS
			Heart block	1.17(0.83,1.65) P=NS
			Sinus Bradycardia	1.38(1.03,1.85) p=0.02
Bhargava B et al, 1995, India	78 patients with proven MI 73 mmol MgSO4 over 24hrs vs saline	PRCT	Incidence of :		Small numbers
			Sustained VT	10 vs 20% p=NS
			Nonsustained VT	23 vs 50% p<0.02
			VF	5 vs 8% p=NS
			SVT	0 vs 6% p=NS
			Bradycardia	5 vs 3% p=NS
			Asystole	0 vs 3% p=NS
			Mortality at 28 days	None
			In hospital mortality	7.5 vs 8% p=NS
ISIS-4 investigators, 1995, multinational	58,050 patients 80 mmol Mg over 24 h vs no infusion	PRCT	Incidence of :
			VF	3.5 vs 3.8%
			other cardiac arrest	3.2 vs 2.9%
			2nd or 3rd degree heart block	3.9 vs 3.7% 0.01 < p <0.05
			Heart failure	17.8 vs 16.6% p<0.001
			Cardiogenic Shock	4.6 vs 4.1% p<0.01
			profound hypotension	16.8 vs 15.1% p<0.0001
			5 week mortality	7.64 vs 7.24% p=NS
Gyamlani G et al, 2000, India	100 patients with proven MI 50 mmol Mg in 1st 24hr then 12 mmol Mg in next 24hr vs glucose	PRCT	Incidence of:		Small numbers
			SVT	2 vs 8%p=NS
			Sustained VT	2 vs 10%p=NS
			Nonsustained VT	4 vs 12%p=NS
			VF	0 vs 4%p=NS
			Total arrhythmias	8 vs 34%p<0.01
			Mortality	4 vs 20%p<0.05

Comment(s)

A number of small studies published have suggested that magnesium therapy significantly improves mortality following myocardial infarction. While the two larger studies show a trend to reduction in the incidence of VF but also demonstrates that this benefit is outweighed by an increased incidence of detrimental effects.

Clinical Bottom Line

Routine prophylactic magnesium in patients with myocardial infarction is not indicated.

References

1. Abraham AS, Rosenmann D, Kramer M et al. Magnesium in the prevention of lethal arrhythmias in acute Myocardial Infarction. Arch Int Med 1987;147:753-5.
2. Roffe C, Fletcher S, Woods KL. Investigation of the effects of intravenous magnesium sulphate on cardiac rhythm in acute myocardial infarction. Br Heart J 1994;71:141-5.
3. Bhargava B, Chandra S, Agarwal VV et al, Adjunctive magnesium infusion therapy in acute myocardial infarction. Int J Cardiol 1995;52:95-9.
4. Anonymous. ISIS 4: A randomised factorial trial assessing early oral captopril, oral mononitrate, and intravenous magnesium sulphate in 58050 patients with suspected acute myocardial infarction. Lancet 1995;345:669-85.
5. Gyamlani G, Parikh C, Kulkarni AG et al. Benefits of magnesium in acute myocardial infarction : Timing is crucial. Am Heart J 2000;139:703.