Prophylactic magnesium is not indicated in myocardial infarction
Date First Published:
August 10, 2000
Last Updated:
April 18, 2001
Report by:
Mark Davies, Senior Clinical Fellow (Manchester Royal Infirmary)
Search checked by:
Angai Ghosh, Manchester Royal Infirmary
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.
Search Details:
[(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.
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):
| Study Title | Patient Group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
|---|---|---|---|---|---|
| Magnesium in the prevention of lethal arrhythmias in acute Myocardial Infarction. Abraham AS, Rosenmann D, Kramer M et al. 1987, Israel | 94 patients with proven MI 2.4 g MgSO4 daily for 3 days vs glucose |
PRCT | Incidence of: | 8 vs 13% p=NS | Analysed by group sequential design (interim analysis) |
| Ventricular Triplets | 0 vs 2% p=NS | ||||
| R-on-T | 7 vs 15% p=NS | ||||
| VT | 0 vs 4% p=NS | ||||
| VF | 14 vs 34% p=0.05 | ||||
| Total of above | |||||
| Investigation of the effects of intravenous magnesium sulphate on cardiac rhythm in acute myocardial infarction. Roffe C, Fletcher S, Woods KL. 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) | 0.74(0.46,1.20) P=NS | Clinical significance of arrhythmias not described |
| VF | 0.87(0.63,1.20) P=NS | ||||
| VT | 0.69(0.38,1.26) P=NS | ||||
| SVT | 0.92(0.69,1.23) P=NS | ||||
| AF | 1.17(0.83,1.65) P=NS | ||||
| Heart block | 1.38(1.03,1.85) p=0.02 | ||||
| Sinus Bradycardia | |||||
| Adjunctive magnesium infusion therapy in acute myocardial infarction. Bhargava B, Chandra S, Agarwal VV et al, 1995, India | 78 patients with proven MI 73 mmol MgSO4 over 24hrs vs saline |
PRCT | Incidence of : | 10 vs 20% p=NS | Small numbers |
| Sustained VT | 23 vs 50% p<0.02 | ||||
| Nonsustained VT | 5 vs 8% p=NS | ||||
| VF | 0 vs 6% p=NS | ||||
| SVT | 5 vs 3% p=NS | ||||
| Bradycardia | 0 vs 3% p=NS | ||||
| Asystole | 7.5 vs 8% p=NS | ||||
| Mortality at 28 days | |||||
| In hospital mortality | |||||
| ISIS 4: A randomised factorial trial assessing early oral captopril, oral mononitrate, and intravenous magnesium sulphate in 58050 patients with suspected acute myocardial infarction. Anonymous. 1995, multinational | 58,050 patients 80 mmol Mg over 24 h vs no infusion |
PRCT | Incidence of : | 3.5 vs 3.8% | |
| VF | 3.2 vs 2.9% | ||||
| other cardiac arrest | 3.9 vs 3.7% 0.01 < p <0.05 | ||||
| 2nd or 3rd degree heart block | 17.8 vs 16.6% p<0.001 | ||||
| Heart failure | 4.6 vs 4.1% p<0.01 | ||||
| Cardiogenic Shock | 16.8 vs 15.1% p<0.0001 | ||||
| profound hypotension | 7.64 vs 7.24% p=NS | ||||
| 5 week mortality | |||||
| Benefits of magnesium in acute myocardial infarction : Timing is crucial. Gyamlani G, Parikh C, Kulkarni AG 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: | 2 vs 8%p=NS | Small numbers |
| SVT | 2 vs 10%p=NS | ||||
| Sustained VT | 4 vs 12%p=NS | ||||
| Nonsustained VT | 0 vs 4%p=NS | ||||
| VF | 8 vs 34%p<0.01 | ||||
| Total arrhythmias | 4 vs 20%p<0.05 | ||||
| Mortality |
Author Commentary:
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.
Bottom Line:
Routine prophylactic magnesium in patients with myocardial infarction is not indicated.
References:
- Abraham AS, Rosenmann D, Kramer M et al.. Magnesium in the prevention of lethal arrhythmias in acute Myocardial Infarction.
- Roffe C, Fletcher S, Woods KL.. Investigation of the effects of intravenous magnesium sulphate on cardiac rhythm in acute myocardial infarction.
- Bhargava B, Chandra S, Agarwal VV et al,. Adjunctive magnesium infusion therapy in acute myocardial infarction.
- 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.
- Gyamlani G, Parikh C, Kulkarni AG et al.. Benefits of magnesium in acute myocardial infarction : Timing is crucial.