Background: Magnesium deficiency is associated with cardiac adverse events such as arrhythmias.
Objective: We aimed to determine whether early treatment with intravenous magnesium would lower the incidence of major cardiac events among ischemic and hemorrhagic stroke patients.
Methods: Subjects participated in the NIH Field Administration of Stroke Therapy Magnesium Clinical Trial (FAST-MAG), a phase 3 randomized blinded placebo-controlled study of prehospital initiation of magnesium sulfate (20 grams/24 hours) vs. placebo initiated within 2 hours of symptom onset. Serious cardiac adverse events were recorded and characterized in all participants. We determined the relationship of treatment with magnesium to overall and specific cardiac events.
Results: There were 1700 cases enrolled in the study with a mean age of 69, 42.7% female, with 1245 cases of cerebral ischemia and 387 cases of intracerebral hemorrhage. Overall there were 255 serious cardiac events recorded in 218 patients (13%), most often cardiac arrhythmia (186 events, 11% of patients) including newly diagnosed atrial fibrillation in 72 (4%), symptomatic bradycardia in 48 (3%) and cardiac arrest in 29 (2%). In subjects with a final diagnosis of cerebral ischemia, treatment with magnesium did not affect the number of overall cardiac adverse events (13.4% with magnesium vs. 14.1% with placebo) or arrhythmia-related events (11.6% magnesium vs 11.7% in placebo). Among cases with intracerebral hemorrhage, treatment with magnesium was associated with a non-significant increased number of serious adverse cardiac events (14% with magnesium vs. 8% with placebo, p = 0.052) and arrhythmia-related events (12.4% vs. 7.3%, p = 0.091). Factors associated with more frequent cardiac events in hospitalized stroke patients were increasing age, history of hypertension, coronary artery disease and atrial fibrillation.
Conclusions: Prehospital treatment with magnesium did not significantly reduce adverse cardiac events among patients with cerebral ischemia. There were more cardiac events reported in patients with ICH who received magnesium, a finding that may need to be further evaluated.