Magnesium for Palpitations
Magnesium supplementation has limited evidence for treating general palpitations in otherwise healthy adults, but it is definitively indicated for specific life-threatening arrhythmias like torsades de pointes and may reduce ventricular ectopy in heart failure patients. 1, 2, 3
When Magnesium IS Indicated
Life-Threatening Arrhythmias
- Intravenous magnesium sulfate (1-2 g IV over 1-2 minutes) is the first-line treatment for torsades de pointes, regardless of baseline serum magnesium levels. 1, 2, 3
- Magnesium prevents reinitiation of torsades rather than pharmacologically converting the rhythm. 2
- For multifocal atrial tachycardia (MAT), intravenous magnesium may be helpful even in patients with normal magnesium levels. 4
- Magnesium is indicated for digitalis toxicity-induced tachyarrhythmias and ventricular arrhythmias from neuroleptic or tricyclic antidepressant overdoses. 5
Heart Failure Patients with Ventricular Arrhythmias
- In patients with symptomatic heart failure (mean LVEF 23%), intravenous magnesium chloride significantly reduced total ventricular ectopy per hour (70 vs 149 beats, p<0.001), couplets per day (23 vs 94, p=0.007), and episodes of ventricular tachycardia (0.8 vs 2.6 per day, p=0.051). 6
- This benefit occurred without changes in serum potassium, suggesting a direct antiarrhythmic effect. 6
When Magnesium Is NOT Indicated
Cardioversion Enhancement
- Magnesium supplementation does not enhance cardioversion success rates in atrial fibrillation. 4
- The exception is pretreatment with magnesium for ibutilide administration, which can increase efficacy and reduce the risk of torsades de pointes during chemical cardioversion of atrial flutter. 4
Monomorphic Ventricular Tachycardia
- For persistent monomorphic ventricular tachycardia, magnesium controlled the arrhythmia in only a minority of patients (8 of 25 in one study, with no significant difference versus placebo in a randomized trial). 7
- Magnesium injection cannot be recommended for emergency treatment of monomorphic ventricular tachycardia. 7
Clinical Approach to Palpitations
Identify the Underlying Rhythm
- Palpitations can represent normal sinus tachycardia (from exercise, emotions, stress, coffee, nicotine, or adrenergic/anticholinergic drugs) or pathologic arrhythmias. 8
- Many patients with arrhythmias present with syncope, shock, or chest pain rather than palpitations. 8
- Obtain a 12-lead ECG to identify the specific arrhythmia before considering magnesium therapy. 8
Check for Electrolyte Abnormalities
- Hypomagnesemia, hypocalcemia, and hypokalemia can cause life-threatening arrhythmias including torsades de pointes. 9
- Serum potassium should be in the normal range for safe cardioversion; target 4.5-5.0 mEq/L for patients with prolonged QT or torsades. 4, 3
Consider Oral Magnesium for Symptomatic Extrasystoles
- Oral magnesium has been used for many years in patients with symptomatic extrasystoles (premature beats). 5
- Studies show that both the incidence of extrasystoles and patients' symptoms are reduced during oral magnesium therapy. 5
- This represents the most reasonable application of magnesium for benign palpitations in otherwise healthy adults, though the evidence quality is limited. 5
Common Pitfalls
Do Not Delay Treatment Waiting for Magnesium Levels
- For torsades de pointes, administer magnesium immediately without waiting for laboratory results—it is effective regardless of baseline levels. 1, 2, 3
Monitor for Magnesium Toxicity
- Watch for hypotension, bradycardia, loss of deep tendon reflexes, and respiratory depression during continuous infusion. 1
- Toxicity is rare but can occur at levels of 6-8 mEq/L, manifesting as areflexia progressing to respiratory depression. 3