CASE REPORT Dr. Amr EL-Said Professor Of Anaesthesia & Intensive Care Medicine Faculty of Medicine – Ain Shams University

Magnesium Therapy for Acute Management of Rapid Af 77 years old male patient was admitted to ICU on 14/10/2012 for post-operative care after subtotal gastrectomy with primary anastomosis. Past history was unremarkable. Pre-operative lab investigations were within normal limits. Pre-operative echocardiography was quite normal apart from impaired diastolic function and trivial MR and AR.

Patient was haemodynamically stable. Follow up lab investigations including cardiac enzymes were within normal limits. Patient was discharged from ICU following day.

On 27/10/2012: patient was re-admitted to ICU at 11:00 pm with tachypnea and severe irregular tachycardia but without cardiac decompensation. BP was normal and ABG analysis was satisfactory. ECG revealed AF. Last lab investigations were within acceptable levels. Blood work obtained in ICU were within normal limits. Chest X-ray revealed no parenchymal abnormality.

DC cardioversion. After three successive electrical shocks to heart with escalating levels of energy; cardioversion was unsuccessful. Drug treatment. Loading dose of cordarone 300 mg over one hour; tachycardia persisted. Magnesium sulfate infusion: 1gm/hour. After 6 hours, sinus rhythm was restored. Magnesium infusion was discontinued following day at 10:30 am.

On 29/10/2012: patient was discharged from ICU.

Lone Atrial Fibrillation is AF without discernible cardiovascular disease. AF potentially leads to prolonged hospitalization and significant morbidity, particularly hemodynamic deterioration and thromboembolic events especially stroke. AF has been associated with number of diseases primarily involving organs other than heart. Defective Substrate" has become integral to any discussion of cause of LAF. Magnesium (Mg) deficiency has emerged as significant player in etiology of LAF. Funk M, Richards SB, Desjardins J, Bebon C and Wilcox H. Incidence, timing, symptoms, and risk factors for atrial fibrillation after cardiac surgery. Am J Crit Care 2003; 12: 424–33. Burton MA. Magnesium: We Don't Appear to be Getting Enough. Science News Online. August 29, 1998.

Mg involves maintenance of intracellular environment. Mg is also required cofactor in various membrane ATP pumps: Na/K; Ca/Mg; K/H and Na/H pumps. Channels (such as Ca and Na) and exchangers (such as Na-Mg, Na-Ca and Na-H). Mg is Ca channel blocker and Mg deficiency leads to increased intracellular Ca. Mg deficiency also results in dysfunction of Na-Mg exchanger, leading to increased intracellular Na. Mg deficiency also leads to leakage of primarily extracellular cations Na and Ca into cells and primarily intracellular cations K and Mg out cells. Mg is antioxidant and Mg deficiency allows accelerated free radical damage to cell membranes. Agus ZS. Hypomagnesemia. Journal of the American Society of Nephrology. 1999; 10 (7). Larsen HR. Lone Atrial Fibrillation: Towards A Cure. 2003, pp. 96, 63. Chambers P. Magnesium and Potassium in Lone Atrial Fibrillation. The Magnesium Web Site. MAGNESIUM ONLINE LIBRARY. Editor: Paul Mason, February, 2003.

Major cardiac effects of Mg are prolongation of atrial and AV nodal refractory periods. Mg deficiency is relatively common in patients presenting with AF [20% - 53%]. Mg deficiency and AF are common after cardiac surgery, and prophylactic Mg use has resulted in signicant reduction in incidence of post-operative AF. Christiansen EH, Frost L, Andreasen F, Mortensen P, Thomsen PE and Pedersen AK. Dose-related cardiac electrophysiological effects of intravenous magnesium. A double-blind placebo-controlled dose response study in patients with paroxysmal supraventricular tachycardia. Europace. 2000; 2: 320–326. Eray O, Akca S, Pekdemir M, Eray E, Cete Y and Oktay C. Magnesium efcacy in magnesium decient and non-decient patients with rapid ventricular response atrial brillation. Eur J Emerg Med. 2000; 7: 287–290. Miller S, Crystal E, Garnkle M, Lau C, Lashevsky I and Connolly SJ. Effects of magnesium on atrial brillation after cardiac surgery: a meta-analysis. Heart. 2005; 91: 618–623.

Randomized controlled trials comparing IV Mg versus placebo or antiarrhythmic agents for acute management of rapid AF. Mg was more effective than control treatments with respect to rate control and rhythm control. Overall response rate was 86% in Mg group and 56% in control group. Time to response (in hours) was signicantly shorter in Mg group than in control group. Mg administration was also more effective than control treatments in restoration of sinus rhythm. Risk of major adverse effect in Mg group was similar to that in placebo group. Mg deficiency was in as many as 50% of patients presenting with AF. Onalan O, Crystal E, Daoulah A, Lau C, Crystal A and Lashevsky I. Meta-Analysis of Magnesium Therapy for the Acute Management of Rapid Atrial Fibrillation. Am J Cardiol. 2007; 99: 1726–1732.

Mg can be used safely in most patients in whom other antiarrhythmic drugs are contraindicated or considered harmful. Mg has relatively wide toxic/therapeutic window, and most common reported side effects are transient sensation of warmth and ushing. IV Mg has rapid action, which may be useful in controlling symptoms. Mg is inexpensive, easy to use and titrate, and widely available for immediate use in every clinical unit. Delva P. Magnesium and heart failure. Mol Aspects Med. 2003; 24: 79 –105. Crippa G, Sverzellati E, Giorgi-Pierfranceschi M, Carrara GC. Magnesium and cardiovascular drugs: interactions and therapeutic role. Ann Ital Med Int. 1999; 14: 40–45.