A beta-blocker, not magnesium, is effective prophylaxis for atrial tachyarrhythmias after coronary artery bypass graft surgery

Objective: To evaluate magnesium as a sole or adjuvant agent with currently used prophylactic drugs in suppressing postoperative atrial tachyarrhythmi as (POAT) after coronary artery bypass graft (CABG) surgery. Design: Single-center prospective, randomized clinical trial. Setting: University hospital. Participants: Patients (n = 400) undergoing CABG surgery. interventions: Pa tients were randomized among 6 prophylaxis regimens: (1) control (no antiar rhythmics), (2) magnesium only, (3) digoxin only, (4) magnesium and digoxin , (5) propranolol only, and (6) magnesium and propranolol. Patients randomi zed to a regimen including magnesium received 12 g given during 96 hours po stoperatively. Patients in a digoxin regimen received 1 mg after cardiopulm onary bypass and 0.25 mg daily. Patients in a propranolol regimen received 1 mg intravenously every 6 hours until able to take 10 mg orally 4 times a day. Prophylaxis regimens were discontinued after 4 days postoperatively. Measurements and Main Results: The primary outcome was a sustained POAT or discharge from the hospital. Control patients had an incidence of POAT (38% ) not significantly different from patients in magnesium-only (38%), digoxi n-only (31%), and magnesium with digoxin (37%) regimens. Patients treated w ith propranolol had a significant reduction in POAT. Nearly identical POAT rates in the propranolol-only (18%) and propranolol with magnesium (19%) gr oups support the lack of efficacy of magnesium in this trial. Study design allowed analysis of and showed a beta -blocker withdrawal effect in additio n to suppressive benefit of postoperative beta -blockers. Conclusion: beta -Blocker prophylaxis is indicated to reduce the incidence of POAT in CABG surgery patients and to prevent a beta -blocker withdrawal effect in patients receiving these medications preoperatively. Digoxin and magnesium as sole or adjuvant agents do not offer suppressive or ventricula r rate reduction benefits in POAT. Copyright (C) 2001 by W.B. Saunders Comp any.