Intravenous MgSO4 alone and in combination with glucose, insulin and potassium (GIK) prolong the atrial cycle length in chronic atrial fibrillation

Aims To investigate the effects of parenteral administration of MgSO4, and glucose, insulin, and potassium (GIK), on the dominant atrial cycle length during chronic atrial fibrillation (CAF). Methods and Results The length of the dominant atrial cycle (DACL) in the p ower-frequency spectrum of the QRST-suppressed lead V-1 ECG was identified before and after intravenous administration of MgSO4 alone and after 5 and 10 h of MgSO4 and GIK infusion, in 13 patients with CAF. The changes in DAC L were compared with changes in heart rate (HR), blood pressure and blood p arameters. MgSO4 alone increased the DACL from 146(13) (mean(SD)) (control) to 153(14) ms (P<0.01) and decreased the HR from 102(22) to 95(18) beats.m in(-1) (P<0.05). After 5h of MgSO4 and GIK infusion the DACL was increased compared with control, from 146(13) to 152(11) ms (P<0.01). but unchanged c ompared with that after the bolus infusion of MgSO4. HR was decreased compa red with control (102(22)) and the bolus infusion of MgSO4 (95(18)) to 87(1 5) beats.min(-1) after 5h of intervention. The DACL was further increased a fter 10 h of MgSO4 and GIK infusion compared with both control (from 146(13 ) to 157(11) ms), (P<0.01) and the 5h infusion (152(11) to 157(11) ms), (P< 0.05). No further changes were seen in HR after 10 h (87(17)) of interventi on. There were indications of an inverse relationship between total changes in HR (<Delta>HR) and DACL (Delta DACL) during the interventions (P<0.05). Conclusion Bolus infusion of MgSO4 prolongs the DACL and decreases HR in CA F. A further prolongation of DACL was seen after 10h of MgSO4 and GIK infus ion compared with control and with 5h of intervention. Changes in DACL and HR during the entire intervention period showed an inverse relationship. Th e antiarrhythmic properties of MgSO4 and the GIK solution in CAF clearly re quire further attention. (Europace 2000; 2: 106-114) (C) 2000 The European Society of Cardiology.