<

正

>

Prophylactic effect of magnesium sulfate on reperfusion arrhythmias was studiedusing a left anterior descending coronary artery occlusion followed by reperfusion in theisolated rat heart.In the first studies

we have observed a bell-shaped relationship be-tween the incidence of reperfusion-induced ventricular fibrillation（VF）and the durationof preceding ischemia.With 5

10

15

20 and 25 min of ischemia

10

70

60

50 and 20per cent of the hearts exhibited irreversible VF

respectively.In the second studies（10 minischemia）

perfusate magnesium sulfate was increased to 3.6

4.8 and 6.0 mmol/L 1 min be-fore coronary ligation

VF fell in a dose-dependent manner from its control total inci-dence of 100%（1.2mmol/L MgSO

4

）to 82%

73% and 18%（P

<

0.01）

respectively.Heartrate was also reduced in a dose-dependent manner

falling from its control value of326±11 to 227±22 beats/min with the highest concentration of magnesium sulfate.Asperfusate magnesium sulfate was increased to 6.0 mmol/L just before reperfusion

no an-ti-arrhythmic effects were observed.With an anti-arrhythmic concentration of magnesiumsulfate（6.0 mmol/L

increased 1 min before ligation）

calcium concentration was increasedby 1.5 mmol/L at the same time

under these conditions the anti-arrhythmic effect of mag-nesium sulfate was lost and its negative chronotropic effect was also partially abolished.We conclude that magnesium sulfate has a certain prophylactic effect againstreperfusion induced arrhythmias and this could be due to a direct or indirect calci-um-antagonist action.