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Objective: To compare the safety and efficacy of intravenous adenosine with verapamil in terminating acute episodes of paroxysmal supraventricular tachycardia., Methods: A randomized, multicenter trial to evaluate dose response in patients receiving adenosine and to compare the effects of adenosine with those of verapamil. A total of 122 patients with a tachycardia electrocardiographically consistent with paroxysmal supraventricular tachycardia were entered into the protocol. The adenosine group (n = 60) received sequential intravenous bolus doses of 3, 6, and 12 mg of adenosine to terminate PSVT and verapamil group (n = 62) were administrated 5mg or additional 5mg intravenously. Clinical variables and the time interval from the initiation of treatment to the termination of the supraventricular tachycardia, as well as the time from the initial effective dose of medication to the termination of supraventricular tachycardia were compared for adenosine and verapamil., Results: There was no significant difference between the two groups with respect to clinical variables. Relative drug efficacies were 86.0% (52/60) for adenosine versus 87.1% (54/62) for verapamil, P = NS. The average time after injection to termination of tachycardia by adenosine was shorter than that of verapamil significantly [(34.2 +/- 19.5) seconds vs. (414.4 +/- 191.2) seconds, P < 0.0001]. Adenosine caused adverse effects in 18.3% of patients, but they were transient and usually mild., Conclusions: Adenosine in graded doses up to 12 mg rapidly and effectively terminates acute episodes of paroxysmal supraventricular tachycardia. The overall efficacy of adenosine is similar to that of verapamil, but its onset of action is more rapid. Adverse reactions to adenosine are common but are minor and brief.

The obvious effects of magnesium sulfate are noticed not only in ventricular tachyarrhythmia but also in supraventricular tachyarrhythmia (SVTA) which include paroxysmal supraventricular tachycardia (PSVT), chaotic atrial tachycardia (CAT), atrial fibrillation (AF) with rapid heart rate and nonparoxysmal junctional tachycardia (NPJT). This paper reports the effects of magnesium sulfate treatment in 25 cases of SVTA in a self-controlled before and after study. Among 10 cases of PSVT, 6 cases were treated by injection of 25% magnesium sulfate 5-10 ml. Except 2 cases with W-P-W and aberrant ventricular condition, the PS-VT were terminated immediately after half a dose of magnesium sulfate i.v. in 2 cases, other 2 cases were terminated by 5-10 min after a dose of magnesium sulfate i.v.. Some improvements were observed in these 4 cases. The rest 4 cases were prevented by 12 days' intravenous infusion of 1% magnesium sulfate 250 ml per day, 3 cases of them recovered. Three cases of CAT recovered within an hour to two days by infusion of 1% magnesium sulfate 250 ml. Four cases of AF with rapid heart rate were collected, even though it is difficult to determine whether it is due to overdose or inadequacy of digitalis. The heart rates were reduced by magnesium sulfate injection in those 4 cases. Eight cases of NPJT due to heart failure with digitalis intoxication recovered after infusion of 1% magnesium sulfate 250ml within 10 hours to two days. Finally, the mechanism of the effect of magnesium sulfate treatment in SVTA was discussed.