EFFICACY OF ADENOSINE IN TERMINATING CATECHOLAMINE-DEPENDENT SUPRAVENTRICULAR TACHYCARDIA

The purpose of this study was to determine if adenosine is equally eff ective in terminating catecholamine-dependent and independent supraven tricular tachycardia (SVP). The effect of adenosine on termination of SVT was studied in 21 patients: 12 with atrioventricular (AV) reciproc ating tachycardia, and 9 with AV node reentrant tachycardia. Group 1 c omprised 13 patients who had SVT induced in the absence of exogenous c atechol- amines, whereas group 2 comprised 8 who needed isoproterenol (1.6 +/- 0.4 mu g/min) for induction. There was no statistical differe nce between the 2 groups regarding age, weight, mean arterial pressure during sinus rhythm and SVT, cycle length of SVT, or norepinephrine a nd epinephrine levels during sinus rhythm and SVT. Cycle length during sinus rhythm was significantly decreased in group 2. The mean dose of adenosine needed to terminate SVT was 52 +/- 6 mu g/kg of body weight in group 1, and 61 +/- 12 mu g/kg in group 2 (p >0.05). In addition t o isoproterenol not altering the minimal dose of adenosine necessary t o terminate SVT, there was also no correlation between the dose of ade nosine (mean 55 +/- 6 mu g/kg) of each patient, and the corresponding endogenous epinephrine (273 +/- 59 pg/ml) (r = -0.19) and norepinephri ne (400 +/- 58 pg/ml) (r = 0.01) levels during SVT, or cycle length of SVT (323 +/- 9 ms) (r = -0.35). The results show that adenosine is eq ually effective in terminating catecholamine-dependent pendent and ind ependent SVT; higher adenosine doses should not be needed to manage ca techolamine-dependent SVT. In addition, the results suggest that adeno sine may exert its effects on AV node conduction primarily through its effects on adenosine-sensitive potassium channels.