EFFICACY OF ADENOSINE IN TERMINATING CATECHOLAMINE-DEPENDENT SUPRAVENTRICULAR TACHYCARDIA

The purpose of this study was to determine if adenosine is equally effective in terminating catecholamine-dependent and independent supraventricular tachycardia (SVP). The effect of adenosine on termination of SVT was studied in 21 patients: 12 with atrioventricular (AV) reciprocating tachycardia, and 9 with AV node reentrant tachycardia. Group 1 comprised 13 patients who had SVT induced in the absence of exogenous catechol- amines, whereas group 2 comprised 8 who needed isoproterenol (1.6 +/- 0.4 mu g/min) for induction. There was no statistical difference between the 2 groups regarding age, weight, mean arterial pressure during sinus rhythm and SVT, cycle length of SVT, or norepinephrine and 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 to isoproterenol not altering the minimal dose of adenosine necessary to terminate SVT, there was also no correlation between the dose of adenosine (mean 55 +/- 6 mu g/kg) of each patient, and the corresponding endogenous epinephrine (273 +/- 59 pg/ml) (r = -0.19) and norepinephrine (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 equally effective in terminating catecholamine-dependent pendent and independent SVT; higher adenosine doses should not be needed to manage catecholamine-dependent SVT. In addition, the results suggest that adenosine may exert its effects on AV node conduction primarily through its effects on adenosine-sensitive potassium channels.