Search

Discrimination between long RP tachycardias can be difficult but is essential when ablative therapy is contemplated. After diagnosis by EP study, we administered adenosine (Ad) 12 mg to pts during atrial (AT, n = 24) or atypical AV node (ATYP, n = 7) tachycardia (tc). Tc cycle length (CL) and component intervals were measured before and after Ad. Ad caused termination (term) in all AT without prior AV node block. In tc without substantial CL variability, first change (δ) in Cl after Ad was located in either H-H or A-A intervals. For cycles between δ and term in atrium (a) or ventricle (v), presence of CL oscillation (Osc) and net change of A-A were assessed and intervals were examined for Pearson rlinear correlation patterns. 1. Before Ad age (y) sex (m, f) CL (ms) A-H (ms) H-A (ms) AT 43 ± 17 2, 22 425 ± 94 82 ± 52 332 ± 107 ATYP 38 ± 20 3, 4 387 ± 107 113 ± 70 289 ± 86 p: ns l0.005 ns ns ns 2. After Ad δ(kk)(A-A, H-H) Osc(kk)(n) term(kk)[0,5-6](a, v) δ to term(kk)(cycles) net ΔAA(kk)(ms) AT 17 0 15 10 14 3.9 ± 14 2 ± 29 ATYP 2 2 6 2 5 3.5 ± 1.7 25 ± 24 p: ns ns ns ns ns ns ns 3. A-Avs A-H A-Avs H-A (term a) (term v) (term a) (term v) No. of Correlations AT 6/10 2/14 4/10 13/14 with p l 0.05 for r ATYP 1/2 1/5 2/2 3/5 P(AT vs ATYP): ns ns ns ns AT pts were predominantly female. Othervvise, AT and ATYP were not separated by tc CL or intervals before Ad, or by dynamic relationships of intervals analysed by linear correlation. Thus, Ad is not a useful pharmacologic probe for differentiation of AT from ATYP when tc terminates without prior AVnode block.