OVERDRIVE ATRIAL STIMULATION DURING TRANSESOPHAGEAL ELECTROPHYSIOLOGICAL STUDY - USEFULNESS OF POST-PACING VA INTERVAL-ANALYSIS IN DIFFERENTIATING SUPRAVENTRICULAR TACHYCARDIAS WITH 1 1-ATRIOVENTRICULAR RELATIONSHIP/

We evaluated the feasibility and usefulness of overdrive atrial pacing to identify the relationship between atrial and ventricular activatio n in supraventricular tachycardias with a stable 1:1 atrio-ventricular (AV) conduction ratio during a transesophageal electrophysiological i nvestigation. Overdrive atrial stimulation was performed in 42 consecu tive patients (11 males and 31 females; mean age 49+/-17 years) during AV junctional reentrant tachycardia, orthodromic AV reentrant tachyca rdia and ectopic atrial tachycardia (22, 13 and seven subjects, respec tively). Trains of 12 stimuli at a constant rate were introduced start ing at a cycle length 10 ms shorter than the tachycardia cycle length; stimulation was repeated with a IO-ms decrement in pacing cycle lengt h at each step until tachycardia terminated and/or second-degree AV bl ock occurred. The difference between the VA interval duration at basel ine and in the first post-pacing tachycardia beat was measured at each step and provided identification of the AV relationship. At least one post-pacing VA interval was evaluable in 90% of the cases and measure d 2+/-4 and 1+/-3 ms in AV junctional and AV reentrant tachycardia gro ups, respectively, and 83+/-42 ms in the ectopic atrial tachycardia gr oup (P<0.0000001 ectopic atrial tachycardia group vs. others). When th ree or more post-pacing VA intervals were obtained during the same tac hycardia, a curve was constructed by plotting their values against the corresponding pacing cycle lengths. A curve could be constructed in 3 6% of the cases and was flat in all patients with AV junctional and AV reentry, while it was completely irregular in the ectopic atrial tach ycardia group (P<0.003). The analysis of post-pacing VA interval behav iour in response to overdrive atrial stimulation provides a rapid and reliable differentiation between supraventricular tachycardias with 1: 1 AV conduction ratio during a transesophageal electrophysiological st udy. (C) 1997 Elsevier Science Ireland Ltd.