A novel pacing manoeuvre to diagnose atrial tachycardia.

AIMS Currently used diagnostic manoeuvres at the electrophysiology study do not always allow for consistent identification of atrial tachycardia (AT), either because of inapplicability of the technique or because of low predictive value and specificity. The aim of this study was to determine whether overdrive atrial pacing during paroxysmal supraventricular tachycardia (SVT) with the same cycle length from both the high right atrium and the coronary sinus can accurately identify or exclude AT by examining the difference between the V-A intervals of the first returning beat of tachycardia between the two pacing sites. METHODS AND RESULTS Fifty-two patients were included; 24 patients with atrioventricular nodal re-entry tachycardia (AVNRT), 13 patients with atrioventricular re-entry tachycardia (AVRT), and 15 patients with AT. Comparing the 37 non-AT patients with the 15 AT patients, there was a highly significant difference between the mean V-A interval difference, (delta V-A) 2.1 +/- 1.8 ms (range 0-9 ms) vs. 79.1 +/- 42 (range 22-267 ms) (P < 0.001), respectively. None of the patients in the non-AT group had a delta V-A > 10 ms. In contrast, all 15 patients with AT had a delta V-A interval >10 ms. Thus, the diagnostic accuracy of the delta V-A interval cut-off of >10 ms was 100%, with a 95% confidence interval of 93.1-100% for AT. In 11 (73%) of the 15 AT patients, the standard ventricular overdrive pacing manoeuvre was not possible. In 14 of the 15 patients (93%) in the AT group, standard atrial overdrive pacing showed variable V-A intervals, correctly diagnosing AT. In all 52 patients, this measurement was repeated during pacing from the other location. In five patients from the AT group, the result of the second attempt was different from the result of the first attempt. CONCLUSION We found that atrial differential pacing during paroxysmal SVT without termination of tachycardia and the finding of variable returning V-A interval was highly sensitive and specific for the diagnosis of AT. The manoeuvre can be easily performed in all patients with SVT and is highly reproducible. It is a useful adjunct to the currently available ventricular and atrial pacing manoeuvres.