Body surface mapping of retrograde P waves in the intact dog by simulationof accessory pathway re-entry

OBJECTIVES: To investigate a noninvasive technique to localize the atrial i nsertion site of concealed accessory pathways based on the analysis of body surface potential maps (BSPMs) of retrograde P waves in dogs with simulate d retrograde pathways. ANIMALS AND METHODS: Orthodromic tachycardias were simulated by atrial stim ulations at eight different sites around the atrioventricular ring with lon g (250 ms and 300 ms) and short (100 ms and 130 ms) coupling times in 14 an esthetized dogs to have P waves well separated from the T wave or occurring during the T wave, respectively. The distance between pacing sites was 15 to 40 mm in group 1 (eight dogs) and 2 mm (in the right atrial free wall re gion) in group 2 (six dogs). Beats were signal-averaged during 30 s and BSP Ms were constructed from 63 unipolar leads. RESULTS: The P wave BSPM pattern for any specific stimulation site was stab le and reproducible (correlation coefficient greater than 0.98), and simila r in different dogs at long coupling interval stimulations. The thoracic di stribution of negative potentials and position of the potential minimum cle arly identified the stimulation site when long coupling time stimulations w ere used. The spatial resolution of the technique as determined by comparis on of correlation coefficients in group 2 was 6 mm (P<0.05). When short cou pling time stimulations were used (fast tachycardia simulation), the T wave masked the P wave potential distribution in four of eight dogs, but the re trograde P wave map could still be accurately extracted by subtracting a st raight line joining the onset and offset of the P wave in 24 of 28 (86%) of the tachycardia simulation sites in these four dogs. CONCLUSIONS: The BSPM patterns of simulated retrograde P waves are specific ally related to the site of atrial stimulation. Although the T wave altered these BSPM patterns, a subtraction technique recovered the pattern of the retrograde P wave in 93% of all simulated orthodromic tachycardias. The spa tial resolution of the retrograde P wave BSPM method was 6 mm.