RESOLUTION OF PACE MAPPING STIMULUS SITE SEPARATION USING BODY-SURFACE POTENTIALS

Background Several Studies have related 12-lead ECG waveform during ve ntricular tachycardia to ECG waveform during ventricular pacing to ide ntify ablation sites for therapy of ventricular tachycardia. QRS isopo tential maps and QRS isointegral maps derived from body surface isopot ential maps have also been correlated with left ventricular pacing sit es with the same objective. The comparison process used is subjective and only semiquantitative. Improved accuracy of catheter placement may improve success rates of ablation therapy. Methods and Results This a nimal study was performed to determine the spatial resolution with whi ch left ventricular pacing sites could be distinguished by body surfac e isopotential mapping. Potentials were recorded from 64 evenly spaced thoracic leads. Hexapolar or octapolar pacing catheters with 2-mm int erelectrode spacing were placed percutaneously in the left ventricle i n each of six dogs, and bipolar endocardial pacing was performed using each pair of adjacent electrodes. QRS isopotential maps of each pacin g site for each catheter placement were cross-correlated by computer. Difference maps for each pair of pacing sites were calculated lead by lead and time instant by time instant, and root-mean-square voltage di fferences were calculated. Results indicated that correlation coeffici ents and root-mean-square error of voltage differences monotonically d ecrease and increase, respectively, with stimulus site separation. Bot h measures were significantly different (P<.05) for separations of 4 m m or more. Conclusions A method of quantitative comparison of body sur face potential maps can be used in normal hearts to localize ventricul ar pacing sites within a 4-mm range. The method may have utility in de termining potential ablation sites for therapy of ventricular tachycar dia or preexcitation syndromes.