LATE POTENTIALS ARE UNAFFECTED BY RADIOFREQUENCY CATHETER ABLATION INPATIENTS WITH VENTRICULAR-TACHYCARDIA

Reentrant ventricular tachycardia is dependent on an area of myofibers , embedded in scar tissue, which exhibit slow conduction. Late potenti als recorded by signal-averaged electrocardiography appear to correspo nd to these zones of slow conduction and frequently are present in pat ients with VT, We hypothesized that elimination of inducible VT by cat heter-mediated ablation of critical areas of slow conduction would alt er late potentials. Four patients underwent catheter ablation in which radiofrequency current was delivered to zones of slow conduction exhi biting isolated mid-diastolic potentials that could not be dissociated from the tachycardia. The four patients had developed VT (cycle lengt h 382 +/- 50 msec; mean +/- SEM) 13-180 months after inferior myocardi al infarction. Late potentials were present in each patient before cat heter ablation was attempted. Although VT was not inducible in any pat ient immediately after ablation, late potentials were still present in all fo ur patients and there was no significant difference in the QRS duration (136.5 +/- 4.0 msec postablation; 135.7 +/- 4.5 msec preabla tion), root mean square voltage in the terminal 40 msec of the QRS (10 .0 +/- 1.0 mu V postablation; 5.9 +/- 0.4 mu V preablation), or in the duration of the low amplitude signal (69.2 +/- 2.0 msec postablation; 62.7 +/- 3.4 msec preablation). At follow-up electrophysiology study performed 14 +/- 7 days after ablation, one of the four patients had i nducible VT. In conclusion, late potentials persist even after success ful radiofrequency catheter ablation and do not appear to be useful fo r predicting results of follow-up electrophysiology study.