DIAGNOSTIC CLUES FROM THE SURFACE ECG TO IDENTIFY IDIOPATHIC (FASCICULAR) VENTRICULAR-TACHYCARDIA - CORRELATION WITH ELECTROPHYSIOLOGIC FINDINGS

ECG in Idiopathic Fascicular VT. Introduction: An RS interval > 100 ms ec in precordial leads has been recently described for the diagnosis o f ventricular tachycardia (VT). The aim of this study was to assess th e value of this criterion when applied to patients with right bundle b ranch block pattern, left-axis deviation (fascicular) VT sensitive to verapamil. Methods and Results: Eleven patients (mean age 31 +/- 11 ye ars; range 16 to 51) had a mean heart rate of 164 +/- 37 beats/min (ra nge 107 to 230) during VT. The QRS complex axis was -92 degrees +/- -1 5 degrees (range -80 to -115). The mean QRS duration was 121 +/- 9 mse c (range 105 to 140). The mean RS interval was 67 +/- 9 msec (range 60 to 80). Fusion beats were present in 2 patients (18%), and AV dissoci ation confirmed by electrophysiologic study was found on ECG in 8 (73% ) of 11. During tachycardia, the QRS-H' interval was 19 +/- 10 msec (r ange 10 to 30) in 6 of 11 patients. In seven patients, a fast, unique (or double) presystolic potential lasting 32 msec (range 12 to 40) occ urring before the onset of the QRS complex was found at the site of or igin of VT, localized in the inferior apical left ventricular septum. In all cases, VT was successfully treated by catheter ablation. Conclu sion: A wide QRS complex tachycardia with right bundle branch block an d left-axis deviation sensitive to verapamil observed in a young patie nt without structural heart disease should not be confused with suprav entricular tachycardia with aberrancy but rather suggests the presence of fascicular VT. As opposed to VT associated with structural heart d isease, the RS interval is < 80 msec in all precordial leads in all ca ses. Independent of this parameter, AV dissociation detectable on surf ace ECG has a sensitivity of 73%, which increases to 82% in the presen ce of fusion beats.