Value of dynamic substrate mapping to identify the critical diastolic pathway in postoperative ventricular reentrant tachycardias after surgical repair of tetralogy of fallot.

UNLABELLED: Characterization of the Critical Isthmus in VT in TOF.

INTRODUCTION

The complexity of postoperative ventricular reentrant tachycardias may limit success of catheter ablation. The objective of this analysis was to compare the usefulness of dynamic substrate mapping (DSM) versus color-coded isopotential mapping of the noncontact mapping system for the identification of the critical diastolic pathway of postoperative ventricular reentrant tachycardias (VT) after surgical repair of tetralogy of Fallot (TOF).

METHODS

Postoperative VT had been studied applying isopotential maps with the noncontact mapping system EnSite in 7 patients, and radiofrequency current lesion lines had been applied across the shortest isthmus to target during sinus rhythm. Data of the noncontact mapping system were reanalyzed applying the DSM algorithm. For DSM, a 2-Hz filter and color settings between 0 mV and 50% of peak negative voltage (PNV) with autofocus turned off were used. DSM was initially applied over the QRS complex duration during sinus rhythm. Abnormal myocardium was defined as <35-40% of PNV. DSM was subsequently applied to ventricular diastole during the final 33% of VT cycle length. Areas with >70% of PNV within this time frame were to identify the critical diastolic pathway.

RESULTS

Applying DSM, the critical diastolic pathway of the VT was identified in all 7 patients that corresponded to the regions targeted for ablation.

CONCLUSION

By focusing the time reference to electrical diastole, when the VT wavefront is moving through the low-voltage area, the region of greatest relative voltage could be highlighted, which corresponded to the diastolic pathway. (J Cardiovasc Electrophysiol, Vol. 23, pp. 930-937, September 2012).