Correlation between perfusion/innervation mismatch and ventricular scar-related arrhythmic substrate: impact on ablation outcome

BACKGROUNG and OBJECTIVES: In scar related VA denervation is thought to play an important role and elimination of Local Abnormal Ventricular Activities (LAVA) was independently associated with a better outcome. The purpose of this research project is to prove the correlation between arrhythmic substrate detected by LAVA and Perfusion/Innervation Mismatch (PIM) detected by Cadmium Zinc Telluride (CZT) camera. METHODS: We enrolled consecutive patients referred for of post ischemic VA catheter ablation. They underwent pre-procedural 123I-MIBG (for innervation) and 99mTctetrofosmin rest (for perfusion) CZT single-photon emission computed tomography (SPECT). The operator was blinded to SPECT results. During electro-anatomical mapping (EAM) a LV voltage map to define respectively infarct scar and infarct border zone. A 17 segments LV analysis was used both for the SPECT and the EAM LV reconstruction. Correlation between PIM and ablation sites was off line evaluated by a physician blinded to the EP results. After 1 month from the EP procedure a double tracer SPECT was repeated to evaluate the evolution of the MIP after the substrate modification targeting LAVA. Regarding the outcome, we define the ablation treatment efficient if was reached no recurrence of VTs or a reduction≥ 75% of premature ventricular contraction (PVCs). All patients underwent close follow up (FU). RESULTS: We enrolled 17 patients. A PIM area was found in all the patients. The mean voltage in the PIM segment was higher than in the scar ones but lower than in the normal ones. Innervation was reduced in the PIM segments but not perfusion. After correction for innervation and scar quantified by SPECT, the presence of PIM remained an independent predictor of LAVA. The significant reduction of PIM at FU was mainly due to an increase in summed rest score for perfusion. According to previous definitions, the study population was divided in Responders and Not Responders, in order to identify possible predicting factors. No difference was found in perfusion summed rest score, while the PIM reduction was significant higher in the responders, identifying a novel predictive factor for successful ablation. CONCLUSIONS: Dual tracer SPECT can show the presence and the distribution of Perfusion/Innervation Mismatch, which is a independent predictor of LAVA and may provide a novel road map to guide the a substrate approach in VA ablation. After LAVA elimination there is a significant reduction of PIM and this was a positive predictive factor.