Purpose: Aim of this study was to prove that PIM evaluated by SPECT can identify areas of local abnormal ventricular activities (LAVA) on electro-anatomic mapping (EAM).
Methods: Sixteen patients with IHD referred to VA trans-catheter ablation underwent pre-procedural and 6 months post-ablation 123I-MIBG/99mTc-tetrofosmin rest SPECT myocardial imaging on a camera equipped with Cadmium-Zinc-Telluride detectors. PIM was defined according to the segmental distributions of 99mTc-tetrofosmin and 123I-MIBG. The EAM, performed with a dedicated system. During sinus rhythm, the LV and RV endocardium were mapped in order to obtain a bipolar voltage map with <20 mm point-to-point distance, at least in the segments of interest. Co-registration of scintigraphic and EAM LV reconstruction was achieved off-line by identifying the LV septum on the LV voltage maps and then defining the myocardial walls accordingly. A 17 segments LV analysis was used for either SPECT and LV EAM voltage map. All patients were followed-up clinically for at least 1 year.
Results: Ablation was clinically successful in 11/16 (69%) patients. At baseline, the mean summed rest score (SRS) and PIM score were 16±7 and 9±3, respectively. Before ablation, the mean voltage in the PIM segments (2.9±1.7 mV) was higher than in the scarred ones (1.4±0.9 mV; P<0.001 vs PIM) but lower than in the normal regions (4.4±2.3 mV; P<0.001 vs both PIM and scar). The presence of PIM in a specific LV zone was an independent predictor of LAVA (P<0.001). After ablation, PIM value was significantly reduced (6±4, P=0.027 vs baseline), mainly due to an increase in the SRS (21±8, P=0.054 vs baseline), in particular in patients that were responders to ablation (PIM 5±3, P=0.004 vs baseline; SRS 23±9, P=0.003 vs baseline).
Conclusions: PIM co-localizes with VA substrate expressed by LAVA, possibly providing a novel guide for trens-catether ablation. A significant reduction of PIM predicts a positive clinical response to ablation.