Abstract 148: Degree of Fractionation and Local Activation Time in Voltage Measurements: Integration of Positron Emission Tomography with 3-Dimensional Voltage Maps for Guidance in Ventricular Tachycardia Ablations
Background High degrees of signal fractionation and sites with delayed local activation time (LAT) [late systolic/diastolic potentials] are thought to represent sites of myocardial fibrosis interspersed with surviving myocardium. Those locations are presumed to often harbor channels critical for reentrant VT and are targeted in ablation of non-mappable VT using a substrate-guided approach.
Methods Nine ICD patients (age 62 ± 13 years, 100% male) with ischemic (78%) and non- ischemic (22%) cardiomyopathy (EF 28.1 ± 9.4 %) admitted for VT ablation underwent Rubidium-82 perfusion/F18 Fluorodeoxyglucose positron emission tomography (PET) imaging. Three-dimensional (3D) LV and RV shells as well as metabolic scar (<50% normalized metabolic activity) were reconstructed from PET images and registered into a clinical mapping system. Scar and signal characteristics were compared between PET scar reconstructions and high density voltage scar maps.
Results The grade of fractionation within the PET defined scar area was 4.11 ± 1.37, whereas value of fractionation in the normal area was 3.35 ± 0.78 (P <0.001). Local activation times within myocardium with normal PET activity were 15 ± 62 ms prior to the end of the QRS with a significant delay to 20 ± 78 ms after the QRS in PET scar (P <0.001). Voltage map measurements within the PET defined scar area demonstrated a bipolar and unipolar voltage amplitude of 0.85 ± 0.87 mV and 3.25 ± 1.64 mV respectively, compared with 3.25 ± 2.55 mV and 7.38 ± 3.76 mV respectively in the PET defined normal area (P <0.001). Using ROC curves the best cut-offs for LAT was 5.5 ms prior to end of QRS (Area under the curve [AUC] 0.66), fractionation of 3.5 (AUC 0.64), bipolar voltage of 1.41 mV (AUC 0.82) and unipolar voltage 4.21 mV (AUC 0.81)
Conclusion Signal characteristics of common ablation targets in substrate-guided VT ablation, such as increased fractionation and late systolic/diastolic potentials, can frequently be found in areas that display <50% PET activity. Integration of 3D PET scar maps may be able to facilitate VT ablations and shorten procedure times.
- © 2012 by American Heart Association, Inc.