The importance of the right ventricular insertion area for the functional substrate of ventricular tachycardia after myocardial infarction

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. BACKGROUND: Conducting systematic annotation and ablation of evoked delayed potentials (EDP) in response to short coupled right ventricular extra-stimuli (RV-ES) has improved ablation outcome of post myocardial infarction (MI) ventricular tachycardia (VT). The reported short radiofrequency catheter ablation (RFCA) times suggests the presence of predilection areas for these functional substrates. PURPOSE: To evaluate the electroanatomical characteristics and distribution of EDPs in post-MI patients referred for RFCA of VT. METHODS: Electroanatomical mapping (EAM) data of 48 post-MI patients (69 ± 9 years, 39 male, LV ejection fraction 36 ± 10%, anterior MI 20 [42%], inferior MI 28 [58%]), who underwent functional substrate mapping and ablation were analyzed. Pre-procedural cardiac CTs of 16 patients (8 anterior, 8 inferior MI) were integrated with EAM data. Infarct extension (defined as bipolar voltage [BV] <3.0mV, dense scar <0.5mV and scar borderzone [BZ] 0.5-3mV) and EDP location were determined based on the AHA 17-segment model of the left ventricle. RESULTS: RV-ES was performed during mapping at 2180 LV sites (median 46 per patient, range 8-81) and EDPs were observed at 631 (29%) sites. Patients had a median of 11 (range 1-37) EDP sites. Compared to no-EDP sites, EDP sites had lower BV (median 0.57 mV vs. 0.77 mV, P <0.001), longer duration (median 79 ms vs. 66 ms, P <0.001), and larger number of positive sharp deflections (median 6 vs. 5, P <0.001) during sinus rhythm. Of all EDP sites, 278 (44%), 286 (45%), 64 (10%), and 3 (1%) had BV of <0.5mV, ≥ 0.5mV and <1.5 mV, a BV of ≥1.5 mV and <3.0 mV, and a BV of >3.0 mV, respectively. In the 16 patients with CT image integration, a total of 124/272 segments showed EA scar with a median (IQR, range) of 8 (6-9, 4-12) segments per patient. Any EDP was identified in 71/124 (57%) of segments with EA scar. Of note, 73% of all EDPs in inferior MIs and 64% of all EDPs in anterior MI were located in 4 AHA segments, namely 3,4, 9,10 and 7,8,13,14, respectively, close to the inferior or anterior RV insertion. Such a cluster of EDP sites around the RV insertion was found in 6 (75%) patients with inferior MI and in 7 (88%) patients with anterior MI. CONCLUSION: About 10% of EDPs are identified at sites with BV of ≥1.5mV and <3.0mV during sinus rhythm supporting the recently proposed BV threshold <3.0mV for post-MI scars. EDPs are frequently located near the RV insertion in both inferior MI and anterior MI suggesting a role of the RV insertion in the functional substrate of post-MI VT.