Abstract 2136: Intraoperative High Density Global Mapping in Adult Repaired Tetralogy of Fallot: Altered Activation and Implications for Resynchronization Strategies
Introduction: RBBB in adult ToF has been linked with poor outcomes and has led to therapeutic interventions directed at RV resynchronization. Recent work has recognized the role of LV dysfunction in outcomes.
Objectives: To compare and characterize the pattern of ventricular electrical activation delay (EAD) in adults with repaired Tetralogy of Fallot (ToF) vs. Ischemic Cardiomyopathy patients presenting with LBBB.
Methods: Regional characterization of EAD was performed with multi-electrode arrays during intra-operative mapping of ToF undergoing redo surgery (n=15, mean age 37 + 9, 9 males), and compared with a control group of ischemic LBBB patients (n=4, mean age 59 ± 5, 1 male) undergoing intra-operative mapping.
Results: In ToF, RV endocardial (n=15, 112 bipoles) activation at 4 anatomical sections revealed mean activation times of 165 ± 10ms (RVOT), 132 + 6ms (free wall), 126 + 5ms (apex), and 121 + 9.0ms (septum). RVOT was usually latest (73%), followed by the septum (13%), apex (7%) and free wall (7%). When RVOT was latest (n=11), apex was earlier by 49 + 7 ms (p < 0.0001). In a subset of ToF patients with wide QRS (140+), simultaneous mapping of the LV and RV (n=5, 224 bipoles) showed that the LV activated later than the RV in all patients (156 +7 ms vs. 122+ 14 ms, p = 0.09). Moreover, for the ToF patient population, QRS duration (QRSd) poorly correlated with RV delay (R2 = 0.339, p = 0.217, n=15), however, it tended to relate to LV delay (ñ = −0.900, P=0.071, n=5). Comparison of the ToF patients with Ischemic LBBB group showed no difference in median epicardial LV delay (U = 9, n1 =4, n2 = 5, P =0.8065) and RV delay (U = 7, n1 =4, n2 = 5, P =0.4624).
Conclusions: In ToF with wide QRS, this study highlights striking abnormalities in LV electrical activation delay masked by RBBB. Surprisingly, the LV activation delay in ToF was comparable to that of ischemic LBBB. Moreover, RV apex was not the most delayed segment in repaired ToF patients thus implicating that RV apical pacing is unlikely to correct abnormal EAD in the presence of wide QRS.