Clinical Electrophysiology -> Ventricular Arrhythmias -> Mapping & Imaging D-PO05 - Poster Session V (ID 39) Poster

D-PO05-244 - Pseudo Figure-of-8 Patterns During Reentrant Ventricular Tachycardia: Evidence For Single Loop Mechanisms (ID 608)


Background: In reentrant ventricular tachycardia (VT), wavefront exiting from the isthmus with two lateral boundaries classically generates a double loop figure-of-8 (F8) activation pattern. However, single loop mechanism and passive secondary loop can cause a pseudo F8 pattern on activation map.
Objective: To investigate the prevalence and characteristics of pseudo F8 pattern during human VT using high-density mapping.
Methods: 53 reentrant VT with the isthmus formed by two lateral boundaries were analyzed in 50 cardiomyopathy patients (male: 45, mean age: 60±14 years, ischemic: 24). We defined a VT with pseudo F8 based on one or more of the following criteria; 1) asymmetric activation pattern with discontinuous conduction in one loop, 2) asymmetric entrainment response, 3) VT termination with non-inducibility without transection of the isthmus.
Results: VT activation maps were created with 1768±1032 points. 40% of the VT showed asymmetric activation. 25% had asymmetric responses between both sides of the isthmus. 9% were terminated with non-inducibility achieved by ablation of less than half the width of isthmus. As a result, 43% met criteria for pseudo F8. The cycle length of pseudo F8 VT was significantly longer than that of true F8 VT (414±98 vs. 357±68 ms, p = 0.021). Between pseudo F8 and true F8, there was no difference in isthmus length (48 vs. 43 mm, p = 0.35) and width (22 vs. 17 mm, p = 0.12).
Conclusion: Nearly half of F8 activation patterns during VT can be mechanistically demonstrated to require only a single loop to sustain reentry. These findings have important implications for targeted ablation of VT and suggest that human reentry is more spatially confined than previously thought.