Key result
Distal VT isthmuses demonstrate ~69% slower conduction velocity than preceding sinus rhythm zones.
Why the study?
Conduction slowing has gained interest as being related to successful VT ablation, but its mechanism is unclear, prompting investigation into the relationship between sinus rhythm conduction properties and VT isthmuses.
Does conduction slowing during sinus rhythm correlate with VT isthmuses in patients undergoing VT ablation?
Observational (n=19)
Does conduction slowing during sinus rhythm correlate with VT isthmuses in patients undergoing VT ablation?
Absolute Event Rate: 0.4% vs 1.3%
p-value: p=<0.001
Conduction slowing areas during sinus rhythm correlate with the exit portion of VT isthmuses, potentially aiding in the identification of ablation targets in scar-related VT.
Reduced conduction velocity may mark distal VT isthmus during sinus rhythm mapping; leaves open its utility for guiding ablation in scar-related VT.
INTRODUCTION: The voltage map during sinus rhythm (SR) is a cornerstone of substrate mapping (SM) in scar-related ventricular tachycardia (VT) and frequently used with pace mapping (PM). Where to conduct PM is unclear in cases of an extensive or unidentified substrate. Conduction properties are another aspect incorporated by SM, and conduction slowing has gained interest as being related to successful ablation, although its mechanism has not been elucidated. We aimed to investigate the relationship between SR conduction properties and VT isthmuses. METHODS: Nineteen patients (mean age, 62 years) who underwent VT ablation with voltage mapping and PM were reviewed. Isochronal late activation maps (ILAMs) with eight zones were reconstructed and sequentially named from one to eight according to the SR propagation. Good PM sites were superimposed on ILAMs, and the isthmus was defined using different pacing latencies. ILAM properties harboring isthmuses were investigated. RESULTS: Twenty-eight ILAMs (13 epicardium, 1 right ventricular [RV], and 14 left ventricular [LV] endocardium) were reviewed. Eighteen isthmuses of 24 target VTs were identified, in which the proximal ends were in a later zone than the distal ends (zone 6 vs 4; P < .001), suggesting a reverse isthmus vector to the SR. The conduction velocity of the zone involving the distal isthmus was significantly lower than that of the SR preceding zone (0.40 vs 1.30 m/s; P < .001). SR conduction velocity decelerated by 69.5% (range 59.7%-74.5%) before propagating into the isthmus area. CONCLUSION: Conduction slowing area during SR were related with the exit portion of the VT isthmuses.
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Ueda et al. (2020) conducted an observational in scar-related ventricular tachycardia (n=19). Conduction properties during sinus rhythm vs. Sinus rhythm preceding zone was evaluated on Conduction velocity of the zone involving the distal isthmus (p=<0.001). Conduction velocity in the zone involving the distal ventricular tachycardia isthmus was significantly lower than in the preceding sinus rhythm zone (0.40 vs 1.30 m/s; P<0.001).
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