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Revisiting the link between substrate and ventricular tachycardia rate: The critical role of conduction-isthmus
Jean-Baptiste Guichard1, Leticia Castrillo-Golvano2, Sílvia Molero-Pereira3
1Institut Clínic Cardiovascular, ICCV, Hospital Clínic, Universitat de Barcelona, Catalonia, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer, IDIBAPS, Barcelona, Spain; National Heart and Lung Institute, Imperial College London, London, United Kingdom.
Insights
Local conduction isthmus properties, specifically deceleration zone duration and conduction channel length, are key predictors of fast ventricular tachycardia (VT) rate. These local factors are more influential than global metrics in determining VT speed and guiding ablation strategies.
Area of Science:
- Cardiac Electrophysiology
- Cardiovascular Imaging
- Medical Device Technology
Background:
- Ventricular tachycardia (VT) rate significantly impacts hemodynamic stability, risk stratification, and ablation planning.
- While global substrate characteristics are linked to VT dynamics, the precise role of local conduction-isthmus properties remains unclear.
Purpose of the Study:
- To compare the predictive capabilities of global versus isthmus-specific substrate features on ventricular tachycardia (VT) rate.
- To identify key local electrophysiological and structural parameters that determine fast VT episodes.
Main Methods:
- Prospective study of 62 patients undergoing ablation for scar-related VT.
- High-density electroanatomical mapping and late gadolinium-enhanced cardiac magnetic resonance imaging were performed.
- Analysis included global (total activation time, late potential area) and isthmus-specific (deceleration zone, conduction channel) metrics; primary outcome was fast VT (>180 bpm).
Main Results:
- Isthmus-specific features, including deceleration zone duration (<110 ms) and conduction channel length (<3 cm), independently predicted fast VT.
- These metrics demonstrated strong discriminatory power (AUC 0.88-0.89), outperforming global measures.
- Structural and functional metrics showed significant correlations, indicating coupled substrate properties.
Conclusions:
- Conduction isthmus properties are the primary determinants of ventricular tachycardia (VT) rate.
- Quantitative assessment of VT-related conducting segments, particularly isthmus characteristics, can enhance procedural planning for patients with structural heart disease.
Background:
Ventricular tachycardia (VT) rate determines hemodynamic tolerance and informs risk stratification and ablation strategy. Although global-substrate metrics have been associated with VT dynamics, the relative contribution of local conduction-isthmus properties remains incompletely defined.
Objective:
We compared the predictive value of global with isthmus-specific substrate features on VT rate.
Methods:
In a prospective cohort, 62 patients undergoing ablation for scar-related VT underwent high-density electroanatomic mapping and late gadolinium enhancement cardiac magnetic resonance. Functional metrics included total activation time, deceleration zone (DZ) duration/area, and late potential (LP) area; structural metrics included scar/border-zone mass and conduction channel (CC) length, protected volume, and 2-dimensional architecture. The primary outcome was fast VT defined as >180 beats/min.
Results:
We analyzed 107 VT episodes, and 39% (n = 42) were classified as fast. Only isthmus-specific features independently predicted fast VT: a DZ duration of <110 ms (adjusted odds ratio 21.16; P < .001) and a CC length of <3 cm (adjusted odds ratio 10.18; P = .02). These thresholds showed strong discrimination (area under the curve of 0.88 for a DZ duration of <110 ms and 0.89 for a CC length of <30 mm); an LP area of <20 cm2 yielded an area under the curve of 0.79-each with ≥80% global accuracy. Structural-functional coupling was observed: CC length correlated with DZ duration (ρ = 0.54), DZ area (ρ = 0.35), and LP area (ρ = 0.55) (all P ≤ .01). Compared with ischemic cardiomyopathy, nonischemic cardiomyopathy had faster VT and a more compact isthmus; however, etiology was not an independent predictor and did not modify isthmus-VT rate associations.
Conclusion:
Conduction-isthmus properties predominate as determinants of VT rate. Quantitative characterization of VT-related conducting segments may support procedural planning in structural heart disease.
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