Mapping and ablating fast ventricular tachycardias with cycle lengths under 320 milliseconds remains challenging due to hemodynamic instability. A study presented at the European Society of Cardiology Congress 2025 investigated functional isthmus mapping during fast ventricular tachycardia to improve ablation outcomes.

In an experimental model using 30 Large-White swine with anterior myocardial infarction, cardiac magnetic resonance imaging was combined with ultrahigh-density voltage mapping and electrophysiological studies at 4 and 16 weeks post-infarction. Functional ventricular tachycardia isthmuses were identified as high-frequency electrogram corridors spanning the electric diastole in reentrant propagation maps.

Out of 27 mapped fast ventricular tachycardias, 25 exhibited reentrant activation, allowing isthmus identification. All isthmuses colocalized with signal intensity-defined channels. Compared to sinus rhythm, voltage maps during tachycardia revealed increased dense scar areas, longer voltage channels sustaining the isthmus, and functional substrates in 81% of cases. Retrospective adjustment of sinus rhythm voltage thresholds enabled identification of 88% of isthmuses.

These findings suggest that voltage heterogeneity mapping during fast ventricular tachycardia can accurately delineate functional isthmus borders, offering valuable guidance for precise and effective ablation strategies in ventricular tachycardia management.