Development and Clinical Validation of an In Silico Pace Mapping Approach Utilising Implanted Device Electrograms to Accurately Guide Ventricular Tachycardia Ablation

Catheter ablation of ventricular tachycardia (VT) most frequently requires the identification of exit sites of slow-conducting diastolic isthmuses associated with infarcted tissue which are critical to sustain the reentrant arrhythmia. Pace mapping is a technique that identifies exit sites by matching the recorded 12-lead electrocardiogram (ECG) QRS of catheter-paced beats at different myocardial locations with the QRS of the clinical VT. When a high correlation between QRS morphologies is found, it is believed that the paced-beat lies at the VT exit site, helping guide the ablation. Procedures thus involve methodologically moving the catheter to multiple (accessible) locations to produce a pace map. Unfortunately the procedure is inherently limited due to the following reasons:

i) Surface maps - Most often, pacing sites are limited to the endocardium (where catheter access is easiest). Consequently, identification of VTs with an intramural or epicardial substrate can be challenging, with mis-leading and/or difficult to interpret pace maps being obtained.

ii) Low Resolution - Due to time-pressures and practical difficulties in catheter manipulation, pace map sites are often sparsely located (typically 40-60 separate sites). In complex structural VTs, with multiple possible anatomical circuits through the scar, it is often challenging to accurately identify from the map the relevant isthmus exit site responsible for the presenting clinical VT.

iii) VT Induction - Pace mapping usually necessitates VT induction during the procedure, which is time-consuming and carries inherent risk (~80% of induced VTs in ischemic heart disease (IHD) are either non-sustained or not haemodynamically tolerated), but induction of the exact clinical VT itself is often challenging.

A non-invasive, pre-procedural approach that is capable of generating accurate, high-resolution 3-dimensional personalised pace maps that correlate with the presenting clinical VT without the need for VT induction would thus revolutionise VT ablation planning, guidance, safety and efficacy.