Related Experiment Video
Updated: May 29, 2025
Real-Time Cardiac Mapping with a Noninvasive Imageless Electrocardiographic Imaging System
Published on: April 11, 2025
Isochronal Apparent Dispersion at Early Activation Sites Accurately Identifies Outflow Tract Ventricular Ectopy Sites
Robert D Anderson1, Stephane Masse2, Joshua Hawson3
1Hull Family Cardiac Fibrillation Management Laboratory, Division of Cardiology, University Health Network, Toronto General Hospital, Toronto, ON, Canada; Department of Cardiology, Royal Melbourne Hospital, Faculty of Medicine, Dentistry, and Health Science, University of Melbourne, Melbourne, Vic, Australia.
Background:
Localisation of outflow tract (OT) premature ventricular complex (PVC) sites is guided by unipolar and bipolar local activation time (LAT). However, LAT-based localisation can be inaccurate if the site is intramural or distant. Deep foci produce rapid conduction velocity (CV) if the wavefront is tangential to the surface.
Aim:
We evaluated whether supraphysiological CV, referred to as surface isochronal apparent dispersion (IAD) mapping, can be used to accurately differentiate right and left ventricular OT PVC origin, guiding the successful site for OT PVC ablation.
Method:
Left ventricular OT mapping was performed if right ventricular OT mapping demonstrated a bipolar electrogram (EGM) <20 ms. The earliest EGMs underwent analysis of the following: first deflection bipolar EGM (bipolarearliest) to QRS, bipolarearliest to first deflection unipolar EGM (unipolarearliest), bipolarearliest to unipolar -dV/dTmax, unipolar -dV/dTmax to QRS, number of early LAT breakouts, and the surface area of the earliest isochronal breakout. Polynomial CV was calculated using a custom algorithm in MATLAB using cut-offs between 1 and 100,000 cm/s and used to create IAD, referred to as apparent dispersion index. The accuracy of IAD to distinguish between successful and unsuccessful OT sites was assessed and compared with conventional EGM indices.
Results:
Bipolarearliest to QRS (28.5±7.3 ms vs 17.8±5.7 ms; p<0.05) is superior to unipolar -dV/dtmax to QRS (0.4±26.4 ms vs -6.4±13.4 ms; p=0.25) in differentiating successful and unsuccessful OT PVC sites. An early isochronal breakout area of less than 1 cm2 and less than two breakouts indicates a successful side (both p<0.05). Bipolarearliest to unipolar -dV/dTmax and to unipolarearliest were not predictive (28.1±27.7 vs 24.2±13.3 ms; p=0.97 and 6.4±7.3 vs 6.4±5.8 ms; p=0.8, respectively). IAD appears to differentiate between successful and unsuccessful sites using an apparent dispersion index cut-off of 20,000 cm/s, with an accuracy of 93.8% and area under the receiver operator characteristic of 0.95.
Conclusions:
IAD is a realistic two-dimensional interpretation of the three-dimensional activation mapping surface that may be associated with OT origins to guide a successful side of catheter ablation.
Related Concept Videos
01:25Correlation between ECG and Cardiac Cycle
A cardiac action potential originates in the SA node and spreads throughout the atria and the AV node in approximately 0.03 seconds. This results in the P wave in an ECG and triggers atrial contraction. The action potential is then briefly slowed at the AV node, allowing the atria to contract and fill the ventricles with blood before...
01:30Cardiac Action Potential
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
01:19Electrophysiology of Normal Cardiac Rhythm