Catheter Treatment of Ventricular Tachycardia: A Reference-Less Pace-Mapping Method to Identify Ablation Targets

Abstract

A novel method is developed to identify ablation targets for the catheter treatment of ventricular tachycardia (VT). Methods: The method is based on pacemapping, which is a validated technique to determine the catheter ablation targets. Conventionally, it consists of stimulating the heart ventricle from various sites and comparing the resulting activation pathways to that of a clinical VT, by analysis of surface electrocardiograms (ECG). In this work a novel pace-mapping method is presented, that does not require a reference ECG recording of the VT. A 3D correlation gradient map is reconstructed by semi-automatic analysis of ECG morphological changes within the network of pace-mapping sites. In these maps, abnormal points are identified by high correlation gradient values (i.e. corresponding to slow propagation of the electric influx, as in the core of the reentrant VT circuit). The relation between the conventional and reference-less method is described theoretically and evaluated in a retrospective study including 24 VT ablation procedures. Results: The "reference-less" method was able to identify normal points with a high accuracy (negative predictive value: NPV=97%) and to detect more abnormal points, as predicted by the theory. Correlation gradients computed by the proposed method were significantly higher in ablation zones than in other zones of the ventricle (p<10-12), indicating excellent prediction of the ablation targets. Significance: The reference-less method might either be used in complement of the conventional method, or to treat patients in whom VT cannot be induced during the intervention.

A Paced-ECG Detector and Delineator for Automatic Multi-Parametric Catheter Mapping of Ventricular Tachycardia

“…Pacing spike detection in patients with pacemakers has already been developed using slope based [14]- [16] and power envelopes with moving statistical windows [17] detection algorithms but to our knowledge these methods have not been used for catheter pacing. Convolution with a spike template has already been used in [12] for catheter induced pacing detection but the application of this method is complicated by the varying amplitude of the stimulus as well as the great diversity in localization of the pacing. The spike frequency range being higher than the frequency of the other features present on the ECG, we propose a new wavelet-based method for detecting pacing spikes in a catheter-induced pacing environment.…”

“…The bipolar voltage map was directly derived from the vendor's CARTO3® software. Additionally, a 3D surface mesh was generated from the pacemapping sites and used to create the following maps: (i) a sQRS interval map was generated by color-coding the sQRS interval induced by the pacing stimuli; (ii) a reference-less correlation gradient map was generated as described in [12] by calculating the local change in Pearson correlation coefficient (. , . )…”

“…Correlation gradient values were considered to be defined only when the site-to-site distance was less than 20 mm. The rationale for computing these three maps is that sQRS maps are expected to highlight VT circuit entrance sites [13] and correlation gradient maps are expected to highlight VT circuit core zones [12]. Finally, voltage maps are expected to help identify the exit of the VT circuit, which should be at the border between scar and healthy tissue.…”

“…Reference-less pace mapping has also been proposed to identify critical slow conducting zones, independently of any VT recording (i.e. potentially core zones of several VT circuits) [12]. It uses correlation gradient maps, indicating zones of abrupt changes on the surface ECG as the catheter is moved to neighboring ventricular sites.…”

“…Detection of QRS complexes present after each spike using a maximum search of the vectorcardiogram. The synthetic vectorcardiogram ( ), for a given time , was reconstructed by inverse Dower transformation from the available (independent) leads ( ) [22] as already used in [12]: The time , of the QRS complex after spike was determined by the maximum of the module of the vectorcardiogram ‖ ( )‖ between time n of spike and time n+1 of spike + 1:…”