Noncontact Mapping of the Left Ventricle:

Abstract

It is not clear whether the noncontact electrograms obtained using the EnSite system in the left ventricle resemble most closely endocardial, intramural, or epicardial contact electrograms or a summation of transmural electrograms. This study compared unipolar virtual electrograms from the EnSite system with unipolar contact electrograms from transmural plunge needle electrodes using a 256-channel mapping system. The study also evaluated the effects of differing activation sites (endocardial, intramural, or epicardial). A grid of 50-60 plunge needles was positioned in the left ventricles of eight male sheep. Each needle had four electrodes to record from the endocardium, two intramural sites, and the epicardium. Correlations between contact and noncontact electrograms were calculated on 32,242 electrograms. Noncontact electrograms correlated equally well in morphology and accuracy of timing with endocardial (0.88 +/- 0.15), intramural (0.87 +/- 0.15), epicardial (0.88 +/- 0.15), and transmural summation contact electrograms (0.89 +/- 0.14) during sinus rhythm, endocardial pacing, and epicardial pacing. There was a nonlinear relationship between noncontact electrogram accuracy as measured by correlation with the contact electrogram and distance from the multielectrode array (MEA): beyond 40 mm accuracy decreased rapidly. The accuracy of noncontact electrograms also decreased with increasing distance from the equator of the MEA. Virtual electrograms from noncontact mapping of normal left ventricles probably represent a summation of transmural activation. Noncontact mapping has similar accuracy with either endocardial or epicardial sites of origin of electrical activity provided the MEA is within 40 mm of the recording site.

Comparison of Electroanatomic Contact and Noncontact Mapping of Ventricular Scar in a Postinfarct Ovine Model With Intramural Needle Electrode Recording and Histological Validation

“…Local reconstructed noncontact endocardial electrograms are known to be a summation of transmural activation at that point. 25 Quantification of histology with a transmural (endocardium to epicardium) approach at each point allowed direct comparison of the local measured electrogram (contact and PNV indicates peak negative voltage; PPV, peak-to-peak voltage; DSM, dynamic substrate map; ROC, receiver operator characteristic; AUC, area under the curve; Classification 1, Ͻ50% and Ն50% scar used to differentiate dense scar from partial scar/normal myocardium; Classification 2, Յ10% and Ͼ10% scar used to differentiate partial/dense scar from normal myocardium. noncontact) with the underlying transmural source and was not limited to endocardial histopathology.…”

Modern Electrophysiology Mapping Techniques

“…The morphological characteristics of virtual unipolar EGMs collected by the multi-electrode array have been shown to reliably match those acquired by conventional contact catheters [32][33][34][35][36]. Additionally, the morphology of unipolar EGMs provides information about the depolarisation wavefront such as the direction, speed and width of the approaching or retreating wave.…”

“…The array is anchored by means of the pigtail tip or with the aid of a guidewire which may be advanced into distal structures for support. The accuracy of the virtual EGMs is dependent on the distance from the array to the endocardial surface; distances of >40 mm have been shown to provide inaccurate data [32]. Therefore, care must be taken to position the array close to the area of interest.…”

Cardiology at Westmead Hospital from 1990 to 2007

“…This resulted in a seminal article describing the value of noncontact mapping in identification of scarred myocardium. 21,22 Further work by Thiagalingam enabled incorporation of automated contact mapping with noncontact mapping in the identification of scars. 23 …”