3-DIMENSIONAL ELECTROPHYSIOLOGICAL IMAGING OF THE INTACT CANINE LEFT-VENTRICLE USING A NONCONTACT MULTIELECTRODE CAVITARY PROBE - STUDY OF SINUS, PACED, AND SPONTANEOUS PREMATURE BEATS

Background-The feasibility of measuring cavitary electrograms using a noncontact probe and reconstructing endocardial surface electrograms a nd activation sequences during paced beats was previously demonstrated in the isolated canine left ventricle (LV). The objective of the pres ent study was to develop and test a high-resolution, three-dimensional , endocardial electrophysiological imaging technique that simultaneous ly reconstructs endocardial surface electrograms and their correspondi ng activation sequences during normal and abnormal beats with the use of cavitary electrograms measured with a noncontact multielectrode pro be in the intact canine LV. Methods and Results-A 128-electrode probe was inserted into the intact canine LV. Probe unipolar electrograms we re simultaneously acquired during sinus, artificially paced, and spont aneous premature beats. Representative endocardial electrograms were m easured directly using eight needle electrodes (the ''gold standard'') . A probe-cavity realistic, three-dimensional geometric model was cons tructed using two-dimensional epicardial echocardiography. Boundary el ement methods and numeric regularization were used to compute electrog rams at 194 sites on the endocardium. In eight pacing protocols, compu ted endocardial electrograms correlated well with directly measured el ectrograms (r=.88). Corresponding activation times were also in agreem ent with those determined from measured endocardial electrograms (acti vation error, 4.7 ms). The earliest region oi activation was invariabl y in the vicinity of the pacing needle (spatial error, 9.2 mm), Subseq uently, the site oi origin of ischemia-induced spontaneous ventricular premature beats and the ensuing sequence of depolarization was identi fied. Conclusions-Noncontact mapping provides realistic, three-dimensi onal electrophysiological images of the endocardium, on a beat-by-beat basis, that localize the sites oi origin of premature beats and recon struct their activation sequences.