Spatial domain analysis of late ventricular potentials. Intraoperative and thoracic correlations.

Abstract

For investigation of late potentials seen on the signal-averaged electrocardiogram, intracardiac and thoracic distributions of terminal activity were analyzed in 16 patients undergoing cryosurgery for ventricular tachycardia after remote myocardial infarction. The body surface potentials measured with 63 time-averaged unipolar leads were compared with epicardial and endocardial potential maps in six patients without and 10 patients with bundle-branch block. Intracardiac post-QRS activity, defined as extending beyond the thoracic QRS offset, was found in five of six patients without bundle-branch block (83%) and in five of 10 patients with bundle-branch block (50%), corresponding to 4±5% of the total number of electrograms in each patient. Fragmentation, double deflections, and single deflections were observed in 27%, 34%, and 39%, respectively, of these post-QRS electrograms. Post-QRS activation patterns that were stable from beat to beat showed slow propagation around or within areas of conduction block.Post-QRS activity was most often observed on both epicardial and endocardial surfaces (five of 10 patients). In the six patients without post-QRS activity, an area of late activity displaying low-amplitude deflections that were masked by the terminal activation of the normal myocardium was identified. Isopotential maps of the high-pass-filtered (55-Hz) thoracic and intracardiac signals demonstrated a close spatial correlation between the location, amplitude, and orientation of the potential extrema observed over the thoracic, epicardial, or endocardial surfaces during post-QRS activity. The thoracic patterns were generally dipolar with close extrema for anteroseptal or apical sites of post-QRS activity and more distant extrema for other sites. We concluded that the spatial domain analysis of intracardiac and thoracic potential distributions contributes to the understanding of the electrogenesis and electrocardiographic measurement of late potentials. (Circulation Research 1990;66:55-68

Advances in electrical and mechanical cardiac mapping

“…Some specific cardiac events identified by body surface mapping include the origins of P waves in canines (King et al 1972), the origins of the QRS complex and T wave in the intact chimpanzee (Spach et al 1977), and ventricular late potentials in patients with prior myocardial infarction (Lacroix et al 1990, Savard et al 1993. In addition to recording cardiac events occurring at an explicit location within the heart, this noninvasive recording technique has also been used for the analysis of myocardial infarction (Hayashi et al 1989), left ventricular hypertrophy (Flowers andHoran 1973, Yamaki et al 1989), and Wolff-Parkinson-White syndrome (Nadeau et al 1988, Nadeau et al 1993.…”

Low-frequency component of body surface potential maps identifies patients at risk for ventricular tachycardia

“…For all patients in the group we then calculated the average of the spectra from each of these leads and designated it the group mean power spectrum for each of the frequency bands: PS 1-7 ( Fig. 2(b)), PS [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] , PS [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] , PS 40-60 , PS 60-80 , PS 1-100 , PS , PS . The subscripts indicate from which isoharmonic map the power spectrum was extracted; and each group-mean power spectrum spans the entire frequency range (0·05-125 Hz).…”

“…The low-frequency region of the PS [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] obtained from analysis of the QRS-complex data segment most accurately identified patients with a history of risk for ventricular tachycardia, with a predictive accuracy of 74 6%. Non-windowed data also revealed significant lowfrequency differences, in 18 of 30 group-mean power spectra.…”

“…Compared to the Frank lead system, body surface potential maps contain additional spatial information, and it has been noted that spatial features of body surface potential maps can identify myocardial infarction patients at risk of ventricular tachycardia [13][14][15] . Accordingly, a number of groups have attempted to exploit the combined advantages of complete spatial information and spectral analysis.…”

Detection and localization of prolonged epicardial electrograms with 64-lead body surface signal-averaged electrocardiography.

“…As noted above, other authors, using methods different from those used in the present study, have found differences in the distribution of high-frequency signals between patients with anterior and those with inferior left ventricular infarctions. 24 of a larger lead set may increase the sensitivity of the SAECG in detecting abnormal electrograms. Furthermore, the spatial distribution of late potential amplitudes on the body surface may permit localization of abnormal electrograms within the heart, which may be sites of origin for arrhythmias.…”