Noninvasive recording of his bundle electrograms using vectorial leads system

Abstract

Summary:His bundle electrograms were recorded in 8 rats by a signal averaging technique using the Takayasu vectorial lead system. Animals were anesthetized and placed in the prone position. The polarity of three orthogonal leads were: the X axis, from right to left; the Y axis, from top to bottom; the Z axis, from back to front. Potentials from the X, Y, and Z leads were amplified by 20,000 with high-pass 12 dB/octave filtering at 80 Hz, and signal averaging of 2000 beats was performed at a sampling interval of 100 ps. The His bundle potential could be clearly defined in all 8 rats. The mean amplitude of the His potential was larger in the X-axis (23.6f9.2pV) or the Y-axis (28.4k 14.5pV) than the Zaxis lead (1 1.5 f 8.6pV). Directions of the His potential vectors were to the left in 5 of 8 rats (62.5%), to the caudal in 4 of 6 rats (66.7%), and to the dorsal site in 6 of 8 rats (75.0%). This vectorial lead system, devised in accordance with McFee and Johnston's theory on lead field, was useful for recording His bundle electrograms.

Enhancing the Reliability in the Noninvasive Measurement of the His Bundle Magnetic Field Using a Novel Signal Averaging Methodology

“…This is a reasonable test usually done to ensure that the observed feature has its origin in a physiological process since random noise components have a tendency to get smeared out on increasing the number of cycles averaged and eventually disappear. 1,6,7 The observed amplitude of the deflection associated with the feature is markedly high (upto 200 fT) compared to the system noise floor of under 10 fT/sqrt(Hz). (3) Figure 4 shows the H feature observed on a subject previously diagnosed with a first degree AV Block characterized by a prolonged PR interval of 214 ms (PR segment of 115 ms; see Table 1) along with that of a normal subject with the PR interval of 144 ms (PR segment of 65 ms).…”

“…(1) It is known [1][2][3][4][5][6][7][8][9][10][11][12] that the His bundle activity occurs in the PR segment. The known contributions to the feature in the PR segment come from (i) atrial repolarization and (ii) His bundle activity.…”

“…Noninvasive surface recordings of the HB electrical activity have been made using both signal averaged electrocardiography (SAECG) [1][2][3][4][5][6][7][8] and magnetocardiography (SAMCG). [9][10][11][12] A common methodology is the averaging over many cardiac cycles to reduce the random noise components and artifacts that are uncorrelated with reference to a chosen fiducial point in the cardiac cycle.…”

“…4,6 The overall success in recovering the HB activity from body surface potential studies has been assessed by different workers to be in the region of 33-100%. 8 However, a common feature in these studies is the use of the R wave peak 9,12 or the rising slope of the QRS complex [1][2][3][4][5][6][7]10,11 as the fiducial point for averaging. Use of an external trigger from an atrial pacing stimulator as the fiducial reference has also been reported.…”

The applicability of noninvasive his bundle electrogram to assessing the effect of digitalis on atrioventricular conduction

“…Nihon Kohden), as reported previously (Nojima et al, 1985). Amplified signals recorded on the data recorder were connected to the voltage-controlled-voltage-source active high-pass filter.…”