Intraoperative Study of Polarization and Evoked Response Signals in Different Endocardial Electrode Designs

Abstract

Some new generation pacemakers use an algorithm based on evoked response (ER) detection to verify beat-to-beat capture and to enable automatic adjustment of output. This is a prospective acute study of polarization signal (PS) and ER in nine currently available electrodes. Intraoperative testing of ventricular bipolar electrodes used the Autocapture (AC) algorithm. The intrinsic R wave, PS, ER, acceptance of AC function, and stimulation thresholds (STs) were obtained. Ventricular electrodes were categorized as follows: titanium nitride (TiN)-coated passive and active fixation, high impedance (HI), passive fixation (VP), iridium oxide-coated titanium (IROX) (VI), and platinum helix (PH) active fixation. Acute testing was performed in 217 patients with an average age of 74.26 years, 59.6% were men with primary pacing indication-SSS (46.3%). There were no significant differences found with respect to R wave and threshold between the various electrodes. PH active-fixation electrodes had significantly higher ER and PS than other groups including the TiN-coated active-fixation electrodes. TiN-coated electrodes (active and passive fixation) had significantly lower PS than other electrodes. As a result, TiN electrodes had a significantly higher functional rate of AC (91.7%), whereas PH had the lowest rate (0%). In conclusion, (1) polarization characteristics are significantly different for commercially available ventricular electrodes, (2) certain physical features at the tissue to electrode interface like TiN coating appears to be more important in determining PS than electrode tip size and fixation method, and (3) the current algorithm for AC requires electrodes that provide low polarization for satisfactory performance.

Clinical Evaluation of Two Different Evoked Response Sensing Methods for Automatic Capture Detection in the Left Ventricle

“…Alternative methods shown to be effective in reducing polarization include coating of the lead with titanium nitride or iridium oxide, thereby increasing the lead/tissue interface surface area and reducing polarization, 14 and separation of the pacing and sensing vectors 18 . Both of these methods restrict the leads compatible with the feature to low polarization leads, 23–25 or bipolar leads, respectively.…”

“…Numerous approaches have been investigated to decrease the effect of ART on the ER, thereby enabling reliable detection of cardiac capture. These approaches include modification of the lead electrode design, 14 increased signal processing of the ER, 15,16 reduction of the coupling capacitor in the pacing output circuitry, 12,17 or modification of the ER sensing vector 13,18 . However, ACV features based on these approaches have been shown to be limited by compatible lead technology, 19,20 the programmable pacing pulse parameters, 17 or the available pacing vectors 18 …”

Dissipative Electron Drift Modes in the H1-NF Stellarator

“…The electrode diameter was 1 mm, which is comparable to that used previously to measure cardiac excitations (Lewis and Rothschild 1915, Cardinal et al 1981, Coronel et al 2000, Lau et al 2001. Polyimide insulation was spun onto the plate and patterned to cover ITO runs from electrodes to wire attachment areas located at edges of the plate.…”

Pacing lead/myocardium interface: modelling and characterization of the impedance

“…The contact between the electrode and endocardium in the blood electrolytes electrically forms a capacitor C. This capacitor, highly imperfect, is shunted by its leakage resistor R connected in parallel with C. Resistor r, in series with this parallel RC circuit, corresponds to the ohmic resistance of the wire, the tissue resistance and the plasma resistance (electrolytes) [3][4][5][6][7].…”