Sputter-Deposited TiN Electrode Coatings for Superior Sensing and Pacing Performance

SCHALDACH, M., ET AL.: Sputter-Deposited TiN Electrode Coatings for Superior Sensing and Pacing Performance. The sensing and pacing performance of pacemaker electrodes is characterized by the electrochemical properties of the electrode/tissue interface affecting tissue reactions and the kinetics of the ionic exchange. The usually smooth metallic electrode surface results in a high pass filter characteristic. To better match the electrode's filter characteristic to the spectral content of the depolarization signal, various combinations of electrode shape, material and surface structure have been researched. The electrode with sputter-deposited TiN coating presented in this report has been designed to meet the demand for low acute as well as chronic thresholds and superior sensing performance not only with respect to spontaneous activity but also regarding the detection of the evoked response. The clinical results obtained with this electrode prove the excellent pacing and sensing properties resulting from minimized polarization losses and optimized filtering of the signal to be detected, respectively. The acute and chronic clinical advantages over previous concepts are attributed mainly to the biocompatibility of the material used and the microcrystalline surface structure achieved by the coating process. The design concept of the new electrode is presented together with the clinical results obtained. While the advancements in microelectronics and battery technology have certainly formed the basis for the development of pulse generators featuring an ever increasing versatility of functions at the same or even smaller pacemaker dimensions, from a point of view of pacing system performance the development of improved electrode concepts as the one presented must be regarded as equally indispensable.     

Evaluation of Autosensing as an Automatic Means of Maintaining a 2:1 Sensing Safety Margin in an Implanted Pacemaker

As intracardiac signal amplitudes fluctuate due to patient activity, drug intake, and other factors, it is imperative that an adequate sensing safety margin in an implanted pacemaker be used to compensate. We studied an investigational autosensing feature that automatically adjusts the device's sensitivity. Data were collected from 55 patients, with Intermedics model 292–03 or 294–03 pacemakers, upon inclusion of the study (Visit 1); 1 month postinclusion (Visit 2); 1 month, 1 day postinclusion (Visit 3); then 1 month, 2 days postinclusion (Visit 4). Atrial (N = 45) and/or ventricular (N = 54) thresholds were assessed at each visit; during Visit 2, myopotential tests were performed at two sensitivity settings. Autosensing was activated following Visit 1, then programmed on randomly at Visit 2 or Visit 3. From Visit 2 - Visit 4, patients were monitored during daily activities (D), exercise (E), and sleep (S) with 24-hour Holter. With Autosensing on, atrial undersensing episodes were D = 33 (p > 0.2), and S = 28 (p < 0.05); ventricular undersensing episodes were D = 6 (p > 0.5). Ventricular oversensing episodes were S = 2; atrial oversensing episodes were S = 34 (p > 0.5), D = 2, and E = 3. Comparing Autosensing adjusted sensitivity with the recommended 2:1 safety margin, 4 patients (p = 0.15) experienced atrial myopotential oversensing, and 2 patients (p = 0.15) ventricular. No unanticipated clinical events occurred. Compared with the recommended 2:1 sensing safety margin, the Autosensing feature performed equal to manual programming in preventing episodes of under/oversensing, and was better for atrial undersensing during sleep. Autosensing obviates the need for periodic reprogramming of a fixed sensitivity value.     

How Reliable is Atrial Sensing in Single-Lead VDD Pacing: Comparison of Three Systems

This study evaluated the reliability of atrial sensing, expressed as AV synchronous stimulation, in three VDD systems with the atrial sensitivity (AS) programmed to a conventional value with a 2:1 safety margin compared to most-sensitive values. We studied 34 sex- and age-matched patients with 3 VDD systems: 14 with Unity 292–07, 10 with Saphir 600, and 10 with Thera VDD (5 model 8948 and 5 model 8968i). Two 24-hour Hollers were performed on consecutive days. The AS was programmed in a randomized order to its most-sensitive value or to a 2:1 safety margin. All other parameters were programmed identically. The patients underwent a myopotential oversensing test and a daily life activity protocol. A beat-to-beat analysis of the Holters was performed to determine AV synchrony. For the entire group AV synchrony with conventional AS was 98.63%± 2.57%, compared to 99.80%± 0.43% with most-sensitive values (p = 0.002). There was no difference between the three systems with conventional AS. With the most-sensitive AS, AV synchrony was: Unity 99.99%± 0.03%, Saphir 99.42%± 0.60% (P = 0.002), Thera 99.81 %± 0.35% (ns). In the Saphir system with an atrial blanking period of 150 ms, ventricular far-field sensing could be demonstrated in 5 of 10 patients. This reduced the percentage of AV synchrony due to an unwanted mode-switch to a nontracking mode. Myopotential oversensing was not detected in any patient. Conclusion: The VDD systems tested under identical conditions showed reliable P wave sensing at the most-sensitive atrial sensing setting without myopotential oversensing. Ventricular far-field sensing reduced AV synchrony and must be avoided by appropriate refractory periods.     

How Can We Identify the Best Implantation Site for an ECG Event Recorder?

ZELLERHOFF, C., et al. : How Can We Identify the Best Implantation Site for an ECG Event Recorder? The aim of this study was to show how to find the preferable implantation site for an ECG event recorder (ECG‐ER). We compared the quality of bipolar ECG recordings (4‐cm electrode distance, vertical position) in 65 patients at the following sites: left and right subclavicular, left and right anterior axillary line (4th‐5th interspace), left and right of the sternum (4th‐5th interspace), heart apex, and subxyphoidal. The results were compared to the standard ECG lead II. In 30 patients, an additional comparison between vertical and horizontal ECG registrations was done using the same sites. ECG signals in five patients were compared positioning the electrodes towards the skin with turning them towards the muscle during ECG‐ER implantation. The best ECG quality (defined as highest QRS amplitude, best visible P wave and/or pacemaker spike, best measurable QRS duration, and QT interval) and best agreement with the standard lead II was found in 68% on the left of the sternum, significantly less often (P < 0.001 ) on the right of the sternum (14.1%), left subclavicular (6.9%), apical (5.5%) and subxyphoidal (4.2%). A significantly higher QRS amplitude was measured and the P wave was more often visible in the vertical electrode position than in the horizontal position. In all five ECG‐ER patients, there was a good agreement between the bipolar surface ECG at the implantation site and ECG‐ER stored signals. A significant noise signal occurred in all five patients when the ECG‐ER was implanted with electrodes towards the muscle. A P wave was visible in only three of those patients, but there was an insignificantly higher QRS amplitude than in ECG‐ERs implanted with electrodes towards the skin. From these results, it can be concluded that the best implantation site for an ECG‐ER is right or left of the sternum, positioning the electrodes vertically and towards the skin.     

Pain Sensation during Intradermal Injections of Three Different Botulinum Toxin Preparations in Different Doses and Dilutions

BACKGROUND: Pain sensation associated with injections of botulinum neurotoxin (BoNT) is commonly reported. To date differences in pain sensation between the commercially available products containing BoNT have not been quantified. OBJECTIVES: The pain sensations during injection of Dysport, Botox, Neurobloc, and pure saline (control) were compared. In addition, the nociceptive effect of different volumes used for the dilution of the same BoNT dose was investigated. METHODS: In a prospective, double-blind, controlled trial, 10 healthy subjects were injected intradermally with Dysport (12 U), Botox (3 and 4 U), Neurobloc (150 and 300 U) reconstituted in 0.9% saline, and pure saline. Pain sensation was quantified during injections. RESULTS: Neurobloc injections caused significantly more injection pain than Botox, Dysport, and saline. No significant differences between Dysport, Botox, and saline were found, although there was a trend toward less pain with pure saline injections. Higher pain levels with higher volumes could not be demonstrated significantly. CONCLUSION: Our data demonstrate that BoNT type B injections are associated with substantial pain. There is a considerable difference between the commercially available BoNT type B compared to the two BoNT type A preparations. Therefore, considering mitigation of injection pain seems necessary when using BoNT type B.     

Holter Recordings with Continuous Marker Annotations: A New Tool in Pacemaker Diagnostics

Pacemakers provide marker annotations to facilitate the interpretation of pacemaker electrocardiograms (ECGs) and can be used in cases of suspected pacemaker malfunction or to understand pacemaker behavior. Due to the need for a programmer, only short-term evaluations are possible. We evaluated a prototype Telemetry Data Logger (TDL) designed to continuously transfer markers from the pacemaker to a conventional Holter recorder. A miniaturized telemetry receiving coil was attached to patient's skin above the pacemaker, which was programmed to transmit markers continuously. The TDL, which receives and converts markers into eight positive and eight negative deflections, ranging from -2.5 to +2.5 mV in amplitude, was connected to one channel of a conventional Holter recorder (Tracker 2). We performed 20 Holters in 13 patients who had implanted VDDB or DDDR devices from the same manufacturer and evaluated three versions of software. Marker transmission was possible in all patients, producing Holter ECGs with complete marker annotations. Artifacts occurred < 4 % of the time. A 50-ms rectangular pulse was optimal for marker interpretation. The device, which was easy to use and well accepted by the patients, assisted in the diagnosis of inappropriate pacemaker programming, even when the surface ECG seemed to show regular pacemaker function. In the presence of low quality surface ECGs, marker annotations allowed the assessment of pacemaker function. The capability to annotate the onset of special algorithms, like tachycardia termination algorithms or mode switching, facilitates interpretation of pacemaker behavior, enabling a reliable assessment of the appropriateness of such algorithms. Conclusion: The TDL effectively enables pacemaker markers to be inscribed onto a conventional Holter recording, facilitating the interpretation of pacemaker ECGs and the diagnosis of inappropriate pacemaker programming even when not discernible from the surface ECG alone.     

Assessment of Time Domain and Spectral Components of Heart Rate Variability Immediately Before Ischemic ST Segment Depression Episodes

In an attempt to study autonomic function during the 5-minute period preceding ischemic ST segment depression (↓ST) episodes, we selected 138 ↓ST episodes, without preceding ↓ST during the last 15 minutes before each episode, from the Holler tapes of 35 patients with multivessel coronary artery disease. For the 5-minute period preceding each ↓ST episode, we calculated the following heart rate variability (HRV) indices; the mean RR interval (RR5), the standard deviation of all RR intervals (SD Index5), the corresponding coefficient of variation (CV5), and the natural log (Ln) of the spectral components, total power at 0.000 to 0.400 Hz (TP5), low frequency power at 0.040 to 0.150 Hz (LF5), high frequency power at 0.150 to 0.400 Hz (HF5), and the ratio of the low to high frequency power (LF5/HF5). As HRV indices of the 24-hour period, we calculated the respective RR, SD Index, CV, LnTP, LnLF, LnHF, and Ln LF/HF. RR5, SD Index5, CV5, and LnTP5 were all significantly lower than RR (t =−5.343, p = 3.7 × 10⁻⁷), SD Index (t =−19.091, p = 1.99 × 10⁻⁴⁰), CV(t -15.780, p = 1.28 × 10⁻³²), and LnTP (t =−3.210, p = 0.0016), respectively. LnHF5 was inversely correlated with the magnitude of the ↓ST; r =−0.174, P < 0.05, and CV5 was inversely correlated with the natural log (Ln) of the ischemic event duration; r =−0.183, P < 0.05. Analogous results were obtained for both the painful and silent ↓ST episodes. It is concluded that HRV is decreased during the 5-minute period preceding ↓ST episodes, and is inversely related with the magnitude and the duration of the ↓ST.     

Mobilization of CD34-positive tumour cells in a patient with testicular mixed germ cell tumour

Summary. Tumour cells from a patient with recurrent testicular germ cell cancer and bone marrow infiltration were found to express CD33 and CD34 in the absence of other haemopoiesis-associated antigens. After myelosup-pression and treatment with G-CSF for stem cell mobilization, CD34-positive tumour cells were detected in the peripheral blood in addition to normal haemopoietic progenitor cells. The tumour cells were decreased in the leukapheresis product. Retrospectively, the appearance of tumour cells in the peripheral blood after stem cell mobilization was the first indication of impending relapse.