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Publisher's version (útgefin grein), Background Electrical stimulation is widely used in experimental pain research but it lacks selectivity towards small nociceptive fibers. When using standard surface patch electrodes and rectangular pulses, large fibers are activated at a lower threshold than small fibers. Pin electrodes have been designed for overcoming this problem by providing a higher current density in the upper epidermis where the small nociceptive fibers mainly terminate. At perception threshold level, pin electrode stimuli are rather selectively activating small nerve fibers and are perceived as painful, but for high current intensity, which is usually needed to evoke sufficient pain levels, large fibers are likely co-activated. Long duration current has been shown to elevate the threshold of large fibers by the mechanism of accommodation. However, it remains unclear whether the mechanism of accommodation in large fibers can be utilized to activate small fibers even more selectively by combining pin electrode stimulation with a long duration pulse. Results In this study, perception thresholds were determined for a patch- and a pin electrode for different pulse shapes of long duration. The perception threshold ratio between the two different electrodes was calculated to estimate the ability of the pulse shapes to preferentially activate small fibers. The perception threshold ratios were compared between stimulation pulses of 5- and 50 ms durations and shapes of: exponential increase, linear increase, bounded exponential, and rectangular. Qualitative pain perception was evaluated for all pulse shapes delivered at 10 times perception threshold. The results showed a higher perception threshold ratio for long duration 50 ms pulses than for 5 ms pulses. The highest perception threshold ratio was found for the 50 ms, bounded exponential pulse shape. Results furthermore revealed different strength-duration relation between the bounded exponential- and rectangular pulse shapes. Pin electrode stimulation at high intensity was mainly described as "stabbing", "shooting", and "sharp". Conclusion These results indicate that long duration pulses with a bounded exponential increase preferentially activate the small nociceptive fibers with a pin electrode and concurrently cause elevated threshold of large non-nociceptive fibers with patch electrodes., Center for Neuroplasticity and Pain (CNAP) is supported by the Danish National Research Foundation (DNRF121)., "Peer Reviewed"

Fish freshness plays a vital role in the fish industry and also affects human health from a nutrition point of view. Here, an Au metal patch electrode capacitive sensor is introduced for rapid and accurate detection of volatile gases generated from raw fish to determine its freshness status. The MIS structured sensor was fabricated on a silicon substrate using Ag–SnO2 as sensing material over SiO2 layer and Au as a metal electrode. The calibration of the sensor was carried out with known composition of volatile gases (NH3, TMA, DMA and H2S) in the ppb-ppm regime. Our sensor using the proposed technique delivers sensor response to raw fish within 4 min, reflecting its freshness status in comparison to the TVB-N and TVC method which takes many hours to complete involving many sophisticated steps. The sensor response to volatile gases from Rohu (Labeo Rohita), Tilapia (Oreochromis Niloticus) and Illish (Tenualosa Ilisha) obtained by using our developed sensor system at 20 °C, 25 °C, and 30 °C, shows high correlation with TVB-N and TVC results. The acceptance limit for safe consumption of Tilapia, Rohu, and Illish at 30 °C was found to be 11 h, 12.5 h, and 10 h of storage time respectively. The result in this work assures a portable low-cost sensor for onsite monitoring of fish freshness at room temperature.

In this paper, a MIS based patch electrode multilayered capacitive sensor has been modelled mathematically. The sensor consists of ZnO sensing layer having patch top electrode, SiO2 layer and silicon substrate with bottom electrode. The overall capacitance of electrode is formulated by considering central, corner and fringe capacitances. The simulation was performed using mathematical mode to design the sensing layer thickness, patch electrode height and area and oxide layer thickness .

Transcoronary pacing is used for treatment of unheralded bradycardias in the setting of percutaneous coronary interventions (PCI). In the present study we introduced a new concept – the double guidewire approach – for transcoronary pacing in a porcine model. Transcoronary pacing was applied in 16 adult pigs under general anaesthesia in an animal catheterization laboratory. A special guidewire with electrical insulation by PTFE coating except for the distal part of the guidewire was positioned in the periphery of a coronary artery serving as the cathode. As the indifferent anode, an additional standard floppy tip guidewire was advanced into the proximal part of the same coronary vessel. The efficacy of double guidewire transcoronary pacing was assessed by measurement of threshold and impedance data and the magnitude of the epicardial electrogram compared with unipolar transcoronary pacing using a standard cutaneous patch electrode as indifferent anode. Transcoronary pacing was effective in all cases. Pacing thresholds obtained with the double guidewire technique (1.5 ± 0.9 V) were similar to those obtained by standard unipolar transcoronary pacing with a cutaneous patch electrode (1.2 ± 0.7 V) and unipolar transvenous pacing against the same cutaneous patch electrode (1.5 ± 1.0 V). Bipolar transvenous pacing yielded the lowest pacing threshold at 0.8 ± 0.4 V. Transcoronary pacing in the animal model with the novel “double guidewire approach” is a simple and effective pacing technique with comparable pacing thresholds obtained by standard unipolar transcoronary and transvenous pacing.

An Au patch electrode Ag-SnO2/SiO2/Si MIS capacitive sensor equipped with a microcontroller was designed and developed to sense low concentration (ppb to ppm regime) of volatiles (NH3, TMA, ethanol, and H2S) generated from chicken meat spoilage at room temperature. The quality threshold or the acceptance limit for consumption of chicken meat samples stored at 4 °C, 15 °C and 25 °C using our proposed technique was found to be 105 h, 48 h, and 17 h respectively, highly correlated with TVB-N, TVC, pH and sensory evaluation analysis. When these well established standard methods (TVB-N, TVC and pH analysis) take many hours to complete the analysis involving many complicated steps, our fabricated sensor takes 55 sec to deliver sensing response reflecting the meat spoilage status. The sensor calibrated with our compact technique promises portable and inexpensive onsite rapid and accurate quality assessment of meat spoilage at room temperature.

In this research article we have explained the design and fabrication process of ECG patch electrodes that are highly stretchable, flexible and almost similar to skin these electrodes are going to be used in the long term and unconscious sensing of electrical activity of heart. The overall design and fabrication process is highly motivated by the developments of the nanotechnology. As the result of these developments in nanotechnology we are able to reduce the size, cost, and power requirements of the electrodes used in the sensing of various bio signal, in our design we have used the Carbon NanoTube (CNT) / PolyDiMethylSiloxane (PDMS) composite material for the fabrication of patch electrodes. These electrodes provides better performance over conventional electrodes and one more important thing is that these microelectrodes are waterproof and hence patient can also be monitored at the time of showering.

Background: Low vagal tone (VT) is a marker of vulnerability to stress and the risk of developing necrotizing enterocolitis in preterm infants. Electric fields produced by equipment in the neonatal intensive care unit (NICU) induce an electric potential measurable on the skin in reference to ground. An electrical connection to ground reduces the skin potential and improves VT in adults. Objectives: We aimed to measure the electric field strengths in the NICU environment and to determine if connecting an infant to electrical ground would reduce the skin potential and improve VT. We also wished to determine if the skin potential correlated with VT. Methods: Environmental magnetic flux density (MFD) was measured in and around incubators. Electrical grounding (EG) was achieved with a patch electrode and wire that extended to a ground outlet. We measured the skin potential in 26 infants and heart rate variability in 20 infants before, during, and after grounding. VT was represented by the high-frequency power of heart rate variability. Results: The background MFD in the NICU was below 0.5 mG, but it ranged between 1.5 and 12.7 mG in the closed incubator. A 60-Hz oscillating potential was recorded on the skin of all infants. With EG, the skin voltage dropped by about 95%. Pre-grounding VT was inversely correlated with the skin potential. VT increased by 67% with EG. After grounding, the VT fell to the pre-grounding level. Conclusion: The electrical environment affects autonomic balance. EG improves VT and may improve resilience to stress and lower the risk of neonatal morbidity in preterm infants.

Electrophysiological signal in plant is a weak electrical signal, which can fluctuate with the change of environment. An amplification detection system was designed for plant electrical signal acquisition by using integrated op-amps (CA3140, AD620, and INA118), patch electrode, data acquisition card (NI USB-6008), computer, and shielded box. Plant electrical signals were also studied under pressure and flooding stress. The amplification detection system can make nondestructive acquisition for Aquatic Scindapsus and Guaibcn with high precision, high sensitivity, low power consumption, high common mode rejection ratio, and working frequency bandwidth. Stress experiments were conducted through the system; results show that electrical signals were produced in the leaf of Aquatic Scindapsus under the stress of pressure. Electrical signals in the up-leaf surface of Aquatic Scindapsus were stronger than the down-leaf surface. Electrical signals produced in the leaf of Guaibcn were getting stronger when suffering flooding stress. The more the flooding stress was severe, the faster the electrical signal changed, the longer the time required for returning to a stable state was, and the greater the electrical signal got at the stable state was.

The aim of this review was to provide an overview of the most important stages in the development of cellular electrophysiology. The period covered starts with Bernstein's formulation of the membrane hypothesis and the measurement of the nerve and muscle action potential. Technical innovations make discoveries possible. This was the case with the use of the squid giant axon, allowing the insertion of “large” intracellular electrodes and derivation of transmembrane potentials. Application of the newly developed voltage clamp method for measuring ionic currents, resulted in the formulation of the ionic theory. At the same time transmembrane measurements were made possible in smaller cells by the introduction of the microelectrode. An improvement of this electrode was the next major (r)evolution. The patch electrode made it possible to descend to the molecular level and record single ionic channel activity. The patch technique has been proven to be exceptionally versatile. In its whole‐cell configuration it was the solution to measure voltage clamp currents in small cells. See also: https://doi.org/10.14814/phy2.13860 & https://doi.org/10.14814/phy2.13862

Introduction: Increasing duration of ventricular fibrillation (VF) is associated with a higher risk of ineffective resuscitation. In addition, precountershock chest compression can influence defibrillation success. Transesophageal defibrillation may increase defibrillation success because of the proximity of the esophagus to the heart. We evaluated the efficacy of transesophageal defibrillation compared with standard transthoracic defibrillation after long episodes of VF. Methods: Defibrillation success after 10 minutes of untreated VF was evaluated in 12 sheep randomized into 2 groups: (group A) in 6 sheep, up to 3 transthoracic shocks were applied, followed by up to 3 transesophageal shocks (first shock: 150 J, second and third shocks: 200 J). (group B) In 6 sheep, 2 minutes of precountershock chest compression preceded the defibrillation shocks. Truncated biphasic shocks were delivered between a sternal and an apical patch electrode for transthoracic defibrillation and between an esophageal and a cutaneous patch electrode for transesophageal defibrillation. Results: In group A with no precountershock chest compression, external defibrillation failed despite shocks with maximum energy (200 J) in all 6 sheep. Transesophageal defibrillation was successful in 3 sheep (50%). In group B with precountershock chest compression, external defibrillation failed in all 6 sheep. Transesophageal defibrillation was successful with the first shock in all 6 sheep. Conclusions: Transesophageal defibrillation may terminate VF of long duration that is refractory to standard defibrillation. Precountershock chest compression may increase transesophageal defibrillation success.

This report describes the implantation of a transcutaneous ICD system using a small patch electrode in the subscapular position, and an active-can device in a 5.3-kg infant. The indication for ICD implantation was recurrent cardiac arrest in the presence of normal coronary anatomy. Metabolic evaluation suggested a defect in fatty acid oxidation.

We have developed a scanning patch-clamp technique that facilitates single-channel recording from small cells and submicron cellular structures that are inaccessible by conventional methods. The scanning patch-clamp technique combines scanning ion conductance microscopy and patch-clamp recording through a single glass nanopipette probe. In this method the nanopipette is first scanned over a cell surface, using current feedback, to obtain a high-resolution topographic image. This same pipette is then used to make the patch-clamp recording. Because image information is obtained via the patch electrode it can be used to position the pipette onto a cell with nanometer precision. The utility of this technique is demonstrated by obtaining ion channel recordings from the top of epithelial microvilli and openings of cardiomyocyte T-tubules. Furthermore, for the first time we have demonstrated that it is possible to record ion channels from very small cells, such as sperm cells, under physiological conditions as well as record from cellular microstructures such as submicron neuronal processes.

Implantable pacemaker cardioverter defibrillators are now available with biphasic waveforms, which have been shown to markedly improve defibrillation thresholds (DFTs). However, in a number of patients the DFT remains high. Also, DFT may increase after implantation, especially if antiarrhythmic drugs are added. We report on the use of a subcutaneous patch in the pectoral position in 15 patients receiving a transvenous defibrillator as a method of easily reducing the DFT. A 660-mm2 patch electrode was placed beneath the generator in a pocket created on the pectoral fascia. The energy required for defibrillation was lowered by 56% on average, and the system impedance was lowered by a mean of 25%. This maneuver allowed all patients to undergo a successful implant with adequate safety margin.

Since the observation by Haissaguerre et al that triggers of atrial fibrillation (AF) mapped to the pulmonary veins (PVs), circumferential PV isolation has become the cornerstone of most AF ablation strategies. As efforts have been made to improve the efficacy and safety of PV isolation, there also has been a push to simplify the circumferential ablation process in order to reduce the learning curve and expedite this time-consuming procedure. The ongoing challenge of the catheter-based ablation procedure remains: How can we best deliver a complex lesion set in a beating heart? As with all procedures, the answer lies in the interplay of the operator’s skills and the available tools. For many years, the only available technology for ablation involved a focal catheter, delivering unipolar radiofrequency (RF) energy between the catheter tip and a surface patch electrode. The first major technological improvement in AF ablation involved saline irrigation of the focal RF catheter. By reducing the temperature at the electrode-tissue interface, irrigation reduced the incidence of char formation and simultaneously enabled higher power delivery. Despite the advent of steerable sheaths, a high level of manual skill is still required for precise point-to-point movement of the focal ablation catheter in order to achieve a truly contiguous lesion set, which remains a time-consuming procedure. Given the approximately circular shape of the PV ostia, more recent ablation platforms have logically been built with circumferential energy delivery. Of the balloon-based ablation platforms, the high-intensity focused ultrasound balloon has been largely abandoned owing to safety concerns. The laser balloon continues to undergo clinical evaluation in the United States. As a true single-shot PV isolation tool, the cryoballoon has achieved widespread use in recent years, with efficacy and safety data comparable to those of focal RF ablation. Other variations of this theme have combined the circular mapping catheter and the focal ablation catheter into 1 tool, obviating the need for a second transseptal catheter. Furthermore, since energy delivery to each circumferential electrode is individually controlled, these platforms allow the choice of

Pericardial constriction associated with the placement of intrapericardial defibrillator patches is a rare occurrence that is reported only one tenth as often in defibrillator patients as in patients undergoing other types of cardiac operations. Although this discrepancy may be attributable to a lower incidence of constriction with the defibrillator patch electrode procedure, it may also indicate a failure to recognize that progressive right heart failure and signs of low cardiac output that could be due to pericardial constriction and not progressive systolic dysfunction. Because surgical removal of the patches and decortication of the epicardial surface is the only effective therapy, it is important to recognize this uncommon, but profoundly debilitating entity.

A new 83 cm3 implantable cardioverter-defibrillator (ICD) designed for pectoral implantation has been implanted most frequently using right ventricular and superior vena cava (RV--SVC) electrodes; a patch electrode (RV--patch + SVC) has been added when necessary to decrease the defibrillation threshold (DFT). The goal of this prospective study was to compare biphasic waveform DFTs for 3 electrode configurations: RV--patch, RV--SVC, and RV--patch + SVC in 25 consecutive patients. The patch was positioned in a left retro-pectoral pocket, and the SVC electrode was positioned with the tip at the junction of the SVC and innominate vein. In the first 15 patients, all 3 electrode configurations were tested in random order; in the last 10 patients, only the RV--patch and RV--patch + SVC configurations were tested. In the first 15 patients, the stored-energy DFT for the RV--SVC configuration (15.2 +/- 7.7 J) was higher (p0.001) than the DFT for the RV--patch configuration (11.3 +/- 6.2 J) and the RV--patch + SVC configuration (10.0 +/- 5.8 J). For all 25 patients, the DFT was lower for the RV--patch + SVC configuration (9.7 +/- 5.1 J) than for the RV--patch configuration (12.4 +/- 6.6 J, p = 0.005). The pathway resistance was highest for the RV--patch configuration (72 +/- 9 omega), lower for the RV--SVC configuration (63 +/- 6 omega, p0.01), and lowest for the RV--patch + SVC configuration (46 +/- 3 omega, p0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

We tried to detect minimal stimulation-induced glutamate overflow from the surface of a hippocampal slice using an outside-out patch electrode excised from pyramidal cell membranes. The amplitude of the stimulation-induced patch current was dependent on the distance between the slice surface and the tip of patch sensor. The current-voltage relations of the stimulation-induced patch current were similar to those of the current evoked by puff application of l-glutamate to the patch. This indicates that the stimulation-induced patch current was produced by glutamate released from presynaptic terminals, and thus this technique may be useful in the study of transmitter release evoked by minimal electrical stimulation in brain slices.

Previous studies have shown that low internal defibrillation thresholds (DFTs) can be attained by using two pairs of electrodes and combining biphasic shocks with sequential timing. The purpose of this two-part study was to test the defibrillation efficacy of two new shock sequences, an interleaved biphasic, and a common phase sequential biphasic, that utilized two pairs of electrodes and were developed from the concept of sequential biphasic shocks. In the first part, defibrillation catheters were placed in the right ventricle and the superior vena cava of six anesthetized pigs. A small patch electrode was placed on the LV apex through a subxiphoid incision and a cutaneous patch was placed on the left thorax. The mean DFT energies for the interleaved biphasic (5.2 +/- 0.4 J) and the common phase sequential biphasic waveforms (5.4 +/- 0.4 J) were substantially less (P < 0.0001) than those for either the sequential monophasic (10.6 +/- 1.0 J) or single biphasic waveforms (9.0 +/- 1.0 J). In the second study, which used nine anesthetized pigs, the importance of phase reversal was demonstrated by the finding that the DFT energy of a common phase sequential biphasic shock (6.2 +/- 0.4 J) was much less than a common phase sequential monophasic shock (17.9 +/- 1.3 J, P < 0.0001); furthermore, the average DFT for four common phase sequential biphasic configurations (5.7 +/- 0.2 J) was much less than for a configuration that was similar except that current flow was not reversed in one phase so that no biphasic effect was present (19.7 +/- 1.2 J). The efficacy of common phase sequential biphasics was comparable to that of sequential biphasics. The effectiveness of sequential biphasics, interleaved biphasics, and common phase sequential biphasics is possibly due to two mechanisms: (A) an increase in the potential gradient during a later phase in regions that were low during the first phase, and (B) the exposure of most of the myocardium to a biphasic shock that reduces the minimum extracellular potential gradient needed to defibrillate.

Cardioverter-defibrillator implantation in 22 consecutive patients after aborted sudden cardiac death was followed by prospective determination of the correct anatomic position of epicardial patch electrodes by chest X-ray study and cine computed tomography; the data were compared with the defibrillation threshold obtained intraoperatively. Patch electrode position was qualitatively graded. Computed tomography improved the assessment as compared with X-ray study in 13 patients (59%), visualizing electrodes in relation to the underlying myocardial and vascular structures. Although the computed tomographic technique provided more precise visualization, its grading of patch position correlated as poorly as that of the X-ray study with the measured acute defibrillation threshold. Three-dimensional reconstruction by computed tomography made it possible to determine quantitatively left ventricular mass (free wall and septum) and the mass encompassed by the patch electrodes. The 34.6 ± 13.7% (range 12.6 to 61.1%) of the left ventricular mass encompassed by both patch electrodes showed a linear relation to the defibrillation threshold (r = 0.64, p = 0.01). Differentiation of free wall and septal mass in these measurements revealed that the proportion of septal mass encompassed by patch electrodes correlated closely with the defibrillation threshold (r = −0.6, p = 0.019), whereas that of the free wall mass, although significantly larger (35.4 ± 15.8 vs. 20.6 ± 15.4 g, p = 0.007), did not. Thus, the position of epicardial patch electrodes could be reliably determined by computed tomography. Although the tomographically measured fraction of left ventricular mass encompassed by patch electrodes was predictive of defibrillation threshold, for achievement of a low threshold, it was more important to include the interventricular septal mass than the free wall mass.

To investigate effects of serum factor on the Ca2(+)-spike and neurite outgrowth in cultured nerve cells, dorsal root ganglia (DRG) neurons of the adult guinea pig were cultured in a serum-free N1 medium (N1 group) and a serum-containing medium (FCS group). The maximum rate of rise (MRR) of the Ca2(+)-spike, an indicator of the maximum Ca2(+)-current, was enhanced in the FCS group on day 5 in culture. The MRR of Ca2(+)-spike remained at a low level in the N1 group (2-10 days), but neurites outgrew rapidly during 2-5 days in both the FCS and N1 groups. Replacement of a serum-free medium by a serum-containing one on day 5 caused faster increase in the MRR of the Ca2(+)-spike. The active serum component for the Ca2(+)-spike enhancement was a heat-stable, small molecule. Chronic application of dibutyryl cyclic AMP (10 microM) mimicked the serum action on the Ca2(+)-spike. Whole-cell voltage-clamp experiment by a patch electrode showed that currents through the L- and T-type Ca-channels were enhanced in FCS group. Since kinetic and voltage-dependent gating properties of Ca-channels were similar between the FCS and N1 groups, available channel density might be increased by a serum factor.

There are many known complications of implantable cardioverter-defibrillator placement. We treated a patient in whom a left ventricular pseudoaneurysm developed secondary to epicardial patch electrode placement and cardioverter-defibrillator implantation. The presenting symptoms, diagnostic evaluation, and surgical repair are described.

There are more than 20 years of experience with implantation of defibrillator devices in humans and the procedure is an important therapeutic option for patients at high risk of life-threatening ventricular arrhythmias. The incidence of new defibrillator implantation has gradually increased, being used even in children, 1 although pediatric use is associated with several complications, especially with epicardial systems,2 including fracture of the subcutaneous patch,3-5 mainly because of growth.3 We present a case of subcutaneous patch electrode fracture in the left axillary pectoral region of a patient who needed the patch for effective defibrillation, and we discuss the methods of treatment. (Circ J 2005; 69: 116 -118)

The efficacy of six implantable defibrillator electrode configurations was compared using a boundary element model that incorporated a realistic thorax with detailed internal structure. Configurations 1-3 consisted of an (inferior) endocardial electrode positioned in the right ventricle (RV) together with a (superior) endocardial electrode positioned high or low in the superior vena cava (SVC) or in the pulmonary artery (PA). Configurations 4-6 were the same as 1-3 but with the addition of a subcutaneous (SQ) patch electrode on the left chest wall. The energy used to achieve minimum voltage gradients of 5 V/cm was much lower for configurations 4-6 with the SQ patch (2.9-3.8 J). Without the SQ patch, the PA electrode used less energy (10.3 J) than low (12.4) and high SVC (15.1). The subcutaneous patch results in substantial reductions in required voltage and energy for implantable defibrillators. >

A mathematical model was reconstructed based on the upstroke and sodium current separately recorded from enzymatically dispersed ventricular myocytes of a guinea pig, using the patch clamp technique. After holding the membrane potentials ranging from -120 to -60 mV for 500 ms, the upstroke was induced by applying the stimulus through the patch electrode with the constant latency to obtain voltage-dependence of availability for V/sub max/. Phase plane plots (membrane potential vs. dV/dt) were used for optimization of a mathematical model. Experimental results could be reproduced by the model. >

The patch electrode and the array electrode are the two types of subcutaneous leads available as an adjunct to a transvenous lead system in patients with high defibrillation thresholds. A prospective randomized study was conducted in 30 consecutive patients comparing the efficacy and the long-term performance of a patch electrode with an array electrode. After determination of the defibrillation threshold for the transvenous lead alone, a subcutaneous patch or an array electrode was implanted in random order. Adding a patch electrode decreased the defibrillation threshold in seven out of 15 patients (47%) from 13.2+/-6.6 to 10.5+/-5.1 J (P0.05). In 13 out of 15 patients (87%), the implantation of an array electrode caused a significant lowering of the defibrillation threshold from 15.4+/-6.6 to 8.2+/-5.0 J (P0.0001). The array electrode was significantly more effective in lowering the defibrillation threshold than the patch electrode (P0.01). Complications during follow-up associated with the subcutaneous patch electrode were observed in four patients whereas no complications were associated with the array electrode (P0.01). The additional implantation of an array electrode is more effective and associated with fewer complications compared to a patch electrode.

In hippocampal slices from rats, dialysis with rhodamine-123 (Rh-123) and/or fura-2 via the patch electrode allowed monitoring of mitochondrial potential (ΔΨ) changes and intracellular Ca2+([Ca2+]i) of CA1 pyramidal neurons. Plasmalemmal depolarization to 0 mV caused a mean [Ca2+]irise of 300 nM and increased Rh-123 fluorescence signal (RFS) by ≤50% of control. The evoked RFS, indicating depolarization of ΔΨ, and the [Ca2+]itransient were abolished by Ca2+-free superfusate or exposure of Ni2+/Cd2+. Simultaneous measurements of RFS and [Ca2+]ishowed that the kinetics of both the Ca2+rise and recovery were considerably faster than those of the ΔΨ depolarization. The plasmalemmal Ca2+/H+pump blocker eosin-B potentiated the peak of the depolarization-induced RFS and delayed recovery of both the RFS and [Ca2+]itransient. Thus the ΔΨ depolarization due to plasmalemmal depolarization is related to mitochondrial Ca2+sequestration secondary to Ca2+influx through voltage-gated Ca2+channels. CN−elevated [Ca2+]iby 2+]i. In the presence of oligomycin, CN−and p-trifluoromethoxy-phenylhydrazone (FCCP) elevated [Ca2+]iby 2+]i. Imaging techniques revealed that evoked [Ca2+]irises are distributed uniformly over the soma and primary dendrites, whereas corresponding changes in RFS occur more localized in subregions within the soma. The results show that microfluorometric measurement of the relation between mitochondrial function and intracellular Ca2+is feasible in whole cell recorded mammalian neurons in situ.

We studied a new technique for creating long linear lesions in hearts using a custom-made linear probe. Radiofrequency (RF) energy applications using a 25-mm long stainless steel linear probe and a corresponding 500-kHz energy generator were tested, creating 90 lesions in isolated porcine hearts. The RF current was applied between the linear probe and a large patch electrode attached to the back of the specimen. Three parameters, comprising the power of the delivered energy, the pressure of contact between the probe and the specimen, and the duration of energy delivery were changed independently and the size of the resulting lesions was measured. All 90 lesions were transmural, well demarcated and created by a single stationary RF application. Lesion length and width increased with: 1) increasing power, when the other two parameters were maintained at constant levels, 2) increasing contact pressure, when the other two parameters were maintained at constant levels, and 3) increasing duration of energy delivery when the other two paramaters were maintained at constant levels. The maximum width of the lesions was 3.7 mm. No overheating of any of the specimens was observed. In conclusion, the new original long linear probe used in this study was effective for creating transmural linear lesions, presenting the possibility of a worthwhile contribution to the maze surgical procedure applied to atrial fibrillation.

Successful implantation of a biphasic nonthoracotomy implantable cardioverter defibrillator may not be achieved with a conventional system. We describe a successful device implantation using a pectoral and abdominal patch electrode system.

Nonthoracotomy defibrillator systems can be implanted with a lower morbidity and mortality, compared to epicardial systems. However, implantation may be unsuccessful in up to 15% of patients, using a monophasic waveform. It was the purpose of this study to prospectively examine the efficacy of a second chest patch electrode in a nonthoracotomy defibrillator system. Fourteen patients (mean age 62 +/- 11 years, ejection fraction = 0.29 +/- 0.12) with elevated defibrillation thresholds, defined as > or = 24 J, were studied. The initial lead system consisted of a right ventricular electrode (cathode), a left innominate vein, and subscapular chest patch electrode (anodes). If the initial defibrillation threshold was > or = 24 J, a second chest patch electrode was added. This was placed subcutaneously in the anterior chest (8 cases), or submuscularly in the subscapular space (6 cases). This resulted in a decrease in the system impedance at the defibrillation threshold, from 72.3 +/- 13.3 omega to 52.2 +/- 8.6 omega. Additionally, the defibrillation threshold decreased from > or = 24 J, with a single patch, to 16.6 +/- 2.8 J with two patches. These changes were associated with successful implantation of a nonthoracotomy defibrillator system in all cases. In conclusion, the addition of a second chest patch electrode (using a subscapular approach) will result in lower defibrillation thresholds in patients with high defibrillation thresholds, and will subsequently increase implantation rates for nonthoracotomy defibrillators.

We performed a blinded controlled analysis of transthoracic echocardiograms on IK patients before and after epicardial defibrillator patch electrode placement to determine the accuracy of echocardiography in identifying defibrillator patches and to determine possible echocardiographic findings that may correlate with defibrillator function or perioperative complications. The sensitivity of two-dimensional echocardiography in detecting defibrillator electrodes was 72% by one observer and 39% by a second observer. Corresponding specificities were 67% and 83%, respectively. The discordance rate was 27%. The echocardiographic finding of patch buckling was not observed, and echocardiographic estimates of the distance from patch to epicardium did not correlate with defibrillator threshold at the time of surgery. We conclude that: echocardiography is only moderately sensitive and specific in identifying epicardial defibrillator electrodes; significant interobserver variability does exist; and echocardiography therefore cannot be used reliably to assess for pericardia] changes or possible complications of patch electrode placement.

Placement of Implantable cardioverter devices in young children is complicated because of the relatively large size and heavy weight of these devices. A technique is described where the device is implanted in the left perirenal space while an endovascular lead is used instead of an epicardial patch electrode.