Advanced Data Analytics for Clinical Research Part II: Application to Cardiothoracic Surgery.

In the first part of this series, we introduced the tools of Big Data, including Not Only Standard Query Language data warehouse, natural language processing (NLP), optical character recognition (OCR), and Internet of Things (IoT). There are nuances to the utilization of these analytics tools, which must be well understood by clinicians seeking to take advantage of these innovative research strategies. One must recognize technical challenges to NLP, such as unintended search outcomes and variability in the expression of human written texts. Other caveats include dealing written texts in image formats, which may ultimately be handled with transformation to text format by OCR, though this technology is still under development. IoT is beginning to be used in cardiac monitoring, medication adherence alerts, lifestyle monitoring, and saving traditional labs from equipment failure catastrophes. These technologies will become more prevalent in the future research landscape, and cardiothoracic surgeons should understand the advantages of these technologies to propel our research to the next level. Experience and understanding of technology are needed in building a robust NLP search result, and effective communication with the data management team is a crucial step in successful utilization of these technologies. In this second installment of the series, we provide examples of published investigations utilizing the advanced analytic tools introduced in Part I. We will explain our processes in developing the research question, barriers to achieving the research goals using traditional research methods, tools used to overcome the barriers, and the research findings.

Prediction of the service life of surgical instruments from the surgical instrument management system log using radio frequency identification.

BACKGROUND: Bar code- or radio frequency identification (RFID)-based medical instrument management systems have gradually been introduced in the field of surgical medicine for the individual management and identification of instruments. We hypothesized that individual management of instruments using RFID tags can provide previously unavailable information, particularly the precise service life of an instrument. Such information can be used to prevent medical accidents caused by surgical instrument failure. This study aimed to predict the precise service life of instruments by analyzing the data available in instrument management systems. METHODS: We evaluated the repair history of instruments and the usage count until failure and then analyzed the data by the following three methods: the distribution of the instrument usage count was determined, an instrument failure probability model was generated through logistic regression analysis, and survival analysis was performed to predict instrument failure. RESULTS: The usage count followed a normal distribution. Analysis showed that instruments were not used uniformly during surgery. In addition, the Kaplan-Meier curves plotted for five types of instruments showed significant differences in the cumulative survival rate of different instruments. CONCLUSIONS: The usage history of instruments obtained with RFID tags or bar codes can be used to predict the probability of instrument failure. This prediction is significant for determining the service life of an instrument. Implementation of the developed model in instrument management systems can help prevent accidents due to instrument failure. Knowledge of the instrument service life will also help in developing a purchase plan for instruments to minimize wastage.

Sound analysis of the magnetically levitated left ventricular assist device HeartMate 3™.

INTRODUCTION: The HeartMate 3™ has shown lower rates of adverse events compared to previous devices due to the design and absence of mechanical bearings. For previous devices, sound analysis emerged as a way to assess pump function. The aims of this study were to determine if sound analysis can be applied to the HeartMate 3 in vivo and in vitro and to evaluate an electronic stethoscope. METHOD: Sound recordings were performed with microphones and clinical accessible electronic stethoscope. The recordings were studied in both the time and the frequency domains. Recordings from four patients were performed to determine if in vivo and in vitro recordings are comparable. RESULTS: The results show that it is possible to detect sound from HeartMate 3 and the sound spectrum is clear. Pump frequency and frequency of the pulsatile mode are easily determined. Frequency spectra from in vitro and in vivo recordings have the same pattern, and the major proportion (96.7%) of signal power is located at the pump speed frequency ±40 Hz. The recordings from the patients show low inter-individual differences except from location of peaks originating from pump speed and harmonics. Electronic stethoscopes could be used for sound recordings, but the dedicated equipment showed a clearer sound spectrum. DISCUSSION: The results show that acoustic analysis can also be performed with the HeartMate 3 and that in vivo and in vitro sound spectrum is similar. The frequency spectra are different from previous devices, and methods for assessing pump function or thrombosis need further evaluation.

Scoping the scope: endoscopic evaluation of endoscope working channels with a new high-resolution inspection endoscope (with video).

BACKGROUND AND AIMS: Outbreaks of transmission of infection related to endoscopy despite reported adherence to reprocessing guidelines warrant scrutiny of all potential contributing factors. Recent reports from ambulatory surgery centers indicated widespread significant occult damage within endoscope working channels, raising concerns regarding the potential detrimental impact of this damage on the adequacy of endoscope reprocessing. METHODS: We inspected working channels of all 68 endoscopes at our academic institution using a novel flexible inspection endoscope. Inspections were recorded and videos reviewed by 3 investigators to evaluate and rate channel damage and/or debris. Working channel rinsates were obtained from all endoscopes, and adenosine triphosphate (ATP) bioluminescence was measured. RESULTS: Overall endoscope working channel damage was rated as minimal and/or mild and was consistent with expected wear and tear (median 1.59 on our 5-point scale). Our predominant findings included superficial scratches (98.5%) and scratches with adherent peel (76.5%). No channel perforations, stains, or burns were detected. The extent of damage was not predicted by endoscope age. Minor punctate debris was common, and a few small drops of fluid were noted in 42.6% of endoscopes after reprocessing and drying. The presence of residual fluid predicted higher ATP bioluminescence values. The presence of visualized working channel damage or debris was not associated with elevated ATP bioluminescence values. CONCLUSION: The flexible inspection endoscope enables high-resolution imaging of endoscope working channels and offers endoscopy units an additional modality for endoscope surveillance, potentially complementing bacterial cultures and ATP values. Our study, conducted in a busy academic endoscopy unit, indicated predominately mild damage to endoscope working channels, which did not correlate with elevated ATP values.

A Real-Time Gait Event Detection for Lower Limb Prosthesis Control and Evaluation.

Lower extremity amputees suffer from mobility limitations which will result in a degradation of their quality of life. Wearable sensors are frequently used to assess spatio-temporal, kinematic and kinetic parameters providing the means to establish an interactive control of the amputee-prosthesis-environment system. Gait events and the gait phase detection of an amputee's locomotion are vital for controlling lower limb prosthetic devices. The paper presents an approach to real-time gait event detection for lower limb amputees using a wireless gyroscope attached to the shank when performing level ground and ramp activities. The results were validated using both healthy and amputee subjects and showed that the time differences in identifying Initial Contact (IC) and Toe Off (TO) events were larger in a transfemoral amputee when compared to the control subjects and a transtibial amputee (TTA). Overall, the time difference latency lies within a range of ±50 ms while the detection rate was 100% for all activities. Based on the validated results, the IC and TO events can be accurately detected using the proposed system in both control subjects and amputees when performing activities of daily living and can also be utilized in the clinical setup for rehabilitation and assessing the performance of lower limb prosthesis users.

Mitral Valve Regurgitation in the LVAD-Assisted Heart Studied in a Mock Circulatory Loop.

Permanent closure of the aortic valve (AVC) is sometimes performed In LVAD patients, usually when a mechanical valve prosthesis or significant aortic insufficiency is present. Mitral valve regurgitation (MVR) present at the time of LVAD implantation can remain unresolved, representing a limitation for exercise tolerance and a potential predictor of mortality. To investigate the effect of MVR on hemodynamics of the LVAD-supported heart following AVC, studies were performed using a mock circulatory loop. Pressure and flow measured for a range of cardiac function, LVAD speed, and MVR show that cardiac contraction augments aortic pressure by 10-27% over nonpulsatile conditions when the mitral valve functions normally, but decreases with MVR until it reaches the nonpulsatile level. Aortic flow displays a similar trend, demonstrating a 25% decrease from fully functioning to open at 7 krpm, a 5% decrease at 9 krpm, and no observable effect at 11 krpm. Pulsatility decreases with increased LVAD speed and MVR. The data indicate that a modest level of cardiac output (1.5-2 L/min) can be maintained by the native heart through the LVAD when the LVAD is off. These results demonstrate that MVR decreases the augmentation of forward flow by improved cardiac function at lower LVAD speeds. While some level of MVR can be tolerated in LVAD recipients, this condition represents a risk, particularly in those patients that undergo AVC closure, and may warrant repair at the time of surgery.

Developments in contact lens measurement: A comparative study of industry standard geometric inspection and optical coherence tomography.

PURPOSE: The aim of this study was to compare a developmental optical coherence tomography (OCT) based contact lens inspection instrument to a widely used geometric inspection instrument (Optimec JCF), to establish the capability of a market focused OCT system. METHODS: Measurements of 27 soft spherical contact lenses were made using the Optimec JCF and a new OCT based instrument, the Optimec is830. Twelve of the lenses analysed were specially commissioned from a traditional hydrogel (Contamac GM Advance 49%) and 12 from a silicone hydrogel (Contamac Definitive 65), each set with a range of back optic zone radius (BOZR) and centre thickness (CT) values. Three commercial lenses were also measured; CooperVision MyDay (Stenfilcon A) in -10D, -3D and +6D powers. Two measurements of BOZR, CT and total diameter were made for each lens in temperature controlled saline on both instruments. RESULTS: The results showed that the is830 and JCF measurements were comparable, but that the is830 had a better repeatability coefficient for BOZR (0.065mm compared to 0.151mm) and CT (0.008mm compared to 0.027mm). Both instruments had similar results for total diameter (0.041mm compared to 0.044mm). CONCLUSIONS: The OCT based instrument assessed in this study is able to match and improve on the JCF instrument for the measurement of total diameter, back optic zone radius and centre thickness for soft contact lenses in temperature controlled saline.

A Novel Method to Detect an Oxygenator Defect Prior to Cardiopulmonary Bypass Initiation.

Cardiopulmonary bypass (CPB) is a common practice in our era. The medical technology used for cardiac surgery goes through rigorous testing to ensure its safety. Unfortunately, it is not fail proof. Oxygenator failures are a rare occurrence but may lead to catastrophic events. We present a case where the preparation for initiating CPB was complicated by an oxygenator defect. After thorough examination, the oxygenator was found leaking from the gas exhaust port suggesting a disruption in continuity of the fibers. This was found by the vigilance of the perfusionist and a creative method to quickly assess the integrity of the oxygenation device. We describe a simple technique to help diagnose an oxygenator leak.

An anthropomorphic sonography phantom for the evaluation of mechatronic devices for heart surgery.

Surgical assistance systems are used to make surgical procedures more precise. The integration of automated intra-operative imaging in surgical interventions can be seen as an important step to further improve patient safety. An automatic soft tissue manipulation system with mechatronic assistance using endoscopic Doppler guidance was developed for minimally invasive coronary artery bypass surgery. To facilitate the complicated development process of the mechatronic system, we manufactured and validated an anthropomorphic phantom. A three-compartment model including soft tissue and a vessel system were manufactured for the phantom. Blood flow simulation was implemented using a pump and blood mimicking fluid in a closed circuit. Eighteen physicians evaluated the anatomical and physiological validity of the phantom in a study. The average rating of the anatomy, as well as the physiology, was good, although particular aspects of the phantom have shown a need for improvement. The validation study provided valuable information on limits and problems concerning the phantom and its applicability for the evaluation of the development steps of the mechatronic system. We showed how to develop and validate a phantom for the evaluation of a surgical assistance system with intraoperative imaging. The described concepts can be applied to similar developmental procedures and help generate a goal-driven and efficient development.

Simple clotting test to detect procoagulant abdominal swabs.

During surgical procedures, abdominal swabs are routinely used to adsorb blood from the operation field and for the retention of tissues and organs. Due to the material characteristics, abdominal swabs exhibit a slight procoagulant activity, which is usually desirable and mostly harmless. However, during cardiac surgery with heart-lung machine (HLM) support, abnormal clot formation may result in life-threatening thromboembolic complications. Therefore, a simple clotting test (SCT) allowing in vitro detection of abdominal swabs with elevated hypercoagulant potency in the presence of heparinized human blood was developed and validated. In order to establish a SCT, heparinized human blood from 100 donors was incubated with five different cotton abdominal swabs for 30 min at 37 °C and then macroscopically analyzed. In a second study, 10 other swabs were screened with the established SCT (n=11) to confirm its suitability. Scanning electron microscopy, measurements of activated clotting times and thrombin-antithrombin were further performed. In the SCT, the results are dichotomized as negative (no detectable blood clot) and positive (blood clot formation). In the first study, three of the five tested abdominal swabs exhibited hypercoagulant potency in at least 25% of the donors. Calculations using the binomial distribution showed that blood of 11 donors is needed for routine testing with the SCT, which was confirmed in the second study using another 10 swabs. The established SCT can be used for detection of abdominal swabs with an elevated procoagulant potency, thereby minimizing the risk of thromboembolic complications during cardiac surgery with HLM support.

[Comparison of IOL-Master 500 vs. Lenstar LS900 concerning the calculation of target refraction: A retrospective analysis]. / Vergleich IOL-Master 500 vs. Lenstar LS900 hinsichtlich der Berechnung der Zielrefraktion: Eine retrospektive Analyse.

BACKGROUND: The choice of a suitable intraocular lens (IOL) and the calculation of postoperative refractive error is one of the most intriguing challenges of modern cataract surgery. This clinical trial compared the accuracy of two laser-assisted optical biometers, the IOL-Master 500 (Carl Zeiss Meditec, Jena, Germany) and the Lenstar LS900 (Haag-Streit, Bern, Switzerland) without taking the postoperative results into consideration. MATERIAL AND METHODS: Artificial lenses (Alcon Pharma) for 114 eyes of 67 patients were measured using both biometric instruments. The deviation of the presumed refractive error from the desired preoperative refractive target was calculated with different formulae (i.e. SRK/T, HofferQ, Haigis and SRKII) based on the intraoperatively chosen IOL. The differences between both instruments were compared using Student's t-test. RESULTS: Using the SRKII formula a mean difference between the IOL-Master and the Lenstar of 0.07 D (p = 0.002) was calculated for 95 eyes, SRK/T used on 47 eyes showed a difference of 0.04 D (p = 0.27), HofferQ measured 0.09 D (p = 0.0001) between both instruments for 88 eyes and the Haigis formula also showed a mean difference of 0.09 D (p = 0.001) based on the calculations of 106 eyes. CONCLUSION: Both instruments gave reproducible and accurate results with only a small deviation from the desired target refraction and can therefore be considered as comparable for the calculation of IOLs. Statistically significant differences in the results were found when using the SRKII, HofferQ and Haigis formulae but these were too low to have any influence on the choice of IOL to be implanted.

Impedance Changes Indicate Proximal Ventriculoperitoneal Shunt Obstruction In Vitro.

Extracranial cerebrospinal fluid (CSF) shunt obstruction is one of the most important problems in hydrocephalus patient management. Despite ongoing research into better shunt design, robust and reliable detection of shunt malfunction remains elusive. The authors present a novel method of correlating degree of tissue ingrowth into ventricular CSF drainage catheters with internal electrical impedance. The impedance based sensor is able to continuously monitor shunt patency using intraluminal electrodes. Prototype obstruction sensors were fabricated for in-vitro analysis of cellular ingrowth into a shunt under static and dynamic flow conditions. Primary astrocyte cell lines and C6 glioma cells were allowed to proliferate up to 7 days within a shunt catheter and the impedance waveform was observed. During cell ingrowth a significant change in the peak-to-peak voltage signal as well as the root-mean-square voltage level was observed, allowing the impedance sensor to potentially anticipate shunt malfunction long before it affects fluid drainage. Finite element modeling was employed to demonstrate that the electrical signal used to monitor tissue ingrowth is contained inside the catheter lumen and does not endanger tissue surrounding the shunt. These results may herald the development of "next generation" shunt technology that allows prediction of malfunction before it affects patient outcome.

Accuracy of a hexapod parallel robot kinematics based external fixator.

BACKGROUND: Different hexapod-based external fixators are increasingly used to treat bone deformities and fractures. Accuracy has not been measured sufficiently for all models. METHODS: An infrared tracking system was applied to measure positioning maneuvers with a motorized Precision Hexapod® fixator, detecting three-dimensional positions of reflective balls mounted in an L-arrangement on the fixator, simulating bone directions. By omitting one dimension of the coordinates, projections were simulated as if measured on standard radiographs. Accuracy was calculated as the absolute difference between targeted and measured positioning values. RESULTS: In 149 positioning maneuvers, the median values for positioning accuracy of translations and rotations (torsions/angulations) were below 0.3 mm and 0.2° with quartiles ranging from -0.5 mm to 0.5 mm and -1.0° to 0.9°, respectively. CONCLUSIONS: The experimental setup was found to be precise and reliable. It can be applied to compare different hexapod-based fixators. Accuracy of the investigated hexapod system was high.

[Intraoperative audiological-technical diagnostics during cochlear implant surgery]. / Intraoperative audiologisch-technische Diagnostik bei der Cochleaimplantatversorgung.

During cochlear implant (CI) surgery, audiological-technical diagnostics is required which includes the proof of the implant function as well as the verification of its physiological coupling to the auditory nerve in order to undertake required interventions before the end of the surgery in case of need. The technical function check implies the coupling check, the implant integrity check, as well as impedance and field telemetry, and allows for assessment of implant electronics and electrode function. The audiological diagnostics used for verification of the physiological implant function incorporate visual registration of the electrically evoked stapedius reflexes and measurement of electrically evoked compound action potentials of the cochlear nerve, including their stimulation thresholds.

Detector system dose verification comparisons for arc therapy: couch vs. gantry mount.

The aim of this study was to assess the performance of a gantry-mounted detector system and a couch set detector system using a systematic multileaf collimator positional error manually introduced for volumetric-modulated arc therapy. Four head and neck and esophagus VMAT plans were evaluated by measurement using an electronic portal imaging device and an ion chamber array. Each plan was copied and duplicated with a 1 mm systematic MLC positional error in the left leaf bank. Direct comparison of measurements for plans with and without the error permitted observational characteristics for quality assurance performance between detectors. A total of 48 different plans were evaluated for this testing. The mean percentage planar dose differences required to satisfy a 95% match between plans with and without the MLCPE were 5.2% ± 0.5% for the chamber array with gantry motion, 8.12% ± 1.04% for the chamber array with a static gantry at 0°, and 10.9%± 1.4% for the EPID with gantry motion. It was observed that the EPID was less accurate due to overresponse of the MLCPE in the left leaf bank. The EPID always images bank-A on the ipsilateral side of the detector, whereas for a chamber array or for a patient, that bank changes as it crosses the -90° or +90° position. A couch set detector system can reproduce the TPS calculated values most consistently. We recommend it as the most reliable patient specific QA system for MLC position error testing. This research is highlighted by the finding of up to 12.7% dose variation for H/N and esophagus cases for VMAT delivery, where the mere source of error was the stated clinically acceptability of 1 mm MLC position deviation of TG-142.

Membrane oxygenator heat exchanger failure detected by unique blood gas findings.

Failure of components integrated into the cardiopulmonary bypass circuit, although rare, can bring about catastrophic results. One of these components is the heat exchanger of the membrane oxygenator. In this compartment, unsterile water from the heater cooler device is separated from the sterile blood by stainless steel, aluminum, or by polyurethane. These areas are glued or welded to keep the two compartments separate, maintaining sterility of the blood. Although quality control testing is performed by the manufacturer at the factory level, transport presents the real possibility for damage. Because of this, each manufacturer has included in the instructions for use a testing procedure for testing the integrity of the heat exchanger component. Water is circulated through the heat exchanger before priming and a visible check is made of the oxygenator bundle to check for leaks. If none are apparent, then priming of the oxygenator is performed. In this particular case, this procedure was not useful in detecting communication between the water and blood chambers of the oxygenator.

Long-term stability of the Leksell Gamma Knife® Perfexion™ patient positioning system (PPS).

PURPOSE: To assess the long-term mechanical stability and accuracy of the patient positioning system (PPS) of the Leksell Gamma Knife(®) Perfexion™ (LGK PFX). METHODS: The mechanical stability of the PPS of the LGK PFX was evaluated using measurements obtained between September 2007 and June 2011. Three methods were employed to measure the deviation of the coincidence of the radiological focus point (RFP) and the PPS calibration center point (CCP). In the first method, the onsite diode test tool with single diode detector was used together with the 4 mm collimator on a daily basis. In the second method, a service diode test tool with three diode detectors was used biannually at the time of the routine preventive maintenance. The test performed with the service diode test tool measured the deviations for all three collimators 4, 8, and 16 mm and also for three different positions of the PPS. The third method employed the conventional film pin-prick method. This test was performed annually for the 4 mm collimator at the time of the routine annual QA. To estimate the effect of the patient weight on the performance of the PPS, the focus precision tests were also conducted with varying weights on the PPS using a set of lead bricks. RESULTS: The average deviations measured from the 641 daily focus precision tests were 0.1 ± 0.1, 0.0 ± 0.0, and 0.0 ± 0.0 mm, respectively, for the 4 mm collimator in the X (left/right of the patient), Y (anterior/posterior of the patient), and Z (superior/inferior of the patient) directions. The average of the total radial deviations as measured during ten semiannual measurements with the service diode test tool were 0.070 ± 0.029, 0.060 ± 0.022, and 0.103 ± 0.028 mm, respectively for the central, long, and short diodes for the 4 mm collimator. Similarly, the average total radial deviations measured during the semiannual measurements for the 4, 8, and 16 mm collimators and using the central diode were 0.070 ± 0.029, 0.097 ± 0.025, 0.159 ± 0.028 mm, respectively. The average values of the deviations as obtained from the five annual film pin-prick tests for the 4 mm collimator were 0.10 ± 0.06, 0.06 ± 0.09, and 0.03 ± 0.03 mm for the X, Y, Z stereotactic directions, respectively. Only a minor change was observed in the total radial deviations of the PPS as a function of the simulated patient weight up to 202 kg on the PPS. CONCLUSIONS: Excellent long-term mechanical stability and high accuracy was observed for the PPS of the LGK PFX. No PPS recalibration or any adjustment in the PPS was needed during the monitored period of time. Similarly, the weight on the PPS did not cause any significant disturbance in the performance of the PPS for up to 202 kg simulated patient weight.

Biomechanical evaluation of the primary stability of pedicle screws after augmentation with an innovative bone stabilizing system.

INTRODUCTION: In today's aging population, diminished bone quality often affects the outcome of surgical treatment. This occurs especially when surgical implants must be fixed to bone, as it occurs when lumbar fusion is performed with pedicle screws. Besides Polymethylmethacrylate (PMMA) injection, several techniques have been developed to augment pedicle screws. The aim of the current study was to evaluate the primary stability of an innovative system (IlluminOss™) for the augmentation of pedicle screws in an experimental cadaveric setup. IlluminOss™ is an innovative technology featuring cement with similar biochemical characteristics to aluminum-free glass-polyalkenoate cement (GPC). MATERIALS AND METHODS: IlluminOss™ was inserted transpedicularly via a balloon/catheter system in 40 human cadaveric lumbar vertebrae. For comparability, each vertebra was treated bilaterally with pedicle screws, augmented and non-augmented. The maximum failure load during pull out test was documented by a universal material testing machine. RESULTS: The results showed significantly higher failure loads for the augmented pedicle screws (Median 555.0 ± 261.0 N, Min. 220.0 N, Max. 1,500.0 N), compared to the native screws (Median 325.0 ± 312.1 N, Min. 29.0 N, Max. 1,400.0 N). CONCLUSIONS: Based on these data, we conclude the IlluminOss™ system can be used to augment primary screw stability regarding axial traction, compared to native screws. The IlluminOss™ monomer offers ease of control for use in biological tissues. In contrast to PMMA, no relevant heat is generated during the hardening process and there is no risk of embolism. Further studies are necessary to evaluate the usefulness of the IlluminOss™ system in the in vivo augmentation of pedicle screws in the future.

Effect of screw insertion torque on mechanical properties of four locking systems.

OBJECTIVE: To evaluate the effect of screw insertion torque on the mechanical properties of four 3.5 mm locking systems: New Generation Devices (NGD), Securos (PAX), Synthes (SYN), and Veterinary Orthopedic Implants (VOI). STUDY DESIGN: In vitro mechanical study. METHODS: Screws were inserted at 1.5 Nm, 2.5 Nm, and 3.5 Nm torques, using dedicated drill guides and a calibrated torque screwdriver. Locking mechanisms were tested under shear loading conditions using a custom-design probe. Tests were conducted under displacement control until failure. Load to failure and interface stiffness were compared between and within groups using a two-factor ANOVA (P < .05). Failure modes were described. RESULTS: The SYN group had significantly greater mechanical properties compared to all other groups at any given insertion torque. Insertion torque had a significant effect on the PAX group, increasing the load to failure by 126% when increasing the insertion torque from 1.5 Nm to 3.5 Nm. Insertion torque had no significant effect on the mechanical properties of the VOI group and limited effect on the NGD and SYN groups. Single failure mode, by screw head decoupling or screw shaft fracture, occurred in the SYN and VOI groups, respectively. In contrast, NGD and PAX systems failed through a combination of screw decoupling and/or bending. CONCLUSIONS: Regardless of insertion torque, the SYN locking mechanism showed the highest failure loads, interfacial stiffness as well as consistent failure mode. These findings highlight the dependability of this system. When using the PAX system an insertion torque of at least 2.5 Nm should be recommended.

Prolonged burst as a new method for cardioverter-defibrillator testing.

AIM: To find out whether it is possible to anaesthetize patients safely without analgesia and sedation, using burst pacing prolonged until the patient becomes unconscious. METHODS: One hundred and four patients undergoing implantation or reimplantation of a cardioverter-defibrillator were included. Patients randomized into Group B underwent prolonged burst pacing without analgesia and sedation. Patients in Group T underwent a T-wave shock under analgesia and sedation. Blood samples for measurement of serum neuron-specific enolase were taken before surgery and 6, 24, and 48 h after the procedure. RESULTS: From the 104 patients, 51 were randomly assigned to Group B and 53 to Group T. Four patients from Group B were switched to Group T (ventricular fibrillation not induced by burst pacing). The clinical characteristics of both groups were similar. The mean total time of cardiac arrest was significantly longer in Group B (23.0 ± 4.4 s, median 22.7) vs. Group T (10.3 ± 3.0 s, median 10.0), P < 0.0001 (Mann-Whitney U-test). The effectiveness of both induction methods was similar (92.1% in Group B and 100% in Group T). The mean neuron-specific enolase levels after 6, 24, and 48 h were similar in Groups B and T (13.1 ± 6.3 and 11.6 ± 5.8 mg/L, 14.5 ± 7.5 and 13.4 ± 6.0 mg/L, and 14.9 ± 5.9 and 12.2 ± 6.0 mg/L, respectively) as were these levels compared with baseline neuron-specificenolase levels (14.0 ± 5.9 and 13.4 ± 4.0 mg/L, respectively), P = NS for all. CONCLUSION: Despite a longer time of total cardiac arrest, prolonged burst pacing appears to be a safe and effective method for induction of ventricular fibrillation during cardioverter-defibrillator testing, which enables omission of analgesia and sedation or general anaesthesia.