Electrogram morphology discriminators in implantable cardioverter defibrillators: A comparative evaluation.

BACKGROUND: Morphology algorithms are currently recommended as a standalone discriminator in single-chamber implantable cardioverter defibrillators (ICDs). However, these proprietary algorithms differ in both design and nominal programming. OBJECTIVE: To compare three different algorithms with nominal versus advanced programming in their ability to discriminate between ventricular (VT) and supraventricular tachycardia (SVT). METHODS: In nine European centers, VT and SVTs were collected from Abbott, Boston Scientific, and Medtronic dual- and triple-chamber ICDs via their respective remote monitoring portals. Percentage morphology matches were recorded for selected episodes which were classified as VT or SVT by means of atrioventricular comparison. The sensitivity and related specificity of each manufacturer discriminator was determined at various values of template match percentage from receiving operating characteristics (ROC) curve analysis. RESULTS: A total of 534 episodes were retained for the analysis. In ROC analyses, Abbott Far Field MD (area under the curve [AUC]: 0.91; P < .001) and Boston Scientific RhythmID (AUC: 0.95; P < .001) show higher AUC than Medtronic Wavelet (AUC: 0.81; P < .001) when tested for their ability to discriminate VT from SVT. At nominal % match threshold all devices provided high sensitivity in VT identification, (91%, 100%, and 90%, respectively, for Abbott, Boston Scientific, and Medtronic) but contrasted specificities in SVT discrimination (85%, 41%, and 62%, respectively). Abbott and Medtronic's nominal thresholds were similar to the optimal thresholds. Optimization of the % match threshold improved the Boston Scientific specificity to 79% without compromising the sensitivity. CONCLUSION: Proprietary morphology discriminators show important differences in their ability to discriminate SVT. How much this impact the overall discrimination process remains to be investigated.

Loop Recorder Implantation on a Telemetry Ward.

The implantable loop recorder (ILR) is a valuable tool used in the evaluation of syncope, arrhythmia, and cryptogenic stroke. In the inpatient setting, ILRs are routinely implanted in the electrophysiology (EP) lab despite the low complication rate. The purpose of this study was to evaluate the safety, feasibility, and cost of implanting ILRs at the patient's bedside by both electrophysiologists and advanced practice providers (APPs). This was a single center, retrospective study of consecutive ILR implantations performed from February 2018 to May 2019. We examined 3 groups: implantations in the EP lab by electrophysiologists (EP Lab/MD), implantations at the bedside by electrophysiologists (Floor/MD), and implantations at the bedside by APPs (Floor/APP). Over 15 months, 152 patients underwent ILR implantation: 48 in the EP Lab/MD group, 57 in the Floor/MD group, and 47 in the Floor/APP group. The procedure duration was longer in the Floor/APP group (14.2 ± 5.9 minutes) compared with the EP Lab/MD and Floor/MD groups (6.8 ± 4.3 minutes, 9.1 ± 4.9 minutes, p <0.001). The overall complication rate was low (2.6%) with no differences between the groups (p = 0.83). The calculated costs per implant for the EP Lab/MD group, Floor/MD group, and Floor/APP group were $482.05, $162.82, and $73.08, respectively.

ReStore: A wireless peripheral nerve stimulation system.

BACKGROUND: The growing use of neuromodulation techniques to treat neurological disorders has motivated efforts to improve on the safety and reliability of implantable nerve stimulators. NEW METHOD: The present study describes the ReStore system, a miniature, implantable wireless nerve stimulator system that has no battery or leads and is constructed using commercial components and processes. The implant can be programmed wirelessly to deliver charge-balanced, biphasic current pulses of varying amplitudes, pulse widths, frequencies, and train durations. Here, we describe bench and in vivo testing to evaluate the operational performance and efficacy of nerve recruitment. Additionally, we also provide results from a large-animal chronic active stimulation study assessing the long-term biocompatibility of the device. RESULTS: The results show that the system can reliably deliver accurate stimulation pulses through a range of different loads. Tests of nerve recruitment demonstrate that the implant can effectively activate peripheral nerves, even after accelerated aging and post-chronic implantation. Biocompatibility and hermeticity tests provide an initial indication that the implant will be safe for use in humans. COMPARISON WITH EXISTING METHOD(S): Most commercially available nerve stimulators include a battery and wire leads which often require subsequent surgeries to address failures in these components. Though miniaturized battery-less stimulators have been prototyped in academic labs, they are often constructed using custom components and processes that hinder clinical translation. CONCLUSIONS: The results from testing the performance and safety of the ReStore system establish its potential to advance the field of peripheral neuromodulation.

Characteristics of ventricular intracardiac electrograms of ventricular tachycardias originating from the epicardia in patients with an implantable cardioverter defibrillator.

INTRODUCTION: While characteristic waveforms of 12-lead electrocardiograms have been reported to predict the epicardial origin of ventricular tachycardia (VT), it has not been fully examined whether ventricular intracardiac electrograms (VEGMs) recorded from the implantable cardioverter defibrillator (ICD) via telemetry can determine the origin of VT or not. The aim of this study was to investigate the VEGM characteristics of VT originating from the epicardia. METHOD AND RESULTS: Intracardiac VEGMs of the induced VTs, with detected sites of origin during the VT study, were recorded in 15 (23 VTs) of the 46 patients. The characteristics of the 23 VTs were evaluated using far-field and near-field VEGMs recorded via telemetry. Five of 23 VTs were found to be focused on the epicardial site (epi group) and 18 VTs were focused on the endocardium (endo group). VTs of the epi group had longer VEGM duration in far-field EGM than those of the endo group (epi group: 240 ± 49 ms vs endo group: 153 ± 45 ms; P = 0.002) and the duration from the onset to the peak of VEGM was also longer than that of the endo group (epi group: 153 ± 53 ms vs endo group: 63 ± 28 ms; P < 0.001). There was no difference in the V wave duration in tip-ring EGM between both groups (epi group: 122 ± 52 ms vs endo group: 98 ± 6 ms; P = 0.377). CONCLUSION: Evaluation of intracardiac VEGM before VT ablation may be helpful to predict the epicardial origin of VT in patients with an ICD.

Effectiveness of Medtronic CareLink Express System in identifying patients with high-energy electrotherapy devices requiring clinically significant intervention.

BACKGROUND: The number of patients with implantable cardioverter-defibrillator (ICD) or cardiac resynchronization therapy and defibrillator (CRT-D) is growing. This results in high workloads for centers performing standard controls (SC) of these systems. Medtronic CareLink Express® (MCLE) is a solution enabling remote controls (RC) of implantable devices. In cases of detecting arrhythmias or device malfunctioning, it automatically generates alarms transmitted to the controlling physician. The objective of the study was to evaluate the effectiveness of alarms generated by MCLE in identification of patients that require clinically significant intervention during SC. METHODS: A total of 119 patients (age 64 ± 14, 17 women) implanted with ICD/CRT-D were included in the trial. Device reprogramming or pharmacological treatment modifications during SC were as-sessed as significant if they were required for optimal clinical management of the patient (effectiveness of antiarrhythmic and resynchronization therapy, also patient safety). Analysis of generated alarms was then performed to assess the effectiveness (sensitivity and specificity) of MCLE in identifying patients that require changes in therapy. RESULTS: Data from 129 transmissions and 129 subsequent SCs were analyzed. 179 alarms were recorded during 96 (74%) transmissions. A total of 333 program changes of implanted devices took place during 107 (83%) SCs. Device reprogramming was considered clinically significant in 27 cases Additionaly, 13 pharmacological treatment modifications were performed. Sensitivity and specificity of alarms generated by MCLE with regards to identification of patients requiring clinically significant intervention was 87% and 31%, respectively. Finally, a statistically significant difference was observed in the number of clinically significant interventions among patients with and without MCLE alarms (33 [86.8%] vs. 5 [13.2%], p = 0.037). CONCLUSIONS: Medtronic CareLink Express® is an RC system enabling high-sensitivity supervision of patients with cardiac.

Automatic remote monitoring utilizing daily transmissions: transmission reliability and implantable cardioverter defibrillator battery longevity in the TRUST trial.

Aims: Benefits of automatic remote home monitoring (HM) among implantable cardioverter defibrillator (ICD) patients may require high transmission frequency. However, transmission reliability and effects on battery longevity remain uncertain. We hypothesized that HM would have high transmission success permitting punctual guideline based follow-up, and improve battery longevity. This was tested in the prospective randomized TRUST trial. Methods and results: Implantable cardioverter defibrillator patients were randomized post-implant 2:1 to HM (n = 908) (transmit daily) or to Conventional in-person monitoring [conventional management (CM), n = 431 (HM disabled)]. In both groups, five evaluations were scheduled every 3 months for 15 months. Home Monitoring technology performance was assessed by transmissions received vs. total possible, and number of scheduled HM checks failing because of missed transmissions. Battery longevity was compared in HM vs. CM at 15 months, and again in HM 3 years post-implant using continuously transmitted data. Transmission success per patient was 91% (median follow-up of 434 days). Overall, daily HM transmissions were received in 315 795 of a potential 363 450 days (87%). Only 55/3759 (1.46%) of unsuccessful scheduled evaluations in HM were attributed to transmission loss. Shock frequency and pacing percentage were similar in HM vs. CM. Fifteen month battery longevity was 12% greater in HM (93.2 ± 8.8% vs. 83.5 ± 6.0% CM, P < 0.001). In extended follow-up of HM patients, estimated battery longevity was 50.9 ± 9.1% (median 52%) at 36 months. Conclusion: Automatic remote HM demonstrated robust transmission reliability. Daily transmission load may be sustained without reducing battery longevity. Home Monitoring conserves battery longevity and tracks long term device performance. Clinical trial registration: ClinicalTrials.gov; NCT00336284.

A devices' game of thrones: cardiac resynchronization therapy vs. pacemaker.

AIMS: Oversensing can interfere with biventricular pacing. Cardiac Resynchronization Therapy (CRT) output inhibition due to automatic brady mode change from a sensing to a pacing mode of a previously implanted pacemaker as it reached battery capacity depleted indicator has not been previously published in the medical literature. METHODS AND RESULTS: We report the first case of CRT output inhibition in a pacemaker dependent patient due to electrical stimuli from a previously right-sided implanted pacemaker, after unaware reversion of OVO mode (O = no chambers paced; V = ventricular sensing; O = no response to sensing) to backup VVI (V = ventricular pacing; V = ventricular sensing; I = inhibitory response to sensing) when it reached the elective replacement interval. CONCLUSION: This paper emphasizes the importance of knowing the distinct pacemaker brady mode behaviours after battery capacity depleted indicator has been reached, according to the pacemakers' manufacturer, including the possibility of automatic brady mode change from sensing to pacing mode. It also highlights the potential for severe bradycardia or asystole of this automatic brady mode change from a previously implanted pacemaker in pacemaker dependent patients submitted to CRT upgrade.

GLIMPSE: Google Glass interface for sensory feedback in myoelectric hand prostheses.

OBJECTIVE: Providing sensory feedback to the user of the prosthesis is an important challenge. The common approach is to use tactile stimulation, which is easy to implement but requires training and has limited information bandwidth. In this study, we propose an alternative approach based on augmented reality. APPROACH: We have developed the GLIMPSE, a Google Glass application which connects to the prosthesis via a Bluetooth interface and renders the prosthesis states (EMG signals, aperture, force and contact) using augmented reality (see-through display) and sound (bone conduction transducer). The interface was tested in healthy subjects that used the prosthesis with (FB group) and without (NFB group) feedback during a modified clothespins test that allowed us to vary the difficulty of the task. The outcome measures were the number of unsuccessful trials, the time to accomplish the task, and the subjective ratings of the relevance of the feedback. MAIN RESULTS: There was no difference in performance between FB and NFB groups in the case of a simple task (basic, same-color clothespins test), but the feedback significantly improved the performance in a more complex task (pins of different resistances). Importantly, the GLIMPSE feedback did not increase the time to accomplish the task. Therefore, the supplemental feedback might be useful in the tasks which are more demanding, and thereby less likely to benefit from learning and feedforward control. The subjects integrated the supplemental feedback with the intrinsic sources (vision and muscle proprioception), developing their own idiosyncratic strategies to accomplish the task. SIGNIFICANCE: The present study demonstrates a novel self-contained, ready-to-deploy, wearable feedback interface. The interface was successfully tested and was proven to be feasible and functionally beneficial. The GLIMPSE can be used as a practical solution but also as a general and flexible instrument to investigate closed-loop prosthesis control.

Mapping-guided characterization of mechanical and electrical activation patterns in patients with normal systolic function using a sensor-based tracking technology.

AIMS: In times of evolving cardiac resynchronization therapy, intra-procedural characterization of left ventricular (LV) mechanical activation patterns is desired but technically challenging with currently available technologies. In patients with normal systolic function, we evaluated the feasibility of characterizing LV wall motion using a novel sensor-based, real-time tracking technology. METHODS AND RESULTS: Ten patients underwent simultaneous motion and electrical mapping of the LV endocardium during sinus rhythm using electroanatomical mapping and navigational systems (EnSite™ NavX™ and MediGuide™, SJM). Epicardial motion data were also collected simultaneously at corresponding locations from accessible coronary sinus branches. Displacements at each mapping point and times of electrical and mechanical activation were combined over each of the six standard LV wall segments. Mechanical activation timing was compared with that from electrical activation and preoperative 2D speckle tracking echocardiography (echo). MediGuide-based displacement data were further analysed to estimate LV chamber volumes that were compared with echo and magnetic resonance imaging (MRI). The lateral and septal walls exhibited the largest (12.5 [11.6-15.0] mm) and smallest (10.2 [9.0-11.3] mm) displacement, respectively. Radial displacement was significantly larger endocardially than epicardially (endo: 6.7 [5.0-9.1] mm; epi: 3.8 [2.4-5.6] mm), while longitudinal displacement was significantly larger epicardially (endo: 8.0 [5.0-10.6] mm; epi: 10.3 [7.4-13.8] mm). Most often, the anteroseptal/anterior and lateral walls showed the earliest and latest mechanical activations, respectively. 9/10 patients had concordant or adjacent wall segments of latest mechanical and electrical activation, and 6/10 patients had concordant or adjacent wall segments of latest mechanical activation as measured by MediGuide and echo. MediGuide's LV chamber volumes were significantly correlated with MRI (R2= 0.73, P < 0.01) and echo (R2= 0.75, P < 0.001). CONCLUSION: The feasibility of mapping-guided intra-procedural characterization of LV wall motion was established. CLINICAL TRIAL REGISTRATION: http://www.clinicaltrials.gov; Unique identifier: CT01629160.

Silicon-on-insulator-based complementary metal oxide semiconductor integrated optoelectronic platform for biomedical applications.

Microscale optical devices enabled by wireless power harvesting and telemetry facilitate manipulation and testing of localized biological environments (e.g., neural recording and stimulation, targeted delivery to cancer cells). Design of integrated microsystems utilizing optical power harvesting and telemetry will enable complex in vivo applications like actuating a single nerve, without the difficult requirement of extreme optical focusing or use of nanoparticles. Silicon-on-insulator (SOI)-based platforms provide a very powerful architecture for such miniaturized platforms as these can be used to fabricate both optoelectronic and microelectronic devices on the same substrate. Near-infrared biomedical optics can be effectively utilized for optical power harvesting to generate optimal results compared with other methods (e.g., RF and acoustic) at submillimeter size scales intended for such designs. We present design and integration techniques of optical power harvesting structures with complementary metal oxide semiconductor platforms using SOI technologies along with monolithically integrated electronics. Such platforms can become the basis of optoelectronic biomedical systems including implants and lab-on-chip systems.

Implementation and Analysis of ISM 2.4 GHz Wireless Sensor Network Systems in Judo Training Venues.

In this work, the performance of ISM 2.4 GHz Wireless Sensor Networks (WSNs) deployed in judo training venues is analyzed. Judo is a very popular martial art, which is practiced by thousands of people not only at the competition level, but also as part of physical education programs at different school levels. There is a great variety of judo training venues, and each one has specific morphological aspects, making them unique scenarios in terms of radio propagation due to the presence of furniture, columns, equipment and the presence of human beings, which is a major issue as the person density within this kind of scenarios could be high. Another key aspect is the electromagnetic interference created by other wireless systems, such as WiFi or other WSNs, which make the radio planning a complex task in terms of coexistence. In order to analyze the impact of these features on the radio propagation and the performance of WSNs, an in-house developed 3D ray launching algorithm has been used. The obtained simulation results have been validated with a measurement campaign carried out in the sport facilities of the Public University of Navarre. The analysis is completed with the inclusion of an application designed to monitor biological constants of judokas, aimed to improve their training procedures. The application, that allows the simultaneous monitoring of multiple judokas (collective workouts) minimizing the efforts of the coach and medical supervisor, is based on commercial off-the-shelf products. The presented assessment of the presence of interfering wireless systems and the presence of human beings within judo training venues shows that an in-depth radio planning is required as these issues can have a great impact in the overall performance of a ISM 2.4 GHz WSN, affecting negatively the potential applications supported by wireless channel.

Digital monitoring and care: Virtual medicine.

Remote digital health monitoring technologies can be synergistically organized to create a virtual medical system providing more continuous care centered on the patient rather than the bricks and mortar medical complex. Utilization of the digitalized patient health monitoring can facilitate diagnosis, treatment plans, physician-patient interaction, and accelerate the progress of medical research, education, and training. The field of cardiac electrophysiology has been an early adopter of this shift in care and serves as a paradigm applicable to all areas of medicine. The overall impact of this remote virtual care model on the quality of medical care and patient experience requires greater study, as well as vigilance as to the differences between technology and care in order to preserve the intangible and immeasurable factors that bring humanity to the art and science of medicine.

Health and training monitoring system based on wearable sensors.

ITEA2 project CareWare approach efficiently perform wearable sensor data processing and data fusion in order to visualize the holistic view of user's health and training status personalized, intuitively and trustworthy way and give feedback for user about individualized intensity and time of exercising control.

ECG telemetry in conscious guinea pigs.

INTRODUCTION: During preclinical drug development, monitoring of the electrocardiogram (ECG) is an important part of cardiac safety assessment. To detect potential pro-arrhythmic liabilities of a drug candidate and for internal decision-making during early stage drug development an in vivo model in small animals with translatability to human cardiac function is required. METHODS: Over the last years, modifications/improvements regarding animal housing, ECG electrode placement, and data evaluation have been introduced into an established model for ECG recordings using telemetry in conscious, freely moving guinea pigs. Pharmacological validation using selected reference compounds affecting different mechanisms relevant for cardiac electrophysiology (quinidine, flecainide, atenolol, dl-sotalol, dofetilide, nifedipine, moxifloxacin) was conducted and findings were compared with results obtained in telemetered Beagle dogs. RESULTS AND CONCLUSION: Under standardized conditions, reliable ECG data with low variability allowing largely automated evaluation were obtained from the telemetered guinea pig model. The model is sensitive to compounds blocking cardiac sodium channels, hERG K(+) channels and calcium channels, and appears to be even more sensitive to ß-blockers as observed in dogs at rest. QT interval correction according to Bazett and Sarma appears to be appropriate methods in conscious guinea pigs. Overall, the telemetered guinea pig is a suitable model for the conduct of early stage preclinical ECG assessment.

Can we rely on machines? Device-detected atrial high rates correspond well with atrial arrhythmias in cardiac resynchronization recipients.

AIMS: The aim of the study was to verify in what proportion of patients, device-detected atrial high rate (AHR) episodes are indeed atrial arrhythmias (AAs). We investigated also the reasons for inappropriate arrhythmia classification and assessed if patients with misdiagnosed arrhythmias have distinct characteristics that would help to identify them. METHODS AND RESULTS: The study population consisted of 304 consecutive patients implanted with cardiac resynchronization therapy defibrillators (CRT-Ds) and subsequently monitored via remote monitoring for a median follow-up (FU) of 30.5 months. Intracardiac electrograms of every recorded AHR episode were assessed and classified (AA vs. no AA) by two experienced cardiologists. During FU, 14 386 episodes of AHR were recorded and classified in 176 (57.9%) patients. In 89.2% of them, these episodes were true AA (94% atrial fibrillation, 62% de novo). The reasons for AHR misdiagnosis were atrial far-field signals (89.5%) and noise (10.5%). The mean per cent of day spent in AHR (54.9 vs. 5.86%; P < 0.001) and the occurrence of periods with low CRT pacing (82.8 vs. 55%; P = 0.003) were significantly higher in AA subjects than in those with misdiagnosed AHR. Episode duration of properly detected AHRs was longer than that of misdiagnosed AHRs. Higher per cent of time spent in AHR was an independent marker of appropriate arrhythmia detection [adjusted hazard ratio (HR) 1.04; P = 0.023]. CONCLUSION: Nearly two-thirds of CRT-D patients had AHR episodes within 2.5 years after implantation. Almost 90% of AHRs were indeed AA. Misdetections were caused by far-field sensing or noise. A two-step diagnostic algorithm (>9% of time spent in AHRs and episode duration >36 s) allowed for proper detection of AA with a high hit-rate and specificity.

Flexible and waterproof micro-sensors to uncover zebrafish circadian rhythms: The next generation of cardiac monitoring for drug screening.

Flexible electronics are the next generation of sensors for mobile health and implantation. Zebrafish (Danio rerio) is an emergent strategy for pre-clinical drug development and toxicity testing. To address the confounding effects from sedation of fish and removal from the aquatic habitat for micro-electrocardiogram (µECG) measurements, we developed waterproof and wearable sensors to uncover the circadian variation in heart rate (HR) and heart rate variability (HRV) (Massin et al., 2000). The parylene-C based ECG sensor consisted of an ultra-soft silicone integrated jacket designed to wrap around the fish during swimming. The Young's modulus of this silicone jacket matched with the fish surface, and an extended parylene cable connected the underwater chest electrodes with the out-of water electronics. In addition, embedded micro-glass spheres in the silicone effectively reduced the effective density of the jacket to ~1 g cm(-3). These innovations enabled physiological ECG telemetry in the fish's natural habitat without the need for sedation. Furthermore, a set of non-linear signal processing techniques filtered out the breathing and electromagnetic artifacts from the recorded signals. We observed a reduction in mean HR and an increase in HRV over 24h at 10 dpa, accompanied by QT prolongation as well as diurnal variations, followed by normalization in mean HR and QT intervals at 26 days post ventricular amputation (dpa). We revealed Amiodarone-mediated QTc prolongation, HR reduction and HRV increase otherwise masked by sedation. The novel features of the flexible silicon jacket for µECG telemetry unraveled the biological clock and normalization of QT intervals at 26 dpa, providing the first evidence of new physiological phenomena during cardiac injury and repair as well as cardiac drug-mediated aberrant rhythms. Thus, the light weight and waterproof design holds promise to advance the next generation of mobile health and drug discovery.

An evaluation of wellness assessment visualizations for older adults.

BACKGROUND: Smart home technologies provide a valuable resource to unobtrusively monitor health and wellness within an older adult population. However, the breadth and density of data available along with aging associated decreases in working memory, prospective memory, spatial cognition, and processing speed can make it challenging to comprehend for older adults. We developed visualizations of smart home health data integrated into a framework of wellness. We evaluated the visualizations through focus groups with older adults and identified recommendations to guide the future development of visualizations. MATERIALS AND METHODS: We conducted four focus groups with older adult participants (n=31) at an independent retirement community. Participants were presented with three different visualizations from a wellness pilot study. A qualitative descriptive analysis was conducted to identify thematic content. RESULTS: We identified three themes related to processing and application of visualizations: (1) values of visualizations for wellness assessment, (2) cognitive processing approaches to visualizations, and (3) integration of health data for visualization. In addition, the focus groups highlighted key design considerations of visualizations important towards supporting decision-making and evaluation assessments within integrated health displays. CONCLUSIONS: Participants found inherent value in having visualizations available to proactively engage with their healthcare provider. Integrating the visualizations into a wellness framework helped reduce the complexity of raw smart home data. There has been limited work on health visualizations from a consumer perspective, in particular for an older adult population. Creating appropriately designed visualizations is valuable towards promoting consumer involvement within the shared decision-making process of care.

Differences in the yield of the implantable loop recorder between secondary and tertiary centers.

BACKGROUND: The implantable loop recorder (ILR) is a useful tool for diagnosis of syncope or palpitations. Its easy use and safety have extended its use to secondary hospitals (those without an Electrophysiology Lab). The aim of the study was to compare results between secondary and tertiary hospitals. METHODS: National prospective and multicenter registry of patients with an ILR inserted for clinical reasons. Data were collected in an online database. The follow-up ended when the first diagnostic clinical event occurred, or 1 year after implantation. Data were analyzed according to the center of reference; hospitals with Electrophysiology Lab were considered Tertiary Hospitals, while those hospitals without a lab were considered Secondary Hospitals. RESULTS: Seven hundred and forty-three patients (413 [55.6%] men; 65 ± 16 year-old): 655 (88.2%) from Tertiary Centers (TC) and 88 (11.8%) from Secondary Centers (SC). No differences in clinical characteristics between both groups were found. The electrophysiologic study and the tilt table test were conducted more frequently in Tertiary Centers. Follow-up was conducted for 680 (91.5%) patients: 91% in TC and 94% in SC. There was a higher rate of final diagnosis among SC patients (55.4% vs. 30.8%; p < 0.001). Tertiary Hospital patients showed a trend towards a higher rate of neurally mediated events (20% vs. 4%), while bradyarrhythmias were more frequent in SC (74% vs. 60%; p = 0.055). The rate of deaths and adverse events was similar in both populations. CONCLUSIONS: Patients with an ILR in SC and TC have differences in terms of the use of complementary tests, but not in clinical characteristics. There was a higher rate of diagnosis in Secondary Hospital patients.