Role of the lead structure in MRI-induced heating: In vitro measurements on 30 commercial pacemaker/defibrillator leads.

MRI-induced heating on endocardial leads is a serious concern for the safety of patients with implantable pacemakers or cardioverter-defibrillator. The lead heating depends on many factors and its amount is largely variable. In this study, we investigated the role of those structural properties of the lead that are reported on the accompanying documents of the device: (1) fixation modality (active vs. passive); (2) number of electrodes (unipolar vs. bipolar); (3) length; (4) tip surface; and (5) tip and ring resistance. In vitro temperature and specific absorption rate measurements on 30 leads (27 pacemakers, three implantable cardioverter-defibrillator leads) exposed to the radiofrequency field typical of a 1.5 T MRI scanner are presented. The data show that each lead has its own attitude to radiofrequency-induced heating and that the information that is available in the accompanying documents of the pacemaker is not sufficient to explain such attitude. Even if combined with that of the implant geometry, this information is still not sufficient to estimate the amount of heating due to the exposure to the radiofrequency field during MRI examination.

Daily distribution of atrial arrhythmic episodes in sick sinus syndrome patients: implications for atrial arrhythmia monitoring.

AIMS: Disorders such as paroxysmal atrial fibrillation (AF) and atrial tachyarrhythmias (AT) are difficult to investigate because of their intermittent, and sometimes asymptomatic, nature. The aim of this study was to investigate the daily temporal distribution of AT/AF episodes--onset and occurrence--by analysing data from 250 pacemaker-implanted, brady-tachy syndrome patients who have been enrolled in the Burden II Study. METHODS AND RESULTS: Data were analysed accounting for the mode switch list which includes date, time, and duration of each mode switch episode. Chi-squared tests for goodness of fit were used to determine whether AT/AF episode were uniformly distributed. The population analysed in the present study suggests the occurrence of a circadian rhythm of paroxysmal AF episodes, similar to that described for other cardiovascular diseases, with clustering of events in the morning from 08:00 and (to a lesser degree) in the afternoon (03:00 to 18:00). The relative risk of AT/AF onset is 13% higher during daytime, 40% lower at night (P < 0.000001). CONCLUSION: The use of monitoring devices based on daily electrocardiogram (ECG) recording could be optimized with these data, thus increasing the probability to detect AT/AF episodes.

International Winter Wheat nurseries data: Facultative and Winter Wheat Observation Nurseries and International Winter Wheat yield trials for semi-arid and irrigated conditions.

This data paper describes the content of 16 datasets collected under the International Winter Wheat Improvement Program (IWWIP), an alliance between Turkey-CIMMYT-ICARDA (TCI), during the 2015-2016, 2016-2017, 2017-2018 and 2018-2019 seasons. Data was collected from the Facultative and Winter Wheat Observation Nursery (FAWWON) and the International Winter Wheat Yield Trials (IWWYT) conducted under semi-arid and irrigated conditions across different countries. Data on all nurseries was collected during the growing season by IWWIP's team and cooperators in their local environments. It was compiled at the end of the wheat season by IWWIP's team. Multi-locational data can be used to select advanced lines that fit to collaborators' growing environment. The selected germplasm can either be used as a parent in their breeding programs or be released as a variety in their country.

Experimental on-farm trials data of faba bean and wheat intercropping field validation in Lebanon and Morocco.

This data paper describes the content of four datasets collected by the International Center for Agricultural Research in the Dry Areas (ICARDA) as a partner in the project "Designing InnoVative plant teams for Ecosystem Resilience and agricultural Sustainability (DIVERSify)" with the objective of assessing the feasibility of faba bean-wheat mixture in Mediterranean environments under diverse rainfed conditions. Data was collected during the trials conducted in Kfardan-Lebanon during 2017/2018 where 40 faba bean varieties were evaluated as sole and as mixture with 2 wheat cultivars 'Margherita' and 'Miki' and during 2018/2019 where 40 faba bean varieties and one durum wheat cultivar 'Margherita' were evaluated under low rainfall environments. Trials were also conducted in Tal Amara-Lebanon during 2019/2020 where 20 faba bean lines and one durum wheat cultivar 'Margherita' were evaluated under high rainfall environments and in Marchouch-Morocco during 2019/2020 where 7 faba bean lines with 3 cultivars and one durum wheat cultivar 'Margherita' were evaluated under extremely low rainfall environments. A detailed list of the different biological traits collected for wheat and faba bean is found in the specification table in this article. The Kfardan 2018/ 2019, Tal Amara and Marchouch data is related to the conference paper "Performance of faba bean-wheat mixture under diverse Mediterranean environments" [1].

Data on how tree planting and management practices influence tree seedling survival in Kenya and Ethiopia.

Understanding which trees farmers prefer, what determines their survival and enhancing farmer knowledge of tree management is key to increasing tree cover in agricultural landscapes. This article presents data on tree seedling survival under different tree planting and management practices in Kenya and Ethiopia. Data were collected from 1600 households across three Counties in Kenya and 173 households across four Woredas in Ethiopia, using a structured questionnaire which was administered through the Open Data Kit. Data on seedling survival were collected at least six months after tree seedlings were planted. To understand how planting and management practices influence tree planting across the different socioeconomic and biophysical contexts, both household level and individual tree level data were collected. Household level data included socio-economic and biophysical characteristics of the households while tree specific data included when the tree seedling was planted, where it was planted, the management practices employed and whether surviving. The datasets described in this article help understand which options confer the best chance survival for the planted seedlings and in which socio-economic and biophysical contexts they are most successful.

Autonomic function during closed loop stimulation and fixed rate pacing: heart rate variability analysis from 24-hour Holter recordings.

AIM: Aim of this retrospective study was to analyze the effect of closed-loop stimulation (CLS) and DDD pacing mode on autonomic balance, and to evaluate heart rate variability (HRV) during CLS stimulation. METHODS AND MATERIALS: Autonomic balance was estimated by a 24-hour HRV analysis of paced and spontaneous beats in patients implanted with a dual-chamber pacemaker (Inos(2+) CLS-Biotronik GmbH, Berlin, Germany) and randomly assigned to CLS or DDD pacing mode. Patients underwent two 24-hour electrocardiogram Holter recordings at the end of each 3-month pacing mode period. Each Holter recording was automatically scanned to extract sequences of consecutive beats of the same type [atrial paced (Ap)-sequence and atrial spontaneous (As)-sequence], lasting at least 130 beats. RESULTS: Eight hundred and ten sequences were extracted from 15 patients, and the following spectral parameters were evaluated during both CLS and DDD mode: the total power (variance), the absolute and percentage (relative to the total power) powers of the low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.4 Hz) components, as well as the LF/HF power ratio. DISCUSSION: The two main findings of this study were: in all the patients, CLS seems to mimic short-term physiological HRV, although the variability (total power) was lower than that relative to the spontaneous beats; the HRV of the spontaneous beats had an higher LF/HF when the pacemaker was programmed as DDD respect to CLS, consistent with a shift toward sympathetic predominance.

Time-domain and morphological analysis of the P wave. Part II: effects of atrial pacing on P-wave features.

BACKGROUND: The aim of this study was to compare time-domain and morphological descriptors of paced and spontaneous P wave in patients prone to atrial fibrillation (AF). METHODS: Nineteen patients (nine women, aged 72 +/- 10 years) affected by paroxysmal AF and implanted with dual-chamber pacemakers (PM) were studied. Two 5-minute recordings were performed during spontaneous and paced rhythm. Electrocardiogram (ECG) signals were acquired using a 32-lead mapping system. Patients were grouped into two classes: no previous AF and previous AF groups, according to the number of AF episodes in the 6 months before the analysis. RESULTS AND CONCLUSION: During atrial pacing P wave appeared prolonged and morphologically more complex with respect to sinus rhythm. We also found that in patients at lower risk for AF, the atrial pacing changes the atrial activation to a greater extent than in patients at higher risk for AF. Finally, all time-domain and morphological descriptors of the P wave except one succeed in discriminating "no previous AF" and "previous AF" patients in spontaneous rhythm, while no significant differences have been observed during pacing for any parameters.

Time-domain and morphological analysis of the P-wave. Part I: Technical aspects for automatic quantification of P-wave features.

INTRODUCTION: Time-domain and morphological analysis of P-wave from surface electrocardiogram has been extensively used to identify patients prone to atrial arrhythmias, especially atrial fibrillation (AF). However, since no standard procedure exists for P-wave preprocessing, standardization of cut-off values for P-wave duration and morphological features is difficult. This study is a methodological investigation of P-wave preprocessing procedures for automatic time-domain and morphological analysis. METHODS: We compared, on simulated and real data, the P-wave template obtained applying three alignment algorithms with that obtained without alignment, in terms of template error, shift error, P-wave duration, and morphological parameters. We also proposed automatic algorithms for estimation of P-wave duration. RESULTS: We found that alignment is necessary for a reliable extraction of P-wave template by the averaging procedure, in order to perform time-domain and morphological analysis. On simulated and real data, the error on P-wave duration can be as high as 30 ms on a template obtained without alignment; if alignment procedure is performed, the error on P-wave duration is negligible. Analogously, morphological features are correctly estimated only on a P-wave template obtained with P-waves alignment. We also found that the proposed algorithm for the automatic estimation of the P-wave duration gave reliable results.

Complexity of MRI induced heating on metallic leads: experimental measurements of 374 configurations.

BACKGROUND: MRI induced heating on PM leads is a very complex issue. The widely varying results described in literature suggest that there are many factors that influence the degree of heating and that not always are adequately addressed by existing testing methods. METHODS: We present a wide database of experimental measurements of the heating of metallic wires and PM leads in a 1.5 T RF coil. The aim of these measurements is to systematically quantify the contribution of some potential factors involved in the MRI induced heating: the length and the geometric structure of the lead; the implant location within the body and the lead path; the shape of the phantom used to simulate the human trunk and its relative position inside the RF coil. RESULTS: We found that the several factors are the primary influence on heating at the tip. Closer locations of the leads to the edge of the phantom and to the edge of the coil produce maximum heating. The lead length is the other crucial factor, whereas the implant area does not seem to have a major role in the induced temperature increase. Also the lead structure and the geometry of the phantom revealed to be elements that can significantly modify the amount of heating. CONCLUSION: Our findings highlight the factors that have significant effects on MRI induced heating of implanted wires and leads. These factors must be taken into account by those who plan to study or model MRI heating of implants. Also our data should help those who wish to develop guidelines for defining safe medical implants for MRI patients. In addition, our database of the entire set of measurements can help those who wish to validate their numerical models of implants that may be exposed to MRI systems.

Electromagnetic immunity of medical devices: the European regulatory framework.

In this paper, the international standards and the European Regulation on medical devices are discussed, with particular attention to the collateral standards and the particular standards concerning the electromagnetic compatibility and immunity of medical devices. In addition, recommended guidelines to be used by health care organizations to assess the immunity of medical devices to radiated electromagnetic fields from portable radio frequency transmitters are indicated and discussed. As far as electromagnetic immunity of active implantable devices are concerned, the difference between United States and European Union (EU) regulatory frameworks is presented (standard ANSI/AAMI PC69:2000 for US and EN45502-1 framework in EU). Finally, some considerations on how to address the risk assessment of workers with implanted devices are discussed.

Electromagnetic immunity of infusion pumps to GSM mobile phones: a systematic review.

Electromagnetic interference with life-sustaining medical care devices has been reported by various groups. Previous studies have demonstrated that volumetric and syringe pumps are susceptible to false alarm buzzing and blocking, when exposed to various electromagnetic sources. The risk of electromagnetic interference depends on several factors such as the phone-emitted power, distance and carrier frequency, phone model and antenna type. The main recommendations and the relevant harmonized standard are also reported and discussed. >From the data available in literature emerges that, for distances lower than 1 m there is a non negligible risk of electromagnetic interferences, although significant differences exists in the reported minimum distances. Interference effects clinically relevant for the patients are rare. No permanent damage to the pumps has been ever reported, although in several cases intervention of personnel is required to resume normal operation.

Interference between mobile phones and pacemakers: a look inside.

In this study we analyzed the problem of electromagnetic interference (EMI) between mobile telephones and cardiac pacemakers (PM), by looking at the mechanisms by which the radiated radio frequency (RF) GSM signal may affect the pacemaker function. From a literature review on this topic, we noticed that older pacemakers had a higher rate of being affected by mobile phones when compared to newer ones. This is probably due to the fact that new generation of PM are more protected against electromagnetic field, being equipped with RF feedthrough filters incorporated to the internal PM circuitry. In some experiments conducted by our group, we found that modulated RF signals are somehow demodulated by the PM internal non-linear circuit elements, if no feedthrough assembly is incorporated inside the PM. Such demodulation phenomenon poses a critical problem because digital cellular phones use extremely low-frequency modulation (as low as 2 Hz), that can be mistaken for normal heartbeat. The feedthrough assembly seems instead to prevents the RF signals from accessing the PM enclosure, thus attenuating EMI signals over a broad range of frequencies.

Magnetic-resonance-induced heating of implantable leads.

In this study a methodological approach for measuring temperature and local absorption rate (SAR) on thin metallic structures, such as pacemaker (PM) leads, is provided. First preliminary experiments were performed to evaluate the error in temperature and SAR measurements made by fluoroptic temperature probes when the temperature probe is in different contact configuration with the PM lead tip. Our results show how the position of temperature probes affects the temperature and SAR value measured at the lead tip. The transversal contact between the thermal sensor and the lead tip is the configuration which leads to the highest values for temperature and SAR. In the second part of this paper we describe two physical models of a human trunk and an experimental set-up to investigate the influence of the implant geometry and of the lead path on the heating and the local SAR deposition. Experiments reveled that the implant location and configuration are crucial elements for the heat generation at the lead tip.

Electromagnetic interference with infusion pumps from GSM mobile phones.

Electromagnetic interference with critical medical care devices has been reported by various groups. Previous studies have demonstrated that volumetric and syringe pumps are susceptible to false alarm buzzing and blocking when exposed to various electromagnetic sources. The risk of electromagnetic interference depends on several factors such as the phone-emitted power, distance, and carrier frequency. The aim of this study was to assess the risk of GSM phone-induced electromagnetic interference with volumetric and syringe pumps, at various distances and emitted powers. Malfunctions were observed in 6 out of 8 volumetric pumps and in 1 out of 4 syringe pumps exposed to mobile phones at their maximum output, at distances up to 30 cm. The maximum power that did not induce any malfunction at zero distance was 50 mW at 900 MHz and 2.5 mW at 1,800 MHz. In state-of-the-art pumps, the presence of moderate-good base station coverage would significantly reduce the risk of electromagnetic interference.

Cardiac resynchronization by pacing: an electrical treatment of heart failure.

Various modalities of cardiac pacing have been proposed in the past to improve hemodynamics, either directly or indirectly. Some of these are conventional ways of cardiac stimulation, others such as biventricular or left ventricular pacing, represent dedicated pacing techniques. Left ventricular and biventricular pacing are successfully applied in those patients with congestive heart failure who have conduction disturbances (i.e. left bundle branch block) as they correct the ensuing intra- and interventricular dyssynchrony. This is the reason why these pacing modalities are described as cardiac resynchronization therapy. According to the results of a series of studies, the cardiac resynchronization therapy seems to have a favourable clinical impact in terms of quality of life, morbidity and hospitalization rate. On-going and future studies should assess the impact of resynchronization therapy on overall mortality and its cost-effectiveness profile in specific subgroups of patients. Other open issues regard (i) the convenience of using biventricular pacing as a pacing-alone therapy or in combination with ventricular defibrillation capability, especially for potential candidates to heart transplantation, and (ii) the ways to identify properly the responders to resynchronization therapy.

The linear ablation of atrial fibrillation in the right atrium: can the isthmus ablation improve its efficacy?

OBJECTIVES: The aims of this study were to compare the efficacy of a 2- versus a 3 RF lesions ablation procedure in the RA in patients with paroxysmal AF, and to map right atrial activation during AF. BACKGROUND: RF catheter-mediated ablation lines mimicking the Maze operation have been proposed as a novel curative approach for AF. The relationship between this type of ablation and right atrial mapping has not been extensively studied. METHODS: Twenty-four patients with recurrent, drug-refractory, paroxysmal AF underwent an extensive mapping of the RA before attempting linear lesion RF ablation. Patients were divided into two groups: 15 patients received two linear lesions (Group 1), 9 patients three linear lesions (Group 2). RESULTS: One-month success rate AF did not recur in 40% of Group 1 patients (6/15) and in 66% (6/9) of Group 2 patients. 27% of patients in Group 1 and 11% of patients in Group 2 had recurrences controlled by drugs. No benefit in 33% of Group 1 patients and 22% of Group 2. Long-term follow-up In the absence of any drug treatment, no AF recurrences were observed in 26% of Group 1 patients (FU: 23 to 47 months) and 55% of Group 2 (FU: 14 to 23 months). No complications were reported. CONCLUSIONS: Right atrial linear ablation is safe and may be proposed for AF treatment in selected patients.

Prediction of atrial fibrillation from surface ECG: review of methods and algorithms.

The study aims to review the mathematical methods developed for the prediction of atrial fibrillation by analysis of surface electrocardiographic records in paroxysmal or post-cardiosurgery patients. A risk stratification based on ECG analysis would be very useful either to optimise the prophylactic antiarrhythmic treatment in high risk patients, or to limit drugs administration in low risk subjects. The works published so far managed to achieve good results in terms of sensitivity and specificity. However, since these methods are not completely reliable yet, their clinical application is still limited. The present study is divided in sections about time domain, frequency domain, premature complexes detection, heart rate variability, and non linear ECG analysis based methods.

Radiofrequency identification and medical devices: the regulatory framework on electromagnetic compatibility. Part I: medical devices.

Radiofrequency identification (RFID) technology has acheived significant success and has penetrated into various areas of healthcare. Several RFID-based applications are used in various modalities with the ultimate aim of improving patient care. When a wireless technology is used in a healthcare environment, attention must be paid to the potential risks deriving from its use; one of the most important being electromagnetic interference with medical devices. In this paper, the regulatory framework concerning the electromagnetic compatibility between RFID and medical devices is analyzed to understand whether and how the application of the current standards allows for the effective control of the risks of electromagnetic interference.

Radiofrequency identification and medical devices: the regulatory framework on electromagnetic compatibility. Part II: active implantable medical devices.

The number and the types of electromagnetic emitters to which patients with active implantable medical devices (AIMD) are exposed to in their daily activities have proliferated over the last decade. Radiofrequency identification (RFID) is an example of wireless technology applied in many fields. The interaction between RFID emitters and AIMD is an important issue for patients, industry and regulators, because of the risks associated with such interactions. The different AIMDs refer to different standards that address the electromagnetic immunity issue in different ways. Indeed, different test setups, immunity levels and rationales are used to guarantee that AIMDs are immune to electromagnetic nonionizing radiation. In this article, the regulatory framework concerning electromagnetic compatibility between RFID systems and AIMDs is analyzed to understand whether and how the application of the current AIMD standards allows for the effective control of the possible risks associated with RFID technology.

On the resolution of ECG acquisition systems for the reliable analysis of the P-wave.

The analysis of the P-wave on surface ECG is widely used to assess the risk of atrial arrhythmias. In order to provide reliable results, the automatic analysis of the P-wave must be precise and reliable and must take into account technical aspects, one of those being the resolution of the acquisition system. The aim of this note is to investigate the effects of the amplitude resolution of ECG acquisition systems on the P-wave analysis. Starting from ECG recorded by an acquisition system with a less significant bit (LSB) of 31 nV (24 bit on an input range of 524 mVpp), we reproduced an ECG signal as acquired by systems with lower resolution (16, 15, 14, 13 and 12 bit). We found that, when the LSB is of the order of 128 µV (12 bit), a single P-wave is not recognizable on ECG. However, when averaging is applied, a P-wave template can be extracted, apparently suitable for the P-wave analysis. Results obtained in terms of P-wave duration and morphology revealed that the analysis of ECG at lowest resolutions (from 12 to 14 bit, LSB higher than 30 µV) could lead to misleading results. However, the resolution used nowadays in modern electrocardiographs (15 and 16 bit, LSB <10 µV) is sufficient for the reliable analysis of the P-wave.