Survival and Neurologic Outcomes From Pharmacologic Peptide Administration During Cardiopulmonary Resuscitation of Pulseless Electrical Activity.

BACKGROUND: Outcomes from cardiopulmonary resuscitation (CPR) following sudden cardiac arrest are suboptimal. Postresuscitation targeted temperature management has been shown to have benefit in subjects with sudden cardiac arrest due to ventricular fibrillation, but there are few data for outcomes from sudden cardiac arrest due to pulseless electrical activity. In addition, intra-CPR cooling is more effective than postresuscitation cooling. Physical cooling is associated with increased protein kinase B activity. Therefore, our group developed a novel peptide, TAT-PHLPP9c, which regulates protein kinase B. We hypothesized that when given during CPR, TAT-PHLPP9c would improve survival and neurologic outcomes following pulseless electrical activity arrest. METHODS AND RESULTS: In 24 female pigs, pulseless electrical activity was induced by inflating balloon catheters in the right coronary and left anterior descending arteries for ≈7 minutes. Advanced life support was initiated. In 12 control animals, epinephrine was given after 1 and 3 minutes. In 12 peptide-treated animals, 7.5 mg/kg TAT-PHLPP9c was also administered at 1 and 3 minutes of CPR. The balloons were removed after 2 minutes of support. Animals were recovered and neurologically scored 24 hours after return of spontaneous circulation. Return of spontaneous circulation was more common in the peptide group, but this difference was not significant (8/12 control versus 12/12 peptide; P=0.093), while fully intact neurologic survival was significantly more common in the peptide group (0/12 control versus 11/12 peptide; P<0.00001). TAT-PHLPP9c significantly increased myocardial nicotinamide adenine dinucleotide levels. CONCLUSIONS: TAT-PHLPP9c resulted in improved survival with full neurologic function after sudden cardiac arrest in a swine model of pulseless electrical activity, and the peptide shows potential as an intra-CPR pharmacologic agent.

Comparison Between a Single-Lead ECG Garment Device and a Holter Monitor: A Signal Quality Assessment.

Wearable electronics are increasingly common and useful as health monitoring devices, many of which feature the ability to record a single-lead electrocardiogram (ECG). However, recording the ECG commonly requires the user to touch the device to complete the lead circuit, which prevents continuous data acquisition. An alternative approach to enable continuous monitoring without user initiation is to embed the leads in a garment. This study assessed ECG data obtained from the YouCare device (a novel sensorized garment) via comparison with a conventional Holter monitor. A cohort of thirty patients (age range: 20-82 years; 16 females and 14 males) were enrolled and monitored for twenty-four hours with both the YouCare device and a Holter monitor. ECG data from both devices were qualitatively assessed by a panel of three expert cardiologists and quantitatively analyzed using specialized software. Patients also responded to a survey about the comfort of the YouCare device as compared to the Holter monitor. The YouCare device was assessed to have 70% of its ECG signals as "Good", 12% as "Acceptable", and 18% as "Not Readable". The R-wave, independently recorded by the YouCare device and Holter monitor, were synchronized within measurement error during 99.4% of cardiac cycles. In addition, patients found the YouCare device more comfortable than the Holter monitor (comfortable 22 vs. 5 and uncomfortable 1 vs. 18, respectively). Therefore, the quality of ECG data collected from the garment-based device was comparable to a Holter monitor when the signal was sufficiently acquired, and the garment was also comfortable.

MR-Safe Cartesian Platform for Active Cardiac Shimming: Preliminary Validation.

OBJECTIVE: Implanted Cardioverter Defibrillators (ICDs) induce a large (100 parts per million) inhomogeneous magnetic field in the magnetic resonance imaging (MRI) scanner which cannot be corrected by the scanner's built-in shim coils, leading to significant image artifacts that can make portions of the heart unreadable. To compensate for the field inhomogeneity, an active shim coil capable of countering the field deviation in user-defined regions was designed that must be optimally placed at patient-specific locations. We aim to develop and evaluate an MR-safe robotic solution for automated shim coil positioning. METHODS: We designed and fabricated an MR-safe Cartesian platform that holds the shim coil inside the scanner. The platform consists of three lead screw stages actuated by pneumatic motors, achieving decoupled translations of 140 mm in each direction. The platform is made of plastics and fiberglass with the control electronics placed outside the scanner room, ensuring MR safety. Mechanical modeling was derived to provide design specifications. RESULTS: Experiments show that the platform achieves less than 2 mm average motion error and 0.5 mm repeatability in all directions, and reduces the adjustment time from 5 min to a few seconds. Phantom and animal trials were conducted, showing that the proposed system is able to position a heavy shim coil ( kg) for improved ICD artifact suppression. CONCLUSION: This robotic platform provides an effective method for reliable shim coil positioning inside the scanner. SIGNIFICANCE: This work contributes to improving cardiac MRI quality that could facilitate accurate diagnosis and treatment planning for patients with implanted ICDs.

Balanced-force shim system for correcting magnetic-field inhomogeneities in the heart due to implanted cardioverter defibrillators.

Background: In the US, 1.4 million people have implanted ICDs for reducing the risk of sudden death due to ventricular arrhythmias. Cardiac MRI (cMR) is of particular interest in the ICD patient population as cMR is the optimal imaging modality for distinguishing cardiac conditions that predispose to sudden death, and it is the best method to plan and guide therapy. However, all ICDs contain a ferromagnetic transformer which imposes a large inhomogeneous magnetic field in sections of the heart, creating large image voids that can mask important pathology. A shim system was devised to resolve these ICD issues. A shim coil system (CSS) that corrects ICD artifacts over a user-selected Region-of-Interest (ROI), was constructed and validated. Methods: A shim coil was constructed that can project a large magnetic field for distances of ~15 cm. The shim-coil can be positioned safely anywhere within the scanner bore. The CSS includes a cantilevered beam to hold the shim coil. Remotely controlled MR-conditional motors allow 2 mm-accuracy three-dimensional shim-coil position. The shim coil is located above the subjects and the imaging surface-coils. Interaction of the shim coil with the scanner's gradients was eliminated with an amplifier that is in a constant current mode. Coupling with the scanners' radio-frequency (rf) coils, was reduced with shielding, low-pass filters, and cable shield traps. Software, which utilizes magnetic field (B0) mapping of the ICD inhomogeneity, computes the optimal location for the shim coil and its corrective current. ECG gated single- and multiple-cardiac-phase 2D GRE and SSFP sequences, as well as 3D ECG-gated respiratory-navigated IR-GRE (LGE) sequences were tested in phantoms and N = 3 swine with overlaid ICDs. Results: With all cMR sequences, the system reduced artifacts from >100 ppm to <25 ppm inhomogeneity, which permitted imaging of the entire left ventricle in swine with ICD-related voids. Continuously acquired Gradient recalled echo or Steady State Free Precession images were used to interactively adjust the shim current and coil location. Conclusion: The shim system reduced large field inhomogeneities due to implanted ICDs and corrected most ICD-related image distortions. Externally-controlled motorized translation of the shim coil simplified its utilization, supporting an efficient cardiac MRI workflow.

Electrocardiogram Monitoring Wearable Devices and Artificial-Intelligence-Enabled Diagnostic Capabilities: A Review.

Worldwide, population aging and unhealthy lifestyles have increased the incidence of high-risk health conditions such as cardiovascular diseases, sleep apnea, and other conditions. Recently, to facilitate early identification and diagnosis, efforts have been made in the research and development of new wearable devices to make them smaller, more comfortable, more accurate, and increasingly compatible with artificial intelligence technologies. These efforts can pave the way to the longer and continuous health monitoring of different biosignals, including the real-time detection of diseases, thus providing more timely and accurate predictions of health events that can drastically improve the healthcare management of patients. Most recent reviews focus on a specific category of disease, the use of artificial intelligence in 12-lead electrocardiograms, or on wearable technology. However, we present recent advances in the use of electrocardiogram signals acquired with wearable devices or from publicly available databases and the analysis of such signals with artificial intelligence methods to detect and predict diseases. As expected, most of the available research focuses on heart diseases, sleep apnea, and other emerging areas, such as mental stress. From a methodological point of view, although traditional statistical methods and machine learning are still widely used, we observe an increasing use of more advanced deep learning methods, specifically architectures that can handle the complexity of biosignal data. These deep learning methods typically include convolutional and recurrent neural networks. Moreover, when proposing new artificial intelligence methods, we observe that the prevalent choice is to use publicly available databases rather than collecting new data.

A cell-penetrating PHLPP peptide improves cardiac arrest survival in murine and swine models.

Out-of-hospital cardiac arrest is a leading cause of death in the US, with a mortality rate over 90%. Preclinical studies demonstrate that cooling during cardiopulmonary resuscitation (CPR) is highly beneficial, but can be challenging to implement clinically. No medications exist for improving long-term cardiac arrest survival. We have developed a 20-amino acid peptide, TAT-PHLPP9c, that mimics cooling protection by enhancing AKT activation via PH domain leucine-rich repeat phosphatase 1 (PHLPP1) inhibition. Complementary studies were conducted in mouse and swine. C57BL/6 mice were randomized into blinded saline control and peptide-treatment groups. Following a 12-minute asystolic arrest, TAT-PHLPP9c was administered intravenously during CPR and significantly improved the return of spontaneous circulation, mean arterial blood pressure and cerebral blood flow, cardiac and neurological function, and survival (4 hour and 5 day). It inhibited PHLPP-NHERF1 binding, enhanced AKT but not PKC phosphorylation, decreased pyruvate dehydrogenase phosphorylation and sorbitol production, and increased ATP generation in heart and brain. TAT-PHLPP9c treatment also reduced plasma taurine and glutamate concentrations after resuscitation. The protective benefit of TAT-PHLPP9c was validated in a swine cardiac arrest model of ventricular fibrillation. In conclusion, TAT-PHLPP9c may improve neurologically intact cardiac arrest survival without the need for physical cooling.

Algorithm for Mobile Platform-Based Real-Time QRS Detection.

Recent advancements in smart, wearable technologies have allowed the detection of various medical conditions. In particular, continuous collection and real-time analysis of electrocardiogram data have enabled the early identification of pathologic cardiac rhythms. Various algorithms to assess cardiac rhythms have been developed, but these utilize excessive computational power. Therefore, adoption to mobile platforms requires more computationally efficient algorithms that do not sacrifice correctness. This study presents a modified QRS detection algorithm, the AccYouRate Modified Pan-Tompkins (AMPT), which is a simplified version of the well-established Pan-Tompkins algorithm. Using archived ECG data from a variety of publicly available datasets, relative to the Pan-Tompkins, the AMPT algorithm demonstrated improved computational efficiency by 5-20×, while also universally enhancing correctness, both of which favor translation to a mobile platform for continuous, real-time QRS detection.

Implantable Defibrillator System Shock Function, Mortality, and Cause of Death After Magnetic Resonance Imaging.

BACKGROUND: Studies have shown that magnetic resonance imaging (MRI) does not have clinically important effects on the device parameters of non-MRI-conditional implantable cardioverter-defibrillators (ICDs). However, data on non-MRI-conditional ICD detection and treatment of arrhythmias after MRI are limited. OBJECTIVE: To examine if non-MRI-conditional ICDs have preserved shock function of arrhythmias after MRI. DESIGN: Prospective cohort study. (ClinicalTrials.gov: NCT01130896). SETTING: 1 center in the United States. PATIENTS: 629 patients with non-MRI-conditional ICDs enrolled consecutively between February 2003 and January 2015. INTERVENTIONS: 813 total MRI examinations at a magnetic field strength of 1.5 Tesla using a prespecified safety protocol. MEASUREMENTS: Implantable cardioverter-defibrillator interrogations were collected after MRI. Clinical outcomes included arrhythmia detection and treatment, generator or lead exchanges, adverse events, and death. RESULTS: During a median follow-up of 2.2 years from MRI to latest available ICD interrogation before generator or lead exchange in 536 patients, 4177 arrhythmia episodes were detected, and 97 patients received ICD shocks. Sixty-one patients (10% of total) had 130 spontaneous ventricular tachycardia or fibrillation events terminated by ICD shocks. A total of 210 patients (33% of total) are known to have died (median, 1.7 years from MRI to death); 3 had cardiac arrhythmia deaths where shocks were indicated without direct evidence of device dysfunction. LIMITATIONS: Data were acquired at a single center and may not be generalizable to other clinical settings and MRI facilities. Implantable cardioverter-defibrillator interrogations were not available for a subset of patients; adjudication of cause of death relied solely on death certificate data in a subset. CONCLUSION: Non-MRI-conditional ICDs appropriately treated detected tachyarrhythmias after MRI. No serious adverse effects on device function were reported after MRI. PRIMARY FUNDING SOURCE: Johns Hopkins University and National Institutes of Health.

Extracorporeal cardiopulmonary resuscitation (eCPR) and cerebral perfusion: A narrative review.

Extracorporeal cardiopulmonary resuscitation (eCPR) is emerging as an effective, lifesaving resuscitation strategy for select patients with prolonged or refractory cardiac arrest. Currently, a paucity of evidence-based recommendations is available to guide clinical management of eCPR patients. Despite promising results from initial clinical trials, neurological injury remains a significant cause of morbidity and mortality. Neuropathology associated with utilization of an extracorporeal circuit may interact significantly with the consequences of a prolonged low-flow state that typically precedes eCPR. In this narrative review, we explore current gaps in knowledge about cerebral perfusion over the course of cardiac arrest and resuscitation with a focus on patients treated with eCPR. We found no studies which investigated regional cerebral blood flow or cerebral autoregulation in human cohorts specific to eCPR. Studies which assessed cerebral perfusion in clinical eCPR were small and limited to near-infrared spectroscopy. Furthermore, no studies prospectively or retrospectively evaluated the relationship between epinephrine and neurological outcomes in eCPR patients. In summary, the field currently lacks a comprehensive understanding of how regional cerebral perfusion and cerebral autoregulation are temporally modified by factors such as pre-eCPR low-flow duration, vasopressors, and circuit flow rate. Elucidating these critical relationships may inform future strategies aimed at improving neurological outcomes in patients treated with lifesaving eCPR.

Establishing a multicenter, preclinical consortium in resuscitation: A pilot experimental trial evaluating epinephrine in cardiac arrest.

BACKGROUND: Large animal studies are an important step in the translation pathway, but single laboratory experiments do not replicate the variability in patient populations. Our objective was to demonstrate the feasibility of performing a multicenter, preclinical, randomized, double-blinded, placebo-controlled cardiac arrest trial. We evaluated the effect of epinephrine on coronary perfusion pressure (CPP) as previous single laboratory studies have reported mixed results. METHODS: Forty-five swine from 5 different laboratories (Ann Arbor, MI; Baltimore, MD; Los Angeles, CA; Pittsburgh, PA; Toronto, ON) using a standard treatment protocol. Ventricular fibrillation was induced and left untreated for 6 min before starting continuous cardiopulmonary resuscitation (CPR). After 2 min of CPR, 9 animals from each lab were randomized to 1 of 3 interventions given over 12 minutes: (1) Continuous IV epinephrine infusion (0.00375 mg/kg/min) with placebo IV normal saline (NS) boluses every 4 min, (2) Continuous placebo IV NS infusion with IV epinephrine boluses (0.015 mg/kg) every 4 min or (3) Placebo IV NS for both infusion and boluses. The primary outcome was mean CPP during the 12 mins of drug therapy. RESULTS: There were no significant differences in mean CPP between the three groups: 14.4 ± 6.8 mmHg (epinephrine Infusion), 16.9 ± 5.9 mmHg (epinephrine bolus), and 14.4 ± 5.5 mmHg (placebo) (p = NS). Sensitivity analysis demonstrated inter-laboratory variability in the magnitude of the treatment effect (p = 0.004). CONCLUSION: This study demonstrated the feasibility of performing a multicenter, preclinical, randomized, double-blinded cardiac arrest trials. Standard dose epinephrine by bolus or continuous infusion did not increase coronary perfusion pressure during CPR when compared to placebo.

Reduced motion external defibrillation: Reduced subject motion with equivalent defibrillation efficiency validated in swine.

BACKGROUND: External defibrillators are used for arrhythmia cardioversion and for defibrillating during cardiac arrest. During defibrillation, short-duration biphasic pulses cause intense motion due to rapid chest-wall muscle contraction. A reduced motion external defibrillator (RMD) was constructed by integrating a commercial defibrillator with a Tetanizing-waveform generator. A long-duration, low-amplitude, tetanizing waveform slowly stimulated the chest musculature before the biphasic pulse, reducing muscle contraction during the shock. OBJECTIVE: The purpose of this study was to evaluate RMD defibrillation in swine for subject motion during defibrillation pulses and for defibrillation effectiveness. RMD defibrillation can reduce the duration of arrhythmia ablation therapy or simplify cardioversion procedures. METHODS: The tetanizing unit delivered a triangular 1-kHz pulse of 0.25- to 2.0-second duration and 10- to 100-V peak amplitude, subsequently triggering the conventional defibrillator to output standard 1- to 200-J energy biphasic pulses at the next R wave. Forward limb motion was evaluated by measuring peak acceleration and limb work during RMD (tetanizing + biphasic) or biphasic pulse-only waveforms at 10-3-second sampling rate. Seven swine were arrested electrically and subsequently defibrillated. Biphasic pulse-only and RMD defibrillations were repeated 25-35 times per swine, varying tetanizing parameters and biphasic pulse energy. Defibrillation thresholds (DFTs) were established by measuring the minimum energy required to restore sinus rhythm with biphasic pulse-only or RMD defibrillations. RESULTS: Two forward-limb acceleration peaks occurred during both the tetanizing waveform and biphasic pulse, indicating rapid and slower nociceptic (pain sensation) nerve fiber activation. Optimal RMD tetanizing parameters (25-35 V, 0.25- to 0.75-second duration), relative to biphasic pulse-only defibrillations, resulted in 74% ± 10% smaller peak accelerations and 85% ± 10% reduced limb work. DFT energies were identical when comparing RMD to biphasic pulse-only defibrillations. CONCLUSION: Relative to conventional defibrillations, RMD defibrillations maintain rhythm restoration efficiency with drastically reduced subject motion.

MR-Tracked Deflectable Stylet for Gynecologic Brachytherapy.

Brachytherapy is a radiation based treatment that is implemented by precisely placing focused radiation sources into tumors. In advanced interstitial cervical cancer bracytherapy treatment, this is performed by placing a metallic rod ("stylet") inside a hollow cylindrical tube ("catheter") and advancing the pair to the desired target. The stylet is removed once the target is reached, followed by the insertion of radiation sources into the catheter. However, manually advancing an initially straight stylet into the tumor with millimeter spatial accuracy has been a long-standing challenge, which requires multiple insertions and retractions, due to the unforeseen stylet deflection caused by the stiff muscle tissue that is traversed. In this paper, we develop a novel tendon-actuated deflectable stylet equipped with MR active-tracking coils that may enhance brachytherapy treatment outcomes by allowing accurate stylet trajectory control. Herein we present the design concept and fabrication method, followed by the kinematic and mechanics models of the deflectable stylet. The hardware and theoretical models are extensively validated via benchtop and MRI-guided characterization. At insertion depths of 60 mm, benchtop phantom targeting tests provided a targeting error of 1. 23 ± 0. 47 mm, and porcine tissue targeting tests provided a targeting error of 1. 65 ± 0. 64 mm, after only a single insertion. MR-guided experiments indicate that the stylet can be safely and accurately located within the MRI environment.

Intracardiac MR imaging (ICMRI) guiding-sheath with amplified expandable-tip imaging and MR-tracking for navigation and arrythmia ablation monitoring: Swine testing at 1.5 and 3T.

PURPOSE: Develop a deflectable intracardiac MR imaging (ICMRI) guiding-sheath to accelerate imaging during MR-guided electrophysiological (EP) interventions for radiofrequency (500 kHz) ablation (RFA) of arrythmia. Requirements include imaging at three to five times surface-coil SNR in cardiac chambers, vascular insertion, steerable-active-navigation into cardiac chambers, operation with ablation catheters, and safe levels of MR-induced heating. METHODS: ICMRI's 6 mm outer-diameter (OD) metallic-braided shaft had a 2.6 mm OD internal lumen for ablation-catheter insertion. Miniature-Baluns (MBaluns) on ICMRI's 1 m shaft reduced body-coil-induced heating. Distal section was a folded "star"-shaped imaging-coil mounted on an expandable frame, with an integrated miniature low-noise-amplifier overcoming cable losses. A handle-activated movable-shaft expanded imaging-coil to 35 mm OD for imaging within cardiac-chambers. Four MR-tracking micro-coils enabled navigation and motion-compensation, assuming a tetrahedron-shape when expanded. A second handle-lever enabled distal-tip deflection. ICMRI with a protruding deflectable EP catheter were used for MR-tracked navigation and RFA using a dedicated 3D-slicer user-interface. ICMRI was tested at 3T and 1.5T in swine to evaluate (a) heating, (b) cardiac-chamber access, (c) imaging field-of-view and SNR, and (d) intraprocedural RFA lesion monitoring. RESULTS: The 3T and 1.5T imaging SNR demonstrated >400% SNR boost over a 4 × 4 × 4 cm3 FOV in the heart, relative to body and spine arrays. ICMRI with MBaluns met ASTM/IEC heating limits during navigation. Tip-deflection allowed navigating ICMRI and EP catheter into atria and ventricles. Acute-lesion long-inversion-time-T1-weighted 3D-imaging (TWILITE) ablation-monitoring using ICMRI required 5:30 min, half the time needed with surface arrays alone. CONCLUSION: ICMRI assisted EP-catheter navigation to difficult targets and accelerated RFA monitoring.

Magnetic resonance imaging safety in patients with cardiac implantable electronic devices.

High strength magnetic and electric fields used in magnetic resonance imaging (MRI) render images with unmatched soft tissue contrast. These imaging attributes have made MRI an increasingly preferred diagnostic tool in many medical conditions. Initially there was substantial concern regarding the safety of performing these imaging studies in patients with cardiac implantable electronic devices (CIEDs), which have the potential to be affected by the intense electric and magnetic fields of the MRI. More recently, there has been increasing evidence that MRI can be performed safely in patients with devices that have not been specifically labelled by regulatory agencies for use in an MRI environment (MRI nonconditional devices), which has allowed the Centers for Medicare and Medicaid Services (CMS) to start providing reimbursement for MRIs of patients with MRI nonconditional devices. For CMS to reimburse scans, a rigorous protocol must be followed, which recognizes that there are still potential adverse effects that can be mitigated by appropriate procedures. In this review we will survey the initial experiences and efforts to understand the magnitude of risk for device malfunction and harm, as well as current efforts to minimize the potential risks of MRI effects on devices and leads (heating, device movement, lead dislodgement, and device malfunction, the latter including inhibition of pacing and generation of arrhythmias).

An endovaginal MRI array with a forward-looking coil for advanced gynecological cancer brachytherapy procedures: Design and initial results.

PURPOSE: To develop an endovaginal MRI array that provides signal enhancement forward into the posterior parametrium and sideways into the vaginal wall, accelerating multiple-contrast detection of residual tumors that survive external beam radiation. The array's enclosure should form an obturator for cervical cancer brachytherapy, allowing integration with MRI-guided catheter placement, CT, and interstitial radiation dose delivery. METHODS: The endovaginal array consisted of forward-looking and sideways-looking components. The forward-looking element imaged the cervix and posterior endometrium, and the sideways-looking elements imaged the vaginal wall. Electromagnetic simulation was performed to optimize the geometry of a forward-looking coil placed on a conductive-metallic substrate, extending the forward penetration above the coil's tip. Thereafter, an endovaginal array with one forward-looking coil and four sideways-looking elements was constructed and tested at 1.5 Tesla in saline and gel phantoms, and three sexually mature swine. Each coil's tuning, matching, and decoupling were optimized theoretically, implemented with electronic circuits, and validated with network-analyzer measurements. The array enclosure emulates a conventional brachytherapy obturator, allowing use of the internal imaging array together with tandem coils and interstitial catheters, as well as use of the enclosure alone during CT and radiation delivery. To evaluate the receive magnetic field ( B 1 - ) spatial profile, the endovaginal array's specific absorption-rate (SAR) distribution was simulated inside a gel ASTM phantom to determine extreme heating locations in advance of a heating test. Heating tests were then performed during high SAR imaging in a gel phantom at the predetermined locations, testing compliance with MRI safety standards. To assess array imaging performance, signal-to-noise-ratios (SNR) were calculated in a saline phantom and in vivo. Swine images were acquired with the endovaginal array combined with the scanner's body and spine arrays. RESULTS: Simulated B 1 - profiles for the forward-looking lobe pattern, obtained while varying several geometric parameters, disclosed that a forward-looking coil placed on a metal-backed substrate could double the effective forward penetration from approximately 25 to ∼40 mm. An endovaginal array, enclosed in an obturator enclosure was then constructed, with all coils tuned, matched, and decoupled. The ASTM gel-phantom SAR test showed that peak local SAR was 1.2 W/kg in the forward-looking coil and 0.3 W/kg in the sideways-looking elements, well within ASTM/FDA/IEC guidelines. A 15-min 4 W/kg average SAR imaging experiment resulted in less than 2o C temperature increase, also within ASTM/FDA/IEC heating limits. In a saline phantom, the forward-looking coil and sideways-looking array's SNR was four to eight times, over a 20-30 mm field-of-view (FOV), and five to eight times, over a 15-25 mm FOV, relative to the spine array's SNR, respectively. In three sexually mature swine, the forward-looking coil provided a 5 + 0.2 SNR enhancement factor within the cervix and posterior endometrium, and the sideways-looking array provided a 4 + 0.2 SNR gain factor in the vaginal wall, relative to the Siemens spine array, demonstrating that the array could significantly reduce imaging time. CONCLUSIONS: Higher SNR gynecological imaging is supported by forward-looking and sideways-looking coils. A forward-looking endovaginal coil for cervix and parametrium imaging was built with optimized metal backing. Array placement within an obturator enhanced integration with the brachytherapy procedure and accelerated imaging for detecting postexternal-beam residual tumors.

Pulseless Electrical Activity as the Initial Cardiac Arrest Rhythm: Importance of Preexisting Left Ventricular Function.

Background Pulseless electrical activity (PEA) is a common initial rhythm in cardiac arrest. A substantial number of PEA arrests are caused by coronary ischemia in the setting of acute coronary occlusion, but the underlying mechanism is not well understood. We hypothesized that the initial rhythm in patients with acute coronary occlusion is more likely to be PEA than ventricular fibrillation in those with prearrest severe left ventricular dysfunction. Methods and Results We studied the initial cardiac arrest rhythm induced by acute left anterior descending coronary occlusion in swine without and with preexisting severe left ventricular dysfunction induced by prior infarcts in non-left anterior descending coronary territories. Balloon occlusion resulted in ventricular fibrillation in 18 of 34 naïve animals, occurring 23.5±9.0 minutes following occlusion, and PEA in 1 animal. However, all 18 animals with severe prearrest left ventricular dysfunction (ejection fraction 15±5%) developed PEA 1.7±1.1 minutes after occlusion. Conclusions Acute coronary ischemia in the setting of severe left ventricular dysfunction produces PEA because of acute pump failure, which occurs almost immediately after coronary occlusion. After the onset of coronary ischemia, PEA occurred significantly earlier than ventricular fibrillation (<2 minutes versus 20 minutes). These findings support the notion that patients with baseline left ventricular dysfunction and suspected coronary disease who develop PEA should be evaluated for acute coronary occlusion.

A comparison of three conducted electrical weapons in a surrogate swine cardiac safety model.

We used a previously described methodology in a swine model to compare the relative cardiac safety of the Axon T7 Conducted Electrical Weapon (CEW), released in October of 2018, to two prior generations of Axon CEWs to include the X2 and the X26E. A total of 5 swine (252 total CEW exposures) were tested by alternating the three weapons at each chest exposure location. Our testing, using systemic hypotension as the quantitative surrogate for cardiac capture, demonstrated that the T7 and X2 were not statistically different. Both were superior, in terms of reduced hypotension during exposure, to the X26E. This study is important as it demonstrates that the newly released weapon is non-inferior to the X2 and superior to the X26E using this surrogate safety model. It is also important because it is the first study to examine the cardiac effects of simultaneous multi-bay exposures. Our prior study compared the X2 to the X26E but examined only single bay exposures from the X2. Lastly, we feel we have improved the methodology for studying the comparative cardiac effects of CEWs.

CPR and ECMO: The Next Frontier.

Cardiopulmonary resuscitation (CPR) is a first-line therapy for sudden cardiac arrest, while extracorporeal membrane oxygenation (ECMO) has traditionally been used as a means of countering circulatory failure. However, new advances dictate that CPR and ECMO could be complementary for support after cardiac arrest. This review details the emerging science, technology, and clinical application that are enabling the new paradigm of these iconic circulatory support modalities in the setting of cardiac arrest.

The Relationship between MRI Radiofrequency Energy and Function of Nonconditional Implanted Cardiac Devices: A Prospective Evaluation.

Background The risks associated with MRI in individuals who have implanted cardiac devices are thought to arise from the interaction between the implanted device and static, gradient, and radiofrequency magnetic fields. Purpose To determine the relationship between the peak whole-body averaged specific absorption rate (SAR) and change in magnetic field per unit time (dB/dt), maximum specific energy dose, imaging region, and implanted cardiac device characteristics and their function in patients undergoing MRI. Materials and Methods This prospective observational cohort study was conducted from October 16, 2003, to January 22, 2015 (https://ClinicalTrials.gov, NCT01130896). Any individual with an implanted cardiac device who was referred for MRI was included. Clinical MRI protocols without SAR restriction were used. Exclusion criteria were newly implanted leads, abandoned or epicardial leads, and dependence on a pacemaker with an implantable cardioverter defibrillator without asynchronous pacing capability. For each MRI pulse sequence, the calculated whole-body values for SAR, dB/dt, and scan duration were collected. Atrial and ventricular sensing, lead impedance, and capture threshold were evaluated before and immediately after (within 10 minutes) completion of each MRI examination. Generalized estimating equations with Gaussian family, identity link, and an exchangeable working correlation matrix were used for statistical analysis. Results A total of 2028 MRI examinations were performed in 1464 study participants with 2755 device leads (mean age, 67 years ± 15 [standard deviation]; 930 men [64%]). There was no evidence of an association between radiofrequency energy deposition, dB/dt, or scan duration and changes in device parameters. Thoracic MRI was associated with decreased battery voltage immediately after MRI (ß = -0.008 V, P < .001). Additionally, right ventricular (RV) lead length was associated with decreased RV sensing (ß = -0.012 mV, P = .05) and reduced RV capture threshold (ß = -0.002 V, P < .01) immediately after MRI. Conclusion There was no evidence of an association between MRI parameters that characterize patient exposure to radiofrequency energy and changes in device and lead parameters immediately after MRI. Nevertheless, device interrogation before and after MRI remains mandatory due to the potential for device reset and changes in lead or generator parameters. © RSNA, 2020 See also the editorial by Shellock in this issue.