IMPORTANCE How to appropriately care for patients who become PCR-negative for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still not known.Patients who have recovered from coronavirus disease 2019 (COVID-19) could profoundly impact the health care system if a subset were to be PCR-positive again with reactivated SARS-CoV-2.OBJECTIVE To characterize a single center COVID-19 cohort with and without recurrence of PCR positivity, and develop an algorithm to identify patients at high risk of retest positivity after discharge to inform health care policy and case management decision-making. DESIGN, SETTING, AND PARTICIPANTSA cohort of 414 patients with confirmed SARS-CoV-2 infection, at The Second Affiliated EXPOSURES Polymerase chain reaction (PCR) and IgM-IgG antibody confirmed SARS-CoV-2 infection. MAIN OUTCOMES AND MEASURES Univariable and multivariable statistical analysis of the clinical, laboratory, radiologic image, medical treatment, and clinical course of admission/quarantine/readmission data to develop an algorithm to predict patients at risk of recurrence of PCR positivity.RESULTS 16.7% (95CI: 13.0%-20.3%) patients retest PCR positive 1 to 3 times after discharge, despite being in strict quarantine. The driving factors in the recurrence prediction model included: age, BMI; lowest levels of the blood laboratory tests

Interventional magnetic resonance imaging (MRI) is a growing field, and the strength of MRI guidance for procedures rests fundamentally in the high-contrast imaging of soft tissue structures. Combined with the avoidance of radiation exposure, the potential for functional assessment and the ability to exploit MR signals for calculation of the location of interventional instruments, it is clear that the implementation of interventional MRI will continue to grow. For general cardiac interventions, the visualisation of thin, mobile structures presents particular challenges for MRI guidance. Cardiac electrophysiological (EP) procedures add a further dimension, as the accurate detection of intracardiac electrograms must be performed in a highly active electromagnetic environment. This review focuses on the technical considerations for the performance of EP procedures under MRI guidance (MR-guided EP). Potential Benefits of MR-guided Electrophysiological ProceduresMRI techniques offer a high soft-tissue contrast-to-noise ratio (CNR) in comparison with that seen with X-ray, computed tomography (CT) and ultrasound. However, the environment can present challenges and is an expensive procedure; therefore, all the benefits of MR-guided EP must be fully considered to justify the additional difficulties and expense. Broadly speaking, these benefits can be divided into three main areas: improved precision of ablation targeting (substrate identification), improved intra-procedural guidance and improved assessment of ablation lesion formation. Emerging data also suggest that CMR imaging may be used to guide atrial ablation procedures. Although the atrial wall is thinner, native fibrosis and ablation scar can be identified using primarily threedimensional LGE techniques. 2,11 Findings from some studies have been interpreted to suggest that successful ablation of fibrotic regions, distant to the pulmonary veins (PVs), may help improve AF ablation success rates. 12 Similarly, atrial re-entrant circuits can be modelled in silico based on atrial scar location and can be used to inform ablation strategies. 13 Sites of PV reconnection have been identified using CMR, with successful ablation guided by the CMR-derived substrate, 14 but these findings have not been replicated in all studies. Substrate Identification 15To date, all studies that have used CMR-derived substrate identification to guide ablation have relied on fusion of the imaging to electroanatomic Abstract MR-guidance of electrophysiological (EP) procedures offers the potential for enhanced arrhythmia substrate assessment, improved procedural guidance and real-time assessment of ablation lesion formation. Accurate device tracking techniques, using both active and passive methods, have been developed to offer an interface similar to electroanatomic mapping platforms, and MR-compatible EP equipment continues to be developed. Progress to clinical implementation of these technically complex fields has been relatively slow over the last 10 years, but recent developments have...

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Identifying the atrial tissue that is capable of supporting sustained re-entrant spiral wave activation patterns offers a potential ablation target for atrial arrhythmias. Current strategies for identifying this substrate require the patient to be in atrial fibrillation and require a large specialized catheter or an inverse ECG vest. We propose a novel method to personalize biophysical ionic models from standard multi-electrode catheter measurements and to predict spiral wave stability using computer simulations of a tissue region. The developed method was applied to 5 clinical cases; the spiral wave stability was analyzed on a 5X5 cm 2 homogeneous tissue slab and stable (2/5) and unstable self-terminating (3/5) rotors were identified.

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BackgroundKawasaki disease (KD) is the leading cause of acquired heart disease in children. The major challenge in KD diagnosis is that it shares clinical signs with other childhood febrile control (FC) subjects. We sought to determine if our algorithmic approach applied to a Taiwan cohort.MethodsA single center (Chang Gung Memorial Hospital in Taiwan) cohort of patients suspected with acute KD were prospectively enrolled by local KD specialists for KD analysis. Our previously single-center developed computer-based two-step algorithm was further tested by a five-center validation in US. This first blinded multi-center trial validated our approach, with sufficient sensitivity and positive predictive value, to identify most patients with KD diagnosed at centers across the US. This study involved 418 KDs and 259 FCs from the Chang Gung Memorial Hospital in Taiwan.FindingsOur diagnostic algorithm retained sensitivity (379 of 418; 90.7%), specificity (223 of 259; 86.1%), PPV (379 of 409; 92.7%), and NPV (223 of 247; 90.3%) comparable to previous US 2016 single center and US 2020 fiver center results. Only 4.7% (15 of 418) of KD and 2.3% (6 of 259) of FC patients were identified as indeterminate. The algorithm identified 18 of 50 (36%) KD patients who presented 2 or 3 principal criteria. Of 418 KD patients, 157 were infants younger than one year and 89.2% (140 of 157) were classified correctly. Of the 44 patients with KD who had coronary artery abnormalities, our diagnostic algorithm correctly identified 43 (97.7%) including all patients with dilated coronary artery but one who found to resolve in 8 weeks.InterpretationThis work demonstrates the applicability of our algorithmic approach and diagnostic portability in Taiwan.

Ceramides and dihydroceramides are sphingolipids that present in abundance at the cellular membrane of eukaryotes.Although their metabolic dysregulation has been implicated in many diseases, our knowledge about circulating ceramide changes during the pregnancy remains limited. In this study, we present the development and validation of a highthroughput liquid chromatography-tandem mass spectrometric (LC/MS/MS) method for simultaneous quantification of 16 ceramides and 10 dihydroceramides in human serum within 5 mins by using stable isotope-labeled ceramides as internal standards (ISs). This method employs a protein precipitation method for high throughput sample preparation, reverse phase isocratic elusion for chromatographic separation, and Multiple Reaction Monitoring (MRM) for mass spectrometric detection. To qualify for clinical applications, our assay was validated against the FDA guidelines: the Lower Limit of Quantitation (LLOQ as low as 1 nM), linearity (R 2 >0.99), precision (Coefficient of Variation<15%), accuracy (Percent Error<15%), extraction recovery (>90%), stability (>85%), and carryover (<0.1%). With enhanced sensitivity and specificity from this method, we have, for the first time, determined the serological levels of ceramides and dihydroceramides to reveal unique temporal gestational patterns. Our approach could have value in providing insights into disorders of pregnancy.