On the use of probabilistic worst-case execution time estimation for parallel applications in high performance systems

Some high performance computing (HPC) applications exhibit increasing real-time requirements, which call for effective means to predict their high execution times distribution. This is a new challenge for HPC applications but a well-known problem for real-time embedded applications where solutions already exist, although they target low-performance systems running single-threaded applications. In this paper, we show how some performance validation and measurement-based practices for real-time execution time prediction can be leveraged in the context of HPC applications on high-performance platforms, thus enabling reliable means to obtain real-time guarantees for those applications. In particular, the proposed methodology uses coordinately techniques that randomly explore potential timing behavior of the application together with Extreme Value Theory (EVT) to predict rare (and high) execution times to, eventually, derive probabilistic Worst-Case Execution Time (pWCET) curves. We demonstrate the effectiveness of this approach for an acoustic wave inversion application used for geophysical explorationThis research was funded by the Horizon 2020 Framework Programme, grant number 801137, project RECIPEPeer ReviewedPostprint (published version

Multimodality imaging for atrial fibrosis detection in the era of precision medicine

In recent years, atrial fibrillation (AF) has increasingly become a focus of attention because it represents the most encountered arrhythmia in clinical practice and a major cause of morbidity and mortality. Issues underlying AF have long been debated; nevertheless, electrical, contractile, and structural remodeling is demonstrated to be the pivotal contributor to arrhythmic substrate. Fibrosis is a hallmark of arrhythmogenic structural remodeling, resulting from an accumulation of fibrillar collagen deposits, as a reparative process to replace degenerating myocardium with concomitant reactive fibrosis, which causes interstitial expansion. Although the precise role of fibrosis in AF initiation and maintenance remains to be fully elucidated, a better definition of its extent and distribution may assist in designing individually tailored ablation approaches and improving procedure outcomes by targeting the fibrotic substrates with an organized strategy employing imaging resources. A deep comprehension of the mechanisms underlying atrial fibrosis could be crucial to setting up improved strategies for preventing AF-promoting structural remodeling. Imaging modalities such as echocardiography, cardiac computed tomography, and cardiac magnetic resonance, combined sometimes with invasive electroanatomical mapping, could provide valuable information for the optimal patients’ management if their use is not limited to cardiac anatomy study but extended to characterize abnormal left atrial substrate. Although pulmonary vein isolation is usually efficacious in treating paroxysmal AF, it is not sufficient for many patients with nonparoxysmal arrhythmias, particularly those with longstanding persistent AF. Noninvasive imaging techniques play a pivotal role in the planning of arrhythmic substrates ablation and show a strong correlation with electro-anatomic mapping, whose novel multipolar mapping catheters allow nowadays a more precise comprehension of atrial substrate. This review aims to explore the impact of the various imaging modalities for the detection of atrial fibrosis and their role in the management of AF

Total nucleated cells as a sole predictor of distinct targets of hematopoietic potential (CD34+ cells) in cord blood units: the results of a large series analysis in autologous cord blood units

Background Rapid identification of eligible cord blood units (CBUs) for banking is an important issue in hematopoietic stem cell procurement. Distinct contents of CD34+ cells in CBU can contribute to identify grafts that may be banked also for unrelated transplants or limited to family-directed or autologous use. Study Design and Methods Considering thresholds of CD34+ cell content of 3\u2009 7\u2009106, 2\u2009 7\u2009106, and 1\u2009 7\u2009106 CD34+ cells, we analyzed a consecutive series of 1309 CBUs. CBUs were collected for autologous banking without any volume-based preselection criteria. Predictors of distinct content of CD34+ cells have been assessed by receiver operating characteristic (ROC) curve analysis. Results Median total nucleated cell (TNC) and CD34+ cell counts of the series were 6.97\u2009 7\u2009108 (range, 0.36\u2009 7\u2009108-34.9\u2009 7\u2009108) and 1.47\u2009 7\u2009106 (0-20.56\u2009 7\u2009106). Volumes ranged from 21 to 163\u2009mL, with a median of 73.8\u2009mL. For the CD34+ target of 1\u2009 7\u2009106, the best predictor was TNC count with a threshold of 6.63\u2009 7\u2009108; volume results were less predictive with a value of 68.1\u2009mL. For CD34+ targets of 2\u2009 7\u2009106 and 3\u2009 7\u2009106, ROC curves confirmed a stronger predictive power of TNC, above the collected volume, with thresholds of 7.55\u2009 7\u2009108 and 8.98\u2009 7\u2009108. ROC analysis by combining all predictors (TNC, volume, TNC2, volume2, age of mothers, types of delivery, birthweight) gave worse results than TNC count alone. Conclusions This analysis, carried out on a large, unrestricted CBU series, shows that TNC alone is the best predictor of distinct targets of hematopoietic potential with the chance to predict CBU potentially useful for unrelated recipients or limited for family-directed or autologous use

Clinical impact of high-density mapping on the acute and long term outcome of atypical atrial flutter ablations

Purpose We evaluated the clinical impact of the high-density (HD) mapping compared with the standard low-density (LD) ablation catheter mapping technique in the treatment of AFLs. Methods We retrospectively evaluated short and long outcomes of patients approached with an HD and a LD electro-anatomical strategy for atypical AFLs. Results Eighty-seven patients were included. Patients were almost male (60%), relatively old (65 +/- 8 years), with a moderate CHA2DS2Vasc score (2.3 +/- 1.3), a preserved ejection fraction (58 +/- 6), and moderate atrial dilatation (44 +/- 7 mm). Baseline clinical characteristics were comparable between groups (p = NS). Among AFLs, 10 (11%) were located in the right and 78 (89%) in the left atrium, including 22 (28%) roof dependent and 37 (47%) mitral dependent (p = NS). Sinus rhythm restoration during ablation was more frequently observed in the HD group (79% vs 56%, p = 0.037), without differences in mapping time, procedural time, and radiological dose (p = NS). Overall AFL/AT/AF recurrence rate at 1, 2, and 3 years was lower in the HD group (14% vs 37% p = 0.02, 14% vs 48% p = 0.002 and 14% vs 50% p < 0.001, respectively) with a time-dependent trend only in the LD group (37% vs 48% vs 50% at 1, 2, and 3 years respectively, p = 0.059). HD mapping (OR 0.17; 95% CI 0.04-0.66) and younger age (OR 1.09; 95% CI 1.01-1.19) resulted independent predictors of overall arrhythmias at follow-up. Conclusions Short- and long-term outcomes of atypical AFL ablation were better in the case of HD mapping, which resulted independent predictor of arrhythmia recurrences

Ventricular tachycardia ablation guided or aided by scar characterization with cardiac magnetic resonance: rationale and design of VOYAGE study

Background Radiofrequency ablation has been shown to be a safe and effective treatment for scar-related ventricular arrhythmias (VA). Recent preliminary studies have shown that real time integration of late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) images with electroanatomical map (EAM) data may lead to increased procedure efficacy, efficiency, and safety. Methods VOYAGE is a prospective, randomized, multicenter controlled open label study designed to compare in terms of efficacy, efficiency, and safety a CMR aided/guided workflow to standard EAM-guided ventricular tachycardia (VT) ablation. Patients with an ICD or with ICD implantation expected within 1 month, with scar related VT, suitable for CMR and multidetector computed tomography (MDCT) will be randomized to a CMR-guided or CMR-aided approach, whereas subjects unsuitable for imaging or with image quality deemed not sufficient for postprocessing will be allocated to standard of care ablation. Primary endpoint is defined as VT recurrences (sustained or requiring appropriate ICD intervention) during 12 months follow-up, excluding the first month of blanking period. Secondary endpoints will include procedural efficiency, safety, impact on quality of life and comparison between CMR-guided and CMR-aided approaches. Patients will be evaluated at 1, 6 and 12 months. Discussion The clinical impact of real time CMR-guided/aided ablation approaches has not been thoroughly assessed yet. This study aims at defining whether such workflow results in more effective, efficient, and safer procedures. If proven to be of benefit, results from this study could be applied in large scale interventional practice. Trial registrationClinicalTrials.gov, NCT04694079, registered on January 1, 2021