3PO: Programmed Far-Memory Prefetching for Oblivious Applications

Using memory located on remote machines, or far memory, as a swap space is a promising approach to meet the increasing memory demands of modern datacenter applications. Operating systems have long relied on prefetchers to mask the increased latency of fetching pages from swap space to main memory. Unfortunately, with traditional prefetching heuristics, performance still degrades when applications use far memory. In this paper we propose a new prefetching technique for far-memory applications. We focus our efforts on memory-intensive, oblivious applications whose memory access patterns are independent of their inputs, such as matrix multiplication. For this class of applications we observe that we can perfectly prefetch pages without relying on heuristics. However, prefetching perfectly without requiring significant application modifications is challenging. In this paper we describe the design and implementation of 3PO, a system that provides pre-planned prefetching for general oblivious applications. We demonstrate that 3PO can accelerate applications, e.g., running them 30-150% faster than with Linux's prefetcher with 20% local memory. We also use 3PO to understand the fundamental software overheads of prefetching in a paging-based system, and the minimum performance penalty that they impose when we run applications under constrained local memory.Comment: 14 page

Cardiac anomalies in the setting of the Abernethy malformation of the portal vein

We describe a child with tricuspid atresia associated with a porto-systemic shunt and complete absence of the portal vein, the latter known as the Abernethy malformation. As far as we are aware, this association has not previously been reported. We review the various cardiac defects that have been reported in children with the Abernethy malformation, emphasizing the interesting clinical presentations of this rare malformation of the portal venous system

Low Recurrence Rate in Treating Atrioventricular Nodal Reentrant Tachycardia with Triple Freeze‐Thaw Cycles

Background Cryoablation is an alternative to radiofrequency ablation in treating atrioventricular nodal reentrant tachycardia (AVNRT). However, its long‐term effectiveness is in question when compared to radiofrequency ablation. We reviewed the results of cryoablation in children with AVNRT at our institute. Methods We performed a retrospective single‐center chart review of consecutive patients ≤18 years of age with AVNRT who underwent cryoablation between January 2007 and August 2009. During cryoablation, a 6‐mm‐tip cryocatheter was used with temperature set to −80°C. Test lesions were performed at the presumed slow pathway location based on combined anatomic and electrophysiologic approach. If successful, ablation was then continued with triple freeze‐thaw cycles (FTC) of 4 minutes each. Results A total of 53 patients (age range: 6.1–18.4 years, mean: 13.6 years, median: 13.2 years) underwent slow pathway modification with cryoablation. Acute success was achieved in 51 (96.2%) cases. Transient atrioventricular block was seen in 19 cases. The block occurred during FTC in eight patients (15%). The number of FTC was three in 47 (92.2%) patients. Less than three FTC were given in two patients due to transient heart block and four FTC were given in two patients with suspected catheter movement. Procedure duration was 177 ± 56 minutes; fluoroscopic time was 14 ± 11 minutes. Mean follow‐up was 30.7 ± 10 (range 12–52, median 31) months. Recurrence of supraventricular tachycardia was seen in only one (1.96%) patient. Conclusions Triple FTC cryoablation lesions resulted in a low recurrence rate comparable to RF ablation in treating AVNRT without increased complications

Associations between neurohormonal and inflammatory activation and heart failure in children

Adult heart failure (HF) has been shown to be associated with neuroendocrine and inflammatory activation. We hypothesize that neuroendocrine and inflammatory activation also associate with symptom severity and echocardiographic measurements in pediatric HF. Nineteen children with HF were divided into 3 symptom severity groups. Measurements were made of left ventricular (LV) ejection fraction, LV shortening fraction (LVSF), LV shortening fraction Z score (LVSFz), and LV end-systolic (LVSDz) and diastolic diameter Z scores. Blood levels of N-terminal prohormone brain natriuretic peptide (NT-proBNP), high-sensitivity C-reactive protein (hsCRP), tumor necrosis factor alpha, and soluble tumor necrosis factor receptor II were measured. NT-proBNP and hsCRP were significantly elevated with more severe symptoms (P < or = .003) and discriminated between clinical severity groups (volume under the receiver operating characteristic surface = 0.58 and 0.62, P = .007 and P = .002, respectively). NT-proBNP was negatively associated with LV ejection fraction, LVSF, and LVSFz (P < or = .05) and positively associated with LVSDz (P < .001). High-sensitivity C-reactive protein was negatively associated with LVSF (P = .02) and positively associated with NT-proBNP (P = .03). Tumor necrosis factor alpha was negatively associated with LVSF and LVSFz (P < or = .03) and positively associated with LVSDz and NT-proBNP (P < or = .02). Soluble tumor necrosis factor receptor II was negatively associated with LVSFz (P = .03). Neuroendocrine and inflammatory activation are associated with more severe symptoms and worse cardiac characteristics in pediatric HF. Blood levels of these biomarkers could be used to better assess the severity of HF in children

Serial measurements of serum NT-proBNP as markers of left ventricular systolic function and remodeling in children with heart failure

Increasing serum levels of N-terminal pro-hormone brain natriuretic peptide (NT-proBNP) are associated with worsening heart failure (HF) in adults. We determined whether changes in NT-proBNP level are associated with changes in symptoms and left ventricular (LV) systolic function and remodeling in children with HF secondary to dilated cardiomyopathy. We retrospectively examined associations between serum NT-proBNP levels and NYHA/Ross functional class, LV systolic and diastolic diameter (LVSD-z and LVDD-z), LV ejection fraction (LVEF), and LV shortening fraction (LVSF-z) using generalized linear mixed models. Fluctuation in functional class of subjects was also modeled using logistic regression and receiver operating characteristic (ROC) curves. In 36 children (14 males), a 10-fold increase in NT-proBNP serum levels was associated ( P < .001) with a 9.8% decrease in LVEF, a 3.25-unit drop in LVSF-z, a 1.53-unit increase in LVDD-z, a 2.64-unit increase in LVSD-z, and an increased odds of being in functional class III/IV (OR 85.5; 95% CI, 10.9 to 671.0). An NT-proBNP level greater than 1000 pg/mL identified children constantly or intermittently in functional class III-IV with 95% sensitivity and 80% specificity. The reliability of a single NT-proBNP value was 0.61, but the means for two and three NT-proBNP values were 0.76 and 0.82, respectively. In children with HF, NT-proBNP is associated with cardiac symptoms and indices of LV systolic dysfunction and remodeling. NT-proBNP >1000 pg/mL identifies highly symptomatic children. Within subject serial measurements of NT-proBNP are needed for a reliable and accurate determination of disease status and/or course

Serial measurements of serum NT-proBNP as markers of left ventricular systolic function and remodeling in children with heart failure

BACKGROUND: Increasing serum levels of N-terminal pro-hormone brain natriuretic peptide (NT-proBNP) are associated with worsening heart failure (HF) in adults. We determined whether changes in NT-proBNP level are associated with changes in symptoms and left ventricular (LV) systolic function and remodeling in children with HF secondary to dilated cardiomyopathy. METHODS: We retrospectively examined associations between serum NT-proBNP levels and NYHA/Ross functional class, LV systolic and diastolic diameter (LVSD-z and LVDD-z), LV ejection fraction (LVEF), and LV shortening fraction (LVSF-z) using generalized linear mixed models. Fluctuation in functional class of subjects was also modeled using logistic regression and receiver operating characteristic (ROC) curves. RESULTS: In 36 children (14 males), a 10-fold increase in NT-proBNP serum levels was associated (P<0.001) with a 9.8% decrease in LVEF, a 3.25-unit drop in LVSF-z, a 1.53-unit increase in LVDD-z, a 2.64-unit increase in LVSD-z, and an increased odds of being in functional class III/IV (OR 85.5; 95% CI, 10.9 to 671.0). An NT-proBNP level greater than 1000 pg/mL identified children constantly or intermittently in functional class III-IV with 95% sensitivity and 80% specificity. The reliability of a single NT-proBNP value was 0.61, but the means for two and three NT-proBNP values were 0.76 and 0.82, respectively. CONCLUSIONS: In children with HF, NT-proBNP is associated with cardiac symptoms and indices of LV systolic dysfunction and remodeling. NT-proBNP >1000 pg/mL identifies highly symptomatic children. Within subject serial measurements of NT-proBNP are needed for a reliable and accurate determination of disease status and/or course