Machine learning to identify a composite indicator to predict cardiac death in ischemic heart disease

BACKGROUND

Machine learning (ML) employs algorithms that learn from data, building models with the potential to predict events by aggregating a large number of variables and assessing their complex interactions. The aim of this study is to assess ML potential in identifying patients with ischemic heart disease (IHD) at high risk of cardiac death (CD).

METHODS

3987 (mean age 68 ± 11) hospitalized IHD patients were enrolled. We implemented and compared various ML models and their combination into ensembles. Model output constitutes a new ML indicator to be employed for stratification. Primary variable importance was assessed with ablation tests.

RESULTS

An ensemble classifier combining three ML models achieved the best performance to predict CD (AUROC of 0.830, F1-macro of 0.726). ML indicator use through Cox survival analysis outperformed the 18 variables individually, producing a better stratification compared to standard multivariate analysis (improvement of ∼20%). Patients in the low risk group defined through ML indicator had a significantly higher survival (88.8% versus 29.1%). The main variables identified were Dyslipidemia, LVEF, Previous CABG, Diabetes, Previous Myocardial Infarction, Smoke, Documented resting or exertional ischemia, with an AUROC of 0.791 and an F1-score of 0.674, lower than that of 18 variables. Both code and clinical data are freely available with this article.

CONCLUSION

ML may allow a faster, low-cost and reliable evaluation of IHD patient prognosis by inclusion of more predictors and identification of those more significant, improving outcome prediction towards the development of precision medicine in this clinical field.

Anhydrous Phase B: Transmission Electron Microscope Characterization and Elastic Properties

Anhydrous phase B and stishovite formed directly from olivine in experiments at 14 GPa and 1400 °CThe structure of anhydrous phase B is determined ab initio from precession electron diffraction tomography in transmission electron microscopyElastic and seismic properties of anhydrous phase B are calculated.

World Health Organization cardiovascular risk stratification and target organ damage

BACKGROUND

Prediction charts allow treatment to be targeted according to simple markers of cardiovascular risk; many algorithms do not recommend screening asymptomatic target organ damage which could change dramatically the assessment.

OBJECTIVE

To demonstrate that target organ damage is present in low cardiovascular risk hypertensive patients and it is more frequent and severe as global cardiovascular risk increases.

METHODS

Consecutive hypertensive patients treated at a single Latin American center. Cardiovascular risk stratified according to 2013 WHO/ISH risk prediction chart America B. Left ventricular mass assessed by Devereux method, left ventricular hypertrophy considered >95g/m(2) in women and >115g/m(2) in men. Transmitral diastolic peak early flow velocity to average septal/lateral peak early diastolic relaxation velocity (E/e' ratio) measured cut off value >13. Systolic function assessed by tissue Doppler average interventricular septum/lateral wall mitral annulus rate systolic excursion (s wave).

RESULTS

A total of 292 patients were included of whom 159 patients (54.5%) had cardiovascular risk of <10%, 90 (30.8%) had cardiovascular risk of 10-20% and 43 (14.7%) had cardiovascular risk of >20%. Left ventricular hypertrophy was detected in 17.6% low risk patients, 27.8% in medium risk and 23.3% in high risk (p<0.05), abnormal E/e' ratio was found in 13.8%, 31.1% and 27.9%, respectively (p<0.05). Mean s wave was 8.03+8, 8.1+9 and 8.7+1cm/s for low, intermediate and high risk patients, respectively (p<0.025).

CONCLUSIONS

Target organ damage is more frequent and severe in high risk; one over four subjects was misclassified due to the presence of asymptomatic target organ damage.

Investigation of nucleation processes during dynamic recrystallization of ice using cryo-EBSD

Nucleation mechanisms occurring during dynamic recrystallization play a crucial role in the evolution of microstructures and textures during high temperature deformation. In polycrystalline ice, the strong viscoplastic anisotropy induces high strain heterogeneities between grains which control the recrystallization mechanisms. Here, we study the nucleation mechanisms occurring during creep tests performed on polycrystalline columnar ice at high temperature and stress (T=-5°C;σ=0.5 MPa) by post-mortem analyses of deformation microstructures using cryogenic electron backscatter diffraction. The columnar geometry of the samples enables discrimination of the nuclei from the initial grains. Various nucleation mechanisms are deduced from the analysis of the nuclei relations with the dislocation sub-structures within grains and at grain boundaries. Tilt sub-grain boundaries and kink bands are the main structures responsible for development of polygonization and mosaic sub-structures. Nucleation by bulging at serrated grain boundaries is also an efficient nucleation mechanism near the grain boundaries where strain incompatibilities are high. Observation of nuclei with orientations not related to the 'parent' ones suggests the possibility of 'spontaneous' nucleation driven by the relaxation of the dislocation-related internal stress field. The complexity of the nucleation mechanisms observed here emphasizes the impact of stress and strain heterogeneities on dynamic recrystallization mechanisms.This article is part of the themed issue 'Microdynamics of ice'.

A new method to integrate ZnO nano-tetrapods on MEMS micro-hotplates for large scale gas sensor production

A new method, which is easily scalable to large scale production, has been developed to obtain gas sensor devices based on zinc oxide (ZnO) nanostructures with a 'tetrapod' shape. The method can be easily extended to other kinds of nanostructures and is based on the deposition of ZnO nanostructures through polymeric masks by centrifugation, directly onto properly designed MEMS micro-hotplates. The micromachined devices, after the mask is peeled off, are ready for electrical bonding and sensing test. Sensor response has been successfully measured for some gases and volatile organic compounds with different chemical properties (ethanol, methane, nitrogen dioxide, hydrogen sulfide).

Morphologic and Functional Heart Abnormalities Associated to High Modified Tei Index in Hypertensive Patients

INTRODUCTION

LV dysfunction develops early in hypertension, even previously to left ventricular remodeling.

AIMS

To determine the frequency of morphologic and functional heart abnormalities associated to abnormal modified Tei Index in untreated hypertensive (HBP) patients (p) with preserved ejection fraction (pEF).

METHODS

Case-control study. Three groups: (1) HBP without left ventricular hypertrophy (LVH); (2) HBP with LVH; (3) non-HBP controls. Ejection fraction >54 % identified pEF. LVH measured by Devereux method. Systolic and diastolic functions assessed by standard echocardiography and tissue Doppler. 2013 ESH/ESC Hypertension Guidelines normal values were considered. Tei index measured at the lateral and septal LV walls in apical 4-chamber view by tissue Doppler, value >0.40 considered abnormal.

STATISTICAL ANALYSIS

multifactorial ANOVA test adjusted by sex and age, p < 0.05 statistically significant.

RESULTS

The study included 14 controls, 88 HBP p without LVH, and 19 HBP p with LVH. The HBP p sample mean age was 58.7 ± 13.5 years and 52 (44.1 %) were males. Mean Tei Index was 0.35 ± 0.03 in controls; 0.42 ± 0.05 in HBP without LVH; and 0.42 ± 0.06 in HBP with LVH (p < 0.025). Abnormal Tei Index was present in 2p (14.3 %) controls; 64 p (72.7 %) HBP without LVH; and 15 p (78.9 %) HBP with LVH (p < 0.0009). Tissue Doppler's wave was 8.4 ± 0.9 cm/s in controls; 8 ± 1.6 cm/s in HBP without LVH and 7.8 ± 1.1 cm/s in HBP with LVH.

CONCLUSIONS

(1) Left ventricular dysfunction is frequent in HBP p, even without LVH; (2) modified tissue Doppler Tei index is a useful tool for the diagnosis of left ventricular dysfunction.

Implant-prosthetic rehabilitation after excision of hard palate gland carcinoma

In Summer 2002, a patient with frequent epistaxis was admitted to the San Gerardo Hospital. Local examination showed a big mass in the nasal fossa. TC and RMN revealed a diffuse erosion of the palatal bone and infiltration of the maxilla. The tumor was removed and histological examination showed a gland carcinoma. The young age of the patient and the need of an adequate bone reconstruction led to use osteoperiosteal calf bone graft. Subsequently, using local anesthesia, 6 implants were positioned. After normal healing and the period of osteointegration, a Toronto bridge was made on implants that the patient wears with no problem.

Anisotropy of thermal diffusivity in the upper mantle

Heat transfer in the mantle is a key process controlling the Earth's dynamics. Upper-mantle mineral phases, especially olivine, have been shown to display highly anisotropic thermal diffusivity at ambient conditions, and seismic anisotropy data show that preferred orientations of olivine induced by deformation are coherent at large scales (>50 km) in the upper mantle. Thus heat transport in the upper mantle should be anisotropic. But the thermal anisotropy of mantle minerals at high temperature and its relationship with deformation have not been well constrained. Here we present petrophysical modelling and laboratory measurements of thermal diffusivity in deformed mantle rocks between temperatures of 290 and 1,250 K that demonstrate that deformation may induce a significant anisotropy of thermal diffusivity in the uppermost mantle. We found that heat transport parallel to the flow direction is up to 30 per cent faster than that normal to the flow plane. Such a strain-induced thermal anisotropy implies that the upper-mantle temperature distribution, rheology and, consequently, its dynamics, will depend on deformation history. In oceans, resistive drag flow would result in lower vertical diffusivities in both the lithosphere and asthenosphere and hence in less effective heat transfer from the convective mantle. In continents, olivine orientations frozen in the lithosphere may induce anisotropic heating above mantle plumes, favouring the reactivation of pre-existing structures.

Prevalence of hypertension in patients on peritoneal dialysis: results of an Italian multicentre study

BACKGROUND

The tenet that peritoneal dialysis is capable of either normalizing or improving blood pressure control in uraemic patients is based on outdated or monocentric experiences. Therefore, we assessed the prevalence of hypertension and the efficacy of antihypertensive therapy in a large, multicentric cohort of patients on peritoneal dialysis.

METHODS

Twenty seven out of the 50 centres belonging to the Italian Co-operative Peritoneal Dialysis Study Group took part in the study. The main patient selection criteria were: peritoneal dialysis therapy for at least 3 months and no peritonitis or changes in dialysis technique for at least 1 month. Clinical blood pressure was measured according to WHO/ISH guidelines. Ambulatory blood pressure monitoring was carried out using a SpaceLabs 90207 recorder. Hypertension was defined according to WHO/ISH criteria and staged according to the criteria of the Joint National Committee on Detection, Evaluation and Treatment of High Blood Pressure (JNC), 5th Report. Ambulatory blood pressure monitoring recordings were used to evaluate white-coat hypertension, blood pressure load and the dipping phenomenon.

RESULTS

Five hundred and four subjects were evaluated. Hypertension was prevalent in 88.1% of the population, and 362 out of 444 hypertensive patients were on antihypertensive therapy. JNC staging revealed that 188 patients had moderate to severe hypertension. Blood pressure load was pathological in 77.3% of the patients receiving antihypertensive treatment. White-coat hypertension was identified in 9.1% of the hypertensive patients not on antihypertensive therapy, and 53.1% of the patients were non-dippers.

CONCLUSIONS

The study demonstrates that hypertension is a dramatic, unsolved problem in uraemic patients treated with peritoneal dialysis, and casts doubts on the effectiveness of our current peritoneal dialysis strategies and pharmacological management of hypertension.

On-line computer analysis of chemiluminescent reactions, with application to a luminescent immunoassay for free cortisol in urine

We interfaced a microcomputer on-line with a luminometer to acquire the light signal of chemiluminescent reactions from a photomultiplier and then compute significant parameters of light emission and kinetic "shape" indices. Using this system to study interferences from biological samples on the measurement of chemiluminescent reactions, we observed that such effects are usually associated with modifications of the shape of the light-emission kinetics. These results suggest that a simultaneous evaluation of the shape of a chemiluminescent reaction and the measurement of light emission can be combined to assess luminescent immunoassays as an internal control of the interferences in measurements of the chemiluminescent tracer. As an example of this approach, we developed and validated a luminescent immunoassay for free cortisol in diluted urine. Dextran-coated charcoal is used for bound-free separation.

On-line computer analysis of chemiluminescent reactions, with application to a luminescent immunoassay for free cortisol in urine

We interfaced a microcomputer on-line with a luminometer to acquire the light signal of chemiluminescent reactions from a photomultiplier and then compute significant parameters of light emission and kinetic "shape" indices. Using this system to study interferences from biological samples on the measurement of chemiluminescent reactions, we observed that such effects are usually associated with modifications of the shape of the light-emission kinetics. These results suggest that a simultaneous evaluation of the shape of a chemiluminescent reaction and the measurement of light emission can be combined to assess luminescent immunoassays as an internal control of the interferences in measurements of the chemiluminescent tracer. As an example of this approach, we developed and validated a luminescent immunoassay for free cortisol in diluted urine. Dextran-coated charcoal is used for bound-free separation.

Homogeneous luminescence immunoassay for total estrogens in urine

We describe an homogeneous luminescence immunoassay for "total" estrogens in enzymically hydrolyzed urine from nonpregnant women. The antiserum, raised against estriol-16,17- dihemisuccinate conjugated to bovine serum albumin, specifically bound the C-19 steroids carrying the estrogen-characteristic phenolic group. 17 beta-Estradiol conjugated with aminobutylethyl isoluminol was used to monitor the immunological reaction; this conjugate was stable for at least two years. Because binding to the antiserum markedly enhances the light-producing efficiency of the tracer, no separation of bound and free antigen is necessary. Results (microgram/24 h) by this method (y) correlated well (r = 0.958) with those by a conventional fluorometric (x) method (y = 2. 51x - 2.83). The sensitivity (detection limit) is 4 micrograms/L and the precision compares well with that of commonly used RIA methods. The method appears suited to large numbers of samples, as in menstrual cycle monitoring.

Homogeneous luminescence immunoassay for total estrogens in urine

We describe an homogeneous luminescence immunoassay for "total" estrogens in enzymically hydrolyzed urine from nonpregnant women. The antiserum, raised against estriol-16,17- dihemisuccinate conjugated to bovine serum albumin, specifically bound the C-19 steroids carrying the estrogen-characteristic phenolic group. 17 beta-Estradiol conjugated with aminobutylethyl isoluminol was used to monitor the immunological reaction; this conjugate was stable for at least two years. Because binding to the antiserum markedly enhances the light-producing efficiency of the tracer, no separation of bound and free antigen is necessary. Results (microgram/24 h) by this method (y) correlated well (r = 0.958) with those by a conventional fluorometric (x) method (y = 2. 51x - 2.83). The sensitivity (detection limit) is 4 micrograms/L and the precision compares well with that of commonly used RIA methods. The method appears suited to large numbers of samples, as in menstrual cycle monitoring.

Luminescent immunoassay (LIA) for progesterone in a heterogeneous system

An immunoassay procedure for determination of progesterone in human plasma is described which utilizes chemiluminescence as the endpoint. The assay utilized progesterone-11-hemisuccinate-aminobutyl-ethyl-isoluminol (P-11-HS-ABEI) as the chemiluminescent marker conjugate and dextran coated charcoal for the separation of bound and free fractions of the ligand. An assay procedure for progesterone was established and validated in terms of sensitivity and precision, and assay results were compared with radioimmunoassay, using tritiated progesterone as the tracer. The two methods agreed well (n=35, r=0.96). The most important advantage of this assay is the elimination of problems inherent in the use of radioactive materials.

Evaluation of different progesterone-isoluminol conjugates for chemiluminescence immunoassay

The effect of varying the length of the alkyl bridge linking the chemiluminescent label isoluminol to progesterone on the light yield and binding affinity of progesterone chemiluminescent-marker conjugates was investigated. For this purpose five different derivatives of isoluminol, aminoethyl isoluminol (AEI), aminoethylethyl isoluminol (AEEI), aminobutyl isoluminol (ABI), aminobutyl-ethyl isoluminol (ABEI) and aminoethyl-ethyl isoluminol (AHEI) were covalently linked through a peptide bond to progesterone-11 alpha -hemisuccinate (P-11-HS). The resulting progesterone chemiluminescent-marker conjugates were then evaluated as potential labels for the development of an immunoassay based on monitoring chemiluminescence. These conjugates were able to compete with tritiated progesterone for the binding sites of an antibody raised against progesterone-11 alpha-HS bovine serum albumin, and they showed higher affinity than unaltered progesterone. These conjugates produced light upon oxidation by a hydrogen peroxide-microperoxidase system. The chemiluminescent reaction was optimized in terms of pH, concentration of oxidant, catalyst and conjugate design. Under optimal conditions, all the conjugates were detectable at femtomolar levels. The lowest detection limit was obtained using P-11-HS-ABEI (0.1 fmol). These results indicated that immunoassay techniques based on chemiluminescence can be developed with these labels.