115 research outputs found
Racial Differences in Clinical Treatment and Self-Care Behaviors of Adults with Chronic Heart Failure
BackgroundIn the United States, the highest prevalence of heart failure (HF) is in blacks followed by whites. Compared with whites, blacks have a higher risk of HFârelated morbidity and mortality and HFârelated hospitalization. Little research has focused on explaining the reasons for these disparities. The purpose of this study was to examine racial differences in demographic and clinical characteristics in blacks and whites with HF and to determine if these characteristics influenced treatment, or together with treatment, influenced selfâcare behaviors.Methods and ResultsThis was a secondary analysis of existing data collected from adults (n=272) with chronic HF enrolled from outpatient sites in the northeastern United States and followed for 6 months. After adjusting for sociodemographic and clinical characteristics within reduced (HFrEF) and preserved ejection fraction (HFpEF) groups, there were 2 significant racial differences in clinical treatment. Blacks with HFrEF were prescribed ACE inhibitors and hydralazine and isosorbide dinitrate (HâISDN) more often than whites. In the HFpEF group, blacks were taking more medications and were prescribed digoxin and a diuretic when symptomatic. Deficits in HF knowledge and decreased medication adherence, objectively measured, were more prominent in blacks. These racial differences were not explained by sociodemographic or clinical characteristics or clinical treatment variables. Premorbid intellect and the quality of support received contributed to clinical treatment and selfâcare.ConclusionAlthough few differences in clinical treatment could be attributed solely to race, knowledge about HF and medication adherence is lower in blacks than whites. Further research is needed to explain these observations, which may be targets for future intervention research
The Brink of the Abyss: From Transcatheter Aortic Valve Implantation, to Impella, to Left Ventricular Assist Device Destination Therapy
Acute valvular emergencies are common causes of cardiogenic shock. Patients with critical aortic pathologies causing shock frequently undergo percutaneous interventions for valve replacement. However, in cases of persistent cardiogenic shock after valve replacement, there are limited options for further mechanical support. In this case study, we report a patient with a prior history of aortic valve replacement who presented in cardiogenic shock. After a transcatheter aortic valve-in-valve replacement, he remained in persistent shock with worsening clinical parameters requiring escalating inotropic and vasopressor support. With input from a multidisciplinary care team, an Impella 5.5 (Abiomed, Inc.) was placed through the valve for mechanical circulatory support, ultimately serving as a bridge to a durable left ventricular assist device as destination therapy. This technically challenging approach was successful, and the patient was discharged to acute rehabilitation with improved symptoms
On "many black hole" space-times
We analyze the horizon structure of families of space times obtained by
evolving initial data sets containing apparent horizons with several connected
components. We show that under certain smallness conditions the outermost
apparent horizons will also have several connected components. We further show
that, again under a smallness condition, the maximal globally hyperbolic
development of the many black hole initial data constructed by Chrusciel and
Delay, or of hyperboloidal data of Isenberg, Mazzeo and Pollack, will have an
event horizon, the intersection of which with the initial data hypersurface is
not connected. This justifies the "many black hole" character of those
space-times.Comment: several graphic file
Resolving Curvature Singularities in Holomorphic Gravity
We formulate holomorphic theory of gravity and study how the holomorphy
symmetry alters the two most important singular solutions of general
relativity: black holes and cosmology. We show that typical observers (freely)
falling into a holomorphic black hole do not encounter a curvature singularity.
Likewise, typical observers do not experience Big Bang singularity. Unlike
Hermitian gravity \cite{MantzHermitianGravity}, Holomorphic gravity does not
respect the reciprocity symmetry and thus it is mainly a toy model for a
gravity theory formulated on complex space-times. Yet it is a model that
deserves a closer investigation since in many aspects it resembles Hermitian
gravity and yet calculations are simpler. We have indications that holomorphic
gravity reduces to the laws of general relativity correctly at large distance
scales.Comment: 14 pages, 7 figure
The many symmetries of Calabi-Yau compactifications
We review the major mathematical concepts involved in the dimensional
reduction of D=11 N=1 supergravity theory over a Calabi-Yau manifold with
non-trivial complex structure moduli resulting in ungauged D=5 N=2 supergravity
theory with hypermultiplets. This last has a particularly rich structure with
many underlying geometries. We reproduce the entire calculation and
particularly emphasize its symplectic symmetry and how that arises from the
topology of the underlying subspace. The review is intended to fill in a
specific gap in the literature with the hope that it would be useful to both
the beginner and the expert alike.Comment: 47 page
Interim analyses of data as they accumulate in laboratory experimentation
BACKGROUND: Techniques for interim analysis, the statistical analysis of results while they are still accumulating, are highly-developed in the setting of clinical trials. But in the setting of laboratory experiments such analyses are usually conducted secretly and with no provisions for the necessary adjustments of the Type I error-rate. DISCUSSION: Laboratory researchers, from ignorance or by design, often analyse their results before the final number of experimental units (humans, animals, tissues or cells) has been reached. If this is done in an uncontrolled fashion, the pejorative term 'peeking' has been applied. A statistical penalty must be exacted. This is because if enough interim analyses are conducted, and if the outcome of the trial is on the borderline between 'significant' and 'not significant', ultimately one of the analyses will result in the magical P = 0.05. I suggest that Armitage's technique of matched-pairs sequential analysis should be considered. The conditions for using this technique are ideal: almost unlimited opportunity for matched pairing, and a short time between commencement of a study and its completion. Both the Type I and Type II error-rates are controlled. And the maximum number of pairs necessary to achieve an outcome, whether P = 0.05 or P > 0.05, can be estimated in advance. SUMMARY: Laboratory investigators, if they are to be honest, must adjust the critical value of P if they analyse their data repeatedly. I suggest they should consider employing matched-pairs sequential analysis in designing their experiments
Description and validation of a Markov model of survival for individuals free of cardiovascular disease that uses Framingham risk factors
BACKGROUND: Estimation of cardiovascular disease risk is increasingly used to inform decisions on interventions, such as the use of antihypertensives and statins, or to communicate the risks of smoking. Crude 10-year cardiovascular disease risk risks may not give a realistic view of the likely impact of an intervention over a lifetime and will underestimate of the risks of smoking. A validated model of survival to act as a decision aid in the consultation may help to address these problems. This study aims to describe the development of such a model for use with people free of cardiovascular disease and evaluates its accuracy against data from a United Kingdom cohort. METHODS: A Markov cycle tree evaluated using cohort simulation was developed utilizing Framingham estimates of cardiovascular risk, 1998 United Kingdom mortality data, the relative risk for smoking related non-cardiovascular disease risk and changes in systolic blood pressure and serum total cholesterol total cholesterol with age. The model's estimates of survival at 20 years for 1391 members of the Whickham survey cohort between the ages of 35 and 65 were compared with the observed survival at 20-year follow-up. RESULTS: The model estimate for survival was 75% and the observed survival was 75.4%. The correlation between estimated and observed survival was 0.933 over 39 subgroups of the cohort stratified by estimated survival, 0.992 for the seven 5-year age bands from 35 to 64, 0.936 for the ten 10 mmHg systolic blood pressure bands between 100 mmHg and 200 mmHg, and 0.693 for the fifteen 0.5 mmol/l total cholesterol bands between 3.0 and 10.0 mmol/l. The model significantly underestimated mortality in those people with a systolic blood pressure greater than or equal to 180 mmHg (p = 0.006). The average gain in life expectancy from the elimination of cardiovascular disease risk as a cause of death was 4.0 years for all the 35 year-old men in the sample (n = 24), and 1.8 years for all the 35 year-old women in the sample (n = 32). CONCLUSIONS: This model accurately estimates 20-year survival in subjects from the Whickham cohort with a systolic blood pressure below 180 mmHg
Light propagation in statistically homogeneous and isotropic universes with general matter content
We derive the relationship of the redshift and the angular diameter distance
to the average expansion rate for universes which are statistically homogeneous
and isotropic and where the distribution evolves slowly, but which have
otherwise arbitrary geometry and matter content. The relevant average expansion
rate is selected by the observable redshift and the assumed symmetry properties
of the spacetime. We show why light deflection and shear remain small. We write
down the evolution equations for the average expansion rate and discuss the
validity of the dust approximation.Comment: 42 pages, no figures. v2: Corrected one detail about the angular
diameter distance and two typos. No change in result
The Anemia Stress Index-Anemia, Transfusions, and Mortality in Patients with Continuous Flow Ventricular Assist Devices
We aimed to identify a simple metric accounting for peri-procedural hemoglobin changes, independent of blood product transfusion strategies, and assess its correlation with outcomes in patients undergoing left ventricular assist device (LVAD) implantation We included consecutive patients undergoing LVAD implantation at a single center between 10/1/2008 and 6/1/2014. The anemia stress index (ASI), defined as the sum of number of packed red blood cells transfused and the hemoglobin changes after LVAD implantation, was calculated for each patient at 24 h, discharge, and 3 months after LVAD implantation. Our cohort included 166 patients (80.1% males, mean age 56.3 ± 15.6 years) followed up for a median of 12.3 months. Increases in ASI per unit were associated with a higher hazard for all-cause mortality and early RV failure. The associations between the ASI and all-cause mortality persisted after multivariable adjustment, irrespective of when it was calculated (adjusted HR of 1.11, 95% CI 1.03-1.20 per unit increase in ASI). Similarly, ASI at 24 h after implant was associated with early RV failure despite multivariable adjustment (OR 1.09, 95% CI 1.05-1.14). We present a novel metric, the ASI, that is correlated with an increased risk for all-cause mortality and early RV failure in LVAD recipients
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Predicting Long Term Outcome in Patients Treated With Continuous Flow Left Ventricular Assist Device: The PennâColumbia Risk Score
Background: Predicting which patients are unlikely to benefit from continuous flow left ventricular assist device (LVAD) treatment is crucial for the identification of appropriate patients. Previously developed scoring systems are limited to past eras of device or restricted to specific devices. Our objective was to create a risk model for patients treated with continuous flow LVAD based on the preimplant variables. Methods and Results: We performed a retrospective analysis of all patients implanted with a continuous flow LVAD between 2006 and 2014 at the University of Pennsylvania and included a total of 210 patients (male 78%; mean age, 56±15; mean followâup, 465±486 days). From all plausible preoperative covariates, we performed univariate Cox regression analysis for covariates affecting the odds of 1âyear survival following implantation (P<0.2). These variables were included in a multivariable model and dropped if significance rose above P=0.2. From this base model, we performed stepâwise forward and backward selection for other covariates that improved power by minimizing Akaike Information Criteria while maximizing the Harrell Concordance Index. We then used KaplanâMeier curves, the logârank test, and Cox proportional hazard models to assess internal validity of the scoring system and its ability to stratify survival. A final optimized model was identified based on clinical and echocardiographic parameters preceding LVAD implantation. Oneâyear mortality was significantly higher in patients with higher risk scores (hazard ratio, 1.38; P=0.004). This hazard ratio represents the multiplied risk of death for every increase of 1 point in the risk score. The risk score was validated in a separate patient cohort of 260 patients at Columbia University, which confirmed the prognostic utility of this risk score (P=0.0237). Conclusion: We present a novel risk score and its validation for prediction of longâterm survival in patients with current types of continuous flow LVAD support
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