Intrahepatic cholestasis in sickle cell disease: A review of diagnostic criteria, treatments, and case reports.

Objective To delineate the etiology, symptomatology, and treatment of sickle cell intrahepatic cholestasis (SCIC). Sickle cell disease (SCD) is the most frequently inherited hematologic disease, and SCIC is one rare and often fatal complication and comorbid disease. The literature contains only a small number of case reports involving SCIC and hence limited guidance can be obtained. Methods We reviewed the scientific literature to evaluate the science of SCIC to determine if there were consistencies in presentation, evaluation, treatment, and clinical outcomes. Results We reviewed 6 case reports and a limited number of clinical papers on SCIC. We reported consistencies in clinical presentation and treatment outcomes among cases as well as serological and hematological finding. Conclusions While there is some consistency in the symptom presentation of individuals with SCIC, reliable evaluation and clinical procedures were not demonstrated in what we reviewed. Further research is needed to delineate the attributes of this complicated disease that occurs within SCD.

A validation of estimated total peripheral resistance using twin data.

Chronically elevated total peripheral resistance (TPR) is a suspected contributor to the greater rates of hypertension in African Americans. Previous research suggests that over 50% of the variability in measures of vascular resistance may be attributable to genetic effects and genetic effects may play an even greater role in variability of TPR in African Americans. We have previously demonstrated the coherence of a simple equation-based estimate of total peripheral resistance (TPRest) with TPR obtained via a validated method (Hill et al, 2013). We sought further validation by estimating heritability for this measure. Using quantitative genetic analysis, heritabilites were calculated for TPRest during both a resting baseline and orthostasis in a population-based sample of African American mono- and dizygotic twins (mean age = 49.82 ± 14.62). Estimated heritability was greater for males (h2 = .40) both at rest and during orthostasis, compared to all other groups. This value is consistent with previously published point estimates of heritability. Collectively, these findings provide additional support for the validity of TPRest as a practical alternative for deriving additional hemodynamic data from archival sources.

Resistance reconstructed estimation of total peripheral resistance from computationally derived cardiac output - biomed 2013.

Efficient functioning of the peripheral vasculature is an essential component in healthy cardiovascular regulation. Alterations in this functioning have been linked to the etiology and pathophysiological course of cardiovascular disease (CVD), especially hypertension. Given its significant role in the maintenance of both healthy and pathological blood pressure, total peripheral resistance (TPR), an index of the vasoconstrictive and elastic properties of the peripheral vasculature, has received much attention in this regard. However, obtaining a reliable estimate of TPR remains a complex and costly endeavor, primarily due to the necessity for sophisticated instrumentation as well as associated limitations in deriving cardiac output (CO). We have previously described a simple estimation method for CO using only arterial blood pressure and heart rate (Hill et al, 2012). In the present study we extend this technique to the estimation of TPR using beat-to-beat blood pressure data from the same sample of 67 young (mean age = 20.04± 2.8), healthy men (n = 30) and women (n = 37). Estimated TPR (TPRest) was calculated from the computationally-derived estimate of CO and mean arterial pressure (MAP). Correlation between TPR obtained via the validated Model-Flow technique and TPRest was moderate (r =.73, p <. 000) and stronger in men (r =.78, p <. 000) compared to women (r =.66, p <. 001). These data further suggest that reconstructed measures of hemodynamic functioning may be validly and adequately estimated from limited data sources.

Evaluation of a simple estimation method for the derivation of cardiac output from arterial blood pressure and heart rate.

Cardiac Output (CO) is an important hemodynamic index of blood flow from and to the heart. Numerous estimation methods have been developed and validated for obtaining CO in clinical applications; however, the invasive nature of these may preclude their utility in less controlled settings. Additionally, several of the available non-invasive applications feature algorithms which are computationally complex or proprietarily-restricted and may not be feasible in all research contexts, such as ambulatory investigations. Among the many simple mathematical transforms purported to estimate CO, a common approach has been to multiply the stroke volume (SV) by the heart rate (HR), where stroke volume is obtained by multiplying the pulse pressure (PP) by a constant value (k). Contemporary interpretations have identified k = 2 as the ideal multiplier; however there is some controversy regarding the origin of this factor as well as the reliability of the resulting estimate. In the present study we evaluated this simple technique using baseline beat-to-beat blood pressure data from 67 young (mean age = 20.04 ± 2.8 years), healthy men (n = 30) and women (n = 37). Using Modelflow-derived CO as a reference, estimated CO (COest) was calculated from the mean Systolic and Diastolic blood pressures and the heart rate. Overall, the correlation between CO & COest was moderate (r = .60, p <.001). This association was stronger in men (r = .70, p <.001) compared to women (r = .54, p <.001). Bland-Altman analysis confirmed this pattern as 97% of cases for men fell within the limits of agreement. Overall, our results indicate that under resting conditions this derivation is comparable to the Modelflow estimate and seemingly more consistent in men compared to women.

A user-friendly application for the extraction of kubios hrv output to an optimal format for statistical analysis - biomed 2011.

The aim of the present manuscript is to present a user-friendly and flexible platform for transforming Kubios HRV output files to an .xls-file format, used by MS Excel. The program utilizes either native or bundled Java and is platform-independent and mobile. This means that it can run without being installed on a computer. It also has an option of continuous transferring of data indicating that it can run in the background while Kubios produces output files. The program checks for changes in the file structure and automatically updates the .xls- output file.

Effects of autonomic innervation on the heart as a function of effector tissue - biomed 2010.

Conceptualizations of parasympathetic and sympathetic activity of the autonomic nervous system as representing a bi-dimensional autonomic space have driven recent discussions surrounding the degree of respective and interactive influence of each branch on visceral organs (e.g. heart). An important consideration of autonomic influences on cardiac function is the presence of at least three types of functions: chronotropy, inotropy and dromotropy, each of which shares a unique relationship with ANS activation including sympathetic-parasympathetic interactions. Additionally, the heart is composed of a number of types of effector tissues such that the influence of ANS activation at the sinoatrial (SA) node differs from that at the atrioventricular (AV) node, and these effector sites may reflect sympathetic contributions to the interactive ANS dynamic even under tonic conditions. Given recent indications that tonic cardiac parasympathetic influences appear to vary significantly as a function of ethnicity, it is not yet known to what extent this difference may extend to sympathetic cardiac influences or the degree to which the modes of interaction between the PNS and SNS may be affected. The present investigation sought to further delineate the respective and interactive contributions of parasympathetic and sympathetic influences on the heart, and to explore the influence of individual differences on these measures.

Data transforms for spectral analyses of heart rate variability.

Autoregressive and fast Fourier transform spectral analyses of high-frequency heart rate variability (HF-HRV) result in exponentially-distributed values that make standard parametric statistical analyses problematic. In this paper, we evaluate three transforms of raw HF-HRV spectral power. Two occur commonly in the literature (a natural log [ln] transform and a reactivity transform); a third is novel (a "percent deviation from the mean" transform). A single data set was used, with each subject providing two data points and for which we predicted a significant difference in HF-HRV power. We quantified the effect size of each transform by noting the percentage of (non)overlap between the +/- 1 standard errors surrounding the two period means, with less overlap indicating a stronger effect. Overlap was 19.2% in the raw data (Fig 1b.), 3.7% in the ln transform (Fig. 2b), -57.1% in the reactivity transform (Fig. 3b), and -70.2% in the percent deviation transform (Fig. 4b). The percent deviation transform resulted in more normally-distributed data than the reactivity transform and more tightly distributed data than the ln transform, making it a favorable choice for investigators.