Adaptation of the standard 12-lead electrocardiogram system dedicated to the analysis of atrial fibrillation

Objective

The objective of the study was to design a lead system aimed at studying atrial fibrillation (AF), while being anchored to the standard 12-lead system.

Methods

The location of 4 of the 6 precordial electrodes was optimized while leaving the remaining 5 of the 9 electrodes of the standard 12-lead system in place. The analysis was based on episodes of 11 different variants of AF simulated by a biophysical model of the atria positioned inside an inhomogeneous thorax. The optimization criterion used was derived from the singular value decomposition of the data matrices.

Results

While maintaining VR, VL, VF, V₁ and V₄, the 4 new electrode positions increased the ratio of the eighth and the first singular values of the data matrices of the new configuration about 5-fold compared with that of the conventional electrode positions.

Conclusion

The adapted lead system produces a more complete view on AF compared with that of the standard 12-lead system.     

Outcome of pregnancy in women with congenital heart disease: a literature review

A search of peer-reviewed literature was conducted to identify reports that provide data on complications associated with pregnancy in women with structural congenital heart disease (CHD). This review describes the outcome of 2,491 pregnancies, including 377 miscarriages (15%) and 114 elective abortions (5%). Important cardiac complications were seen in 11% of the pregnancies. Obstetric complications do not appear to be more prevalent. In complex CHD, premature delivery rates are high, and more children are small for gestational age. The offspring mortality was high throughout the spectrum and was related to the relatively high rate of premature delivery and recurrence of CHD.     

Drug Insight: pharmacology and toxicity of thiopurine therapy in patients with IBD

Thiopurines are frequently used for the treatment of IBD. The complex pharmacology, metabolism, mechanism of action and toxicity profile of these immunosuppressive drugs have now been partly elucidated. The activity of thiopurines is partly mediated by the metabolite 6-thioguanosine 5'-triphosphate, which inhibits the function of the small GTPase Rac1, leading to apoptosis of activated T cells, and influences the conjugation of T cells with antigen-presenting cells. The activity of the enzyme thiopurine S-methyltransferase has a major influence on the bioavailability and toxicity of thiopurines, and several thiopurine metabolites might have adverse effects in patients. Myelotoxicity can be caused by grossly elevated levels of 6-thioguanine nucleotides, and elevated levels of 6-methylmercaptopurine ribonucleotides have been associated with hepatotoxicity. The sensitivity and specificity of these methylated metabolites for predicting thiopurine-induced liver enzyme abnormalities are, however, poor. 6-Thioguanine has been suggested as an alternative to the classical thiopurines azathioprine and 6-mercaptopurine for the treatment of IBD, but there are concerns about its toxicity profile, especially with regard to the induction of nodular regenerative hyperplasia of the liver. Data now suggest that the induction of nodular regenerative hyperplasia of the liver during 6-thioguanine therapy might be dose-dependent or dependent on the level of 6-thioguanine nucleotides.     

A specific attentional bias in panic disorder?

According to cognitive theories, panic patients are assumed to have an attentional bias toward bodily sensations. To date, there is only some indirect evidence of such a bias measured by an emotional Stroop task. Moreover, the content and disorder specificity of this bias is rather unclear. The aim of this study was to investigate the specificity of attentional bias in patients with panic disorder (PD). Patients with PD (n=32), patients with mixed anxiety disorders (n=25), and a healthy control group (n=26) performed an emotional Stroop task with three word types: panic threat, general threat, and neutral. There were no differences on reaction times between the different groups, or on the different word types. Despite the generally accepted existence of attentional biases in anxiety disorders, we found no evidence of a specific attentional bias in patients with PD.     

Serum calcium and cognitive function in old age

OBJECTIVES: To determine whether serum calcium is associated with cognitive function in elderly individuals in the general population.
DESIGN: Prospective follow-up study of two independent, population-based cohorts.
SETTING: The Rotterdam Study (median follow-up 11 years) and the Leiden 85-plus Study (median follow-up 5 years).
PARTICIPANTS: Three thousand nine hundred ninety-four individuals, mean age 71, from the Rotterdam Study and 560 individuals, all aged 85, from the Leiden 85-plus Study.
MEASUREMENTS: Global cognitive function was assessed in both cohorts using the Mini-Mental State Examination; attention, psychomotor speed, and memory function were assessed in the Leiden 85-plus Study only. Linear regression and linear mixed models were used for statistical analyses.
RESULTS: In the Rotterdam Study, high serum calcium was associated with worse global cognitive function at baseline ( P <.05) and a faster rate of decline in cognitive function during follow-up ( P =.005) in individuals aged 75 and older but not in younger individuals. In the Leiden 85-plus Study, high serum calcium was associated with worse global cognitive function from age 85 through 90 ( P <.001). This observation also held for the specific cognitive domains tested (all P <.01). These results did not change when individuals with serum calcium levels greater than normal (>2.55 mmol/L) were excluded from the analyses.
CONCLUSION: In the general population, high serum calcium levels are associated with faster decline in cognitive function over the age of 75.     

Simplified parametric methods for [11C]PIB studies

The purpose of the present study was to evaluate the performance of various parametric reference tissue models for quantification of [11C]PIB studies. Several models with and without fixing the reference tissue efflux rate constant (k'(2)) were investigated using both simulations and clinical data. The following parametric methods were evaluated: receptor parametric mapping (basis function implementation of the simplified reference tissue model with and without fixed k'(2)), reference Logan, and several multi-linear reference tissue methods (again with and without fixed k'(2)). In addition, standardised uptake value ratios with cerebellum (SUV(r)) were evaluated. Simulations were used to assess the effects of variation in flow (R(1)), fractional blood volume (V(b)) and binding potential (BP(ND)) itself on precision and accuracy of parametric BP(ND). For clinical studies, most parametric methods showed comparable performance, with poorest results for SUV(r). Best performance was obtained for receptor parametric mapping (RPM2) and one of the multi-linear reference tissue models (MRTM2), both with fixed k'(2): BP(ND) outcome was less affected by noise and the images showed better contrast than other tested methods. RPM2 and MRTM2 also provided best accuracy and precision in the simulation studies and are therefore the methods of choice for parametric analysis of clinical [11C]PIB studies.