Improved accuracy in flow mapping of congenital heart disease using stationary phantom technique

<p>Abstract</p> <p>Background</p> <p>Flow mapping by cardiovascular magnetic resonance has become the gold standard for non-invasively defining cardiac output (CO), shunt flow and regurgitation. Previous reports have highlighted the presence of inherent errors in flow mapping that are improved with the use of a stationary phantom control. To our knowledge, these studies have only been performed in healthy volunteers.</p> <p>Results</p> <p>We analyzed the variation in flow measurements made with and without stationary phantom correction in 31 patients with congenital heart disease. Variation in stroke volume (SV) measurements was seen in all vessels across all patient groups. The variation was largest when analyzing the right ventricular outflow tract (RVOT), with a range of absolute differences in SV from 0.2 to 70 ml and in CO from 0.02 to 4.8 L/min. In patients with repaired Tetrology of Fallot (ToF), the average ratio of pulmonary to systemic blood flow (Qp:Qs) was 1.18 without and 1.02 with phantom correction. Without performing phantom correction, 23% of the repaired ToF patients were classified as having a residual shunt as compared to 0% when flow mapping was performed with phantom correction. Similarly, in patients with known atrial level shunting (ASD/PAPVR) 20% of patients had no shunt when flow mapping was performed without phantom correction as compared to 0% with phantom correction. In patients with bicuspid aortic valves (BAV), the differences in the regurgitant fraction between measuring flow with and without phantom correction ranged from 0 to 30%, while the regurgitant fraction in the RVOT of ToF patients varied by as much as 31%.</p> <p>Conclusion</p> <p>The impact of inherent errors in CMR flow mapping should not be underestimated. While the variation across a population may not display a significant trend, for any individual patient it can be quite large. Failure to correct for such variation can lead to clinically significant misinterpretation of flow data. The use of the stationary phantom correction technique appears to improve accuracy both in normal patients as well as those with congenital heart disease.</p

The GALEX Arecibo SDSS Survey. VIII. Final Data Release -- The Effect of Group Environment on the Gas Content of Massive Galaxies

We present the final data release from the GALEX Arecibo SDSS Survey (GASS), a large Arecibo program that measured the HI properties for an unbiased sample of ~800 galaxies with stellar masses greater than 10^10 Msun and redshifts 0.025<z<0.05. This release includes new Arecibo observations for 250 galaxies. We use the full GASS sample to investigate environmental effects on the cold gas content of massive galaxies at fixed stellar mass. The environment is characterized in terms of dark matter halo mass, obtained by cross-matching our sample with the SDSS group catalog of Yang et al. Our analysis provides, for the first time, clear statistical evidence that massive galaxies located in halos with masses of 10^13-10^14 Msun have at least 0.4 dex less HI than objects in lower density environments. The process responsible for the suppression of gas in group galaxies most likely drives the observed quenching of the star formation in these systems. Our findings strongly support the importance of the group environment for galaxy evolution, and have profound implications for semi-analytic models of galaxy formation, which currently do not allow for stripping of the cold interstellar medium in galaxy groups.Comment: 36 pages, 16 figures. Accepted for publication in MNRAS. Version with supplementary material available at http://www.mpa-garching.mpg.de/GASS/pubs.php . GASS released data can be found at http://www.mpa-garching.mpg.de/GASS/data.ph

Relation between physical activity and oxygen uptake efficiency in men with CVD

Purpose: The oxygen uptake efficiency slope (OUES) represents the rate of increase in V̇O2 in response to a given V̇E during incremental exercise, indicating how effectively oxygen is taken in by the lungs, transported and used in the periphery. OUES, calculated using only submaximal exercise data is identical to the OUES calculated over the entire duration of a cardiopulmonary exercise test (CEPT) , and both maximal and submaximal OUE are significantly related to cardiorespiratory fitness (CRF) measured as V̇O2peak. Currently, little research has been published on how physical activity (PA) assessed by accelerometers is related to submaximal and maximal OUES. The purpose of this study was to determine the relation light (LIPA), moderate (MIPA) and vigorous (VIPA) intensity physical activity and maximal and submaximal OUES in men with cardiovascular disease (CVD). Methods: A total of 56 men (mean ( SD): age of 59.3 ± 9.2 yr., V̇O2 peak (L/min) 2.0 0.50, V̇O2 peak (mL/kg/min) 23.6 5.8, were recruited during an induction to a community-based exercise referral program following completion of phase 2 cardiac rehabilitation program. Participants underwent a graded exercise test on a cycle ergometer with breath by breath open circuit spirometry after which they wore a wrist worn accelerometer (Actigraph) for 7 d. Absolute and relative submaximal and maximal OUES were calculated by plotting V̇O2 in mL/min on the x axis, and the log transformed VE on the y axis (V̇O2 = a log 10 VE + b). Exercise data up to the ventilatory anaerobic threshold and maximal exercise were used to calculate submaximal and maximal OUE, respectively. Results: Participants performed 584.49 73.87 min of daily LIPA, 145.45 60.85 min of MIPA and no daily min of VIPA. There was a significant relation between absolute submaximal OUES (r=0.386; p<0.01), submaximal OUES/Kg (r=0.296; p<0.05) and LIPA. There was a significant relation between maximal OUES (r=0.286; p<0.05), maximal OUES/Kg (r=0.279; p<0.05) and MIPA. Conclusion: Submaximal and maximal OUE are related to levels of LIPA and MIPA, respectively. Submaximal OUES can potentially be used as an objective, effort independent test to estimate LIPA levels among men with CVD

Physical activity patterns and cardiorespiratory fitness in men with cardiovascular disease

Purpose: Cardiorespiratory fitness (CRF) is generally regarded as an objective and reproducible measure of recent habitual physical activity (PA). Considering that the majority of daily PA is performed at light intensity, it is likely that CRF benefits will be detected at submaximal rather than maximal exercise. The purpose of this study was to evaluate daily minutes of light (LIPA), moderate (MIPA) and vigorous (VIPA) intensity physical activity among men with cardiovascular disease (CVD), and to determine the relation between PA and submaximal (oxygen uptake efficiency slope (OUES)) and maximal (V̇O2 peak) indices of CRF. Methods: A total 32 male participants (mean ( SD): age of 60.0 ± 8.7 yr, V̇O2 peak (L/min) 2.0 0.45, V̇O2 peak (mL/kg/min) 23.3 5.7, were recruited during an induction to a community based exercise referral program following completion of phase 2 cardiac rehabilitation. Participants underwent a graded exercise test on a cycle ergometer with breath by breath open circuit spirometry after which they wore a wrist worn accelerometer (Actigraph) for 7 d. Absolute and relative submaximal OUES were calculated by plotting V̇O2 in mL/min on the x axis, and the log transformed VE on the y axis (V̇O2 = a log 10 VE + b). Exercise data up to the ventilatory anaerobic threshold was included in the analysis. Results: Participants performed 589.05 69.41 min of daily LIPA, 161.38 66.16 min of MIPA and no daily min of VIPA. There was no significant relation between peak V̇O2 and either LIPA or MIPA. There was a significant correlation between submaximal OUES (r=0.44; p<0.01) and LIPA. The relation between submaximal OUES/kg and LIPA min almost reached statistical significance (r=0.33; p<0.07). There was no significant relation between MIPA and OUES or OUES/kg. Conclusion: Men with CVD spend the majority (78%) of their day performing LIPA. OUES, a submaximal measure of CRF was related LIPA whereas no relation was found between V̇O2 peak and LIPA

Submaximal oxygen uptake efficiency slope as a predictor of VO2max in men with cardiovascular disease

Purpose: Although V̇O2 max is considered the gold standard measure of cardiorespiratory fitness (CRF), it can be difficult to attain in patients with cardiovascular disease (CVD). The submaximal oxygen uptake efficiency slope (OUES) integrates cardiovascular, musculoskeletal and respiratory function during incremental exercise into a single index and has been proposed as an alternative and effort independent measure of cardiopulmonary reserve (Baba et al., 1996). The purpose of this study was to examine the relation between V̇O2 max and both submaximal absolute OUES and relative OUES (OUES.kg-1). Methods: A total of 55 men ((mean ± SD) age, 59.08 ± 9.03 yr; VO2 max, 1.94 ± 0.53 L.min-1and 22.73 ± 5.95 mL.kg-1.min-1) were recruited during induction to a community based exercise referral program following completion of phase 2 cardiac rehabilitation. Participants performed a graded exercise test on a cycle ergometer with breath-by-breath open circuit spirometry and a 12 lead ECG. Absolute OUES and OUES.kg-1 were calculated by plotting VO2 in mL.min-1 on the x-axis, and the log transformed VE on the y-axis (VO2 = a log 10 VE + b). Exercise data up to the ventilatory anaerobic threshold (VAT) was included in the analysis. Results: The %V̇O2 max corresponding to the VAT was 55.72 ± 11.81. Absolute OUES and OUES.kg-1 were 2164.42 ± 540.96 and 25.28 ± 5.99, respectively. There was a significant positive correlation between V̇O2 max (L.min-1) and OUES (r= 0.775; p<0.001) and between V̇O2 max (mL.kg-1.min-1) and OUES.kg-1 (r= 0.78; p<0.001). Conclusion: Determination of V̇O2 max is not often feasible in individuals with CVD where maximal exercise testing is contraindicated or when performance may be impaired by pain, dyspnea or angina. The findings from the present study indicate that the OUES and OUES.kg-1 are significantly related to absolute and relative V̇O2 max, respectively and may be used as a valid sub maximal effort independent measure of CRF

Prevalence of Noncardiac Findings in Patients Undergoing Cardiac Magnetic Resonance Imaging

Purpose. We sought to determine the prevalence of clinically significant non-cardiac abnormalities found in pediatric and adult patients undergoing cardiac magnetic resonance imaging (CMRI), and understand the impact of age on it's occurrence. Methods. We retrospectively reviewed all patients undergoing CMRI between May 2004 and July 2007. Findings were considered significant if they required radiographic or clinical follow-up. Results. A total of 408 patients underwent CMRI during the study period. Twenty two (16%) pediatric patients (age < 19 years, n = 135) were found to have a total of 22 non- cardiac abnormalities, 3 of which were clinically significant. Sixty four (23%) adult patients (age > 19 years, n = 273) were found to have a total of 77 non-cardiac abnormalities, 33 of which were clinically significant. The prevalence of clinically significant non-cardiac abnormalities was 2% in the pediatric cohort and 11% in the adult cohort (P = 0.05). Within the adult population, the prevalence of significant non-cardiac abnormalities increased with advancing age (P = 0.05). Conclusions. In a population of unselected patients undergoing CMRI, unanticipated noncardiac abnormalities were frequently seen. A small number of these were significant, with the prevalence increasing with age

Field responsive mechanical metamaterials.

Typically, mechanical metamaterial properties are programmed and set when the architecture is designed and constructed, and do not change in response to shifting environmental conditions or application requirements. We present a new class of architected materials called field responsive mechanical metamaterials (FRMMs) that exhibit dynamic control and on-the-fly tunability enabled by careful design and selection of both material composition and architecture. To demonstrate the FRMM concept, we print complex structures composed of polymeric tubes infilled with magnetorheological fluid suspensions. Modulating remotely applied magnetic fields results in rapid, reversible, and sizable changes of the effective stiffness of our metamaterial motifs

Methionine synthase interreplacement in diatom cultures and communities : implications for the persistence of B12 use by eukaryotic phytoplankton

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2013. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 58 (2013): 1431–1450, doi:10.4319/lo.2013.58.4.1431.Three proteins related to vitamin B12 metabolism in diatoms were quantified via selected reaction monitoring mass spectrometry: B12-dependent and B12-independent methionine synthase (MetH, MetE) and a B12 acquisition protein (CBA1). B12-mediated interreplacement of MetE and MetH metalloenzymes was observed in Phaeodactylum tricornutum where MetH abundance was highest (0.06 fmol µg−1 protein) under high B12 and MetE abundance increased to 3.25 fmol µg−1 protein under low B12 availability. Maximal MetE abundance was 60-fold greater than MetH, consistent with the expected ∼ 50–100-fold larger turnover number for MetH. MetE expression resulted in 30-fold increase in nitrogen and 40-fold increase in zinc allocated to methionine synthase activity under low B12. CBA1 abundance was 6-fold higher under low-B12 conditions and increased upon B12 resupply to starved cultures. While biochemical pathways that supplant B12 requirements exist and are utilized by organisms such as land plants, B12 use persists in eukaryotic phytoplankton. This study suggests that retention of B12 utilization by phytoplankton results in resource conservation under conditions of high B12 availability. MetE and MetH abundances were also measured in diatom communities from McMurdo Sound, verifying that both these proteins are expressed in natural communities. These protein measurements are consistent with previous studies suggesting that B12 availability influences Antarctic primary productivity. This study illuminates controls on expression of B12-related proteins, quantitatively assesses the metabolic consequences of B12 deprivation, and demonstrates that mass spectrometry–based protein measurements yield insight into the functioning of marine microbial communities.This work was supported by National Science Foundation (NSF) Antarctic Sciences awards 0732665, 1103503, and 0732822; NSF Division of Ocean Science awards 0752291, 0928414, and 1031271; The Gordon and Betty Moore Foundation; Center for Microbial Oceanography Research and Education; an NSF Graduate Research Fellowship (2007037200); and an Environmental Protection Agency Science To Achieve Results (EPA-STAR) Fellowship to E.M.B. (F6E720324)

Ab initio simulation of the two-dimensional vibrational spectrum of dicarbonylacetylacetonato rhodium&quot;I…

The complete anharmonic cubic and quartic force field of the two carbonyl stretching vibrations of a rhodium di-carbonyl complex is calculated at the density functional level and used to simulate the third-order vibrational response function. The infrared photon echo spectrum calculated using the diagonalized resulting exciton Hamiltonian is in qualitative agreement with measured values. Quartic terms in the potential are critical for reproducing the experimental transition energies and transition dipoles