Mild hypothermia delays the development of stone heart from untreated sustained ventricular fibrillation - a cardiovascular magnetic resonance study

<p>Abstract</p> <p>Background</p> <p>'Stone heart' resulting from ischemic contracture of the myocardium, precludes successful resuscitation from ventricular fibrillation (VF). We hypothesized that mild hypothermia might slow the progression to stone heart.</p> <p>Methods</p> <p>Fourteen swine (27 ± 1 kg) were randomized to normothermia (group I; n = 6) or hypothermia groups (group II; n = 8). Mild hypothermia (34 ± 2°C) was induced with ice packs prior to VF induction. The LV and right ventricular (RV) cross-sectional areas were followed by cardiovascular magnetic resonance until the development of stone heart. A commercial 1.5T GE Signa NV-CV/i scanner was used. Complete anatomic coverage of the heart was acquired using a steady-state free precession (SSFP) pulse sequence gated at baseline prior to VF onset. Un-gated SSFP images were obtained serially after VF induction. The ventricular endocardium was manually traced and LV and RV volumes were calculated at each time point.</p> <p>Results</p> <p>In group I, the LV was dilated compared to baseline at 5 minutes after VF and this remained for 20 minutes. Stone heart, arbitrarily defined as LV volume <1/3 of baseline at the onset of VF, occurred at 29 ± 3 minutes. In group II, there was less early dilation of the LV (p < 0.05) and the development of stone heart was delayed to 52 ± 4 minutes after onset of VF (P < 0.001).</p> <p>Conclusions</p> <p>In this closed-chest swine model of prolonged untreated VF, hypothermia reduced the early LV dilatation and importantly, delayed the onset of stone heart thereby extending a known, morphologic limit of resuscitability.</p

\u3csup\u3e13\u3c/sup\u3eC NMR Chemical Shielding Tensor of the Bridging Methylene Unit in cis-(μ-CH\u3csub\u3e2\u3c/sub\u3e)(μ-CO)[FeCp(CO)]\u3csub\u3e2\u3c/sub\u3e

The principal elements of the 13C NMR chemical shielding tensor have been determined for the bridging methylene unit in cis-(μ-CH2)(μ-CO)[FeCp(CO)]2 from a combination of a Herzfeld-Berger analysis of the CP/MAS spectrum and a nonlinear least-squares fit of the proton-decoupled 13C powder pattern. The 13CH2 unit is both spatially isolated from other magnetic nuclei in the solid and largely motionally decoupled from dipolar interactions with the Cp ring protons. For the purpose of interpreting the proton-coupled 13C powder pattern, we have assumed that the carbon site of the dimetallocyclopropane unit lies on the intersection of two perpendicular mirror planes of symmetry. With this assumption, there are six possible relative orientations of the 13CH2 unit with respect to the principal axis system of the 13C chemical shielding tensor; simulations of the proton-coupled 13C powder patterns have been compared to the experimental spectrum, and the orientation of the chemical shielding tensor with respect to the molecular frameworks has been assigned. The C-H bond length and the H-C-H bond angle were obtained from the dipolar coupling tensor. A single, very large paramagnetic chemical shielding tensor element is a result of relatively weak carbon-metal bonds through two carbon atomic p orbitals and strong C-H bonds with the remaining carbon p orbital. Thus, these results are consistent with a molecular orbital analysis in which the methylene unit has σ-donating a1 and π-accepting b1 valence orbitals. © 1991, American Chemical Society. All rights reserved

Rotation of the Cyclopentadienyl Ligand in Bis(µ-carbonyl)bis(carbonylcyclopentadienyliron)(Fe-Fe) in the Solid State As Determined from Solid-State Deuterium NMR Spectroscopy

The motion of the cyclopentadienyl ring in (µ-CO)2[FeCpd(CO)]2 (Cpd= ca. 70% deuteriated η5-cyclopentadienyl) in the solid state has been studied from 100 to 300 K by solid-state deuterium NMR methods. The deuterium spin-lattice relaxation times show that the orientation of the cyclopentadienyl ligands, Cp, is averaged among the five sites of the ring with nearest-neighbor jump rates in the range 1.20 (24) × 107 to 2.4 (5) × 1011 s−1. The activation energy for the process is 12.5 (3) kJ/mol. The kinetic parameters obtained in this work are similar to the values for the reorientation of the cyclopentadienyl ligands in other organometallic compounds as determined with different techniques. The results of this work show that solid-state deuterium NMR spectroscopy uniquely complements existing techniques for the study of the motional properties in organometallic systems. © 1990, American Chemical Society. All rights reserved

Accelerated MR parameter mapping with a union of local subspaces constraint

Purpose: A new reconstruction method for multi-contrast imaging and parameter mapping based on a union of local subspaces constraint is presented. Theory: Subspace constrained reconstructions use a predetermined subspace to explicitly constrain the relaxation signals. The choice of subspace size (K) impacts the approximation error vs noise-amplification tradeoff associated with these methods. A different approach is used in the model consistency constraint (MOCCO) framework to leverage the subspace model to enforce a softer penalty. Our proposed method, MOCCO-LS, augments the MOCCO model with a union of local subspaces (LS) approach. The union of local subspaces model is coupled with spatial support constraints and incorporated into the MOCCO framework to regularize the contrast signals in the scene. Methods: The performance of the MOCCO-LS method was evaluated in vivo on T-1 and T-2 mapping of the human brain and with Monte-Carlo simulations and compared against MOCCO and the explicit subspace constrained models. Results: The results demonstrate a clear improvement in the multi-contrast images and parameter maps. We sweep across the model order space (K) to compare the different reconstructions and demonstrate that the reconstructions have different preferential operating points. Experiments on T-2 mapping show that the proposed method yields substantial improvements in performance even when operating at very high acceleration rates. Conclusions: The use of a union of local subspace constraints coupled with a sparsity promoting penalty leads to improved reconstruction quality of multi-contrast images and parameter maps.Technology and Research Initiative Fund (TRIF) - Improving Health and Arizona Biomedical Research Commission (ABRC) [ADHS14-082996]12 month embargo; published online: 15 July 2018This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Early Increases in Breast Tumor Xenograft Water Mobility in Response to Paclitaxel Therapy Detected by Non-Invasive Diffusion Magnetic Resonance Imaging

An important goal in cancer chemotherapy is to sensitively and quantitatively monitor the response of individual patients' tumors to successful, or unsuccessful, therapy so that regimens can be altered iteratively. Currently, tumor response is monitored by frank changes in tumor morphology, yet these markers take long to manifest and are not quantitative. Recent studies suggest that the apparent diffusion coefficient of water (ADC(W)), measured noninvasively with magnetic resonance imaging, is sensitively and reliably increased in response to successful CTx. In the present study, we investigate the combination chemotherapy response of human breast cancer tumor xenografts sensitive or resistant to Paclitaxel by monitoring changes in the ADC(W). Our results indicate that there is a clear, substantial, and early increase in the ADC(W) after successful therapy in drug sensitive tumors and that there is no change in the ADC(W) in p-glycoprotein-positive tumors, which are resistant to Paclitaxel. The mechanism underlying these changes is unknown yet is consistent with apoptotic cell shrinkage and a concomitant increase in the extracellular water fraction