Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 144
Filtrar
1.
J Am Soc Echocardiogr ; 32(9): 1095-1101, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31279619

RESUMO

BACKGROUND: The basis for abnormal microvascular flow responses to demand stress in coronary artery disease (CAD) is affected by resistance changes at both the epicardial stenosis level and within the downstream capillary network. We hypothesized that abnormal microvascular perfusion (MVP) responses during demand stress in patients with intermediate coronary stenoses occur when fractional flow reserve (FFR) across the epicardial stenosis is normal, because of increased microvascular resistance. METHODS: In 49 coronary arteries of 41 patients with intermediate stenoses (40%-80%) who were referred for both coronary angiography and demand stress MVP assessment, invasive coronary hemodynamics were obtained across the stenosis to measure FFR, coronary flow reserve (CFR), and hyperemic microvascular resistance (HMR) during adenosine infusion. MVP in each coronary artery territory (CAT) during demand stress was evaluated by an independent expert reviewer blinded to clinical and angiographic data. RESULTS: Thirty-four of the 49 CATs with intermediate stenoses exhibited abnormal MVP. Although the sensitivity of MVP was high for detecting abnormal FFR (100%), FFR < 0.8 was observed in only 15 of the 34 vessels that exhibited abnormal MVP (positive predictive value 44%). However, HMR was abnormal in 32 of 34 vessels (94%) with abnormal MVP (positive predictive value, 94%). CONCLUSIONS: Although abnormal MVP has high sensitivity for detecting abnormal FFR, MVP is frequently abnormal when FFR is normal. In a large percentage of these patients, invasive assessments of microvascular resistance are abnormal.

2.
Curr Cardiol Rep ; 21(8): 86, 2019 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-31342183

RESUMO

PURPOSE OF REVIEW: This review will provide recent pre-clinical and initial clinical trials exploring the efficacy of sonothrombolysis as an adjunct to current emergent therapies in acute coronary syndromes. RECENT FINDINGS: The initial clinical trials examining the efficacy of short pulse duration diagnostic ultrasound (DUS) high mechanical index impulses in patients with ST segment elevation myocardial infarction (STEMI) have demonstrated that there is improved patency of the infarct vessel, and improved microvascular flow following percutaneous coronary intervention. Subsequent randomized prospective trials have confirmed that in patients with acute STEMI receiving an intravenous microbubble infusion, diagnostic high mechanical index impulses applied in the apical windows pre- and post-percutaneous coronary intervention have reduced myocardial infarction size, as assessed by magnetic resonance imaging at 72 h following presentation, and have been associated with better left ventricular systolic function at 6 month follow-up. Sonothrombolysis has potential for improving early epicardial coronary artery patency and reduce left ventricular remodeling when added to current interventional strategies in STEMI.

3.
ACS Appl Mater Interfaces ; 11(32): 28769-28773, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31311266

RESUMO

The transition between the insulator state and the band-conducting state is investigated by means of cyclic voltammetry in cobalt oxide porous film electrodes in phosphate-buffered solutions. It is shown that a proton-coupled faradaic oxidative process starting in the insulator region eventually builds an ohmic conduction mode upon anodic polarization. This model allows one to understand the origin of the authentic capacitive behavior of conductive metal oxide films rather than the so-called "pseudocapacitive" behavior. The particular example of cobalt oxide serves to illustrate the way in which, more generally, the behavior of "pseudocapacitors", long ascribed to the superposition of faradaic reactions, is in fact that of true capacitors, once band-conduction has been established upon oxidation of the material.

4.
J Am Coll Cardiol ; 73(22): 2832-2842, 2019 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-30894317

RESUMO

BACKGROUND: Preclinical studies have demonstrated that high mechanical index (MI) impulses from a diagnostic ultrasound transducer during an intravenous microbubble infusion (sonothrombolysis) can restore epicardial and microvascular flow in acute ST-segment elevation myocardial infarction (STEMI). OBJECTIVES: This study tested the clinical effectiveness of sonothrombolysis in patients with STEMI. METHODS: Patients with their first STEMI were prospectively randomized to either diagnostic ultrasound-guided high MI impulses during an intravenous Definity (Lantheus Medical Imaging, North Billerica, Massachusetts) infusion before, and following, emergent percutaneous coronary intervention (PCI), or to a control group that received PCI only (n = 50 in each group). A reference first STEMI group (n = 203) who arrived outside the randomization window was also analyzed. Angiographic recanalization before PCI, ST-segment resolution, infarct size by magnetic resonance imaging, and systolic function (LVEF) at 6 months were compared. RESULTS: ST-segment resolution occurred in 16 (32%) high MI PCI versus 2 (4%) PCI-only patients before PCI, and angiographic recanalization was 48% in high MI/PCI versus 20% in PCI only and 21% in the reference group (p < 0.001). Infarct size was reduced (29 ± 22 g high MI/PCI vs. 40 ± 20 g PCI only; p = 0.026). LVEF was not different between groups before treatment (44 ± 11% vs. 43 ± 10%), but increased immediately after PCI in the high MI/PCI group (p = 0.03), and remained higher at 6 months (p = 0.015). Need for implantable defibrillator (LVEF ≤30%) was reduced in the high MI/PCI group (5% vs. 18% PCI only; p = 0.045). CONCLUSIONS: Sonothrombolysis added to PCI improves recanalization rates and reduces infarct size, resulting in sustained improvements in systolic function after STEMI. (Therapeutic Use of Ultrasound in Acute Coronary Artery Disease; NCT02410330).

5.
PLoS One ; 13(12): e0207486, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30551125

RESUMO

BACKGROUND: Microbubbles (MB) can be compressed to nanometer-sized droplets and reactivated with diagnostic ultrasound; these reactivated MB possess unique imaging characteristics. OBJECTIVE: We hypothesized that droplets formed from compressing Definity MB may be used for infarct-enhancement imaging. METHODS: Fourteen rats underwent ligation of their left anterior descending (LAD) artery, and five pigs underwent 90 minute balloon occlusions of their mid LAD. At 48 hours in rats, transthoracic ultrasound was performed at two and four minutes following 200 µL intravenous injections (IVI) of Definity droplets (DD), at which point the MI was increased from 0.5 to 1.5 to assess for a transient contrast enhancement zone (TEZ) within akinetic segments. In pigs, 1.0 mL injections of DD were administered and low frame rate (triggered end systolic or 10 Hz) imaging 2-4 minutes post iVI to selectively activate and image the infarct zone (IZ). Infarct size was defined by delayed enhancement magnetic resonance imaging (DE-MRI) and post-mortem staining (TTC). RESULTS: Increasing MI to 1.5 (at two or four minutes after IVI) resulted in a TEZ in rats, which correlated with infarct size (r = 0.94, p<0.001). A TEZ was not seen at 2-4 minutes in any rat (n = 8) following Definity MB injections. Fluorescent staining confirmed DD presence within the infarct zone 10 minutes after intravenous injection. In pigs, selective enhancement within the IZ was achieved by using a low frame rate single pulse harmonic mode; IZ size matched the location seen with DE-MRI and correlated with TTC defect size (r = 0.90, p<0.05). CONCLUSION: DD formulated from commercially available MB can be acoustically activated for selective infarct enhancement imaging.


Assuntos
Acústica , Imagem por Ressonância Magnética/métodos , Microbolhas , Infarto do Miocárdio/diagnóstico por imagem , Infarto do Miocárdio/patologia , Administração Intravenosa , Animais , Meios de Contraste/administração & dosagem , Meios de Contraste/química , Nanotecnologia , Ratos , Suínos
6.
Echo Res Pract ; 5(3): E7-E8, 2018 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-30303674

RESUMO

In a study, published in this issue of Echo Research and Practice, Ntoskas et al. retrospectively analyzed the safety of a cardiac physiologist performing, and interpreting, Dobutamine stress echocardiography (DSE) in of 300 patients undergoing DSE for the detection of inducible reversible ischemia, myocardial viability and valvular heart disease. While safety during the tests themselves did not appear to be compromised with this unsupervised approach, the interpretation of these DSEs causes concerns regarding broad patient safety relative to misread results. Dobutamine stress echocardiography (DSE) has been utilized extensively in the detection of coronary artery disease (CAD) and prediction of patient outcome (1, 2, 3, 4). Its safety has also been thoroughly investigated in the contemporary era of contrast utilization (4). The test, though, does require giving supra-pharmacologic doses (up to 40 µg/kg/min) of an inotrope to patients with potentially significant CAD. The addition of atropine (up to 2 mg) is associated with other risks associated with anticholinergic side effects. Despite all these potential complications, the administration of these agents to thousands of patients has been shown to be safe, with a low likelihood of myocardial infarction or life-threatening arrhythmias (5). With this degree of safety, the question has been raised as to whether the test could safely be performed in the absence of a physician. In a study, published in this issue of Echo Research and Practice, Ntoskas et al. retrospectively analyzed the safety of a cardiac physiologist performing, and interpreting, the DSEs of 300 patients undergoing DSE for the detection of inducible reversible ischemia, myocardial viability, and valvular heart disease (6). Although the expected complications of arrhythmias and hypotension were observed, the team of cardiac physiologists managed these conditions appropriately, and safety did not appear to be compromised with this unsupervised approach (6). The COCATS 4 Training Guidelines in the United States have given specific instructions for who can perform and supervise stress echocardiograms (7). This requires the minimum performance of 150 echocardiograms and the interpretation of 300 echocardiograms before one can be expected to achieve reasonable competency in the area of regional wall motion analysis. In addition to this, one must also perform 100 stress echocardiograms in the presence of an experienced level III echocardiographer who has experience in running a stress echocardiography laboratory. The main concerning aspect of the study is that interpretation of the study was also done by the cardiac physiologist. Although median duration of follow-up was not reported, case notes for hospital follow-up (but not overall follow-up) were reviewed at 18­24 months. The majority of the referrals were for CAD assessment. Most of the studies appeared to be in patients with low to intermediate pretest probability. Although abnormal studies had high positive predictive value for detecting angiographically relevant CAD, there were seven patients in whom the study was read as negative who returned with significant complications due to multivessel CAD. Although we cannot determine the true false-negative rate in this study population, the results of this small pilot retrospective study tell us that there is a danger with the entire process of a physiologist-run program, if the interpretation of the studies is left in their hands. The authors of this study do not give us the specific training background of the cardiac physiologists in this study, and as imaging cardiologists, we are all aware of the difficulties inherent in interpreting wall motion. Although supra-pharmacologic doses of dobutamine have some potentially dangerous consequences, the pilot study by Ntoskas et al. reminds us that the biggest danger associated with DSE is in misinterpreting the data obtained from the study.

7.
Circ Cardiovasc Imaging ; 11(10): e007483, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30354474

RESUMO

BACKGROUND: Our aim was to determine the cardiovascular outcome of patients with capillary blood flow (CBF) abnormalities detected during demand stress in the absence of obstructive coronary artery disease. METHODS AND RESULTS: We identified 380 consecutive patients referred for coronary angiography (CA) after dobutamine or exercise stress echocardiography (SE) between 2008 and 2013 performed with real-time perfusion imaging to examine myocardial CBF with a continuous ultrasound contrast infusion. Patients with left ventricular ejection fraction <40% were excluded. There were 3 groups based on results: positive SE/negative CA, patients who had abnormal regional CBF but no significant angiographic disease; positive SE/positive CA, those with abnormal CBF and significant disease on subsequent CA; and negative SE/negative CA, patients with normal CBF and negative CA. Event-free survival examining death and nonfatal myocardial infarction was compared. Median follow-up was 4 years. There were 91 positive SE/negative CA, 189 positive SE/positive CA, and 100 negative SE/negative CA patients over the study period. The positive SE/negative CA patients were more frequently women and had a lower prevalence of hypertension and hyperlipidemia (all P<0.001). Analysis of event-free survival with Cox regression demonstrated that death/nonfatal myocardial infarction rates were higher in the positive SE/positive CA (hazard ratio, 2.10; CI, 1.02-4.29) and positive SE/negative CA (hazard ratio, 2.02; CI, 0.99-4.31) groups when compared with negative SE/negative CA groups. CONCLUSIONS: Patients with inducible CBF abnormalities in the absence of significant obstructive disease at CA still have similar death/nonfatal myocardial infarction rates as those with significant disease at CA.

8.
Echo Res Pract ; 5(3): E7-E8, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30078786

RESUMO

In a study, published in this issue of Echo Research and Practice, Ntoskas et al retrospectively analyzed the safety of a cardiac physiologist performing, and interpreting, Dobutamine stress echocardiography (DSE) in of 300 patients undergoing DSE for the detection of inducible reversible ischemia, myocardial viability and valvular heart disease. While safety during the tests themselves did not appear to be compromised with this unsupervised approach, the interpretation of these DSEs causes concerns regarding broad patient safety relative to misread results.

9.
Echo Res Pract ; 2018 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-29991480

RESUMO

In a study, published in this issue of Echo Research and Practice, Ntoskas et al. retrospectively analyzed the safety of a cardiac physiologist performing, and interpreting, DSEs in of 300 patients undergoing DSE for the detection of inducible reversible ischemia, myocardial viability, and valvular heart disease. While safety during the tests themselves did not appear to be compromised with this unsupervised approach, the interpretation of these DSEs causes concerns regarding broad patient safety relative to misread results.

10.
Oman Med J ; 33(2): 176-177, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29657690
12.
J Am Soc Echocardiogr ; 31(6): 683-691, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29580695

RESUMO

BACKGROUND: We compared the long-term outcome of subjects without prior cardiac disease who underwent either vasodilator single-photon emission computed tomography (SPECT) or contrast stress-echocardiography (cSE) for suspected coronary artery disease (CAD). METHODS: Subjects who underwent vasodilator SPECT or cSE between 2008 and 2012 for suspected CAD but no history of cardiac disease were included. We retrospectively compared the association of each method with combined all-cause death and nonfatal myocardial infarction and their positive predictive value (PPV) for angiographically obstructive CAD. RESULTS: A total of 1,387 subjects were selected: 497 who underwent SPECT and 890 who underwent cSE. During 4 years of mean follow-up there were 78 hard events in the cSE group and 51 in the SPECT group. Event-free survival in subjects testing positive for ischemia, either with SPECT or cSE, was significantly worse both in the overall population and after propensity matching patients. In multivariable analyses, vasodilator SPECT or cSE demonstrated significant stratification capability with an ischemic test doubling (SPECT) or more than doubling (cSE) the risk of future hard events independently from other variables. PPV of vasodilator SPECT for the diagnosis of obstructive CAD was inferior to vasodilator cSE (PPV = 63% vs 89%, respectively; P < .001). CONCLUSIONS: Our study suggests that the associations of vasodilator SPECT or cSE with outcome are comparable, with cSE demonstrating better diagnostic PPV for CAD. The absence of ionizing radiation and anticipated lower costs from higher PPV suggest that vasodilator cSE is a valid alternative to vasodilator SPECT as a gatekeeper in subjects without a prior history of CAD.

13.
J Am Soc Echocardiogr ; 31(6): 674-682, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29525249

RESUMO

BACKGROUND: Although microvascular flow abnormalities have been observed following epicardial recanalization in acute ST-segment elevation myocardial infarction (STEMI), the prevalence and severity of these abnormalities in the current era of rapid percutaneous coronary intervention (PCI) has not been evaluated. The objective of this study was to assess microvascular perfusion (MVP) following successful primary PCI in patients with STEMI and how it affects clinical outcome. METHODS: In this single-center, retrospective study, 170 patients who successfully underwent emergent PCI for STEMI were assessed using real-time myocardial contrast echocardiography using a continuous infusion of intravenous commercial microbubbles (3% Definity). Three patterns of myocardial contrast replenishment were observed following intermittent high-mechanical index impulses: infarct zone replenishment within 4 sec (normal MVP), delays in contrast replenishment but normal plateau intensity (delayed MVP [dMVP]), and both delays in replenishment and reduced plateau intensity (microvascular obstruction [MVO]). Changes in left ventricular ejection fraction at 6 months and clinical event rate at 12 months (death, recurrent infarction, need for defibrillator placement, or heart failure admission) were compared. RESULTS: Normal MVP was seen in 62 patients (36%), dMVP in 49 (29%), and MVO in 59 (35%). Left anterior descending coronary artery infarct location was the only parameter independently associated with dMVP or MVO, independent of age, cardiac risk factors, door-to-dilation time, pre-PCI Thrombolysis In Myocardial Infarction flow grade, and thrombus burden. A dMVP pattern had a similar reduction in left ventricular ejection fraction as MVO at hospital discharge but had recovery of left ventricular ejection fraction at 6 months and a greater than fourfold lower event rate than the MVO group (P < .001). CONCLUSIONS: MVO and dMVP are frequently seen following contemporary successful PCI for STEMI, especially following left anterior descending coronary artery infarction. Despite a similar area at risk, a dMVP pattern has better functional recovery and clinical outcome than MVO.

15.
Eur Heart J Acute Cardiovasc Care ; : 2048872617728559, 2017 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-28868906

RESUMO

In the past few decades, cardiac ultrasound has become a widely available, easy-to-use diagnostic tool in many scenarios in acute cardiac care. The introduction of microbubbles extended its diagnostic value. Not long thereafter, several investigators explored the therapeutic potential of contrast ultrasound on thrombus dissolution. Despite large improvements in therapeutic options, acute ST elevation myocardial infarction remains one of the main causes of mortality and morbidity in the western world. The therapeutic effect of contrast ultrasound on thrombus dissolution might prove to be a new, effective treatment strategy in this group of patients. With the recent publication of human studies scrutinising the therapeutic options of ultrasound and microbubbles in ST elevation myocardial infarction, we have entered a new stage in this area of research. This therapeutic effect is based on biochemical effects both at macrovascular and microvascular levels, of which the exact working mechanisms remain to be elucidated in full. This review will give an up-to-date summary of our current knowledge of the therapeutic effects of contrast ultrasound and its potential application in the field of ST elevation myocardial infarction, along with its future developments.

16.
Invest Radiol ; 52(8): 477-481, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28383307

RESUMO

BACKGROUND: Acute ischemic stroke is often due to thromboembolism forming over ruptured atherosclerotic plaque in the carotid artery (CA). The presence of intraluminal CA thrombus is associated with a high risk of thromboembolic cerebral ischemic events. The cavitation induced by diagnostic ultrasound high mechanical index (MI) impulses applied locally during a commercially available intravenous microbubble infusion has dissolved intravascular thrombi, especially when using longer pulse durations. The beneficial effects of this in acute carotid thromboembolism is not known. MATERIALS AND METHODS: An oversized balloon injury was created in the distal extracranial common CA of 38 porcine carotid arteries. After this, a 70% to 80% stenosis was created in the mid common CA proximal to the injury site using partial balloon inflation. Acute thrombotic CA occlusions were created just distal to the balloon catheter by injecting fresh autologous arterial thrombi. After angiographic documentation of occlusion, the common carotid thrombosis was treated with either diagnostic low MI imaging alone (0.2 MI; Philips S5-1) applied through a tissue mimicking phantom (TMP) or intermittent diagnostic high MI stable cavitation (SC)-inducing impulses with a longer pulse duration (0.8 MI; 20 microseconds' pulse duration) or inertial cavitation (IC) impulses (1.2 MI; 20 microseconds' pulse duration). All treatment times were for 30 minutes. Intravenous ultrasound contrast (2% Definity; Lantheus Medical) was infused during the treatment period. Angiographic recanalization in 4 intracranial and extracranial vessels downstream from the CA occlusion (auricular, ascending pharyngeal, buccinator, and maxillary) was assessed with both magnetic resonance 3-dimensional time-of-flight and phase contrast angiography. All magnetic resonance images were interpreted by an independent neuroradiologist using the thrombolysis in cerebral infarction (TICI) scoring system. RESULTS: By phase contrast angiography, at least mild recanalization (TICI 2a or higher) was seen in 64% of downstream vessels treated with SC impulses compared with 33% of IC treated and 29% of low MI alone treated downstream vessels (P = 0.001), whereas moderate or complete recanalization (TICI 2b or higher) was seen in 39% of SC treated vessels compared with 10% IC treated and 21% of low MI alone treated vessels (P = 0.001). CONCLUSIONS: High MI 20-microsecond pulse duration impulses during a commercial microbubble infusion can be used to recanalize acutely thrombosed carotid arteries and restore downstream flow without anticoagulants. However, this effect is only seen with SC-inducing impulses and not at higher mechanical indices, when a paradoxical reversal of the thrombolytic effect is observed. Diagnostic ultrasound-induced SC can be a nonsurgical method of dissolving CA thrombi and preventing thromboembolization.


Assuntos
Tromboembolia/diagnóstico por imagem , Ultrassonografia/métodos , Animais , Meios de Contraste , Modelos Animais de Doenças , Fluorcarbonetos , Aumento da Imagem/métodos , Microbolhas , Suínos , Ultrassom
17.
PLoS One ; 12(2): e0172280, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28234978

RESUMO

OBJECTIVE: We sought to determine the prognostic value of qualitative and quantitative analysis obtained by real-time myocardial perfusion echocardiography (RTMPE) in patients with known or suspected coronary artery disease (CAD). BACKGROUND: Quantification of myocardial blood flow reserve (MBFR) in patients with CAD using RTMPE has been demonstrated to further improve accuracy over the analysis of wall motion (WM) and qualitative analysis of myocardial perfusion (QMP). METHODS: From March 2003 to December 2008, we prospectively studied 168 patients with normal left ventricular function (LVF) who underwent dobutamine stress RTMPE. The replenishment velocity reserve (ß) and MBFR were derived from RTMPE. Acute coronary events were: cardiac death, myocardial infarction and unstable angina with need for urgent coronary revascularization. RESULTS: During a median follow-up of 34 months (5 days to 6.9 years), 17 acute coronary events occurred. Abnormal ß reserve in ≥2 coronary territories was the only independent predictor of events hazard ratio (HR) = 21, 95% CI = 4.5-99; p<0.001). Both, abnormal ß reserve and MBFR added significant incremental value in predicting events over qualitative analysis of WM and MP (χ2 = 6.6 and χ2 = 24.6, respectively; p = 0.001 and χ2 = 6.6 and χ2 = 15.5, respectively; p = 0.012, respectively). When coronary angiographic data was added to the multivariate analysis model, ß reserve remained the only predictor of events with HR of 21.0 (95% CI = 4.5-99); p<0.001. CONCLUSION: Quantitative dobutamine stress RTMPE provides incremental prognostic information over clinical variables, qualitative analysis of WM and MP, and coronary angiography in predicting acute coronary events.


Assuntos
Doença da Artéria Coronariana/diagnóstico por imagem , Ecocardiografia sob Estresse/métodos , Infarto do Miocárdio/diagnóstico por imagem , Prognóstico , Idoso , Meios de Contraste/administração & dosagem , Doença da Artéria Coronariana/fisiopatologia , Dobutamina/administração & dosagem , Feminino , Humanos , Estimativa de Kaplan-Meier , Masculino , Pessoa de Meia-Idade , Infarto do Miocárdio/fisiopatologia , Imagem de Perfusão do Miocárdio/métodos , Valor Preditivo dos Testes , Função Ventricular Esquerda/fisiologia
18.
Dalton Trans ; 46(8): 2551-2558, 2017 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-28154851

RESUMO

The bulky 2,6-di-tert-butyl-4-nitrophenolate ligand forms complexes with [TptBuCuII]+ and [TptBuZnII]+ binding via the nitro group in an unusual nitronato-quinone resonance form (TptBu = hydro-tris(3-tert-butyl-pyrazol-1-yl)borate). The Cu complex in the solid state has a five-coordinate κ2-nitronate structure, while the Zn analogue has a four-coordinate κ1-nitronate ligand. 4-Nitrophenol, without the 2,6-di-tert-butyl substituents, instead binds to [TptBuCuII]+ through the phenolate oxygen. This difference in binding is very likely due to the steric difficulty in binding a 2,6-di-tert-butyl-phenolate ligand to the [TptBuMII]+ unit. TptBuCuII(κ2-O2NtBu2C6H2O) reacts with the hydroxylamine TEMPO-H (2,2,6,6-tetramethylpiperidin-1-ol) by abstracting a hydrogen atom. This system thus shows an unusual sterically enforced transition metal-ligand binding motif and a copper-phenolate interaction that differs from what is typically observed in biological and chemical catalysis.

19.
J Am Heart Assoc ; 6(2)2017 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-28219921

RESUMO

BACKGROUND: The assessment of cardiac risk in contemporary liver transplantation (LT) has required more sensitive testing for the detection of occult coronary artery disease as well as microvascular and functional cardiac abnormalities. Because dobutamine stress perfusion echocardiography provides an assessment of both regional systolic and diastolic function as well as microvascular perfusion (MVP), we sought to examine its incremental value in this setting. METHODS AND RESULTS: We evaluated the predictive value of dobutamine stress perfusion echocardiography in 296 adult patients with end-stage liver disease and preserved systolic function who underwent LT between 2008 and 2014. The primary outcome was cardiovascular death, nonfatal myocardial infarction, and/or sustained ventricular arrhythmias following LT. The main causes of liver failure were hepatitis C (25%) and nonalcoholic fatty liver disease (13%). Abnormal MVP during stress was observed in 18 patients (6%), whereas diastolic dysfunction was present in 109 patients (94 grade 1, 15 grade 2). Half of the patients (7 of 14) referred for angiography with abnormal MVP had significant epicardial disease by angiography, and these patients were revascularized prior to LT. Despite these interventions, the primary outcome still occurred in 9 patients (3%). Patients with abnormal MVP during dobutamine stress perfusion echocardiography had a 7-fold higher risk of a cardiovascular event following LT. Cox proportional hazards modeling examining clinical variables, left ventricular ejection fraction, diastolic function, and stress-induced wall motion abnormalities or MVP defects demonstrated that abnormal MVP was the only independent predictor of the primary outcome (P=0.004; hazard ratio 7.7). CONCLUSIONS: Stress MVP assessments are highly predictive of cardiovascular outcome in current LT candidates.


Assuntos
Doença da Artéria Coronariana/diagnóstico , Dobutamina/farmacologia , Ecocardiografia sob Estresse/métodos , Doença Hepática Terminal/cirurgia , Transplante de Fígado , Cardiotônicos/farmacologia , Angiografia Coronária , Doença da Artéria Coronariana/complicações , Doença Hepática Terminal/complicações , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Estudos Retrospectivos
20.
ACS Appl Mater Interfaces ; 9(10): 8649-8658, 2017 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-28195702

RESUMO

Batteries and electrochemical double layer charging capacitors are two classical means of storing electrical energy. These two types of charge storage can be unambiguously distinguished from one another by the shape and scan-rate dependence of their cyclic voltammetric (CV) current-potential responses. The former shows peak-shaped current-potential responses, proportional to the scan rate v or to v1/2, whereas the latter displays a quasi-rectangular response proportional to the scan rate. On the contrary, the notion of pseudocapacitance, popularized in the 1980s and 1990s for metal oxide systems, has been used to describe a charge storage process that is faradaic in nature yet displays capacitive CV signatures. It has been speculated that a quasi-rectangular CV response resembling that of a truly capacitive response arises from a series of faradaic redox couples with a distribution of potentials, yet this idea has never been justified theoretically. We address this problem by first showing theoretically that this distribution-of-potentials approach is closely equivalent to the more physically meaningful consideration of concentration-dependent activity coefficients resulting from interactions between reactants. The result of the ensuing analysis is that, in either case, the CV responses never yield a quasi-rectangular response ∝ ν, identical to that of double layer charging. Instead, broadened peak-shaped responses are obtained. It follows that whenever a quasi-rectangular CV response proportional to scan rate is observed, such reputed pseudocapacitive behaviors should in fact be ascribed to truly capacitive double layer charging. We compare these results qualitatively with pseudocapacitor reports taken from the literature, including the classic RuO2 and MnO2 examples, and we present a quantitative analysis with phosphate cobalt oxide films. Our conclusions do not invalidate the numerous experimental studies carried out under the pseudocapacitance banner but rather provide a correct framework for their interpretation, allowing the dissection and optimization of charging rates on sound bases.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA