Delayed versus primary sternal closure for left ventricular assist device implantation: Impact on mechanical circulatory support infections.

BACKGROUND: Delayed sternal closure may be required after left ventricular assist device (LVAD) implantation due to coagulopathy or hemodynamic instability. There is conflicting data regarding infection risk. METHODS: We performed a single-center, retrospective analysis of patients who received their first LVAD between May 2012 and January 2021. Patients were divided into delayed sternal closure (DSC) and primary sternal closure (PSC) groups. We used chi-squared or Fisher Exact tests, as appropriate, to compare the incidence of postoperative LVAD-related infections (mediastinal/sternal wound) and LVAD-specific infections (driveline and pump pocket) after definitive chest closure between these two groups. RESULTS: A total of 327 patients met eligibility criteria, including 127 (39%) patients that underwent DSC and 200 (61%) patients that had a PSC. Demographic and clinical characteristics were similar except for an overrepresentation of men (87% vs. 75%, p = .016), Interagency Registry of Mechanically Assisted Circulatory Support class I-II patients (89% vs 66%, p < .001), patients with a previous sternotomy (43% vs 13%, p < .001), and patients with chronic kidney disease (55% vs 43%, p = .030) in the DSC group. The median DSC time was 24 (IQR: 24-48) hours. The incidence of LVAD-related mediastinal/sternal wound infection was similar between the DSC and PSC groups (4.7% vs 3.0%, p = .419). There was no difference between DSC and PSC groups in the incidence of driveline infection (6.3% vs 9%, p = .411) and pump pocket infection (1.6% vs 1.5%, p =.901), respectively. CONCLUSIONS: DSC does not seem to increase the incidence of LVAD-related or LVAD-specific infection rates in heart failure patients undergoing device implantation surgery.

Use of Transthoracic Echocardiogram to Detect Left Ventricular Thrombi.

BACKGROUND: The presence of a left ventricular thrombus (LVT) poses a risk of thromboembolic complications and excludes patients from undergoing left ventricular assist device (LVAD) implantation without the aid of cardiopulmonary bypass (CPB). Transthoracic echocardiography (TTE) and transesophageal echocardiography are used to detect LVT in patients with heart disease; however, the detection validity of these imaging studies has not been definitively elucidated. METHODS: A retrospective analysis of patients with end-stage heart failure who underwent LVAD implantation from May 2012 to August 2018 in a single center was completed. To be included, patients' medical records had to have presurgical TTE and transesophageal echocardiographic images, as well as intraoperative digital and visual exploration observations. A total of 301 patients underwent LVAD implantation; 239 of these patients had an LVAD implanted with the use of CPB. A total of 230 patients had complete data sets and were included in the analysis. RESULTS: Preoperative TTE identified LVT in 23 of the 230 patients (10%); 15 patients (6.5%) had LVT confirmed by surgical intraventricular visualization. Of the patients with visual LVT confirmation, preoperative TTE identified an LVT in all but 1 case (93%; 14 of 15). Preoperative TTE of LVT had a high sensitivity (94%) and specificity (96%), as well as high negative predictive value (99%). CONCLUSIONS: The results of this study show that preoperative TTE is highly accurate for LVT detection. The high negative predictive value could have significant implications for the choice of surgical procedure because with TTE, surgeons can reasonably determine whether LVAD placement procedure can be attempted without CPB support.

Clinicopathological manifestations of myocarditis in a heart failure population.

Myocarditis continues to present challenges in diagnosis and management. The goal of this study is to determine the occurrence and manifestations of myocarditis in a heart failure (HF) population. The analyzed patients had acute or persistent HF and were referred over a 6-year period to a quaternary HF center for advanced HF therapies including mechanical circulatory support, left ventricular assist device (LVAD) implantation, and/or heart transplantation. The histopathological diagnosis of myocarditis was made based on the presence of an inflammatory infiltrate of the myocardium, typically with associated cardiomyocyte (CMC) damage, combined as indicated with immunohistochemical and molecular biology characterization. The pathological findings were correlated with a panel of clinical parameters and clinical course of the patients. Myocarditis was identified in 36 patients, with initial diagnoses made in 10 (40%) of 25 by endomyocardial biopsy (EMB), 1 by atrial biopsy (maze procedure), 7 (2.1%) of 331 at LVAD implantation, and 18 (7.8%) of 229 in the explanted heart. There were 20 cases of lymphocytic myocarditis, 4 cases of giant cell myocarditis, 3 cases of eosinophilic myocarditis, and 9 cases of lymphohistocytic with granulomas myocarditis - cardiac sarcoidosis. EMB was performed in 25 patients and was positive in 10 (40%) of cases. Myocarditis was found in 23 explanted hearts including 18 cases de novo and 5 cases with a previously positive specimen. Of the 23 explanted hearts, 21 were nonischemic cardiomyopathy and 2 were ischemic cardiomyopathy. Our findings show that, in patients presenting to a quaternary medical center, myocarditis can be manifest as acute HF as well as a complicating factor in chronic HF.

Estimation of single solute adsorption isotherms applying the nonlinear frequency response method using non-optimal frequencies.

In order to estimate single solute adsorption isotherms, the nonlinear frequency response (FR) of a chromatographic column is analyzed experimentally and evaluated using the concept of higher order frequency response functions (FRFs) based on the Volterra series and generalized Fourier transform. In this case study, it has been investigated the adsorption of ethyl benzoate on octadecyl silica from a mixture of methanol and water (60:40) as a solvent. Experiments are performed using a standard gradient HPLC unit. For estimation of adsorption isotherms by the nonlinear FR method the column inlet concentration is changed in a nearly sine waveform around several steady-state concentrations. Using this method the first three local derivatives of a single solute adsorption isotherm are estimated from the low frequency asymptotes of the corresponding functions, i.e. the phase and first order derivative of the FRFs. For an accurate estimation of isotherm coefficients periodical experiments should be preformed for frequencies below a certain critical frequency. This is the frequency needed for approaching the low frequency asymptotic behaviour of the corresponding functions close enough, so that errors due to the non-feasibility of experiments with zero frequency can be neglected. Unfortunately, depending on the properties of the system, it can happen (as for the system investigated here) that experiments for the critical frequency would be too long and cannot be realized. In order to study the loss of accuracy of the nonlinear FR method, when it is applied for non-optimal frequencies, experiments are performed for frequencies approximately one order of magnitude higher than the critical frequency required to evaluate the FRF phases. The obtained isotherm model coefficients are compared with the ones estimated using conventional frontal analysis as a reference method. The isotherms determined by two methods are similar, however a closer look reveals that peaks predicted under overloading conditions differ.

Assessment of four biochemical markers of bone metabolism in postmenopausal osteoporosis.

In order to sudy the specificity and sensitivity of markers of bone metabolism in postmenopausal osteoporosis we investigated bone alkaline phosphatase, osteocalcin and carboxyl-terminal propeptide of procollagen type I in sera as markers of bone formation, and deoxypyridinoline in urine as a marker of bone resorption. The investigated parameters were determined in 53 women with confirmed osteoporosis and in a control group consisting of 45 healthy postmenopausal women without bone changes who were 40 to 79 years old. All biochemical markers were determined by monoclonal competitive enzyme immunoassay tests obtained by Metra Biosystems. The activity of bone alkaline phosphatase and the concentration of osteocalcin, procollagen type IVC-terminal propeptide (PICP), and deoxypyridinoline were grouped according to age of postmenopausal healthy and osteoporotic women. The values of all bone markers gradually increased with age, but significantly higher values were obtained in groups of postmenopausal osteoporotic women. By using receiver operator characteristic curve analysis, a very high specificity and sensitivity of the investigated biochemical markers in the diagnosis of postmenopausal osteoporosis were proven. The areas under the PICP curve and the osteocalcin curve were significantly higher than the area under the deoxypyridinoline curve, demonstrating a higher discriminating power of PICP and osteocalcin than deoxypyridinoline (p < 0.05).

A thermodynamically consistent explicit competitive adsorption isotherm model based on second-order single component behaviour.

A competitive adsorption isotherm model is derived for binary mixtures of components characterized by single component isotherms which are second-order truncations of higher order equilibrium models suggested by multi-layer theory and statistical thermodynamics. The competitive isotherms are determined using the ideal adsorbed solution (IAS) theory which, in case of complex single component isotherms, does not generate explicit expressions to calculated equilibrium loadings and causes time consuming iterations in simulations of adsorption processes. The explicit model derived in this work is based on an analysis of the roots of a cubic polynomial resulting from the set of IAS equations. The suggested thermodynamically consistent and widely applicable competitive isotherm model can be recommended as a flexible tool for efficient simulations of fixed-bed adsorber dynamics.

Determination of competitive adsorption isotherms applying the nonlinear frequency response method. Part I. Theoretical analysis.

In this work adsorption equilibria of binary mixtures are quantified analyzing the nonlinear frequency response of a chromatographic column. Local partial derivatives of an isotherm model can be estimated for certain steady-states from the low frequency asymptotes of the corresponding frequency response functions (FRFs). The required FRFs correspond to two different compounds and the type of the imposed inlet concentration changes, e.g. periodical inlet concentration changes of only one compound or of both of them. For an accurate determination of isotherm parameters, it is necessary to approach as close as possible the low frequency asymptotic behaviour of these functions. Based on principles valid for the FRFs corresponding to the adsorption of a single solute, frequencies needed to reach the low frequency asymptotes of the functions of interest for estimating competitive isotherms are defined in this paper. The relation between the accuracy of the isotherm parameters determined and numbers and types of periodical inlet concentration changes and steady-states analyzed is also evaluated.

Determination of competitive adsorption isotherms applying the nonlinear frequency response method. Part II. Experimental demonstration.

This paper demonstrates an experimental application of the nonlinear frequency response (FR) method extension to determine adsorption isotherms of binary mixtures. This method, based on the analysis of the response of a chromatographic column subjected to the sinusoidal inlet concentration changes, is shown to be an alternative for isotherm determination. The critical issue related to the successful application of the method is to reach experimentally the low frequency asymptotic behaviour of the corresponding frequency response functions (FRFs). Although, there are different possibilities to perform periodical inlet concentration changes, in this paper only simultaneous changes for both components were considered. The adsorption of phenol and 2-phenylethanol on octadecyl silica was analyzed experimentally using a mixture of methanol and water as a solvent. Parameters of competitive isotherms were also estimated for comparison using the classical perturbation method. Despite certain differences between competitive isotherms estimated with the two methods that were found, the obtained results show the potential of the nonlinear FR method for measuring competitive isotherms.