Efficient parameterisation of non-collinear energy landscapes in itinerant magnets

Magnetic exchange interactions determine the magnetic groundstate, as well as magnetic excitations of materials and are thus essential to the emerging and fast evolving fields of spintronics and magnonics. The magnetic force theorem has been used extensively for studying magnetic exchange interactions. However, short-ranged interactions in itinerant magnetic systems are poorly described by this method and numerous strategies have been developed over the years to overcome this deficiency. The present study supplies a fully self-consistent method for systematic investigations of exchange interactions beyond the standard Heisenberg model. In order to better describe finite deviations from the magnetic ground state, an extended Heisenberg model, including multi-spin interactions, is suggested. Using cross-validation analysis, we show that this extended Heisenberg model gives a superior description for non-collinear magnetic configurations. This parameterisation method allows us to describe many different itinerant magnetic systems and can be useful for high-throughput calculations.

P6477Preoperative renal injury and multi-elevated biomarkers are associated with adverse outcomes in patients with severe aortic stenosis undergoing surgical valve replacement

Background

The presence of early stages of renal injury (AKI) and biomarkers has been associated with adverse outcomes in cardiac surgery.

Purpose

We aimed to determine whether preoperative AKI is associated with long-term all-cause mortality in patients with severe aortic stenosis (AS) undergoing surgical aortic valve replacement (SAVR) and if the combination of AKI with multi-elevated biomarkers (Amino-terminal pro-B-type natriuretic peptide, BNP; high-sensitivity cardiac troponin T, hsTNT; and C reactive protein, CRP) has a better prognostic utility.

Method

From a prospective registry of patients with AS referred for SAVR, 560 participants (68±8.8 years; 329 men) were retrospectively included when echocardiograms, serum creatinine and biomarkers were available within 30-days before surgery. Kaplan-Meier (KM) curves for all-cause mortality were created for groups of patients based on the presence of AKI, defined as a stage I or more according to the Acute Kidney Injury Network classification. To further describe the utility of multi-elevated biomarkers, 4 groups were created and the KM-curves and c-statistics evaluated. Mean follow-up was 737±410 days and 30 (5.4%) patients died.

Results

Patients with preoperative AKI (n=68) were significantly older (70±7.6 vs. 67±8.9 years, p=0.02), more likely to have hypertension, diabetes, a worse functional class (NYHA III-IV: 59% vs. 36%, p<0.001), worse glomerular filtration rate (60±20 vs. 81±26, p<0.001), an elevation of multiple biomarkers (hsTNT, BNP, and CRP), and a higher logistic-EuroScore (3.8±2.8 vs. 3.0±2.2, p=0.04). But there were no differences in the incidence of coronary artery disease, LVEF (57±10 vs. 59±11%), aortic valve area index, or in surgical characteristics. Those patients with AKI exhibited higher 3-year all-cause mortality (11.7% vs. 5.7%, p=0.04). Interestingly, the combination of AKI with 3 elevated biomarkers was associated with a more than fourfold increase in 3-year all-cause mortality (47.5% vs. 4.3%, p<0.0001), and the c-statistics (AUC 0.599 vs 0.710, p<0.001) suggested a better prediction for long-term death.

Figure 1

Conclusions

This study demonstrates an adverse association of preoperative AKI with survival following SAVR, which was accentuated when combined with multi-elevated biomarkers, suggesting the need for less invasive strategies and/or closer postoperative follow–up in such patients.

Tailoring magnetic interlayer coupling in La0.7Sr0.3MnO3/SrRuO3 superlattices

The magnetic interlayer coupling in La0.7Sr0.3MnO3/SrRuO3 superlattices was investigated. High quality superlattices with ultrathin La0.7Sr0.3MnO3 and SrRuO3 layers were fabricated by pulsed laser deposition. The superlattices grew coherently with Mn/Ru intermixing restricted to about one interfacial monolayer. Strong antiferromagnetic interlayer coupling depended delicately on magnetocrystalline anisotropy and intermixing at interfaces. Ab initio calculations elucidated that the antiferromagnetic coupling is mediated by the Mn-O-Ru bond. The theoretical calculations allowed for a quantitative correlation between the total magnetic moment of the superlattice and the degree of Mn/Ru intermixing.

Telematics in Medicine: A Network Infrastructure to Optimize Processes in Cardiology and Heart Surgery

OBJECTIVES

During the past 2 decades, cardiac surgery has developed into a high-tech field. Increasing numbers of urgent surgical procedures mean that the time interval from diagnosis to surgical treatment must become ever shorter. Optimizing inconvenient and slow processes such as postal correspondence by using internet services is therefore mandatory in current cardiosurgical practice, and this includes the electronic transfer of patient data and diagnostic imaging material [12]. This study focuses on the internet connection of several cardiac referral centers to a cardiosurgical institution.

METHODS

Eleven cath lab centers were connected to a cardiosurgical center by internet. Auser program was especially developed to optimize connecting processes with the department. Data conversion was based on HL7 codes and angiograms were based on CD-ROM mediums and the DICOM standard. An online registration based on the HL7 communications standard was provided.

RESULTS

All cath lab centers were successfully connected to the cardiosurgical institution. Angiography data were transmitted within 30 +/- 15minutes. The time interval from diagnosis to decision for surgery decreased from 36 +/- 13 hours to 1 +/- 0.5 hours (p = 0.01). Urgent or emergent surgery could be provided after 18 +/- 19 hours, compared to 56 +/- 35 hours before (p = 0.02).

CONCLUSION

Special programs transmitting data via the internet significantly reduces the time interval from diagnosis to surgical treatment. Standardizing data transmitting processes from referral centers markedly optimizes cardiological and cardiosurgical treatments and could thereby improve survival rates and reduce costs.

The Excor Device - Revival of an Old System with Excellent Results

OBJECTIVE

We report on our experience with the BerlinHeart Excor system in adults and paediatric patients who underwent placement of the mechanical support device under emergency conditions and demonstrate the exceptional advantages and the considerable versatility of the system.

METHODS

Since 2003, 29 consecutive patients (25 adults and 4 infants) with ages ranging from 10 months to 54 years underwent implantation of an Excor system. Main underlying heart diseases in adults were acute myocardial infarction (n = 9), dilative cardiomyopathy (n = 6), acute myocarditis (n = 6), whereas most of the children suffered from dilative cardiomyopathy. Ten patients had undergone implantation of an extracorporeal membrane oxygenation system.

RESULTS

In 26 cases, a left ventricular assist device (LVAD) was implanted, while 3 patients had biventricular support. The support interval of all patients surviving the perioperative period lasted from 30 to 412 days, mean period of support until heart transplantation or explantation was 184 +/- 117 days. Severe complications were rare.

CONCLUSION

The Excor paracorporeal mechanical support system is an excellent and highly versatile device for the support of patients of all ages and different types of underlying heart disease in the mid-term and long-term. The implant procedure and the perioperative management are simple, and complication rates are low.

Harvest of the radial artery: technique of the skeletonization and pedicle preparation

Nowadays, radial artery grafts play a significant role in coronary artery revascularization, however, harvesting techniques are not standardized. We developed various surgical techniques for radial artery harvesting considering the anatomic landmarks of the foramen, including conventional surgery (with scissors and clips) and procedures with ultrasonic scalpel and retrieving the radial artery graft in a pedicle or in a skeletonized manner.

Cardiothoracic Surgery after Heart and Heart-Lung Transplantation

OBJECTIVE

We sought to examine our management and the outcomes of cardiothoracic procedures after heart and heart lung transplantation.

METHODS

We performed a retrospective review of cardiothoracic surgical procedures carried out between 1990 and 2004 in patients who had previously undergone heart or heart-lung transplantation at our institution.

RESULTS

Twenty-one out of 340 patients (6.2 %) were identified. Cardiothoracic surgery was performed 44.4 +/- 33 months (range 1 - 115 months) after transplantation. Predominant types of surgery were coronary artery bypass grafting due to allograft vasculopathy (n = 5), aortic surgery due to acute dissection (n = 3), biventricular assist device implantation due to acute rejection (n = 1), tricuspid valve repair (n = 1), multiple cardiac surgical procedures including coronary artery bypass grafting, retransplantation, and tricuspid valve replacement (n = 2), explantation of a functionless heterotopic transplanted heart (n = 1). Lung surgery was performed in six patients due to pneumonia (n = 2), primary lung carcinoma (n = 3), lung torsion following heart-lung transplantation (n = 1). All patients underwent either lobectomy or segmental lung resection. Single lung retransplantation (n = 2) after prior heart-lung transplantation due to bronchiolitis obliterans was performed. In one patient a pneumonectomy (n = 1) due to severe chronic rejection of the contralateral lung was performed. Six subsequent deaths after cardiothoracic procedures were recorded after 1, 4, 78, 163, 205, and 730 days, respectively. Causes of death were advanced carcinoma (n = 1), multi-organ failure due to sepsis (n = 2), sudden heart death (n = 2), and advanced heart failure (n = 1). Fifteen out of 21 patients having undergone cardiothoracic procedures (71.4 %) survived the observation period of 56.6 +/- 34 months (range 1 - 114).

CONCLUSIONS

Reasons for cardiothoracic procedures after prior heart or heart-lung transplantation were allograft vasculopathy, aortic dissections years after transplantation, chronic rejection, and either lung infections or malignancies. Surgical repair can be performed with an acceptable operative risk and good long-term survival rates.

Clinical situations demanding weaning from long-term ventricular assist devices

OBJECTIVE

Ventricular assist devices are increasingly used to treat patients with acute or chronic end-stage heart failure. We report on circumstances, exemplified on four cases, where a surprisingly favorable clinical course of the patients ultimately demanded early explantation of the device, which was not anticipated prior to its implantation.

METHODS

The four patients were provided with implantable (Micromed BeBakey trade mark, Incor trade mark ) and external pneumatically driven (Thoratec trade mark, Excor trade mark ) devices under emergency conditions and were listed for heart transplantation.

RESULTS

All four patients had an unexpected recovery of myocardial pump function. After careful diagnostic evaluation, all device components were completely removed without extracorporeal circulation. No stepwise weaning protocol was employed.

CONCLUSIONS

Weaning patients from ventricular assist devices after recovery of myocardial pump function can become necessary. Diagnostic evaluation and the implementation of a weaning protocol is still a matter of debate, while complete surgical removal of all device components without extracorporeal circulation is possible with a low risk.