From quantum disorder to magnetic order in an s=1/2 kagome lattice: a structural and magnetic study of herbertsmithite at high pressure.

The structural and magnetic properties of deuterated herbertsmithite have been studied by means of neutron powder diffraction and magnetic susceptibility measurements in a wide range of temperatures and pressures. The experimental data demonstrate that a phase transition from the quantum-disordered spin-liquid phase to the long-range ordered antiferromagnetic phase with the Néel temperature T(N)=6 K is induced at P=2.5 GPa. The observed decrease of T(N) upon compression correlates with the anomalies in pressure behavior of Cu-O bond length and Cu-O-Cu bond angles. The reasons for the observed spin-freezing transition are discussed within the framework of the available theoretical models and the recent observation of the field-induced spin freezing.

High-pressure powder neutron diffraction study on lead scandium niobate.

The structural evolution of PbSc(0.5)Nb(0.5)O(3) (PSN) under pressure has been studied by in situ powder neutron diffraction. Rietveld refinements to the data show that the continuous phase transition detected by x-ray diffraction at p(c) = 4.1 GPa (Maier et al 2010 Phys. Rev. B 81 174116) is associated with long-range ordering of antiphase octahedral tilts and local ordering of ferroic Pb displacements. Similar to PbSc(0.5)Ta(0.5)O(3) (PST) (Maier et al 2010 Acta Crystallogr. 66 280-91), antiphase octahedral tilting even exists below the critical pressure in a regime in which the structure retains a cubic metric. In contrast to PST, in which the Pb atomic displacement parameters (DPs) form ellipsoids elongated along the cubic {111} directions, the atomic DPs of Pb in PSN form flattened discs parallel to the cubic {111}-planes. This indicates that in PST the Pb displacements are along the cubic {111} directions, whereas in PSN the local Pb displacements are randomly distributed along the cubic {110} directions. The latter can be explained by the abundance of underbonded oxygen atoms associated with the chemical B-site disorder.

Electroporation-mediated delivery of a naked DNA plasmid expressing VEGF to the porcine heart enhances protein expression.

Gene therapy is an attractive method for the treatment of cardiovascular disease. However, using current strategies, induction of gene expression at therapeutic levels is often inefficient. In this study, we show a novel electroporation (EP) method to enhance the delivery of a plasmid expressing an angiogenic growth factor (vascular endothelial growth factor, VEGF), which is a molecule previously documented to stimulate revascularization in coronary artery disease. DNA expression plasmids were delivered in vivo to the porcine heart with or without coadministered EP to determine the potential effect of electrically mediated delivery. The results showed that plasmid delivery through EP significantly increased cardiac expression of VEGF compared with injection of plasmid alone. This is the first report showing successful intracardiac delivery, through in vivo EP, of a protein expressing plasmid in a large animal.

Investigation of the changes in hydrogen bonding accompanying the structural reorganization at 103†K in ammonium iodate.

Neutron powder diffraction has been used to observe the changes in hydrogen bonding that occur as a function of temperature in ND4IO3 and, thus, determine the structural features that occur during the low-temperature (103 K) phase transition. It is shown that in the deuterated material the change is not a phase change per se but rather a structural reorganization in which the hydrogen bonding becomes firmly locked in at the phase transition temperature, and stays in this configuration upon further cooling to 4.2 K. In addition, both the differences and changes in the axial thermal expansion coefficients in the region 100-290 K can be explained by the changes involving both the hydrogen bonding and the secondary I...O halogen bonds.

New insights into the phase diagram of a magnetic perovskite, LaCo1/3Mn2/3O3.

We report the crystal structure of the orthorhombic perovskite LaCo1/3Mn2/3O3 as determined by neutron diffraction from 5-300 K. A high-temperature x-ray diffraction study is also reported from 290-900 K. At temperatures above 570 K, LaCo1/3Mn2/3O3 transforms to a rhombohedral structure with space group R3̄c. This rhombohedral phase is also observed in the material at high pressure and the crystal structure has been determined by in situ neutron diffraction at 4.7 GPa. Finally, the ferromagnetic behaviour has been determined by magnetometry and the magnetic structure has been determined using low temperature neutron diffraction at ambient pressure.

Increased complications and prolonged hospital stay in elderly cardiac surgical patients with low serum albumin.

Cardiac surgery in elderly patients is associated with acceptable operative mortality but an increased complication rate. Malnutrition is common in the elderly and may adversely affect surgical outcome. To determine the effect of hypoalbuminemia on postoperative complications, 92 patients greater than or equal to 75 years (range 75 to 90) undergoing a variety of major cardiac surgical procedures were evaluated. Thirteen patients (14%) had a serum albumin level less than 3.5 g/dl preoperatively. Compared to patients with normal albumin, hypoalbuminemic patients had an increased frequency of postoperative confusion, congestive heart failure, low cardiac output, renal dysfunction and gastrointestinal complications (all p less than 0.05). Mean postoperative length of stay was markedly prolonged in these patients (27 vs 12 days; p less than 0.001), and mortality also tended to be higher (31 vs 13%; p = 0.11). Using multivariate analysis, albumin less than 3.5 g/dl was the most powerful predictor of postoperative renal dysfunction (p less than 0.01), and was also an independent predictor of increased length of stay (p less than 0.01) and gastrointestinal disorders (p less than 0.05). Thus, hypoalbuminemia is a powerful indicator of an increased risk of perioperative complications in elderly patients undergoing cardiac surgery. Increased attention to nutritional factors is warranted in these patients.

Eleven-year experience with composite graft replacement of the ascending aorta and aortic valve.

Between September, 1974, and December, 1985, 127 patients had replacement of the ascending aorta and aortic valve with a composite graft. Annuloaortic ectasia was the most common indication for operation (69 patients), followed by aortic dissection (51 patients). Twenty-four patients (19%) had the Marfan syndrome. Hospital mortality was 4.7%. Emergent operation for acute dissection was the only independent predictor of hospital death (p = 0.03). Reoperation for postoperative hemorrhage was required in 15 patients (11.8%) and for prosthesis-related complications (pseudoaneurysm, prosthetic endocarditis, technical problems, and valve thrombosis) in 16 patients (12.6%). Since we adopted a technique of preclotting the prosthesis with whole blood or albumin plus autoclaving and abandoned the inclusion technique, the reoperation rate has declined substantially. At 5 years, the actuarial freedom from reoperation for any reason on the ascending aorta or aortic valve for the 24 patients in whom this modification was used was 90% and for the remaining 103 patients, 73% (p = 0.17). No reoperations for pseudoaneurysms or technical problems were required in these 24 patients, whereas 10 reoperations for these complications were necessary in the other patients. The mean duration of follow-up was 54 months. The actuarial survival rate at 7 years for the entire group was 65%; for the patients with annuloaortic ectasia, 70%; for those with aortic dissection, 61%; for the patients with the Marfan syndrome, 57%. Actuarial freedom from operation on the remainder of the aorta at 7 years was 89%, but it was 78% for the subgroup with the Marfan syndrome. The satisfactory results with extended follow-up support the continued use of the composite graft technique as the preferred method of treatment for patients with annuloaortic ectasia or recurrent aneurysms of the sinuses of Valsalva and for patients with aortic dissection who require aortic valve replacement.

Late results after mitral valve replacement with the Björk-Shiley and porcine prostheses.

The late results of isolated mitral valve replacement were retrospectively evaluated in 357 patients receiving a Björk-Shiley (B-S) tilting disc prosthesis and 96 patients receiving a porcine bioprosthesis (PB) (Vascor or Carpentier-Edwards) between March, 1973, and July, 1978. The groups were comparable with regard to age, sex, New York Heart Association functional class, preoperative cardiac rhythm (sinus or atrial fibrillation), left atrial size (normal or enlarged), and presence of thrombus in the left atrium at operation. All of the B-S and 14 of the PB patients received long-term anticoagulant therapy. The median duration of follow-up was 46 months in the B-S group and 32 months in the PB group. At 5 years, survival was 70% for the B-S and 68% for the PB groups (NS). The percentage of patients free of thromboembolic episodes was 77% for the B-S and 78% for the PB groups (NS). Fifty-six percent of the B-S and 49% of the PB patients were alive and free of thromboembolism, complications related to anticoagulant therapy, or other valve-related complications (dehiscence, degeneration, or endocarditis) (NS). The presence of atrial fibrillation, enlarged left atrium, preoperative thromboembolic episodes, and left atrial thrombus had no effect on the incidence of thromboembolic complications with either prosthesis. From this analysis, it appears that the major advantage of the PB over the B-S prosthesis is its use in patients in whom long-term anticoagulation is contraindicated.

Shunting, release, and distribution of nine and fifteen micron spheres in myocardium.

The shunting, release, and transmural distribution of 9 and 15 mu radioactive microspheres were compared in isolated hearts and intact hearts with and without adenosine triphosphate (ATP) vasodilation. ATP vasodilation caused increase shunting of 9 mu spheres but not 15 mu spheres (p less than 0.05). The transmural distribution of 9 and 15 mu spheres in left ventricle and septum were significantly different (p less than 0.01) and the difference was characteristic for the isolated heart and the nonvasodilated intact heart. There was no difference in distribution across the right ventricle. There appear to be significant differences in regional shunting as well as distribution in the intact heart. We found no systematic correction for comparing flows measured with 9 and 15 mu spheres.

Trapping, nontrapping, and release of nine and fifteen micron spheres in dog kidneys.

Variations in the distribution of different size microspheres trapped within an organ depend upon regional variations in delivery or trapping of different size spheres. We have determined the intrarenal distribution of trapped 9 mu and 15 mu spheres, as well as their nontrapping and release in dog kidneys. More 15 mu spheres than 9 mu spheres are normally trapped in the outer cortex, and fewer 15 mu spheres than 9 mu spheres in the medulla. This is true whether the renal blood flow enters the organ through the hilum or through capsular collaterals with chronic renal artery occlusion. The differences in distribution are due to greater trapping of 15 mu spheres than 9 mu spheres in the outer cortex with subsequent greater delivery and trapping of 9 mu spheres than 15 mu spheres in the vasa rectae of the medulla. Axial migration of the larger 15m spheres with greater distribution to terminal branches of a vessel and less distribution to proximal branches does not explain these observations, because it is independent of the transcortical direction of blood flows. Studies with adenosine triphosphate (ATP) vasodilation show that 15 mu spheres are trapped to a greater degree than 9 mu spheres and that previously trapped 9 mu spheres may be released with ATP vasodilation. Nontrapping and release of microspheres are potential sources of error and are greater with 9 mu than 15 mu spheres.

Technique for visualization of the functioning mitral valve.

A technique is described for visualization of the mitral valve in the beating perfused heart to identify areas of abnormality in the valve apparatus before reconstruction. Risks of air embolus and myocardial ischemia are minimized.

Management of recurrent superior vena caval syndrome with an externally supported femoral vein bypass graft.

Management of superior vena caval syndrome with an autogenous vein bypass graft can be complicated by occlusion of the bypass graft. The case of a patient with recurrent superior vena caval syndrome due to occlusion of a spiraled saphenous vein graft who was managed with a femoral vein graft supported externally by a sleeve of ringed polytetrafluoroethylene is presented. A venogram demonstrated patency of the graft 11 months postoperatively, and the patient remains free from clinically apparent superior vena caval obstruction 18 months postoperatively.

Management during reoperation of aortocoronary saphenous vein grafts with minimal atherosclerosis by angiography.

The proper management of saphenous vein grafts showing minimal angiographic evidence of atherosclerosis at the time of reoperation for progressive atherosclerosis in the native coronary circulation or for severe atherosclerosis in other saphenous vein grafts is uncertain. Following the occlusion of vein grafts in 2 patients 7 and 12 years after operation but only 2 years after arteriography demonstrated no major abnormalities in the grafts, we adopted a policy of elective replacement of all saphenous vein grafts, irrespective of angiographic findings, when reoperation was necessary 5 or more years after the initial operation. Between July, 1984, and May, 1985, 16 patients had repeat coronary artery bypass grafting 6 to 13 years (mean, 9 years) after the initial procedure. Complete revascularization was carried out in all patients. In each, it included replacement of at least 1 saphenous vein graft showing no severe obstruction (less than 30% of the luminal diameter) and no (5 patients), minimal (8), or moderate (3) luminal irregularities by angiography. By pathological examination, 3 of the grafts had minimal, 5 had moderate, and 8 had severe atherosclerotic changes present. These changes were generally more diffuse than those observed by angiography. Because angiography underestimates the severity of the atherosclerotic degeneration in saphenous vein grafts and because of the propensity of the atherosclerotic disease to progress at an unpredictable rate, we recommend routine replacement of all saphenous vein grafts at the time of reoperation if done 5 or more years after the initial procedure.

The coronary-subclavian steal syndrome: report of a case and recommendations for prevention and management.

The coronary-subclavian steal syndrome involves the siphoning of blood from the myocardium through an internal mammary artery graft because of a proximal subclavian artery stenosis or occlusion, and results in myocardial ischemia. With the increased use of the internal mammary artery for myocardial revascularization, the potential exists for recurrence of angina pectoris in patients who have or in whom develops high-grade stenosis or occlusion of the subclavian artery, because of the coronary-subclavian steal syndrome. The coronary-subclavian steal syndrome can be prevented by the identification of patients with or at risk to develop subclavian artery occlusive disease. All patients undergoing cardiac catheterization prior to coronary artery bypass grafting in which use of the internal mammary artery is anticipated should be evaluated for the presence of upper extremity and cerebrovascular ischemia, the presence of cervical or supraclavicular bruits, and an upper extremity blood pressure differential of 20 mm Hg or greater. Patients with these findings or with evidence of diffuse atherosclerotic vascular disease should have brachiocephalic arteriography at the time of coronary arteriography to identify significant subclavian artery occlusive disease. When this is demonstrated, use of the internal mammary artery as a free graft instead of an in situ graft or use of saphenous vein grafts is indicated. Patients in whom recurrent angina develops following coronary artery bypass grafting that included an internal mammary artery graft should have coronary arteriography to evaluate the presence of coronary-subclavian steal syndrome, and brachiocephalic arteriography. Carotid-subclavian bypass grafting, probably best done with a prosthetic conduit, is the procedure of choice for management of the coronary-subclavian steal syndrome.

Coronary artery bypass grafting in patients with a tracheostoma: use of a bilateral thoracotomy incision.

The performance of cardiac surgical procedures via median sternotomy in patients with a tracheostoma can present difficult problems, including stomal necrosis, mediastinitis, and inadequate operative exposure. Bilateral thoracotomy is an alternative approach in such patients. This approach separates the stoma from the operative field and provides satisfactory exposure for internal mammary artery dissection and performance of coronary artery bypass grafting.

Intraoperative ultrasonic imaging of the ascending aorta.

Embolization of atherosclerotic material from the ascending aorta resulting from placement of cannulas or vascular clamps is a major cause of stroke during cardiac surgical procedures. In an effort to identify atherosclerotic disease of the ascending aorta which might predispose to embolization, intraoperative B-mode ultrasonography was performed in 50 patients. The aorta was imaged from the aortic annulus to the origin of the innominate artery in transverse and longitudinal views. The results were compared with visual and tactile examination of the aorta for the presence of atherosclerosis. Ultrasonic imaging demonstrated atherosclerotic disease in 29 patients (58%). Visual examination and palpation identified atherosclerosis in 12 patients (24%). The amount and location of plaque was sufficient to require a change in the site of arterial cannulation or the proximal vein graft anastomoses or the technique of cardiopulmonary perfusion in 12 of the 50 patients (24%). All 12 patients were 65 years of age or older. Palpation underestimates the presence of atherosclerotic disease in the ascending aorta. Intraoperative ultrasonography accurately identifies patients with atherosclerotic disease of the ascending aorta. This allows the surgeon to modify cannulation, perfusion, and operative techniques to reduce the risk of perioperative stroke due to the embolization of atherosclerotic debris from the ascending aorta.

Morbidity and mortality of coronary bypass surgery in patients 75 years of age or older.

To determine factors associated with an increased risk of postoperative complications in elderly patients, 60 consecutive patients 75 years of age or older undergoing isolated coronary artery bypass grafting (CABG) were evaluated. Thirty-nine patients (65.0%) had at least one major postoperative complication, including 2 deaths (3.3%). Low body weight was the only univariate predictor (p less than 0.05) of an increased likelihood of complications overall. Prior cardiac operation, low serum cholesterol value, and prolonged cardiopulmonary bypass time were associated with increased bleeding. Electrocardiographic evidence of left ventricular hypertrophy was associated with prolonged postoperative confusion. Age of 80 years or more and increased cross-clamp time were predictive of pulmonary dysfunction. Low cardiac output occurred more frequently in patients with nonsinus rhythm, prior cardiac operation, recent congestive heart failure, or elevated level of blood urea nitrogen. Identification of risk factors for specific complications should prompt further studies to define ways of reducing morbidity and the resultant high cost associated with CABG in elderly patients.

Risks of bilateral internal mammary artery bypass grafting.

Although use of one internal mammary artery (IMA) for coronary artery bypass grafting does not appear to be associated with increased risk, the results with both IMAs are less certain; the potential for a higher incidence of sternal wound infection as a result of devascularization of the sternum is a major concern. During a 42-month interval ending July 1988, 1,566 patients had coronary artery bypass grafting alone or in combination with other procedures: 633 received only vein grafts, 687 had unilateral IMA grafting, and 246 had bilateral IMA grafting. The IMA patients were younger, were more often male, had better cardiac function, and underwent fewer emergent, urgent, or combined procedures than the patients receiving vein grafts (p less than 0.05). Thirty-day mortality was lower among the IMA patients (unilateral IMA group, 2.8%; bilateral IMA group, 3.7%; and vein graft group, 7.9%; p = 0.001). With the exception of sternal wound problems, occurrence rates for postoperative complications among the IMA patients did not differ significantly from or were lower (p less than 0.05) than those among the patients with vein grafts. Sternal infections occurred with greater frequency among the bilateral IMA patients (6.9%) than among the unilateral IMA (1.9%) or vein graft (1.3%) patients (p = 0.001). By univariate analysis, obesity, diabetes, bilateral IMA grafting, and need for prolonged (greater than 48 hours) mechanical ventilation were associated with a significantly higher incidence of sternal infection (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary artery bypass grafting in dialysis patients.

Cardiac disease continues to be a major cause of death in patients undergoing long-term hemodialysis. The results of coronary artery bypass grafting (CABG) for severe coronary artery disease in long-term hemodialysis patients have been studied in a group of 12 patients who underwent CABG between January 1979 and December 1983. Hospital mortality was 8% (1 of 12 patients). This patient died of ventricular arrhythmia. Two late deaths occurred, 1 from peritonitis in a patient undergoing long-term peritoneal hemodialysis and 1 from metastatic renal cell carcinoma. The two postoperative complications (morbidity 17%) consisted of a sternal dehiscence secondary to mediastinitis and a perioperative cerebrovascular accident. Ten of the 11 hospital survivors experienced complete relief from angina. In the other patient the angina became easier to control with medication. Combining this series of patients with those previously reported in the literature allows determination of actuarial survival in a group of 25 patients followed up for 1 to 79 months (mean, 33 months). Actuarial survival was 83% at one year, 69% at three years, and 48% at five years. This is not significantly different from the survival of long-term hemodialysis patients who have coronary disease but have not undergone CABG. It appears that CABG, when performed in long-term hemodialysis patients, is associated with an only slightly greater risk of mortality and morbidity than CABG performed in routine patients. Although CABG provides considerable symptomatic relief of angina, no statistically significant change in actuarial survival can be demonstrated.

Toward further reducing wound infections in cardiac operations.

BACKGROUND: Serious wound infections such as mediastinitis still occur at a rate of 0.8% to 2.0%, according to the most recently published cardiac operative series. METHODS: Data from careful surveillance for infection have been collected prospectively during a 4.5-year period on 1,717 patients who underwent cardiac operations performed under direct ultraviolet C radiation. RESULTS: The rate for mediastinitis was 0.23%, and for deep incisional infection without mediastinitis, 0.12%; these rates are significantly lower than those for eight of nine of the most recently published cardiac series. When our infection rates were stratified using the National Nosocomial Infection Surveillance risk index, they were also significantly lower in the most important risk categories than the corresponding stratified rates collected from the participating hospitals of the Centers for Disease Control and Prevention National Nosocomial Infection Surveillance system. CONCLUSIONS: Though we lack the proof that only a large, randomized study might provide, certainly, one possible explanation for our lower wound infection rate was the use of bactericidal ultraviolet C radiation during operation. This is a simple and effective means of minimizing operating room airborne bacteria as one possible source of these infections.