Dispersion of multiwalled carbon nanotubes in water using ionic-complementary peptides.

We demonstrate the noncovalent modification of multiwalled carbon nanotubes (MWNTs) immersed in aqueous solution using the ionic-complementary peptide EFK16-II. This modification presumably arises through the interaction between the hydrophobic side of the EFK16-II and MWNT sidewalls and orients hydrophilic functional groups toward the solution phase and enables them to form highly stable dispersions in water. This stability can be attributed to the electrostatic repulsion between self-assembled peptides on the MWNTs. This repulsion as determined by ζ potential measurements increases as the pH diverges from the isoelectric point of ~6.7 for EFK16-II. This trend is confirmed by dynamic light scattering measurements of the suspensions showing a decrease in their particle size as the ζ potential increases. These EFK16-II-MWNT suspensions have been used to modify mica surfaces. Atomic force microscopy and scanning electron microscopy images show that this leads to a uniform distribution of individual modified MWNTs on the mica surfaces. Transmission electron microscopy reveals images of well-dispersed fibers with dimensions similar to those of individual MWNTs. Tissue culture plates previously contacted with EFK16-II-modified MWNTs have been shown to have enough biocompatibility for growth and attachment of cells. The biocompatibility and enhanced electrical conductivity that should result from the modification with these EFK16-II-MWNT suspensions opens up their use in a number of potential biomedical applications such as the design of bioelectrode interfaces and fabrication of biosensors with high sensitivity.

Pulmonary veno-occlusive disease following hematopoietic stem cell transplantation: a rare model of endothelial dysfunction.

Veno-occlusive disease is among the most serious complications following hematopoietic stem cell transplantation. While hepatic veno-occlusive disease occurs more commonly, the pulmonary variant remains quite rare and often goes unrecognized antemortem. Endothelial damage may represent the pathophysiologic foundation of these clinical syndromes. Recent advances in the treatment of hepatic veno-occlusive disease may have application to its pulmonary counterpart.

Anion effect on the nanostructure of a metal ion binding self-assembling peptide.

Effects of copper salts containing different anions (SO(4)(2)(-), Cl(-), and NO(3)(-)) on the self-assembly of a designed peptide EAK16(II)GGH with affinity for Cu(2+) have been investigated. The peptide secondary structure, self-assembled nanostructures, and surface activity were observed to depend strongly on the type of anion. Over a salt concentration range from 0.05 to 10.0 mM, SO(4)(2)(-) induced long fiber formation, whereas Cl(-) and NO(3)(-) caused short fiber formation. The fiber length increased with copper sulfate concentration, but the concentration of copper chloride and copper nitrate did not affect the peptide nanostructures significantly. Analysis by Fourier transform infrared spectroscopy (FTIR) revealed that the addition of the copper salts tended to cause the peptide conformation to change from alpha-helix/random coil to beta-sheet, the extent to which depended on the anion type. This evidence of the anion effect was also supported by surface tension measurements using the axisymmetric drop shape analysis-profile (ADSA-P) technique. An explanation for the effect of anions on the peptide self-assembly was proposed. The divalent anion SO(4)(2)(-) might serve as a bridge by electrostatically interacting with two lysine residues from different peptide molecules, promoting beta-sheet formation. The extensive beta-sheet formation may further promote peptide self-assembly into long fibers. On the other hand, monovalent anions Cl(-) and NO(3)(-) may only electrostatically interact with one charged residue of the peptide; hence, a mixed secondary structure of alpha-helix/random coil and beta-sheet was observed. This observation might explain the predominant formation of short fibers in copper chloride and copper nitrate solutions.

Heart transplant coronary artery disease detected by coronary angiography: a multiinstitutional study of preoperative donor and recipient risk factors. Cardiac Transplant Research Database.

BACKGROUND: Controversy exists regarding donor and recipient factors that promote the development and progression of coronary artery disease after heart transplantation and the likelihood of coronary artery disease causing death or retransplantation. METHODS: To investigate this issue in a large cohort of patients, we analyzed 5963 postoperative angiograms performed in 2609 of the 3837 patients undergoing heart transplantation at 39 institutions between January 1990 and December 1994. Coronary artery disease was classified as mild, moderate, or severe on the basis of left main involvement, primary vessel stenoses, and branch stenoses. Coronary artery disease was considered severe if left main stenosis was > 70% or 2 or more primary vessels stenoses were > 70% or branch stenoses were > 70% in all 3 systems. RESULTS: By the end of 5 years after heart transplantation, coronary artery disease was present in 42% of the patients, mild in 27%, moderate in 8%, and severe in 7%. Coronary artery disease-related events (death or retransplantation) had an actuarial incidence of 7% at 5 years and occurred in 2 of 3 of the patients with development of angiographically severe coronary artery disease. By multivariable logistic analysis, risk factors for donor coronary artery disease included older donor age (P < .0001) and donor hypertension (P=.0002). By multivariable analysis in the hazard function domain, risk factors identified for the earlier onset of allograft coronary artery disease included older donor age (P < .0001 ), donor male sex (P=.0006), donor hypertension (P=.07), recipient male sex (P=.02), and recipient black race (P=.01). The actuarial incidence of severe coronary artery disease was 9% at 5 years. CONCLUSIONS: Angiographic coronary artery disease is very common after heart transplantation, occurring in approximately 42% of the patients by 5 years. Older donor age, donor hypertension, and male donor or recipient predict earlier onset of angiographic allograft coronary artery disease. Although severe angiographic allograft coronary artery disease occurs in only 7% of the patients at 5 years, its presence is highly predictive of subsequent coronary artery disease-related events or retransplantation.

Clinical evaluation of the on-line Sensicath blood gas monitoring system.

BACKGROUND: Blood gas analysis is an integral part of the management of open heart surgery and post-surgical intensive care patients. This study was conducted to compare the results of on-line blood gas analysis using the new Sensicath (SC) optical sensor technology against standard blood gas assay. METHODS: Comparative blood gas analysis was performed on 45 postoperative cardiovascular surgical patients and 5 patients during cardiopulmonary bypass. Simultaneous samples were obtained. One sample was sent to the central hospital laboratory for measurement using a Radiometer ABL 500 blood gas analyzer and the second sample was drawn past the optical sensor. Comparisons between the two methods for pH, pO2 and pCO2 were analyzed using linear regression and the method of Bland and Altman for the intensive care unit samples (N = 451) while the T test was used to compare data points obtained during cardiopulmonary bypass (N = 57). Bias, accuracy and precision were also calculated. RESULTS: The regression lines (r2) for pH, pO2, and pCO2 and were 0.69, 0.94, and 0.68 with slopes of 1.000, 0.0957, and 1.052 respectively for postoperative surgical patients. During cardiopulmonary bypass, the T test did not show any significant difference between the Sensicath and the reference values for the arterial and venous pH, pO2 and pCO2. CONCLUSIONS: In summary, this study found the Sensicath to be an accurate, useful tool which permits immediate blood gas analysis without blood exposure and constitutes an advance in the field of intensive care monitoring.

Policies regarding the transplantation of hepatitis C-positive candidates and donor organs.

Whether hepatitis C virus (HCV)-positive candidates or donor organs should undergo transplantation remains controversial. Seventy-two thoracic transplantation centers responded to a survey soliciting specific information about policies regarding the listing of HCV-positive candidates and the use of HCV-positive donor organs. Most centers (64%) list HCV-positive candidates for heart transplantation. Twenty-six percent of centers refuse to use HCV-positive organs, whereas the remainder restrict the use of HCV-positive organs to status 1 recipients or HCV-positive candidates. More information is needed regarding the clinical outcomes of HCV-positive candidates and recipients of HCV-positive organs before clear-cut candidate selection and organ allocation policies can be established.

Safety and efficacy of epoprostenol in patients with severe congestive heart failure. Epoprostenol Multicenter Research Group.

Patients with advanced heart failure often remain severely symptomatic and have a high mortality rate despite currently available therapy. We studied the safety and efficacy of a new approach to the patient with refractory heart failure: continuous intravenous treatment via a portable infusion pump with epoprostenol (prostacyclin), a potent pulmonary and systemic vasodilator. A group of 33 patients with severe heart failure (64% New York Heart Association class IV and 36% class III) and profound ventricular dysfunction (median left ventricular ejection fraction, 0.15)--despite prior treatment with diuretics (100%), digitalis (91%), angiotensin-converting enzyme inhibitors (85%), and dobutamine (30%)--underwent a baseline 6-minute walk test prior to dose titration with epoprostenol during invasive hemodynamic monitoring. Subjects responding during the dose titration were randomized, on an open basis, to receive either continuous epoprostenol infusion via an indwelling central venous catheter plus conventional therapy or conventional therapy alone for 12 weeks. The initial dose-ranging study with epoprostenol produced a significant decline in systemic and pulmonary vascular resistance and a substantial increase in cardiac index despite a fall in pulmonary capillary wedge pressure. Symptoms related to vasodilation were noted within the first week after randomization to epoprostenol in 9 of 16 patients but resolved with adjustment of the infusion and concomitant medications in all but one subject. Dose adjustments during the chronic epoprostenol infusion were infrequent after the first week and complications related to the drug delivery system were rare. The change in distance walked from baseline to the last available 6-minute walk test was significantly greater in patients who received epoprostenol compared with patients assigned to standard therapy (72 +/- 40 vs -39 +/- 32 m, mean +/- SEM; p = 0.033). Our study suggests that long-term intravenous infusion of epoprostenol is feasible in patients with severe heart failure and our hemodynamic and functional results suggest clinical benefit as well. However, until recent results indicating an adverse effect of epoprostenol on survival are fully evaluated, the role of this drug in the treatment of advanced heart failure will remain uncertain.

Cardiac tamponade masked by bilateral internal jugular vein thrombosis: its occurrence in an orthotopic heart transplant recipient.

We present a case of cardiac tamponade masked by bilateral internal jugular vein thrombosis occurring in a patient 1 month after orthotopic heart transplantation. Because patients who undergo heart transplantation undergo both heart surgery and multiple endomyocardial biopsies, they are at risk for both of these complications. Therefore when evaluating hypotensive patients who are at risk for both pericardial effusion and bilateral internal jugular vein thrombosis, cardiac tamponade should not be excluded, even in the absence of jugular vein distention.

Cytomegalovirus after heart transplantation. Risk factors for infection and death: a multiinstitutional study. The Cardiac Transplant Research Database Group.

Cytomegalovirus infection is a major cause of morbidity and rehospitalization after heart transplantation. To assess its incidence and risk factors in the current era of heart transplantation, we analyzed cytomegalovirus infection data in 1553 patients from 26 institutions (Cardiac Transplant Research Database Group) undergoing primary heart transplantation between Jan. 1, 1990, and June 30, 1992. There were 230 treated cytomegalovirus infections in 200 patients, of which 16 were fatal (6%; 70% confidence limits 5% to 9%). Actuarial freedom from cytomegalovirus infection was 98% 1 month, 88% 3 months, and 83% 24 months after transplantation, with a peak incidence of initial infection at 2 months. Twenty-five (12%) of 200 patients with cytomegalovirus infection had recurrent cytomegalovirus infection during a mean follow-up of 13.9 months. The primary location of cytomegalovirus infection was blood in 100 infections (43%), lung in 69 (30%), gastrointestinal tract in 54 (23%), and other sites in seven patients (3%). Cytomegalovirus pneumonia exhibited the highest mortality rate (13%). Risk factors by multivariate analysis for earlier development of cytomegalovirus infection included pretransplantation cytomegalovirus serology (positive donor, negative recipient [p < 0.0001]; positive donor, positive recipient [p = 0.0002]; and negative donor, positive recipient [p = 0.02]) and cytolytic induction therapy (p = 0.05). A cytomegalovirus-positive recipient with a cytomegalovirus-positive donor had a 15% chance of having cytomegalovirus infection, whereas a cytomegalovirus-negative recipient with a cytomegalovirus-positive donor had a 24% chance. Ganciclovir treatment was administered in 227 (99%) of 230 infections. By multivariable analysis, the likelihood of a fatal cytomegalovirus infection was increased with a higher number of infections of any type during the first post transplantation month (p < 0.0001). There was no increased mortality rate in cytomegalovirus infections associated with cytomegalovirus-positive donor and cytomegalovirus-negative recipient (6% mortality rate) versus all other cytomegalovirus infections (6% mortality rate) (p = 0.9) or with OKT3 induction therapy (0% mortality rate) versus all others (noninduction and induction with other than OKT3) (1.4%) (p = 0.03). In conclusion, the biggest determinant of cytomegalovirus infection is donor and recipient pretransplantation cytomegalovirus serologic results with cytolytic induction therapy adding a small additional risk. The overall mortality rate from cytomegalovirus infections is low (7%) in the current era with rapid culture techniques and ganciclovir therapy. Cytomegalovirus infections are more likely to be fatal if there are more frequent preceding infections of any type, but mortality rates are not increased by OKT3 induction or with a cytomegalovirus-positive donor organ transplanted into a cytomegalovirus-negative recipient.

Practices of cardiothoracic transplant centers regarding hepatitis C-seropositive candidates and donors.

The purpose of this survey was to determine current practices of cardiothoracic transplant centers regarding transplantation of hearts and lungs into hepatitis C (HCV)-seropositive candidates and the use of organs from HCV-seropositive donors. A telephone survey of 48 cardiothoracic transplant centers was conducted in October 1992. Questions included the center's policy for listing HCV-seropositive candidates; if, and under what conditions, organs from HCV-seropositive donors would be used; and which HCV assays were used. Forty-five programs responded; 75% will list an HCV-seropositive candidate, either directly or by lack of routine screening to exclude such patients; only 16% will not accept HCV-seropositive candidates; 9% had no policy. Overall, 69% will accept organs from HCV-seropositive donors, at least for selected recipients (22% for any recipient, 45% for HCV-seropositive and/or status I recipients; 2% do not screen donors). A total of 27% will never accept organs from an HCV-seropositive donor, and 4% had no policy. Thirty centers provided information on HCV methodology. All but one use a second generation ELISA or EIA as a first-line test. A positive result will be followed by a confirmatory assay/liver biopsy in 42%. The variation in practices reflects the ambiguity in the literature. Adequate evaluation of morbidity and mortality due to HCV infection in this population has not yet been possible, although currently available reports do not show a substantial increase. Prospective controlled trials in cardiothoracic transplant patients are necessary.

Implantation of the implantable cardioverter defibrillator in the heart transplant candidate.

Because the major cause of death in patients awaiting heart transplantation results from out-of-hospital sudden cardiac arrest, the use of the implantable cardioverter defibrillator has been proposed as a bridge to transplantation. To provide a safe and simple implantation procedure that also easily allows access to cardiopulmonary bypass at the time of transplantation, a modified subxiphoid approach is reported.

The impact of steroid withdrawal on the development of lipid abnormalities and obesity in heart transplant recipients.

Hyperlipidemia and obesity are common problems after heart transplantation, which may increase the risk of chronic graft atherosclerosis. The intent of this study was to (1) determine the impact of a history of hyperlipidemia on the occurrence of lipid abnormalities after transplantation, (2) compare lipid profiles of those patients being treated with triple-drug immunosuppression versus those patients weaned from prednisone therapy, and (3) identify any factors that would predict which patients are at highest risk for the development of hyperlipidemia after transplantation. Of 89 patients who lived for more than 12 months, 35 patients had a history of hyperlipidemia before heart transplantation (cholesterol level of more than 240 mg/dl; low-density lipoprotein cholesterol level of more than 160 mg/dl). The most dramatic rise in cholesterol level was observed in patients with no history of hyperlipidemia who were treated with triple-drug immunosuppression, in whom a 64% increase occurred versus a 24% increase in patients receiving steroid-free immunosuppression (p < 0.001). In patients with a history of hyperlipidemia, cholesterol level increased by 20% with triple-drug immunosuppression versus 14% with steroid-free immunosuppression (p = 0.613); however, 83% of the patients in the triple-drug group and 92% in the steroid-free group had elevated cholesterol levels. Multiple regression analysis revealed that significant independent and additive (p < 0.00001) contributions with respect to percent change in cholesterol level were evident for (1) a negative history of hyperlipidemia (p = 0.005), (2) triple-drug immunosuppression (p = 0.0021), and (3) female sex (p = 0.0113). A negative history of hyperlipidemia was predictive of the percent change in low-density lipoprotein cholesterol level (p = 0.0049), and triple-drug immunosuppression administration predicted the percent change in high-density lipoprotein cholesterol (p = 0.0119). Patients with a positive history of hyperlipidemia had higher lipid values at 12 and 24 months after transplantation; however, patients with no previous history of hyperlipidemia experienced the greatest percent change in both cholesterol and low-density lipoprotein levels. Patients receiving prednisone therapy gained more weight (9.0 +/- 7.0 kg) as compared with those patients tapered from prednisone therapy (5.9 +/- 8.6 kg); however, neither the increase in actual weight (p = 0.120) nor the increase in percent ideal body weight (14% +/- 11% versus 9% +/- 13%, respectively) were significant (p = 0.133). This study identified that postoperative weight gain is best predicted by premorbid habitus, rather than the type of immunosuppression used.(ABSTRACT TRUNCATED AT 400 WORDS)

Steroid-free maintenance immunotherapy: Minneapolis Heart Institute experience.

Recent advances in immunotherapy have resulted in improved survival after heart transplantation. The use of OKT3 as an induction agent has allowed the identification of a subset of patients who can be successfully withdrawn from prednisone and maintained on only cyclosporine and azathioprine. The latter regimen offers several theoretic advantages in terms of freedom from complications of long-term steroid therapy. To compare both the long-term efficacy and toxicity of steroid-free maintenance immunosuppression with triple-drug therapy, the medical records of 68 patients undergoing transplantation at the Minneapolis Heart Institute during a 3-year period (1988 through 1990) were reviewed. Thirty-six patients were treated with OKT3 induction immunotherapy, 29 were successfully tapered off prednisone by 114 +/- 44 days after transplantation, whereas 32 patients were maintained on triple-drug therapy. The incidence of treated rejection was equivalent in both groups; however, the time to first rejection was longer in patients treated with OKT3/steroid-free maintenance (205 +/- 214 vs 27 +/- 17 days) (p = 0.02). Bacterial infections during the early posttransplant period were more common in the OKT3/steroid-free maintenance group (p = 0.008); however, fungal and viral infections were equally distributed between both groups. The incidence of hypertension was slightly higher in patients maintained on prednisone (67% vs 51%; p = 0.242).(ABSTRACT TRUNCATED AT 250 WORDS)

Experience with the symbion total artificial heart as a bridge to transplantation.

From December 1985 through January 1991, 9 patients underwent bridging to transplantation using a Symbion J-7-70 total artificial heart. There were 4 female and 5 male patients aged 31 +/- 14 years (range, 15 to 52 years). Five patients were supported on an intraaortic balloon pump before total artificial heart support, and 2 had biventricular assist devices as well. Total artificial heart support was maintained for 17 +/- 12 days (range, 4 to 44 days); all patients underwent transplantation. Three patients died after transplantation on day 0 (primary donor organ failure), 25 (acute rejection), and 256 (multiorgan failure). The remainder were discharged at 41 +/- 32 days (range, 13 to 101 days). One patient died 28 months after transplantation of late acute rejection. Actuarial 1-year and 3-year survival is 67% and 55%. There were no surgical wound infections. Problems encountered in the J-7-70 period and the period after transplantation were for the most part related to patient condition in the period before implantation. The Symbion J-7-70 total artificial heart is an effective device for total circulatory support in patients with end-stage cardiogenic shock when an organ donor is not available. Organ system failure and infection before implantation may persist into the transplantation period resulting in long-term complications, increased mortality, and prolonged hospital stay; therefore, early implantation of the device when indicated should be applied.

Summary of the clinical use of the Symbion total artificial heart: a registry report.

Several models of total artificial hearts have been used for transient or permanent circulatory support in patients with decompensation. The most successful and widely used device, however, has been the Symbion total artificial heart. From Dec. 12, 1982, to Jan. 1, 1991, 180 Symbion total artificial hearts were implanted in 176 patients in 28 centers. Five patients received a Symbion total artificial heart as a permanent circulatory support device, whereas 171 patients received the device as a bridge to heart transplantation. Of the 175 bridge devices (171 patients) 141 were Symbion J7-70 hearts and 34 were Symbion J7-100 hearts. Four patients received two total artificial hearts, the second one after the failure of a transplanted heart because of either rejection (two patients) or donor heart failure (2 patients). Most of the recipients were males (152). The age was 42 +/- 12 years (mean +/- SD) with a weight of 74 +/- 14 kg. The most common indications for implantation included deterioration while awaiting heart transplant (36%) and acute cardiogenic shock (32%). The cause of heart disease was primarily ischemic (52%) and idiopathic (35%) cardiomyopathy. Duration of implantation ranged from 0 to 603 days (mean 25 +/- 64 days). One hundred three (60%) patients had the device less than 2 weeks, 37 (22%) between 2 to 4 weeks and 31 (18%) more than 4 weeks. Complications during implantation included infection (37%), thromboembolic events (stroke 7%, transient ischemic attack 4%), kidney failure requiring dialysis (20%), bleeding requiring intervention (26%), and device malfunction (4%). Of the 171 patients, 118 (69%) underwent orthotopic heart transplantation. Actuarial survival for all patients with implants was 62% for 30 days and 42% for 1 year, and for patients with transplants was 72% for 30 days and 57% for 1 year. The main causes of death were sepsis (33%), multiorgan failure (21%), and posttransplant rejection (10%). The results indicate a relative success of this treatment for patients with an otherwise fatal prognosis. Moreover, as the demand for donor organs far exceeds availability, continued investigation of total artificial hearts is justified.

Transesophageal echocardiography in patients with mechanical circulatory assistance.

Transesophageal echocardiography was used to assess myocardial function and to detect complications after mechanical circulatory support for 8 patients with cardiogenic shock. In 3 of 8 patients, serial transesophageal echocardiography documented improvement of systolic ventricular function, and it was possible to wean these 3 patients from the ventricular assist device. In all patients, transesophageal echocardiography added clinically important information including the extent of left and right ventricular dysfunction (6 patients), presence of atrial or ventricular thrombus (5 patients), presence of pericardial effusion or clot (2 patients), and verification of the position of the intravascular device (1 patient). Thus, transesophageal echocardiography may provide clinically useful information regarding both the underlying cardiac disease and potential complications from the mechanical circulatory assistance.