Thrombomodulin and angiotensin-converting enzyme activity during pediatric open heart operations

Endothelial Cell Function and Dysfunction in Critically Ill Children

Endothelial cells (ECs) line the lumen of the entire vascular system and actively regulate blood flow; maintain blood fluidity; control water, solute, and macromolecular transfer between blood and tissue; and modulate circulating immune cell recruitment and activation. These vital functions, combined with the broad anatomic distribution of ECs, implicate them in all forms of critical illness. The present article discusses how ECs adapt and break down during the course of critical illness. We first review the biology of ECs, highlighting the vascular segmental differences and their specific roles in the maintenance of homeostasis. We then discuss how ECs acquire new functions to restore local and systemic homeostasis (activation) as well as how breakdowns in EC functions (dysfunction) contribute to local and systemic pathologic responses, with clinical correlations. Lastly, how these processes have been studied in critically ill children is discussed.

Gene therapy delivery systems for enhancing viral and nonviral vectors for cardiac diseases: current concepts and future applications

Gene therapy is one of the most promising fields for developing new treatments for the advanced stages of ischemic and monogenetic, particularly autosomal or X-linked recessive, cardiomyopathies. The remarkable ongoing efforts in advancing various targets have largely been inspired by the results that have been achieved in several notable gene therapy trials, such as the hemophilia B and Leber's congenital amaurosis. Rate-limiting problems preventing successful clinical application in the cardiac disease area, however, are primarily attributable to inefficient gene transfer, host responses, and the lack of sustainable therapeutic transgene expression. It is arguable that these problems are directly correlated with the choice of vector, dose level, and associated cardiac delivery approach as a whole treatment system. Essentially, a delicate balance exists in maximizing gene transfer required for efficacy while remaining within safety limits. Therefore, the development of safe, effective, and clinically applicable gene delivery techniques for selected nonviral and viral vectors will certainly be invaluable in obtaining future regulatory approvals. The choice of gene transfer vector, dose level, and the delivery system are likely to be critical determinants of therapeutic efficacy. It is here that the interactions between vector uptake and trafficking, delivery route means, and the host's physical limits must be considered synergistically for a successful treatment course.

Cardiac gene therapy: optimization of gene delivery techniques in vivo

Vector-mediated cardiac gene therapy holds tremendous promise as a translatable platform technology for treating many cardiovascular diseases. The ideal technique is one that is efficient and practical, allowing for global cardiac gene expression, while minimizing collateral expression in other organs. Here we survey the available in vivo vector-mediated cardiac gene delivery methods--including transcutaneous, intravascular, intramuscular, and cardiopulmonary bypass techniques--with consideration of the relative merits and deficiencies of each. Review of available techniques suggests that an optimal method for vector-mediated gene delivery to the large animal myocardium would ideally employ retrograde and/or anterograde transcoronary gene delivery,extended vector residence time in the coronary circulation, an increased myocardial transcapillary gradient using physical methods, increased endothelial permeability with pharmacological agents, minimal collateral gene expression by isolation of the cardiac circulation from the systemic, and have low immunogenicity.

Role of the endothelium in pulmonary arterial hypertension

Pulmonary hypertension represents a significant disease burden in both the developed and developing worlds. Certain forms of pulmonary hypertension are more common in some countries than others but people of all races, all ages and both sexes are affected. Treatment options are limited and expensive. The development of new therapies will be determined by improved understanding of endothelial cell biology.

How to optimize in vivo gene transfer to cardiac myocytes: mechanical or pharmacological procedures?

An efficient gene delivery system is a prerequisite for myocardial gene therapy. Among the various procedures studied so far, catheter-based percutaneous gene delivery to the myocardium through the coronary vessels seems the most relevant to routine clinical practice; however, the optimal conditions remain to be determined. We selectively infused adenoviral vectors encoding luciferase (1 x 10(9) PFU) or beta-galactosidase (1 x 10(10) PFU) into coronary arteries of adult rabbits in various experimental conditions. Coronary artery occlusion for 30 sec, during and after adenovirus delivery, was required to observe luciferase activity in the target area of the circumflex artery (4.0 +/- 1.0 x 10(5) vs. 1.1 +/- 0.2 x 10(4) RLU/mg with and without coronary occlusion, respectively, p < 0.01, and 1.0 +/- 0.1 x 10(3) RLU/mg using nonselective infusion). When adenoviruses were delivered using high-pressure infusion (82 +/- 12 vs. 415 +/- 25 mmHg before and during infusion, respectively, p < 0.01), luciferase activity increased to 8.5 +/- 2.5 x 10(5) RLU/mg (p < 0.05 vs coronary occlusion alone). Coronary venous sinus occlusion with saline buffer retroinfusion starting before and during anterograde adenovirus delivery resulted in a further 4.7-fold increase in luciferase activity (4.4 +/- 0.8 x 10(6) RLU/mg, p < 0.01) with 5-25% blue-stained myocytes in the target area, compared with 0-5% with the other procedures. Histamine or VEGF-A(165) pretreatment, used to increase vascular permeability, slightly increased gene transfer efficiency (8.5 +/- 2.0 x 10(5) and 9.0 +/- 2.5 x 10(5) RLU/mg respectively, p < 0.05 vs. coronary occlusion alone). We conclude that catheter-mediated adenoviral gene transfer to cardiac myocytes through coronary vessels can be a very efficient procedure for myocardial gene therapy, particularly when the vector residence time and perfusion pressure in the vessels are increased.

Gene transfer for angiogenesis in coronary artery disease

Angiogenesis is a promising novel therapeutic strategy to provide new venues for blood flow in patients with severe ischemic heart and peripheral vascular disease, who are not candidates for standard revascularization strategies. We describe the underlying mechanisms involved in physiologic and therapeutic angiogenesis, underscoring the relative importance of vasculogenesis, angiogenesis, and arteriogenesis. We then present the various gene transfer vectors including plasmid, viral, and cell-based vectors, and various delivery modalities. The available preclinical data are presented, followed by a description of preliminary clinical experience, with an emphasis on the preliminary nature of these results, which address safety and not efficacy. Finally, we discuss the promises and pitfalls of clinical angiogenesis and gene transfer studies, stressing the importance of proper design of clinical trials and adequate protection of research subjects.

Nitric oxide synthase expression in lungs of pulmonary hypertensive patients with heart disease

Since little is known about the contribution of endothelial nitric oxide synthase (e-NOS) to the mechanism of pulmonary vasospasm and the development of pulmonary vascular occlusive disease, we elucidate how e-NOS is expressed in lung biopsy specimens obtained from operative patients with pulmonary hypertension. Lung biopsy specimens were obtained from 17 patients who underwent open-heart operations for various heart diseases. A piece of normal lung specimen was also obtained from the resected lungs of three lung cancer patients as a control. e-NOS expression was visualized with a monoclonal antibody against e-NOS, and the level of expression was partially quantified. Significantly high levels of e-NOS expression were seen in adult patients, whose preoperative mean pulmonary arterial pressures were greater than 20 mm Hg. In contrast, e-NOS expression in pediatric patients with the same levels of mean pulmonary arterial pressure was the same as that in the controls and in low pulmonary arterial pressure. There was a statistically significant positive correlation between the level of e-NOS expression and Heath--Edwards grading. These data suggest that the e-NOS expression in lung tissue is induced when pulmonary vascular obstructive diseases progress.

Cytokine mediated endothelial activation during and after normothermic cardiopulmonary bypass: heparin-bonded versus non heparin-bonded circuits

Studies evaluating cytokine production under normothermic cardiopulmonary bypass (CPB) are limited. We evaluated cytokine production, levels of thrombomodulin (TM), and soluble endothelium-derived adhesion molecules (ICAM-1) under normothermic CPB with and without heparin-bonded circuits. Nine patients treated with non heparin-bonded circuits (control group), and seven patients treated with heparin-bonded circuits (heparin group) were the subjects. Granulocyte elastase (G-E), and interleukin (IL) -6 and IL-8 were chosen as proinflammatory mediators, and TM and ICAM-1 served as indicators for endothelial damage. Blood samples were obtained before CPB, 30 minutes after initiation of CPB, at the termination of CPB, and 2 and 24 hours after CPB. G-E values in the heparin group were lower than those in the control group after 30 minutes of CPB. A G-E surge occurred at the end of CPB, and IL-6 and IL-8 surges were observed 2 hours after CPB in both groups. TM and ICAM-1 values, which were reduced at the initiation of CPB, returned to initial levels 2 hours after CPB, and exceeded them 24 hours after CPB compared with preCPB levels. Both groups showed similar changes. We conclude that there are no significant differences in serial G-E, IL-6, IL-8, TM, or ICAM-1 levels between the heparin and control groups during or after normothermic CPB for 2 to 3 hours.

Cardiopulmonary bypass exacerbates oxidative stress but does not increase proinflammatory cytokine release in patients with diabetes compared with patients without diabetes: regulatory effects of exogenous nitric oxide

BACKGROUND

Cardiopulmonary bypass induces oxidative stress and a whole-body inflammatory reaction that are believed to increase surgical morbidity.

OBJECTIVES

Our goal was to investigate the effect of nitric oxide supplementation on bypass-induced oxidative stress and inflammatory reaction in patients with and without diabetes undergoing elective coronary bypass graft surgery.

METHODS

Patients with and without diabetes were randomized to receive an infusion of saline solution or the nitric oxide donor nitroglycerin at 1 microg. kg(-1). min(-1) starting 10 minutes before the initiation of cardiopulmonary bypass and then maintained for 4 hours (n = 10 per group). Serial blood samples were taken at various intervals and plasma was analyzed for markers of oxidative stress (lipid hydroperoxides, protein carbonyls, and protein nitrotyrosine) and inflammation (complement C3a, elastase, interleukin 8, and tumor necrosis factor alpha).

RESULTS

Cardiopulmonary bypass significantly increased lipid hydroperoxides, protein carbonyls, protein nitrotyrosine, complement C3a, elastase, soluble E-selectin, interleukin 8, and tumor necrosis factor alpha in both groups. Infusion of nitroglycerin significantly reduced the increase in lipid hydroperoxides and protein carbonyls in patients who have diabetes without affecting levels in patients without diabetes. Nitroglycerin infusion markedly reduced protein nitrotyrosine and tumor necrosis factor alpha levels in both groups. In contrast, nitroglycerin infusion significantly increased C3a in patients without diabetes and increased elastase and interleukin 8 levels in patients with diabetes.

CONCLUSIONS

Cardiopulmonary bypass induces a greater oxidative stress in patients with diabetes than in those without diabetes, and the inflammatory reaction is qualitatively different in the 2 groups of patients. In addition, nitroglycerin reduces oxidative stress in patients with diabetes and differentially affects the inflammatory response to bypass both in patients with and in those without diabetes. The results have important implications with respect to the use of nitric oxide donors during cardiopulmonary bypass.

Off-pump bypass graft operation significantly reduces oxidative stress and inflammation

BACKGROUND

This study investigated whether off-pump coronary bypass graft operations on the beating heart under normothermic conditions reduces the systemic oxidative stress and inflammatory reaction seen in patients operated under cardiopulmonary bypass (CPB).

METHODS

A cardiac stabilizer (Octopus Tissue Stabilizer; Medtronic Inc, Minneapolis, MN) was used to perform the coronary anastomoses on the normothermic beating heart with or without CPB. Serial blood samples were taken at various intervals. Plasma was analyzed for several oxidative stress and inflammatory markers.

RESULTS

Significant increases from prior anesthesia values of lipid hydroperoxides (190% at 4 hours), protein carbonyls (250% at 0.5 hours) and nitrotyrosine (510% at 0.5 hours) were seen in the CPB group, but they were abolished or significantly reduced in the off-pump group. Complement C3a and elastase levels were rapidly increased upon the institution of CPB, and this was followed by increases in IL-8, TNF-alpha, and sE-selectin. In contrast, the rise of these factors was blunted in patients operated without CPB.

CONCLUSIONS

Off-pump coronary bypass graft operation on a beating heart significantly reduces oxidative stress and suppresses the inflammatory reaction associated with the use of CPB.

Angiotensin II concentrations and gut mucosal perfusion in infants undergoing cardiopulmonary bypass

OBJECTIVES

To determine whether hypothermic cardiopulmonary bypass (CPB) per se causes an increase in angiotensin II (A-II) concentration in infants and to investigate the relationship between A-II concentration and gut mucosal perfusion.

DESIGN

Prospective, open, nonrandomized, observational study.

SETTING

Children's teaching hospital.

PARTICIPANTS

Thirty acyanotic infants requiring CPB.

INTERVENTIONS

A-II concentrations were measured on six occasions before, during, and after CPB. An orogastric tonometer allowed intermittent calculations of gastric intramucosal pH (pHi). Gastric mucosal blood flow (flux) was monitored using a laser Doppler flowmeter. Ten infants acted as controls (group 1); 10 infants received captopril, 0.9 mg/kg orally, 45 minutes before induction of anesthesia (group 2), and 10 infants received enalaprilat, 0.06 mg/kg intravenously, just before CPB (group 3).

MEASUREMENTS AND MAIN RESULTS

A-II concentrations were abnormally high in 28 of 30 patients before CPB (median, 450 pg/mL (range, 83 to 5,787 pg/mL). A-II concentrations in groups 1 and 2 decreased during CPB, but values remained at twice normal levels throughout surgery (median, 171 to 198 pg/mL post-CPB). A-II concentrations remained normal (range, 52 to 120 pg/mL) during and after CPB in patients receiving enalaprilat (group 3). The authors found no significant correlation between A-II concentration and pHi or flux before, during, or after surgery.

CONCLUSIONS

Acyanotic infants requiring cardiac surgery may have high perioperative concentrations of A-II. Hypothermic CPB is associated with a decrease in A-II concentration. Reductions in gut mucosal perfusion seen in some infants during hypothermic CPB are not related to increases in A-II concentrations.

Successful autotransplantation of microvessel fragments into the rat heart

We examined whether microvessel fragments (Mvf), autologously transplanted with myofibroblasts (Mf) into the heart, could survive and form connections to the host's coronary microcirculation. Neither achievement has been reported before in the heart. Mvf and Mf were prepared from Sprague-Dawley rat epididymal fat pads. A mixture of Mvf (labeled with the fluorescent probe DiI-acetylated low-density lipoprotein, DiI-Ac-LDL) and Mf was injected into the superficial myocardium under general anesthesia. Rats (n = 5 in each group) were killed on postoperative days 7, 14, 21, 42 and 49, and India ink was perfused through the coronary arteries. Frozen sections of the injected area were examined under fluorescence and light microscopes. Some DiI-Ac-LDL-labeled Mvf survived in each group, and India ink was present in the lumina of microvessels coincident with DiI-Ac-LDL-labeled autotransplanted Mvf. Hematoxylin and eosin staining revealed mild inflammatory reactions followed by some fibrosis at the injection sites. These findings indicate that autotransplanted Mvf can survive for at least 49 days, and that patent microvascular anastomoses can form between them and the host's coronary microvessels. Possibly, autotransplantation of Mvf could lead to the development of a new collateral microcirculation, a phenomenon especially important in the ischemic heart.

In vivo short-term expression of a hypertrophic cardiomyopathy mutation in adult rabbit myocardium: myofibrillar incorporation without early disarray

Cardiac myocyte disarray is the pathological hallmark of hypertrophic cardiomyopathy (HCM), a disease of sarcomeric proteins. Mutations in the cardiac troponin T (cTnT), a major gene responsible for HCM, are associated with severe myocyte disarray. To study the pathogenesis of cardiac myocyte disarray, we expressed normal and mutant cTnT proteins in the myocardium of adult rabbits via direct intramyocardial injection of recombinant adenoviruses. Aliquots of 1010 plaque-forming units of normal (Ad/CMV/cTnT-Arg92) and mutant (Ad/CMV/cTnT-Gln92) recombinant viruses or a control vector (Ad/DeltaE) virus were mixed with equal aliquots of a reporter virus (Ad/CMV/Lac-Z) and co-injected into the myocardium of adult rabbits (n = 12). One week following gene transfer, thin myocardial sections were obtained and analyzed for beta-galactosidase, messenger RNA (mRNA) and protein expression, hematoxylin and eosin, Masson's trichrome, immunofluorescence staining, and electron microscopy. The efficiency of gene transfer varied from 2% to 60% of the cells in an area approximately 2.5 mm in length. Northern blotting confirmed expression of the transgenes into mRNA. Immunoblotting of the myofibrillar protein extracts and indirect immunofluorescence staining confirmed expression and incorporation of the transgene proteins into myofibrils. Expression of the mutant cTnT was up to 18% of the endogenous. Light and electron microscopic studies showed normal cardiac myocyte and sarcomere structures. Thus, despite incorporation of the mutant cTnT-Gln92, stable myofibrillar formation and sarcomere assembly proceeded in vivo. The absence of myocyte and sarcomere disarray may reflect the duration, or the level of expression, or the extent of myofibrillar incorporation of the mutant cTnT-Gln92, as well as the site and timing of expression of the transgenes, and interspecies variation in the pathogenesis of HCM.

Plasma adrenomedullin level after cardiopulmonary bypass

Adrenomedullin is an intrinsic vasodilator which is metabolized mainly in the pulmonary circulation. We measured plasma levels of adrenomedullin in children with congenital cyanotic heart disease (CY group, n = 6), children with high pulmonary blood flow due to congenital heart disease (PH group, n = 8), and in adults with mitral valve disease (MV group, n = 7) before and 3 h after cardiopulmonary bypass (CPB). Before CPB, the adrenomedullin level was the highest in the MV group, possibly due to chronic heart failure. Three hours after CPB, the plasma adrenomedullin level (pg/ml) increased to 1712.7 +/- 498.4 in the CY group, 167.6 +/- 26.4 in the PH group, and 1404.3 +/- 313.7 in the MV group, the level in the PH group being significantly lower than the rest. In the PH group, there was statistically significant negative correlation between the mean pulmonary arterial pressure at the preoperative catheter study, and the adrenomedullin level 3 h after CPB. These results illustrate that the adrenomedullin level increased after CPB, but that the increase was less marked in the PH group, implying that where the pulmonary vasculature was damaged most, this results in increased vasoconstriction.

Increased circulating thrombomodulin in children with septic shock

OBJECTIVES

To test the hypothesis that children diagnosed with septic shock have increased plasma thrombomodulin values as a manifestation of microcirculatory dysfunction and endothelial injury; to determine whether plasma thrombomodulin concentrations are associated with the extent of multiple organ system failure and mortality.

DESIGN

Prospective, cohort study.

SETTING

Pediatric intensive care unit.

PATIENTS

Twenty-two children with septic shock and ten, healthy, control children.

INTERVENTIONS

Blood samples were obtained for plasma thrombomodulin determinations every 6 hrs for 72 hrs in septic shock patients and once in healthy control patients.

MEASUREMENTS AND MAIN RESULTS

Thirty-two children (22 septic shock, and 10 healthy controls) were enrolled in the study. Thrombomodulin concentrations were determined by an enzyme-linked immunosorbent assay. Septic shock nonsurvivors had significantly greater mean thrombomodulin concentrations (10.6 +/- 2.2 ng/mL) than septic shock survivors (5.5 +/- 0.6 ng/mL) (p < .05) and healthy control patients (3.4 +/- 0.2 ng/mL) (p < .01). Mean thrombomodulin values increased as the number of organ system failures increased.

CONCLUSIONS

Pediatric survivors and nonsurvivors of septic shock have circulating thrombomodulin concentrations 1.5 and 3 times greater than healthy control patients. These findings likely represent sepsis-induced endothelial injury. Patients with multiple organ system failure have circulating thrombomodulin concentrations which are associated with the extent of organ dysfunction. We speculate that measurement of plasma thrombomodulin concentrations in septic shock may be a useful indicator of the severity of endothelial damage and the development of multiple organ system failure.

The protective effect of a leucocyte removal filter on the lung in open-heart surgery for ventricular septal defect

We elucidated the protective effect of a leucocyte removal filter on cardiopulmonary bypass (CPB)-induced lung dysfunction during open-heart surgery for ventricular septal defect (VSD). Forty-six VSD patients were divided into two groups: (a) a control group of 22 patients in whom the banked blood was used to prime the CPB circuit, and (b) a leucocyte removal group of 24 patients in whom a leucocyte removal filter was used for priming and every supplement of banked blood during and after the operation. The respiratory index immediately after the CPB was significantly lower in the leucocyte removal group than in the control group (2.23 +/- 0.22 vs 3.90 +/- 0.68; p < 0.05). The duration of stay in the intensive care unit was significantly shorter in the leucocyte removal group (3.0 +/- 0.4 vs 4.1 +/- 0.4 days; p < 0.05). These data suggest that the use of a leucocyte removal filter for blood added to the CPB prime or administered after CPB may have protective effects on lung function after open heart surgery for VSD patients.