Clinical research challenges in the era of cardiovascular medical devices.

New therapeutic alternatives, such as innovative medical devices, are frequently the only treatment options left for patients when other efficient medical modalities are lacking or insufficient. Development of novel devices, which are safe and effective, requires understanding of complex premarket and postmarket provisions, including characteristics of clinical trials. Speeding up patient access to new technologies may imply the need to make choices in terms of extent and robustness of clinical evaluation without losing the patient safety perspective. In such situations, some challenges can readily arise due to existing methodological solutions and aspects of current legislation in the field. In this context, some challenges, occurring at various stages of the device lifecycle, will be presented in order to observe the changes and hopefully to contribute to better knowledge and improvements in the area.

Effect of simulated extracorporeal circulation and glyceryl-tri-nitrate on leukocyte activation.

OBJECTIVES: During extracorporeal circulation (ECC), a mechanical pump and an oxygenator replace the functions of the heart and lungs. The aim of this study is to test the effect of the nitric oxide donor glyceryl-tri-nitrate on activation markers of the innate immune system during simulated ECC. DESIGN: Whole blood concentrations of selected leukocyte adhesion molecules, complement system components and myeloperoxidase (MPO) were measured in an in vitro system of simulated ECC. RESULTS: Simulated ECC stimulated the expression of monocyte LPS-receptor CD14 and C3b-receptor CD35. Glyceryl-tri-nitrate significantly reduced the expression of leukocyte Fcγ receptor CD32 over time, compared to control. Simulated ECC increased the concentrations of MPO, terminal complement complex, and complement component C3a. Addition of glyceryl-tri-nitrate did not significantly affect these changes. CONCLUSIONS: Simulated ECC induces the increased expression of some leukocyte markers. Glyceryl-tri-nitrate addition significantly reduces the expression of some leukocyte activation markers.

Effect of glyceryl trinitrate on staphylococcus aureus growth and leukocyte activation during simulated extracorporeal circulation.

BACKGROUND: Previously, nitric oxide has been shown to possess antimicrobial effects. In this study, we aim to test the effect of glyceryl trinitrate (GTN) on Staphylococcus aureus growth during simulated extracorporeal circulation (SECC) and also to examine the effect of S. aureus, alone and in combination with GTN, on activation markers of the innate immune system during SECC. METHODS: In an in vitro system of SECC, we measured GTN-induced changes in markers of leukocyte activation in whole blood caused by S. aureus infestation, as well as the effect of GTN on S. aureus growth. RESULTS: GTN had no effect on S. aureus growth after 240 minutes SECC. Staphylococcus aureus reduced the expression of granulocyte Fcγ-receptor CD32 but stimulated the expression of monocyte CD32. Staphylococcus aureus stimulated expression of some leukocyte adhesion key proteins, activation marker CD66b, lipopolysaccharide-receptor CD14, and C3b-receptor CD35. Staphylococcus aureus and GTN addition induced significant increases in monocyte CD63 (lysosomal granule protein) levels. CONCLUSION: GTN does not affect S. aureus growth during SECC and has no effect on SECC-induced leukocyte activation.

Loss of arterial and renal nitric oxide bioavailability in hypertensive rats with diabetes: effect of beta-blockers.

BACKGROUND: Endothelial cell (EC) dysfunction contributes to hypertension and mechanisms of atherosclerosis. Agents that improve EC function may provide vascular protection, especially in patients with multiple risk factors. In this study, we examined the effects of beta(1)-selective antagonists, nebivolol and metoprolol, on vascular and renal EC function in spontaneously hypertensive (SH) rats with diabetes. METHODS: Male SH rats were treated with streptozotocin (STZ) to induce type 2 diabetes, followed by treatment with nebivolol or metoprolol at 2 mg/kg/day (vs. vehicle). After 4 weeks, aortic and glomerular ECs were isolated, stimulated with calcium ionophore (CaI), and assayed for nitric oxide (NO), and peroxynitrite (ONOO(-)) release using amperometric approaches. RESULTS: Glucose and mean blood pressure (BP) levels were significantly elevated in diabetic SH rats. In aortic ECs isolated from diabetic SH rats, NO production decreased by 20% whereas ONOO(-) increased by 16%, an effect linked to NAD(P)H oxidase and endothelial NO synthase (eNOS) uncoupling. Nebivolol treatment reduced glucose and BP levels and restored aortic EC function in diabetic SH rats, as indicated by a 30% increase and 23% decrease in NO and ONOO(-) levels, respectively. The NO/ONOO(-) ratio increased by more than twofold with nebivolol treatment in aortic and glomerular ECs. Despite similar reductions in glucose and mean BP levels, metoprolol had a smaller effect on the NO/ONOO(-) ratio in glomerular ECs but no effect in aortic ECs. CONCLUSIONS: Vascular and renal NO was significantly reduced in diabetic hypertensive rats and correlated with metabolic changes. Nebivolol reversed these effects in a manner consistent with enhanced endothelial function.

Assays of urine levels of HNL/NGAL in patients undergoing cardiac surgery and the impact of antibody configuration on their clinical performances.

BACKGROUND: Acute kidney injury (AKI) is one of the most serious postoperative complications of cardiac surgery. The lack of early and powerful markers for AKI makes the morbidity and mortality still very high. HNL (Human neutrophil lipocalin)/NGAL (Neutrophil gelatinase-associated lipocalin) was recently shown as a novel biomarker for AKI after cardiac surgery. METHODS: Serial urine samples from 59 patients undergoing cardiac surgery were analyzed by polyclonal antibody based radioimmunoassay (RIA), monoclonal-polyclonal antibody based enzyme-linked immunosorbent assay (ELISA). RESULTS: We found 10 to 100-fold increases in urine HNL/NGAL levels in about half of the patients 2 h after termination of the operation and elevated levels in all patients 72 h post operation. The urine levels of HNL/NGAL showed a weak, but significant relation with kidney function as measured by plasma levels of cystatin C or creatinine. The 2 h-HNL/NGAL levels were positively correlated to extracorporeal circulation time (p<0001). The assays were well correlated, but had different clinical performances. CONCLUSIONS: We confirmed that urine HNL/NGAL may be a useful early biomarker of postoperative kidney injury. The results indicate that the antibody configuration of the assay has an impact on the clinical performance of the assay.

Improved patency in vein grafts harvested with surrounding tissue: results of a randomized study using three harvesting techniques.

BACKGROUND: The technique of harvesting the saphenous vein for coronary artery bypass grafting influences the fate of vein grafts. The patency rate of a novel "no-touch" technique in which the vein is harvested with a pedicle of surrounding tissue and not distended was compared with two other techniques. METHODS: One hundred fifty-six patients who underwent coronary artery bypass grafting were randomized to three saphenous vein harvesting groups: group C (conventional)--the vein was stripped, distended, and stored in saline; group I (intermediate)--the vein was stripped, local application of papaverine was used instead of distention, and the vessel was then stored in heparinized blood; and group NT (no-touch)--the vein was harvested with surrounding tissue, not distended, and stored in heparinized blood. Surgical and clinical factors that might influence graft occlusion were recorded. One hundred twenty-seven vein grafts in group C, 116 in group I, and 124 in group NT, as well as 118 left internal mammary artery grafts, were angiographically assessed at 18 months mean follow-up time. RESULTS: The vein graft patency was 88.9% in group C, 86.2% in group I, and 95.4% in group NT. There was a statistically significant difference between the patency of the single-vein grafts in NT and the other two groups (p = 0.025). The higher the flow, the better the patency irrespective of the technique used. A higher attrition rate was found in vein segments taken from the knee area in group I. Poor vein quality affected patency in all groups. Forty-seven of all 51 sequential grafts (92.2%) were patent. The patency of left internal mammary artery grafts was 108 of 118 (91.5%). CONCLUSIONS: We conclude that preservation of the surrounding tissue of the saphenous vein using this no-touch technique abolishes venospasm intraoperatively and plays an important role in maintaining vein graft function and patency.