Long noncoding RNA H19-derived miR-675 aggravates restenosis by targeting PTEN.

Restenosis is mainly attributed to excessive proliferation of vascular smooth muscle cells (VSMCs). Noncoding RNAs have been identified as key regulators of diverse pathological processes. We reported that the long noncoding RNA H19 (LncRNA H19) and LncRNA H19-derived microRNA (miR-675) are overexpressed in neointima of balloon-injured artery. Thus, the present study aims to evaluate the role of LncRNA H19 on VSMCs proliferation. To determine the changes of LncRNA H19 and miR-675 expression in the injured arterial wall, the standard rat carotid artery balloon injury model was used. In vivo studies demonstrated that both LncRNA H19 and miR-675 were upregulated after vascular injury. Correlation analysis revealed a positive relationship between LncRNA H19/miR-675 and the ratio of intima to media. Gain-of-function studies showed that the overexpression of LncRNA H19 accelerated T/G HA-VSMC proliferation in vitro. We further validated that PTEN is the target gene of miR-675 as demonstrated by luciferase assay. Finally, the results of the rescue experiment indicated that LncRNA H19 promoted the proliferation of T/G HA-VSMC in a miR-675-dependent manner. This finding not only reveal a novel function of LncRNA H19, but also has important diagnostic and therapeutic implications in the setting of restenosis and perhaps other vascular proliferative disorders as well.

Cocaine-induced very late stent thrombosis.

Cocaine misuse is a known cause of acute coronary syndrome (ACS). Management of these patients has always been a challenge due to medication compliance and eventual risk of stent thrombosis. However, even cocaine misusers who are compliant with dual antiplatelet therapy have been reported to have stent thrombosis. All cases of cocaine-induced stent thrombosis reported in the literature have occurred within first year of stent placement (acute, subacute or late). We report a first case of very late stent thrombosis in a 54-year-old active cocaine misuser who presented with ST segment elevation myocardial infarction, which was successfully managed with percutaneous transluminal coronary angioplasty. A review of all the reported cases of cocaine-induced stent thrombosis is also discussed. Given the high mortality associated with stent thrombosis, treatment option for cocaine misusers presenting with ACS should be conservative when possible. If percutaneous coronary intervention is needed, bare metal stent should be preferred.

Heparin-Induced Thrombocytopenia Associated with a Heparin-Bonded Stent Graft.

We describe a case of heparin-induced thrombocytopenia (HIT) in association with heparin-bonded stent grafts. A 61-year-old man with claudication secondary to a left superficial femoral artery (SFA) occlusion was treated with 2 heparin-bonded polytetrafluorethylene (hep-PTFE) grafts. Despite the use of antiplatelet medication, he presented with thrombosed hep-PTFE grafts 1 week after initial treatment. An additional hep-PTFE graft was placed at the SFA origin because of migration of the first graft. He was discharged on anticoagulation; however, he presented again 2 weeks later with recurrent SFA thrombosis and a platelet count of 60,000, raising suspicion for HIT. All exogenous forms of heparin were discontinued, and he was started on an alternative anticoagulant. The patient returned again 5 days after being discharged with recurrent symptoms of acute limb ischemia. He underwent a left femoropopliteal artery bypass with autogenous conduit and removal of the grafts. He has since had an uneventful recovery. We believe HIT should be considered as a potential cause of hep-PTFE graft thrombosis. Diagnosis and management of these patients is complex and may require explantation of the graft.

Heme oxygenase-1 alleviates cigarette smoke-induced restenosis after vascular angioplasty by attenuating inflammation in rat model.

Cigarette smoke is not only a profound independent risk factor of atherosclerosis, but also aggravates restenosis after vascular angioplasty. Heme oxygenase-1 (HO-1) is an endogenous antioxidant and cytoprotective enzyme. In this study, we investigated whether HO-1 upregulating by hemin, a potent HO-1 inducer, can protect against cigarette smoke-induced restenosis in rat's carotid arteries after balloon injury. Results showed that cigarette smoke exposure aggravated stenosis of the lumen, promoted infiltration of inflammatory cells, and induced expression of inflammatory cytokines and adhesion molecules after balloon-induced carotid artery injury. HO-1 upregulating by hemin treatment reduced these effects of cigarette smoke, whereas the beneficial effects were abolished in the presence of Zincprotoporphyrin IX, an HO-1 inhibitor. To conclude, hemin has potential therapeutic applications in the restenosis prevention after the smokers' vascular angioplasty.

Numerical simulation on the effects of drug eluting stents at different Reynolds numbers on hemodynamic and drug concentration distribution.

BACKGROUND: The changes of hemodynamics and drug concentration distribution caused by the implantation of drug eluting stents (DESs) in curved vessels have significant effects on In-Stent Restenosis. METHODS: A 3D virtual stent with 90° curvature was modelled and the distribution of wall shear stress (WSS) and drug concentration in this model were numerically studied at Reynolds numbers of 200, 400, 600, 800. RESULTS: The results showed that (1) the intensity of secondary flow at the 45° cross-section was stronger than that at the 90° cross-section; (2) As the Reynolds number increases, the WSS decreases. When the Reynolds number reaches 600, the low-WSS region only accounts for 3% of the total area. (3) The effects of Reynolds number on drug concentration in the vascular wall decreases in proportionally and then the blood velocity increased 4 times, the drug concentration in the vascular wall decreased by about 30%. (4) The size of the high drug concentration region is inversely proportional to the Reynolds number. As the blood velocity increases, the drug concentration in the DES decreases, especially at the outer bend. CONCLUSIONS: It is beneficial for the patient to decrease vigorous activities and keep calm at the beginning of the stent implantation, because a substantial amount of the drug is released in the first two months of stent implantation, thus a calm status is conducive to drug release and absorption; Subsequently, appropriate exercise which increases the blood velocity is helpful in decreasing regions of low-WSS.

Anti-platelet factor 4/heparin antibodies in patients with impaired graft function after liver transplantation.

BACKGROUND: Heparin, the standard perioperative anticoagulant for the prevention of graft vessel thrombosis in patients undergoing liver transplantation (LT), binds to the chemokine platelet factor 4 (PF4). Antibodies that are formed against the resulting PF4/heparin complexes can induce heparin-induced thrombocytopenia. LT is a clinical situation that allows the study of T-cell dependency of immune responses because T-cell function is largely suppressed pharmacologically in these patients to prevent graft rejection. OBJECTIVES: To investigate the immune response against PF4/heparin complexes in patients undergoing LT. PATIENTS AND METHODS: In this prospective cohort study, 38 consecutive patients undergoing LT were systematically screened for anti-PF4/heparin antibodies (enzyme immunoassay and heparin-induced platelet aggregation assay), platelet count, liver function, and engraftment. RESULTS: At baseline, 5 (13%) of 38 patients tested positive for anti-PF4/heparin IgG (non-platelet-activating) antibodies. By day 20, an additional 5 (15%) of 33 patients seroconverted for immunoglobulin G (two platelet-activating) antibodies. No patient developed clinical heparin-induced thrombocytopenia. Two of six patients with graft function failure had anti-PF4/heparin IgG antibodies at the time of graft function failure. Graft liver biopsy samples from these patients showed thrombotic occlusions of the microcirculation. CONCLUSIONS: Anti-PF4/heparin IgG antibodies are generated despite strong pharmacologic suppression of T cells, indicating that T cells likely have a limited role in the immune response to PF4/heparin complexes in humans.

In vitro effects of lidocaine hydrochloride on coronary artery bypass grafts.

AIM: Coronary artery bypass grafting (CABG) is one of the most common procedures performed to improve blood supply to myocardium. The characteristics of grafts, mechanical stress and pharmacological agents have substantial influence on the short and long term graft patency. Lidocaine is among the most frequently used antiarrhythmic agents perioperatively. The aim of this study was to evaluate the in vitro effects of lidocaine on internal mammarian artery (IMA), radial artery (RA) and saphenous vein (SV) grafts. METHODS: Using standard tissue bath techniques, responses to increasing concentrations of lidocaine hydrochloride were obtained, in segments of IMA, RA and SV grafts. Twenty patients were enrolled in the study with a total number of 48 grafts (16 for IMA, RA and SV grafts each). In vitro lidocaine concentrations between 10(-9)M and 10(-3.5)M were studied to represent therapeutic plasma concentration of 1.5-5 mcg/mL. RESULTS: In IMA and RA grafts, lidocaine hydrochloride caused vasodilatation (40.5±1.9% and 39.1±2.6 % respectively) at concentrations between 10(-9) to 10(-7.5) M while causing a dose dependent vasoconstriction response at concentrations above 10(-7.5) M. In SV graft samples, lidocain hydrochloride caused vasodilatation (24.4±1.9 %) at concentrations between 10(-9) to 10(-7) M while causing dose dependent vasoconstriction at concentrations above 10(-7) M. For vasoconstriction effect, mean±SD values for E(max) were calculated as: 120.1±6.6% in IMA, 83.35±5.06% in RA, and 154.0±13.8% in SV. The vasoconstriction in the SV samples was higher than in the RA and IMA. The mean ±SD LogEC(50) values were -5.15±0.27, -5.76±0.11 and -5.56±0.19 for SV, IMA and RA grafts respectively.) There was a statiscally significant differences in the Log EC(50) values between SV, IMA and RA (P<0.005) CONCLUSION: Based on the results of our study, we conclude that, increasing doses of lidocaine in the perioperative period may cause vasospasm in IMA, RA and SV grafts. Thus, avoiding high doses may have a role in improving perioperative and long term mortality.

Occlusion of modified Blalock-Taussig shunt after clopidogrel cessation.

It has been suggested previously that rebound hypercoagulability may be responsible for morbidity and mortality following clopidogrel cessation in adults with acute coronary syndrome. We report a case of acute occlusion of a modified Blalock-Taussig shunt in an infant after clopidogrel discontinuation.

High on-treatment platelet reactivity to both aspirin and clopidogrel is associated with the highest risk of adverse events following percutaneous coronary intervention.

AIM: High on-clopidogrel platelet reactivity (HCPR) and high on-aspirin platelet reactivity (HAPR) are associated with atherothrombotic events following coronary stenting. There are, however, few data concerning high on-treatment platelet reactivity to both aspirin and clopidogrel simultaneously. The aim of the present study was to determine the incidence of dual high on-treatment platelet reactivity (DAPR) and its impact on clinical outcome. METHODS: On-treatment platelet reactivity was measured in parallel by ADP- and arachidonic acid-induced light transmittance aggregometry (LTA) (n=921) and the point-of-care VerifyNow system (P2Y12 and aspirin) (n=422) in patients on dual antiplatelet therapy undergoing elective stent implantation. HCPR and HAPR were established by receiver-operator characteristic curve analysis. The primary endpoint was a composite of all-cause death, non-fatal acute myocardial infarction, stent thrombosis and ischaemic stroke at 1-year follow-up. RESULTS: The incidence of DAPR varied between 14.7% and 26.9% depending on the platelet function test used. DAPR, assessed by LTA and the VerifyNow system, was highly associated with an adverse clinical outcome. At 1-year follow-up the primary endpoint occurred more frequently in patients with isolated HCPR (11.7%), isolated HAPR (9.6%) or DAPR (10.7%) compared with patients without high on-treatment platelet reactivity (4.2%, all p<0.01) when platelet function was evaluated with LTA. Using the VerifyNow system, patients exhibiting DAPR had the highest risk for the primary endpoint (17.7% vs 4.1% in patients without high on-treatment platelet reactivity, p=0.001). CONCLUSIONS: In patients undergoing elective percutaneous coronary intervention, DAPR to aspirin and clopidogrel is present in one in five patients and is associated with a high risk for atherothrombotic events. DAPR measured by the point-of-care VerifyNow system has a higher predictability for atherothrombotic events than LTA. CLINICAL TRIAL REGISTRATION INFORMATION: www.clinicaltrials.gov: NCT00352014.

Recombinant factor VIIa affects anastomotic patency of vascular grafts in a rabbit model.

OBJECTIVE: Recombinant factor VIIa can decrease postoperative bleeding after cardiac surgery. However, the potential for recombinant factor VIIa to cause early vascular graft occlusion at the site of new vascular anastomoses has not been fully explored. We hypothesized that recombinant factor VIIa would cause a dose-dependent reduction in vascular graft patency in rabbits. METHODS: Reversed end-to-end interpositional vein grafts were sutured into the carotid artery of heparinized rabbits, and then recombinant factor VIIa (300 µg/kg, 90 µg/kg, or 20 µg/kg intravenously) or placebo was administered (n = 16/group). Graft patency was assessed at 24 hours using a vascular ultrasound probe. Factor VII activity levels were measured using a prothrombin time-based assay. In different rabbits, the patency of venous end-to-side anastomoses and simple carotid arterial repairs was assessed (recombinant factor VIIa, 300 µg/kg vs placebo, n = 8/group). Data were analyzed using Fisher's exact test, t tests, or analysis of variance. RESULTS: Physiologic variables (activated clotting time, hemoglobin, pH, Pao(2)) and vessel diameter were not different between groups. Vein graft patency was reduced (93.8%, 81.2%, 13.8%, and 6.3%) as factor VII activity levels increased (1.8 ± 0.4, 4.4 ± 2.1, 11.8 ± 4.7, and 23.6 ± 16.9 U/mL, respectively) with increasing doses of recombinant factor VIIa administered (0, 20, 90, and 300 µg/kg, respectively, P < .05). Patency in the arterial repairs and end-to-side venous grafts was also reduced in recombinant factor VIIa-treated rabbits (P < .05 for both). CONCLUSIONS: This study suggests that recombinant factor VIIa is associated with a dose-dependent increase in fresh vascular graft occlusion. Higher doses of recombinant factor VIIa may be associated with increased thrombotic outcomes.

Acute thrombosis of drug eluting stent following protamine: a case report.

Reversal of anticoagulant effect of heparin to treat coronary perforation after bare metal stent implantation is an accepted practice. However this practice may not be safe following drug eluting stent implantation. We report a case of acute stent thrombosis following protamine administration for coronary perforation after drug eluting stent implantation.

Serious acute coronary thrombosis associated with heparin-induced thrombocytopenia in off-pump coronary artery bypass grafting.

A 72-year-old female underwent off-pump coronary bypass grafting one month after heparin exposure. Immediately after protamine administration, she developed hypotension due to acute graft failure. Grafting to left anterior descending branch was revised under intra-aortic balloon pump insertion and she was transferred to intensive care unit under stable hemodynamic condition. However, she gradually developed low cardiac output syndrome and echocardiography showed new onset of myocardial infarction. Coronary angiography on the first postoperative day revealed diffuse serious coronary thrombosis involving all grafts and grafted native coronary arteries. Emergent percutaneous coronary intervention (PCI) was performed for native vessels. Laboratory examination revealed severe progressive thrombocytopenia and she was clinically diagnosed as heparin-induced thrombocytopenia (HIT). After cessation of all heparins and alternative anticoagulation with argatroban, thrombocytopenia was improved and some of occluded grafts were recanalized. She was discharged on the 51st postoperative day. Acute graft thrombosis, especially caused by HIT, is a serious complication, which sometimes results in mortality. This is a successful case treated by PCI followed by an alternative anticoagulation.

Prophylactic fibrinogen infusion reduces bleeding after coronary artery bypass surgery. A prospective randomised pilot study.

It has been suggested that preoperative fibrinogen plasma concentration is independently associated to postoperative blood loss after cardiac surgery. Theoretically, prophylactic infusion of fibrinogen concentrate may thus reduce postoperative bleeding, but this has not previously been investigated. Twenty elective coronary artery bypass graft (CABG) patients with preoperative plasma fibrinogen levels <3.8 g/l were included in a prospective randomised pilot study. Patients were randomised to receive an infusion of 2 g fibrinogen concentrate (FIB group) or no infusion before surgery (control group). Primary endpoint was safety with clinical adverse events and graft occlusion assessed by multi-slice computed tomography. Predefined secondary endpoints were postoperative blood loss, blood transfusions, haemoglobin levels 24 hours (h) after surgery, and global haemostasis assessed with thromboelastometry, 2 and 24 hours after surgery. Infusion of 2 g fibrinogen concentrate increased plasma levels of fibrinogen by 0.6 +/- 0.2 g/l. There were no clinically detectable adverse events of fibrinogen infusion. Computed tomography revealed one subclinical vein graft occlusion in the FIB group. Fibrinogen concentrate infusion reduced postoperative blood loss by 32% (565 +/- 150 vs. 830 +/- 268 ml/12 h, p=0.010). Haemoglobin concentration was significantly higher 24 h after surgery in the FIB group (110 +/- 12 vs. 98 +/- 8 g/l, p=0.018). Prophylactic fibrinogen concentrate infusion did not influence global postoperative haemostasis as assessed by thromboelastometry. In conclusion, in this pilot study preoperative fibrinogen concentrate infusion reduced bleeding after CABG without evidence of postoperative hypercoagulability. Larger studies are necessary to ensure safety and confirm efficacy of prophylactic fibrinogen treatment in cardiac surgery.

Extravascular perivenous fibrin support leads to aneurysmal degeneration and intimal hyperplasia in arterialized vein grafts in the rat.

BACKGROUND AND AIMS: External support of vein grafts by fibrin glue possibly prevents overdistension, vascular remodeling, and neointimal hyperplasia. Previous animal models of neointimal hyperplasia showed conflicting results. Here, long-term effects of external fibrin glue support were studied in a new rat model of jugular vein to abdominal aorta transposition. MATERIALS AND METHODS AND METHODS: In male Wistar rats (250-300 g) right jugular vein (1.0-1.5 cm) was transposed to the infrarenal aorta. Fibrin glue (0.25 ml) covered the vein before releasing the vascular clamps (n = 6). Control vein grafts were exposed directly to blood pressure. After 16 weeks vein grafts were pressure-fixed for histology. Intima thickness, luminal and intimal area were measured by planimetry and elastic fibers demonstrated by Elastica van Giesson staining. RESULTS: Intimal thickness (74.04 +/- 6.7 microm vs 1245 +/- 187 microm, control vs fibrin treatment; p < 0.001), intimal area (2517.16 +/- 355 mm(2) vs 18424 +/- 4927 mm(2), control vs fibrin treatment; p < 0.05) and luminal area (2184.75 +/- 347 mm(2) vs 7231.85 +/- 1782 mm(2), control vs fibrin treatment; p < 0.05) were significantly increased, elastic fibers in the vessel wall were diminished and the vessel wall infiltrated by mononuclear cells in fibrin glue supported veins. CONCLUSION: External support of vein grafts by fibrin glue leads to aneurysmal degeneration and intimal hyperplasia, thereby possibly jeopardizing long-term graft patency.

HITT and stent thrombosis: a "clinical" diagnosis not to be missed.

Heparin induced thrombocytopenia and thrombosis (HITT) syndrome is a rare but potentially life threatening disorder, which is increasingly recognized with the widespread use of heparin. We report a rare case of early stent thrombosis secondary to HITT in a patient initially presenting with cardiogenic shock, which occurred 9 days after primary bare metal stent implantation due to subcutaneous heparin exposure. The most important factor in detection of HITT remains a high index of clinical suspicion and close monitoring of the temporal trend of thrombocytopenia, particularly when trying to distinguish HITT from other sources of thrombocytopenia seen in critically ill patients.