Changes of cerebral blood flow in the basilar artery system in patients with neurogenic syncope

Syncope is a short loss of consciousness caused by a transient decrease of global cerebral blood flow. Neurally mediated syncope is associated with vasodilatory response and bradycardia. The Doppler ultrasonography was used to evaluate changes of the basilar artery blood flow mean velocity and pulsatility index during orthostatic challenge and CO2 reactivity testing in patients with neurally mediated syncope and a negative result of the Tilt Test. Eighteen patients aged 20-40 years with a history of cerebral syncope and 10 healthy volunteers were qualified. RESULTS: There were no significant differences between syncope patients and controls in the basilar artery blood flow parameters in various body positions during normocapnia, hypocapnia and hypercapnia. Irrespective of body position, the reactivity index in patients with neurally mediated syncope was lower than that in controls, but not significantly. CONCLUSIONS: No significant pathology was found in cerebrovasoreactivity responses in the area supplied by the basilar artery, which suggests that cerebral autoregulation disorders cannot be the primary cause of neurally mediated syncope.     

A selective microRNA-based strategy inhibits restenosis while preserving endothelial function

Drugs currently approved to coat stents used in percutaneous coronary interventions do not discriminate between proliferating vascular smooth muscle cells (VSMCs) and endothelial cells (ECs). This lack of discrimination delays reendothelialization and vascular healing, increasing the risk of late thrombosis following angioplasty. We developed a microRNA-based (miRNA-based) approach to inhibit proliferative VSMCs, thus preventing restenosis, while selectively promoting reendothelialization and preserving EC function. We used an adenoviral (Ad) vector that encodes cyclin-dependent kinase inhibitor p27^Kip1 (p27) with target sequences for EC-specific miR-126-3p at the 3′ end (Ad-p27-126TS). Exogenous p27 overexpression was evaluated in vitro and in a rat arterial balloon injury model following transduction with Ad-p27-126TS, Ad-p27 (without miR-126 target sequences), or Ad-GFP (control). In vitro, Ad-p27-126TS protected the ability of ECs to proliferate, migrate, and form networks. At 2 and 4 weeks after injury, Ad-p27-126TS–treated animals exhibited reduced restenosis, complete reendothelialization, reduced hypercoagulability, and restoration of the vasodilatory response to acetylcholine to levels comparable to those in uninjured vessels. By incorporating miR-126-3p target sequences to leverage endogenous EC-specific miR-126, we overexpressed exogenous p27 in VSMCs, while selectively inhibiting p27 overexpression in ECs. Our proof-of-principle study demonstrates the potential of using a miRNA-based strategy as a therapeutic approach to specifically inhibit vascular restenosis while preserving EC function.     

Multimarker Approach in Discriminating Patients with Symptomatic and Asymptomatic Atherosclerotic Carotid Artery Stenosis

Background and Purpose

Several circulating biomarkers have been implicated in carotid atherosclerotic plaque rupture and thrombosis; however, their clinical utility remains unknown. The aim of this study was to determine the role of a large biomarker panel in the discrimination of symptomatic (S) vs. asymptomatic (A/S) subjects in a contemporary population with carotid artery stenosis (CS).

Methods

Prospective sampling of circulating cytokines and blood lipids was performed in 300 unselected, consecutive patients with ≥50% CS, as assessed by duplex ultrasound (age 47-83 years; 110 with A/S and 190 with S) who were referred for potential CS revascularization.

Results

CS severity and pharmacotherapy did not differ between the A/S and S patients. The median values of total cholesterol, low-density lipoprotein cholesterol, and lipoprotein(a) did not differ, but high-density lipoprotein (HDL) cholesterol was significantly higher (p<0.001) and triglycerides were lower (p=0.03) in the A/S-CS group than in the S-CS group. Interleukin-6 (IL-6) and high-sensitivity C-reactive protein were higher (p=0.04 and p=0.07, respectively) in the S-CS group. Circulating visfatin, soluble CD 40 receptor ligand, soluble vascular cell adhesion molecule, leptin, adiponectin, IL-1β, IL-8, IL-18, monocyte chemoattractant protein-1, myeloperoxidase, matrix metalloproteinases-8, -9, and -10, and fibrinogen were similar, but tissue inhibitor of matrix metalloproteinases-1 (TIMP) was reduced in S-CS compared to A/S-CS (p=0.02). Nevertheless, incorporation of TIMP and IL-6 did not improve the HDL-cholesterol receiver operating characteristics for S-CS status prediction. S-CS status was unrelated to angiographic stenosis severity or plaque burden, as assessed by intravascular ultrasound (p=0.16 and p=0.67, respectively). Multivariate logistic regression analysis revealed low HDL-cholesterol to be the only independent predictor of CS symptoms, with an odds ratio of 1.81 (95% confidence interval=1.15-2.84, p=0.01) for HDL <1.00 mmol/L (first quartile) vs. >1.37 (third quartile). In S-CS, osteoprotegerin and lipoprotein-associated phospholipase A₂ (Lp-PLA₂) were elevated in those with recent vs. remote symptoms (p=0.01 and p=0.02, respectively).

Conclusions

In an all-comer CS population on contemporary pharmacotherapy, low HDL-cholesterol (but not other previously implicated or several novel circulating biomarkers) is an independent predictor of S-CS status. In addition, an increase in circulating osteoprotegerin and Lp-PLA₂ may transiently indicate S transformation of the carotid atherosclerotic plaque.     

Calcium leak through ryanodine receptors leads to atrial fibrillation in 3 mouse models of catecholaminergic polymorphic ventricular tachycardia

Rationale: Atrial fibrillation (AF) is the most common cardiac arrhythmia, however the mechanism(s) causing AF remain poorly understood and therapy is suboptimal. The ryanodine receptor (RyR2) is the major calcium (Ca(2+)) release channel on the sarcoplasmic reticulum (SR) required for excitation-contraction coupling in cardiac muscle. Objective: In the present study, we sought to determine whether intracellular diastolic SR Ca(2+) leak via RyR2 plays a role in triggering AF and whether inhibiting this leak can prevent AF. Methods and Results: We generated 3 knock-in mice with mutations introduced into RyR2 that result in leaky channels and cause exercise induced polymorphic ventricular tachycardia in humans [catecholaminergic polymorphic ventricular tachycardia (CPVT)]. We examined AF susceptibility in these three CPVT mouse models harboring RyR2 mutations to explore the role of diastolic SR Ca(2+) leak in AF. AF was stimulated with an intra-esophageal burst pacing protocol in the 3 CPVT mouse models (RyR2-R2474S(+/-), 70%; RyR2-N2386I(+/-), 60%; RyR2-L433P(+/-), 35.71%) but not in wild-type (WT) mice (P<0.05). Consistent with these in vivo results, there was a significant diastolic SR Ca(2+) leak in atrial myocytes isolated from the CPVT mouse models. Calstabin2 (FKBP12.6) is an RyR2 subunit that stabilizes the closed state of RyR2 and prevents a Ca(2+) leak through the channel. Atrial RyR2 from RyR2-R2474S(+/-) mice were oxidized, and the RyR2 macromolecular complex was depleted of calstabin2. The Rycal drug S107 stabilizes the closed state of RyR2 by inhibiting the oxidation/phosphorylation induced dissociation of calstabin2 from the channel. S107 reduced the diastolic SR Ca(2+) leak in atrial myocytes and decreased burst pacing-induced AF in vivo. S107 did not reduce the increased prevalence of burst pacing-induced AF in calstabin2-deficient mice, confirming that calstabin2 is required for the mechanism of action of the drug. Conclusions: The present study demonstrates that RyR2-mediated diastolic SR Ca(2+) leak in atrial myocytes is associated with AF in CPVT mice. Moreover, the Rycal S107 inhibited diastolic SR Ca(2+) leak through RyR2 and pacing-induced AF associated with CPVT mutations.     

Simvastatin administration reduces thromboxane production in subjects taking aspirin: links between aspirin resistance and thrombin generation

Background

Growing evidence indicates that statins may reduce thromboxane A₂ synthesis and thrombin generation. We investigated the relationships between thromboxane production, thrombin generation, and oxidative stress in patients receiving aspirin before and after statin administration.

Methods

An open-label study was conducted in 112 men, aged 54.4 ± 7.3 years, at an increased cardiovascular risk receiving aspirin (75 mg/d). Prior to and following a 3-month simvastatin treatment (40 mg/d), we evaluated circulating thromboxane B₂ (TXB₂), inflammatory markers, 8-isoprostane, and prothrombin fragment 1.2 (F1.2), a marker of thrombin generation, which was also measured in blood collected every 60 s at the site of standardized skin incisions.

Results

Subjects (n = 28) with pretreatment TXB₂ concentrations in the highest quartile (“aspirin-resistant patients”) were more frequently current smokers and had elevated C-reactive protein (CRP), interleukin-6, 8-isoprostane, shorter bleeding time, and increased F1.2 production in a model of microvascular injury, when compared with the 3 remaining quartiles (all, p < 0.001). Simvastatin decreased serum TXB₂ in the whole group (by 20%, p = 0.0008). Patients in the highest quartile of the baseline TXB₂ had still higher posttreatment TXB₂, CRP, interleukin-6, and F1.2 formation following injury (all, p < 0.001). Simvastatin-induced change in TXB₂ correlated with the magnitude of changes in maximum levels and the velocity of F1.2 formation (all p < 0.001) but not with changes in inflammatory markers or lipid profile.

Conclusions

The study shows that statins significantly reduce platelet TXA₂ formation in patients taking low-dose aspirin and this effect is associated with attenuated thrombin formation in response to vascular injury.     

Antithrombin Krakow II (c.624+1 G > T): a novel mutation leading to type 1 antithrombin deficiency

Hereditary antithrombin (AT) deficiency is a rare autosomal disease. More than 200 mutations have been described in the AT gene leading to its deficiency. We describe here a case of type I AT deficiency in a 26-year-old Polish man who experienced proximal deep vein thrombosis and pulmonary embolism associated with a transient thrombotic risk factor, the right ankle trauma, despite the use of low-molecular-weight heparin prophylaxis. The family history was negative for venous thromboembolism. The AT activity was initially 47% and on repeated analysis 53%, and the antigen level, 0.15 g/l. The analysis of AT gene revealed the presence at the heterozygous state of a substitution G more than T located at the first nucleotide 3' of exon 3a (c.624 + 1 G > T, Human Genome Variation Society numbering system). The substitution might be detrimental taking account for its position in a donor splice site. To the best of our knowledge this mutation has not been previously described, so it was named antithrombin Krakow II.     

Heart transplantation in the doctors' opinion (results of a questionnaire)]

This report presents the results of the survey aimed to evaluate physicians' attitude and personal opinion on heart transplantation. The study comprised 124 people: 92 physicians (internal medicine) and 32 students of the Faculty of Medicine (sixth year) in Cracow. None of the responders was directly or indirectly involved in cardiac transplantation. Responders were assessed using questionnaire consisting of 17 questions. Participation was voluntary and anonymous. Percentage analysis and non-parametric chi-2 test were applied in statistical analysis of the results. As many as 91.9% responders declared themselves as heart transplantation supporters. As the most important causes of small number of heart transplantations in Poland the following factors were considered: inadequate quantity of cardiosurgical centers and qualified medical staff (72%), shortage of heart donors (53%), insufficient knowledge of the physician on donor's qualification (49%), excessive cost of transplantation and postoperative management (46%). Only 11.3% responders have chosen right criteria for brain death out of given possibilities, 4% identified the factors excluding potential heart donors, 89.5% have known who was authorized to diagnose brain death and 59.6% knew where to refer the donor. The fact that after cardiac transplantation the patient requires long-term immunosuppressive treatment was recognized by 87%. Only 8.3% was able to indicate the essential drug - cyclosporin A, whereas 56.1% of responders were willing to treat the patients after heart transplantation. No statistical correlation between the above-mentioned results and the place of work, degree of specialization, professional experience of the physician was found.(ABSTRACT TRUNCATED AT 250 WORDS)