Background—
Using a resolution 1000-fold higher than prior studies, we studied (1) the degree to which late gadolinium-enhancement (LGE) cardiac magnetic resonance tracks fibrosis from chronic myocardial infarction and (2) the relationship between intermediate signal intensity and partial volume averaging at distinct “smooth” infarct borders versus disorganized mixtures of fibrosis and viable cardiomyocytes.
Methods and Results—
Sprague-Dawley rats underwent myocardial infarction by coronary ligation. Two months later, rats were euthanized 10 minutes after administration of 0.3 mmol/kg intravenous gadolinium. LGE images ex vivo at 7 T with a 3D gradient echo sequence with 50×50×50 μm voxels were compared with histological sections (Masson trichrome). Planimetered histological and LGE regions of fibrosis correlated well (
y
=1.01
x
−0.01;
R
2
=0.96;
P
<0.001). In addition, LGE images routinely detected clefts of viable cardiomyocytes 2 to 4 cells thick that separated bands of fibrous tissue. Although LGE clearly detected disorganized mixtures of fibrosis and viable cardiomyocytes characterized by intermediate signal intensity voxels, the percentage of apparent intermediate signal intensity myocardium increased significantly (
P
<0.01) when image resolution was degraded to resemble clinical resolution consistent with significant partial volume averaging.
Conclusions—
These data provide important validation of LGE at nearly the cellular level for detection of fibrosis after myocardial infarction. Although LGE can detect heterogeneous patches of fibrosis and viable cardiomyocytes as patches of intermediate signal intensity, the percentage of intermediate signal intensity voxels is resolution dependent. Thus, at clinical resolutions, distinguishing the peri-infarct border zone from partial volume averaging with LGE is challenging.
In vascular homeostasis, a functioning endothelial layer inhibits the development of de novo atherosclerosis. After balloon angioplasty and stenting, there is extensive mechanical denudation of the endothelium and subsequently endothelial regeneration. Impaired healing of the endothelium, such that occurs with drug-eluting stents (DES), 1 facilitates lipid deposition within neointima and leads to the development of neoatherosclerosis (NA).
2Pathological and imaging reports have demonstrated that NA is more common and occurs earlier in DES compared with bare-metal stents (BMS). 2,3 Clinical imaging studies of DES-related in-stent restenosis (ISR) by optical coherence tomography (OCT) have identified that >75% of patients presenting with unstable angina have thin-cap or disrupted neointima with overlying thrombi. 4 However, although systematic in vivo imaging data are not available for BMS, it is reported that more than one third of these patients present with acute coronary syndromes 5 and have evidence of atherosclerotic plaque within aspirates of definite stent thrombosis. 6 Taken together, there remains a need to characterizeBackground-Re-endothelialization is delayed after drug-eluting stent (DES) implantation. In this setting, neointima is more prone to become lipid laden and develop neoatherosclerosis (NA), potentially increasing plaque vulnerability. Methods and Results-Optical coherence tomography and near-infrared spectroscopy with intravascular ultrasound were used to characterize NA in 65 (51 DES and 14 bare-metal stents) consecutive symptomatic patients with in-stent restenosis. , and III (peri-strut NA). Type I thin-cap neoatheroma was more common in DES (20% versus 3%; P=0.01) and in areas of the stented segment without significant in-stent restenosis (71%). Periprocedural myocardial infarction occurred only in DES (11 versus 0; P=0.05), of which 6 (55%) could be attributed to segments with >70% in-stent restenosis. By logistic regression, prior DES was the only independent predictor of both NA (odds ratio, 7.0; 95% confidence interval, 1.7-27; P=0.006) and periprocedural myocardial infarction (odds ratio, 1.8; 95% confidence interval, 1.1-2.4; P=0.05). Conclusions-In-stent thin-cap neoatheroma is more prevalent, is distributed more diffusely across the stented segment, and is associated with increased periprocedural myocardial infarction in DES compared with bare-metal stents. These findings support NA as a mechanism for late DES failure. (Circ Cardiovasc Interv. 2013;6:507-517.)
Src tyrosine kinase family was recently identified as a novel upstream modulator of MAP kinase subfamily, p42/p44, whose activation is required for urocortin (Ucn)-mediated cardioprotection. Src kinase was also shown to reduce apoptosis in different cancer cell lines, enhancing phosphorylation and DNA binding affinity of signal transducer and activator of transcription (STAT)3. In order to evaluate the effects of Ucn on the activation status of different STAT family members, HL-1 cardiac cells were incubated with Ucn (10 nM) for increasing periods of time. STAT3 was rapidly phosphorylated at Tyr705, while neither phosphorylation at Ser727 nor induction of total STAT3 was observed. Pretreatment with PP2, a selective inhibitor of Src tyrosine kinase, reduced the pSTAT−T705 phosphorylation and transcriptional activity induced by Ucn in a dose-dependent manner. Overexpression of STAT3 in HL-1 cardiac myocytes pretreated with Ucn reduced the magnitude of cell death as compared with Ucn treatment alone, while transfection of HL-1 cells with a STAT3 mutant functionally inactive, acting as a dominant negative (DN-STAT3), enhanced the extent of cell death in a dose-dependent manner. In line with this finding, in HL-1 cardiac myocytes overexpressing STAT3 treated with Ucn, addition of the Src kinase inhibitor PP2 reversed the cytoprotective effects of Ucn, proving that the cytoprotective effects of Ucn are also mediated via the Src-pSTAT−T705 phosphorylation pathway. By immunocytochemistry, Ucn induced nuclear translocation of pST3-T705, which was inhibited by pretreatment with PP2. Together, these data strongly suggest that Ucn can mediate cardioprotection by activating the Src-pSTAT-T705 phosphorylation pathway.
Increasing use of the new oral anticoagulants (NOACs) - dabigatran, rivaroxaban, and apixaban - has prompted considerable discussion in the medical community even as warfarin remains the mainstay of therapy. This article raises 10 controversial issues regarding the use of NOACs for stroke prevention in patients with atrial fibrillation, and offers a review of the latest available evidence. We provide a brief overview of the mechanism and dosing of these drugs, as well as a summary of the key clinical trials that have brought them into the spotlight. Comparative considerations relative to warfarin such as NOAC safety, efficacy, bleeding risk, reversibility, drug-transitioning and use in patients well controlled on warfarin are addressed. Use in select populations such as the elderly, those with coronary disease, renal impairment, or on multiple anti-platelet drugs is also discussed. Finally, we consider such specific issues as comparative efficacy, off-label use, cost, rebound and management during events. Ultimately, the rise of the NOACs to mainstream use will depend on further data and clinical experience amongst the medical community.
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