False Channel Research Articles

Abstract 473: Dissecting Aortic Aneurym in Angiotensin II - Infused Mice: The Mechanisms Behind Lesion Variability

Angiotensin II-infused mice develop dissecting aneurysms, characterized by intramural rather than intraluminal thrombus, suprarenal rather than infrarenal lesions, medial dissections rather than circumferential elastin degradation and a variability in lesion shape that remained as yet unexplained. In order to provide insight into these intriguing lesions we scanned murine aortas at baseline and after 10, 18 and 29 days of Angiotensin II infusion, both in vivo (ultrasound, micro-CT) and ex vivo (phase-contrast X-ray tomographic microscopy). Dissecting aneurysms of varying severity occurred in 31/34 mice. All of these were characterized by a medial tear near the ostium of thoracic and abdominal aortic side branches, with a predilection for the left and ventral aspects of the ostium of the celiac artery. In 25/31 animals an intramural hematoma was formed. Fully ruptured branch ostia occurred significantly more often in the supraceliac aorta, affecting in particular the left suprarenal artery (the first branch cranial to the celiac artery, 23/25). Animals with a thoracic tear (6/31) had significantly larger intramural hematoma than animals with an abdominal tear (p<0.05), and the length of the hematoma correlated to the number of ruptured side branches (r 2 =0.78). In 11 mice a parallel false channel was formed. The volume of free-flowing intramural blood in the false channel was significantly larger for left than for ventral tears, but was not related to the length of the tear. Our data suggest that (i) medial tears are the primary event in dissecting AAA formation, (ii) an intramural hematoma is formed if the adventitia covering the medial tear dissects and leads to the accumulation of intramural blood from ruptured side branches, (iii) adventitial dissection and hematoma formation progress in the direction of least resistance/smallest side branches (i.e. cranial of the celiac artery) and (iv) a false channel is formed if the radial expansion of the adventitia due to blood flowing out of the medial tear acts in the same (leftward) direction as the expansion due to a ruptured left suprarenal artery. We conclude that Ang II-infused mice can be a valuable model to study the under-researched role of side branches in the formation and progression of aortic dissections.

Acousto-optical devices in optical communications systems: addressing-related limitations

Acousto-optical devices (AODs) are used in optical communications systems to modulate light beam intensity, enable wavelength division multiplexing on the communications system, and also to facilitate addressing of communications channels. This paper provides a detailed discussion of solutions for the third class of applications. For the first time to our knowledge, we have developed a criterion for the spatial resolution of an addressable acousto-optical deflector that maximizes the number of communications channels while maintaining the false channel address probability to a tolerable level. We provide a theoretical demonstration and experimental confirmation of the limit on the number of possible addressable communications channels with increasing aperture of the AOD.

Acute Aortic Dissection With Intussusception of the Partition Between the True and False Channels Leading to Near Total Aortic Occlusion (True Aortic Stenosis)

Described herein are 2 patients with fatal acute aortic dissection resulting in a circumferential intimal-medial tear causing the partition between the true and false channels to roll up and propagate forward as an intra-aortic intussusception (a receiving within).

CASH on Modified Elgamal: A Preventive Technique for False Channel Condition Reporting Attackin Ad-hoc Network

Ad-hoc networks are wireless networks, where the nodes transmit data through other nodes. Many Wireless networks exploit channel condition for routing. Such protocols are known as channel aware protocols. In channel aware protocols, each node reports its channel condition to other nodes and other nodes give its channel condition. However these protocols are vulnerable to false channel condition reporting attack. In this paper, an efficient Coordinate ASH (CASH) algorithm on Modified elgamal signature is proposed to avoid false channel condition reporting attack. Message authentication is ensured by adding signature and this signature is added to routing messages. Analysis demonstrates that proposed scheme is better than current schemes with respect to Computational time.

Change of descending aortic false lumen after repair of type I dissection by De Bakey

Group of authors analyzes the state of thoracoabdominal aorta after reconstruction of ascending and arch of aorta. Currently, there is no single point of view on the amount of interference in the ascending part and the aortic arch in preventing complications of thoracoabdominal aorta. In a group of 46 patients the authors by means of issuing a series of multislice computed tomography, performed at different times after surgery and examine the status thoracoabdominal aorta at different levels. Based on the results of the study revealed that, under the first phase of the surgery department at the ascending aorta and arch over her bundle for DeBakey type I, there is no need to take in a false lumen in the descending thoracic aorta, as it not only does not reduce or slow dilation thoracoabdominal aorta in the long-term, but it is a more rapid increase in comparison with patients with a false lumen was. Saving or suturing the false lumen does not affect the incidence of thrombosis in late postoperative period, and therefore, closure of a false channel in the first phase of intervention is inappropriate.

(Tissue PET) Vascular metabolic imaging and peripheral plasma biomarkers in the evolution of chronic aortic dissections.

Despite adequate medical management, dissection of the descending aorta (type B) may develop complications, including aneurysmal progression and eventually rupture. Partial false lumen thrombosis has been identified as a marker of adverse evolution in chronic dissection. The aim of this study was to test the ability of complementary information, provided by (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT) and peripheral biomarkers, to add pathophysiological significance and a prognostic value to morphological data. We explored serial aortic (18)F-FDG uptake by PET/CT imaging and plasma biomarkers in a series of 23 patients with type B dissection to predict complications from initial data and to investigate potential associations with aneurysmal expansion during follow-up. Complications occurred in 17 patients. Acute initial characteristics associated with complications were male gender (P = 0.021), arterial hypertension (P = 0.040), aortic dissection diameter (P = 0.0086), partial thrombosis of the false channel (P = 0.0046), and enhanced focal (18)F-FDG uptake (P = 0.045). During follow-up (mean 16.7 ± 8.0 months), aneurysmal expansion was associated with false lumen morphology (P< 0.0001), quantitative (18)F-FDG uptake, (P = 0.0029), elevated plasma concentrations of biomarkers of platelets (P-selectin, P = 0.0009) and thrombin activation (TAT complexes, P = 0.0075), and fibrinolysis (PAP complexes, P < 0.0001; D-dimers, P = 0.0006). Plasma markers of coagulation and fibrinolysis were related to false channel morphology, suggesting that thrombus biological dynamics may drive progressive expansion of type B dissections. Enhanced FDG uptake may be considered as a complementary imaging marker associated with secondary complications in type B dissections. During follow-up, aneurysmal progression is related to PET/CT and biomarkers of thrombus renewal and lysis.

First Experiment of Thoracic Stentgrafts with a Proximal Notch

was observed in 54.5% of the cases (n1⁄412) when they were perfused by the false channel, and in 7.9% of the cases (n1⁄43) when they were perfused by the true channel. Conclusion: The extensive deployment of a bare stent in this model of type B acute dissection allowed a re-expansion of the true channel in all the cases but involved a significant fall of the systolic pressure in the digestive and renal arteries in 54.5% of the cases when they originated from the false channel.

A Study on False Channel Condition Reporting Attacks in Wireless Networks

Wireless networking protocols are increasingly being designed to exploit a user's measured channel condition; we call such protocols channel-aware. Each user reports the measured channel condition to a manager of wireless resources and a channel-aware protocol uses these reports to determine how resources are allocated to users. In a channel-aware protocol, each user's reported channel condition affects the performance of every other user. The deployment of channel-aware protocols increases the risks posed by false channel-condition feedback. In this paper, we study what happens in the presence of an attacker that falsely reports its channel condition. We perform case studies on channel-aware network protocols to understand how an attack can use false feedback and how much the attack can affect network performance. The results of the case studies show that we need a secure channel condition estimation algorithm to fundamentally defend against the channel-condition misreporting attack. We design such an algorithm and evaluate our algorithm through analysis and simulation. Our evaluation quantifies the effect of our algorithm on system performance as well as the security and the performance of our algorithm.

Numerical simulation of ions acceleration and extraction in cyclotron DC-110

In Flerov’s Laboratory of Nuclear Reactions of JINR in the framework of project “Beta” a cyclotron complex for a wide range of applied research in nanotechnology (track membranes, surface modification, etc.) is created. The complex includes a dedicated heavy-ion cyclotron DC-110, which yields intense beams of accelerated ions Ar, Kr and Xe with a fixed energy of 2.5 MeV/A. The cyclotron is equipped with external injection on the base of ECR ion source, a spiral inflector and the system of ions extraction consisting of an electrostatic deflector and a passive magnetic channel. The results of calculations of the beam dynamics in measured magnetic field from the exit of spiral inflector to correcting magnet located outside the accelerator vacuum chamber are presented. It is shown that the design parameters of ion beams at the entrance of correcting magnet will be obtained using false channel, which is a copy of the passive channel, located on the opposite side of the magnetic system. Extraction efficiency of ions will reach 75%.

Type A Acute Aortic Dissection

To understand why the false channel (FC) remains patent after surgery of type A acute aortic dissection (TAAAD). Postoperative contrast-enhanced computed tomography scans of 129 patients operated for TAAAD were analyzed, and a color-Doppler ultrasound examination (CDUS) of the supra-aortic vessels (SAVs) was performed in 12 patients. The FC remained patent in 107 (82.9%) patients. The entry site was situated near the distal anastomosis in 43 (40.2%) patients and far from it in 44 (41.1%) patients. In 10 (9.35%) patients, an entry site was observed only in the SAVs. In 10 (9.35%) patients, no entry site was seen. Of the 12 patients explored with CDUS, a retrograde filling of the FC was observed in 11 patients. The frequent postoperative circulating aortic FC can be explained by the persistence of the primary entry tear, the presence of iatrogenic tears, and/or a retrograde filling in the SAVs.

Aortic Dissection or MI? It could be both

Acute aortic dissection is a potentially lethal vascular emergency that involves the rapid development of a false blood channel within the media of the aorta. If left untreated, approximately 50% of patients die in the first 48 hours, and the mortality rate increases by 1% to 3% per hour [1,2]. Despite recent advances in diagnostic methods, misdiagnosis occurs in 25%-50% of patients on initial evaluation with symptoms mimicking those of acute myocardial infarction and other cardiovascular disorders [3-5]. To further complicate an accurate diagnosis, ascending aortic dissections may involve the coronary and carotid arteries, resulting in myocardial infarction and stroke. With prompt diagnosis and treatment, one-year survival has been steadily improving and has been reported as high as 90% [6]. Therefore, timely diagnosis and rapid management of this disorder is imperative in the prehospital setting and in the Emergency Department. It is crucial that paramedics, emergency physicians and nurses maintain appropriate clinical suspicion for aortic dissection in patients presenting with sudden chest, back, or abdominal pain and asymmetrical pulses and blood pressures.

Human ex-vivo model of Stanford type B aortic dissection

To report a new human ex vivo model of type B aortic dissection (TBAD) and to assess if the locations of the primary entry tear determine the patterns of dissection propagation. Twenty fresh human aortas were harvested. TBADs were surgically initiated 2 cm below the left subclavian artery at four different locations (lateral, n = 5; medial, n = 5; anterior, n = 5; posterior, n = 5). Aortas were thereafter connected to a bench-top pulsatile flow model to induce antegrade propagation of the dissection. Antegrade propagation of the dissection was achieved and reached at least the celiac trunk (CT) in all the cases. Dissection was propagated to the renal aorta in 16 (80%) and infrarenal aorta in seven cases (35%). Left renal artery with or without the CT originated more often from the false channel when primary entry tear was lateral. Right renal artery and the CT most often originated from the false channel when primary entry tear was medial. When the CT was the only one originating from the false channel, primary entry tear was more often anterior, whereas when it originated from the true channel, it was more often posterior. This human ex vivo model of TBAD is reproducible, since, in all the aortas, extended dissection was achieved and provides the first model of human aortic dissection with infrarenal aorta extension allowing future assessment of endovascular devices developed for human use. Furthermore, it allows clarification of the patterns of aortic dissection propagation and visceral and renal artery involvement according to the site of the primary entry tear.

Late Pseudocoarctation Syndrome After Stent-Graft Implantation For Traumatic Aortic Rupture

The present observation illustrates an unusual complication occurring after stent-grafting (S-graft) for aortic isthmus rupture. A 22-year-old patient, treated by S-graft in the emergency department for traumatic aortic rupture, was readmitted 10 months later with pseudocoarctation syndrome. A membrane was found inside the stent-graft that had induced a pseudo-dissection, which caused the pseudocoarctation syndrome. Surgical treatment consisted of removing the stent-graft and membrane and replacing it with a vascular implant. The patient's clinical course was fair. The suggested mechanism was circumferential neoendothelialization of the stent-graft. Dehiscence caused the superior part of the membrane to drop into the lumen of the stent-graft creating a "false channel" that compressed the "true lumen" and induced "pseudocoarctation" syndrome. The cause of the extensive neointimalization remains unexplained. Thoracic aortic stent-grafts require regular follow-up monitoring by angioscan or angio-magnetic resonance imaging.

Multilayer stents in the treatment of thoraco-abdominal residual type B dissection

Multilayer stents are already being used for the treatment of peripheral aneurysms. In France, they are currently under evaluation in the treatment of thoraco-abdominal aneurysms. We have used multilayer stents to treat aneurysmal evolution of thoraco-abdominal residual type B dissection. Third month computed tomography (CT)-scan showed a false channel no longer patent. Multilayer stents are promising but it is too soon to draw conclusions on the use of this device in the treatment of patent false channels.

Spontaneous retrograde dissection of ascending aorta from descending thoracic aorta - a case review

A 56-year-old man with sudden onset chest pain, absent right lower limb pulses and ECG changes suggestive of inferior ST elevation MI underwent coronary angiogram through the right radial artery with a view to primary percutaneous coronary intervention (PCI). The left coronary angiogram demonstrated severe proximal stenotic disease in the left anterior descending and circumflex coronary arteries, but the right coronary artery could not be selectively cannulated. An ascending aortogram to visualise the right coronary artery not only failed to demonstrate it, but revealed, instead, a dissection flap in the ascending aorta, arch and descending thoracic aorta, with moderately severe aortic regurgitation. At operation, the patient was found to have an acute dissection of the ascending aorta, arch and descending aorta with an entry tear in the descending aorta below the left subclavian artery origin. Triple coronary artery bypass grafting with re-suspension of the aortic valve, supracoronary replacement of the ascending aorta and hemiarch and transaortic repair of the descending aortic tear was performed. The patient made an uncomplicated recovery, with the re-appearance of right limb pulses. A postoperative magnetic resonance (MR) scan revealed complete thrombosis of the false channel in the residual arch and a considerably shrunken false channel in the descending aorta and no aortic regurgitation. Retrograde dissection of the ascending aorta from the descending aorta has been reported infrequently in the past. We believe the scale of the problem has been underestimated because of the failure to adopt open distal anastomosis routinely in the past and, hence, failure to inspect the arch and the descending aorta routinely, particularly when the intimal tear was not identified in the ascending aorta. Retrograde dissection of the ascending aorta from an intimal tear in the descending aorta, when identified as such, has been managed, either on the principle of exclusion of the tear in the descending aorta by various elephant trunk procedures and their variants or, alternatively, on the principle of excision of the tear by extended one-stage aortic replacement, usually combined with an elephant trunk procedure. Neither of these procedures is widely adopted, owing to procedural, institutional and outcome considerations. We describe a transaortic repair of the intimal tear in the descending aorta with supracoronary interposition graft replacement of the ascending aorta and hemiarch with excellent clinical and radiological result. We also review the diagnostic and therapeutic approaches to this incompletely understood lethal disease.

Turnaround technique for intrastromal corneal ring implantation in eyes with false channel dissection

We describe a turnaround technique for implantation of intrastromal corneal ring segments in eyes with femtosecond laser-assisted channel creation in which inappropriate surgeon maneuvering creates a false channel. The false channel causes difficulty in implantation as further forward maneuvering leads to enlargement of the false channel, finally precluding forward movement of the segment. This may result in suboptimal placement of the segment or abandoning the procedure. The situation can be overcome by removing the segment and turning it around so it is inserted in the opposite direction through the entry incision. It is then advanced using the second segment as an intrachannel instrument. The double-pass turnaround is used if asymmetric segments are planned and obstruction is encountered with the second segment. This technique was used successfully in 4 eyes with a false channel. No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.

Chronic Aortic Dissection (DeBakey Type II) with Infective Thrombus in the False Channel

A 68-year-old man with a DeBakey type II chronic aortic dissection developed bacteremia secondary to a urinary tract infection with the Serratia species. This resulted in an infected thrombus in the false channel and a subsequent rupture of the ascending aorta. An emergency resection of the ascending aorta and a Dacron graft interposition were performed. The patient suffered from severe neurological insufficiency and died of pneumonia 6 months postoperatively. The optimal operation time and surgical options of an infected aortic dissection should be determined.

Turnaround Technique for Overcoming False Channel Dissection During Intracorneal Ring Segment Implantation

Turnaround Technique for Overcoming False Channel Dissection During Intracorneal Ring Segment Implantation

Abstract 5314: A Critical Role for TGF- β Activity in the Protection Against Aortic Aneurysm Formation and Complications in Adult Mice

Complicated abdominal aortic aneurysm is a major cause of mortality in elderly men. Recent studies unexpectedly showed that increased angiotensin II (AII)-dependent transforming growth factor (TGF)- β activity promotes aortic aneurysm progression in a mouse model of Marfan syndrome. However, the direct role of TGF- β activity in other forms of abdominal aortic aneurysm has not been assessed. Here, we show that systemic neutralization of TGF- β activity using two different antibodies, including the one previously shown to inhibit aneurysm formation in Marfan syndrome, breaks the resistance of normo-cholesterolemic C57BL/6 mice to AII-induced abdominal aortic aneurysm formation and markedly increases their susceptibility to the disease (from ~ 10% to 80–95%, P&lt;0.0001). These aneurysms display a large spectrum of complications on echography, including fissuration, false channel formation and rupture, leading to death from aneurysm complications. The disease and its complications are refractory to inhibition of IFN- γ , IL-4, IL-6 or TNF- α signaling. Genetic deletion of T and B cells or inhibition of CX3CR1 chemokine pathway resulted in partial protection. Interestingly, neutralization of TGF- β activity led to enhanced monocyte invasiveness, and monocyte depletion markedly inhibited aneurysm progression and complications. Finally, neutralization of TGF- β activity led to substantial increase in MMP-12 activity, and MMP-12 deficiency completely prevented aneurysm rupture. These results clearly identify a critical role for TGF- β in the taming of the innate immune response and the preservation of vessel integrity in adult normal mice, which contrasts with its reported pathogenic role in Marfan syndrome.

Abdominal Aortic Grafting for Spontaneous Infrarenal Abdominal Aortic Dissection

This case report concerns a 62-year-old woman with spontaneous infrarenal abdominal aortic dissection, which developed into claudication and rest pain in the lower extremity. Multi-row detector computed tomography showed the entry site of the abdominal aortic dissection at the second lumbar artery, while the reentry site was found intraoperatively at the median sacral artery, indicating that the false lumen had progressed and compressed the true lumen. A direct approach involving grafting appears to be an effective procedure for resolving mesenteric and lower extremity hypoperfusion due to aortic dissection with a dilated false channel, even during the acute period.