RESUMEN

In this work, we perform electron energy-loss spectroscopy (EELS) of freestanding graphene with high energy and momentum resolution to disentangle the quasielastic scattering from the excitation gap of Dirac electrons close to the optical limit. We show the importance of many-body effects on electronic excitations at finite transferred momentum by comparing measured EELS to ab initio calculations at increasing levels of theory. Quasi-particle corrections and excitonic effects are addressed within the GW approximation and the Bethe-Salpeter equation, respectively. Both effects are essential in the description of the EEL spectra to obtain a quantitative agreement with experiments, with the position, dispersion, and shape of both the excitation gap and the π plasmon being significantly affected by excitonic effects.

RESUMEN

BACKGROUND: Acute mesenteric ischemia (AMI) represents a severe complication of chronic mesenteric ischemia (CMI) which is a disorder caused by severe stenosis or occlusion of mesenteric arterial supply. If untreated, patients could face mesenteric infarction and death. CASE REPORT: A 41-year-old female smoker and drug abuser, previously treated with angioplasty and stenting of the superior mesenteric artery (SMA) for CMI four years before, was admitted to our institution suffering from acute abdominal pain due to complete occlusion of the stent. After a few hours of thrombolytic therapy, she experienced sudden worsening of clinical conditions, including AMI, due to complete rethrombosis of the SMA. Thereafter, she underwent urgent thrombectomy and a subsequent retrograde 6 mm prosthetic aorto-mesenteric bypass graft. The patient reported complete relief of symptoms afterwards. A CT scan at 1-month follow-up showed primary patency of the bypass in the absence of clinical recurrence. DISCUSSION: In cases of CMI, treatment options include surgical, endovascular or hybrid approaches. Endovascular therapy, based on percutaneous angioplasty with or without stenting, seems to be effective, although it can have worse midterm and long-term results. CONCLUSION: In patients already treated with an endovascular revascularization of the SMA or celiac trunk (CT), open surgical repair through a single retrograde aorto-mesenteric prosthetic bypass in cases of acute mesenteric ischemia, seems to offer a valid and safe approach in order to prevent bowel infarction. KEY WORDS: Acute mesenteric ischemia Angioplasty, Bypass, stent,Thrombolysis.

Asunto(s)

RESUMEN

INTRODUCTION: True aneurysmal degeneration of autogenous vein grafts is unusual, despite their widespread use as arterial substitutes. We report a case of acute lower leg ischemia due to thrombosis of a non-anastomotic venous aneurysm. CASE REPORT: A 71-year old man presented at Emergency Unit at our Institution with left lower limb acute ischemia. The patient had 9 years before undergone left below the knee femoro-popliteal bypass with in situ autologous great saphenous vein (GSV) graft. Doppler ultrasound exam revealed patency of the entire conduit, and subtotal acute thrombosis of a saccular aneurysm of the vein 2 cm before the distal anastomosis of the graft. Aneurysmectomy and distal thrombo- embolectomy with Fogarty catheter of below the knee popliteal artery and tibio-peroneal trunk was performed. Vein graft continuity was restored by a termino-terminal anastomosis. DISCUSSION: Arterialized autologous veins are at risk of degenerative changes because of histological differences with arteries, but the cause of true aneurysmal degeneration of these grafts is still unknown. The mean time from graft implantation to clinical manifestation of the aneurysm is 7 years and the management of venous graft aneurysms should be subjected to the same criteria as other aneurysms. The first choice in detecting vein graft aneurysms is Duplex ultrasonography and the type of surgical intervention depends on the cause, type and extension of aneurysmal dilatation. CONCLUSIONS: Aneurysmal degeneration of deep lower extremity vein conduits implanted for vascular reconstruction has been rarely reported, but when detected they can lead to graft thrombosis, distal embolization, acute rupture, or skin ulceration. Therefore, Doppler ultrasound guided surveillance of GSV grafts should be mandatory and long time from vein graft creation to onset of aneurysms makes long-term graft surveillance even more imperative. KEY WORDS: Acute Leg Ischemia, Great Saphenous Vein, Graft; Aneurysm, Thrombosis.

Asunto(s)

RESUMEN

PURPOSE: To evaluate the safety and efficacy of carotid artery stenting (CAS) performed without an embolic protection device (EPD) in a selected group of asymptomatic patients with primary internal carotid artery (ICA) stenosis or restenosis after carotid endarterectomy (CEA). MATERIALS AND METHODS: Between May 2015 and May 2018, 77 patients (mean age 77 years; 60 men) underwent CAS without any embolic protection device. Forty-seven (61%) patients had primary ICA stenosis and were excluded from CEA because of high surgical risk; the other 30 (39%) patients had post-CEA restenosis (n=26) or a distal ICA flap after eversion CEA (n=4). The mean ICA stenosis was 82%. All procedures were performed from a femoral artery access. Pre- and/or postdilation were used in 64 patients. The primary outcome was the incidence of major complications (death, stroke, or myocardial infarction) during the procedure and within 30 days; the secondary outcome was the incidence of restenosis in follow-up. RESULTS: No relevant bradycardia was encountered during CAS. The combined rate of stroke, death, or myocardial infarction at 30 days was 1.3%. The single stroke patient recovered fully after 2 months. Over a follow-up that ranged to 3 years (mean 24±18 months), no further neurological events were recorded. One (1.3%) patient had a >70% restenosis after 6 months; the lesion was dilated, successfully restoring the lumen contour. CONCLUSION: In our series, endovascular treatment of carotid stenosis without the use of protection devices in patients with primary stenosis or postsurgical restenosis can achieve satisfactory safety and efficacy outcomes. The choice of performing CAS without using EPDs should follow a tailored approach based on the appropriate patient anatomy and specific clinical parameters to minimize neurological complications.

Asunto(s)