Fabrizio Follis

NMDA receptor blockade and spinal cord ischemia due to aortic crossclamping in the rat model.

Recent brain research proposes that, during ischemia, synaptically released excitatory amino acid neurotransmitters accumulate at toxic concentrations with ensuing neuronal death. Their action is mediated by the receptor subtype N-methyl-D-aspartate (NMDA). The protective effect of NMDA receptor blockade with intrathecal MgSO4 and MK-801 was investigated during spinal cord ischemia induced by aortic occlusion of 12 minutes. Male Sprague-Dawley rats, 250-300g, underwent intrathecal administration of 20 microL of normal saline (SA n = 16), MgSO4 1M (MG n = 16), or MK-801, 25 mM solutions (MK n = 16) in a randomized order. After 2 hours, the animals underwent occlusion of the thoracic aorta and subclavian arteries for 12 min. An additional control group (CO n = 16) underwent occlusion for 12 minutes, without intrathecal injection. The animals were scored according to their functional performance (LS = lesion score) each day for four days by a blinded observer. Mean LS were calculated for each group at a given day. Treatment and control groups were not different at day 1 (P = 0.302). Group MG was improved from groups SA (P = < 0.0039) and CO (P = < 0.0048) at day 4. This study demonstrates that although intrathecal NMDA receptor blockade with MgSO4 or MK-801 does not prevent paraplegia due to spinal cord ischemia in the rat, it could however influence the rate of recovery after ischemic injury.

Argatroban as a substitute of heparin during cardiopulmonary bypass: a safe alternative?

OBJECTIVES The patient with a diagnosis of heparin-induced thrombocytopenia and thrombosis who requires urgent cardiac surgery represents a formidable challenge. Among the alternatives to heparin, argatroban has gained widespread use in non-cardiac surgery patients. The object of this communication is to report our recent experience with this agent during cardiopulmonary bypass (CPB) and to review the cases previously published in order to better define indications, dosage, monitoring and limitations in cardiac surgery patients. METHODS A case of mitral valve replacement where argatroban was used for anticoagulation during CPB is described. The literature on the subject is reviewed and the relationship between argatroban dosage and activated clotting time (ACT) is studied by regression analysis. RESULTS Clotting of the oxygenator requiring prompt replacement occurred after release of cross-clamp. Upon termination of the drug, ACT remained elevated beyond the expected half-life. A significative (P<0.05) relationship was disclosed between increasing dosage and ACT, while the same relationship was absent on decreasing dosage. CONCLUSIONS Because of unresolved issues like the possibility of clotting in the extracorporeal circuit and prolonged anticoagulation after discontinuing the drug, at present, the use of argatroban as a substitute of heparin during CPB should be restricted to those cases where the other thrombin inhibitors are contraindicated.

Degeneration of axons in the corticospinal tract secondary to spinal cord ischemia in rats

Occlusion of the thoracic aorta and both subclavian arteries (XC) in the rat model produces spastic paraplegia. In order to characterize the lesion of white matter, 14 male Sprague-Dawley rats underwent XC for 10.5 to 12min, were observed for 32 days and assessed with a lesion score. A sham group of eight underwent surgical manipulations without XC. The spinal cords were studied by optical microscopy and electron microscopy. An additional group of normal animals (n = 8) underwent spinal cord blood flow measurement with the autoradiographic technique. Optical microscopy showed normal histology in sham operated rats and rats with aortic cross-clamp and lesion score = 2–4 (n = 5), rare changes in the white matter of rats with lesion score = 8 (n = 2), and demyelination of the anterior and lateral tracts of the white matter and motor neuron loss in the gray matter of rats with lesion score = 13–15 (n = 7) and spastic paraplegia. In this last group, electron microscopy disclosed severe axonal degeneration of corticospinal tracts. In the same region spinal cord blood flow was higher than the remaining white matter. This study confirms that spastic paraplegia observed in the rat model after XC is due to degeneration of the pyramidal tracts, perhaps more susceptible to injury due to the high spinal cord blood flow.

Midterm follow-up dynamic echocardiography evaluation after ascending aorta replacement and reimplantation of the aortic valve (David operation) in a matched control study

OBJECTIVE Dynamic performance of the aortic valve (AV) after ascending aorta replacement with reimplantation of the native AV (David) was investigated. METHODS We prospectively evaluated 17 patients who underwent David procedure. Rest/stress echocardiography follow-up was performed and results were compared with those of matched healthy controls. RESULTS There were no significant differences in terms of age, height, weight, BSA, left ventricular mass, left ventricular ejection fraction (LVEF) and tele-diastolic volume between the David and control group. At rest echocardiography, patients in the David group had a lower indexed aortic valve area (IAVA) (1.1 ± 0.2 vs. 1.5 ± 0.2 cm(2)/m(2), P < 0.0001), with comparable transvalvular gradients (TVG). At maximal physical stress, although the IAVA in the David group was significantly increased from the rest values (P = 0.001), the difference with the control group persisted (David 1.4 ± 0.3 vs. Control 1.7 ± 0.2 cm(2)/m(2), P < 0.0001) maintaining similar peak TVG (David 13.6 ± 5.3 vs. Control 11.7 ± 4.5 mmHg, P = ns) and mean TVG (David 7.2 ± 3.0 vs. 6.2 ± 2.4 mmHg, P = ns). AV regurgitation in the David group was absent in five (29.4%), grade I in nine (52.9%) and grade II in three (17.6%) patients and remained unchanged during stress. At multiple linear regression, David operation was inversely correlated to rest IAVA (OR = -0.4; P = 0.01; CI: -0.7-0.1). CONCLUSIONS Although IAVA is significantly smaller after David procedure in comparison with matched controls, no pathological increase in TVG is noticed. A significant increase in the IAVA during physical stress documents the preserved pliability/elasticity of the aortic unit after David procedure preventing pathological increase in the TVG even during strenuous effort.

Endovascular graft deployment in the false lumen of type B dissection

OBJECTIVES Thoracic endovascular aortic repair (TEVAR) is particularly indicated in a patient with complicated type B dissection. The object of this communication is to report a case of deployment of the endograft in the false lumen, to propose a protocol in order to prevent it and discuss the possible surgical options when this complication has occurred. METHODS A case of complicated acute type B dissection is described where the endovascular prosthesis was positioned in the false lumen. The literature on the subject is briefly reviewed for the insertion techniques and conversion to surgery. RESULTS The occurrence was recognized and treated with replacement of the entire aorta from the sinotubular junction to a level of the eighth thoracic vertebra under deep circulatory arrest with selective antegrade cerebral perfusion. CONCLUSIONS TEVAR for complicated type B dissection should be carried out according to a precise and stepwise protocol in institutions familiar with all the different options of conversion to open repair.

Haemodynamic predictors of a penetrating atherosclerotic ulcer rupture using fluid-structure interaction analysis.

We present preliminary data on the flow-induced haemodynamic and structural loads exerted on a penetrating atherosclerotic aortic ulcer (PAU). Specifically, one-way fluid-structure interaction analysis was performed on the aortic model reconstructed from a 66-year-old male patient with a PAU that evolved into an intramural haematoma and rupture of the thoracic aorta. The results show that elevated blood pressure (117 mmHg) and low flow velocity at the aortic wall (0.15 m/s(2)) occurred in the region of the PAU. We also found a low value of time-averaged wall shear stress (1.24 N/m(2)) and a high value of the temporal oscillation in the wall shear stress (oscillatory shear index = 0.13) in the region of the PAU. After endovascular treatment, these haemodynamic parameters were distributed uniformly on the luminal surface of the stent graft. These findings suggest that wall shear stress could be considered one of the major haemodynamic factors indicating the structural fragility of the PAU wall, which ultimately lead to PAU growth and rupture.

Early distal remodeling after elephant trunk repair of thoraco-abdominal aortic aneurysms

Hemodynamic alterations occur when the elephant trunk (ET) technique is adopted to treat extensive aortic aneurysms. In planning the 2nd stage operation to complete ET repair, surgeons must weigh an adequate recovery time after initial surgery against the risk of postoperative ET-related complications. The purpose of this study was to understand the mechanistic link between the flow alteration caused by the ET graft and the development of premature aortic rupture before the 2nd stage operation. Specifically, fluid-structure interaction (FSI) analysis was performed using the CT imaging data of aorta at different stages of ET repair, and then computational variables were compared to those observed in patients who underwent a prophylactic 2nd stage operation to complete aortic repair. Results show that intramural stress exerted near the distal ET anastomosis (IMS=37.5kPa) at the time of urgent intervention was comparable to that of the extensive aortic aneurysm (IMS=47.4kPa) at initial in-hospital admission, but was considerably higher than that occurring after the 1st stage procedure (IMS=3.5kPa). Pressure index suggested higher peri-graft pressurization than aortic lumen pressure during diastole, imparting an apparent risk of aortic dilatation. These critical hemodynamic and structural parameters are related to the impending rupture of descending aorta observed clinically and can thus guide prophylactic intervention and optimal timing for the 2nd stage operation of a ET technique.

Computational fluid dynamics simulation to evaluate aortic coarctation gradient with contrast-enhanced CT.

Coarctation of aorta (CoA) is a narrowing of the aorta leading to a pressure gradient (ΔP) across the coarctation, increased afterload and reduced peripheral perfusion pressures. Indication to invasive treatment is based on values of maximal (systolic) trans-coarctation ΔP. A computational fluid dynamic (CFD) approach is herein presented for the non-invasive haemodynamic assessment of ΔP across CoA. Patient-specific CFD simulations were created from contrast-enhanced computed tomography (CT) and appropriate flow boundary conditions. Computed ΔP was validated with invasive intravascular trans-CoA pressure measurements. Haemodynamic indices, including pressure loss coefficient (PLc), time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI), were also quantified. CFD-estimated ΔP values were comparable to the invasive ones. Moreover, the aorta proximal to CoA was exposed to altered TAWSS and OSI suggesting hypertension. PLc was found as a further geometric marker of CoA severity. Finally, CFD-estimated ΔP confirmed a significant reduction after percutaneous balloon dilatation and stenting of the CoA in one patient (e.g. from ΔP∼52 mmHg to ΔP∼3 mmHg). The validation of the ΔP computations with catheterisation measurements suggests that CFD simulation, based on CT-derived anatomical data, is a useful tool to readily quantify CoA severity.

Aortic surgery in Marfan patients with severe pectus excavatum

Aims The optimal surgical management of the aortic root phenotype Marfan patients with severe pectus excavatum is a subject of debate. All the available literature were reviewed according to preferred reporting items for systematic reviews and meta-analyses (PRISMA) principles in order to assess the early outcomes of both pectus excavatum and aortic repair techniques. Methods Searches were done in PubMed and MEDLINE electronic databases dating from July 1953 to December 2015. Results A total of 97 peer-reviewed publications were retrieved, and 27 relevant publications were identified with a total of 39 Marfan patients with pectus excavatum who underwent ascending aorta and aortic root surgery. Emergency acute Type-A aortic dissection repair was reported in five cases. Concomitant pectus excavatum and aortic root repair and composite graft implantation were the most commonly performed procedures. Complications after a staged or a combined approach were uncommon and no deaths occurred. Conclusion Aortic surgery in Marfan patients with pectus excavatum was carried out according to a variety of strategies, surgical techniques and accesses with low complications rate and no mortality. Many of these were well tolerated with minimal complications and no mortality.

Repair of postdissection descending thoracic aneurysm with right-sided aortic arch and aberrant left subclavian artery.

Right-sided aortic arch (RAA) with Kommerll’s diverticulum and aberrant left subclavian artery (LSA) is a rare condition occurring in 0.05 of the population (Figure 1, A). In this group of patients, atherosclerotic aneurysms of the descending thoracic aorta are even less common and only a few cases have been described in the literature. Recently, we operated on a patient with RAA with aberrant LSA who had had a type B dissection in the past and was brought to us with aneurysmal dilatation of the descending aorta.