Germano Melissano

Biomechanics of abdominal aortic aneurysm in the presence of endoluminal thrombus: experimental characterisation and structural static computational analysis.

OBJECTIVES To evaluate the role played by biomechanical and geometrical parameters of endoluminal thrombus and of aortic wall on abdominal aortic aneurysm (AAA) behaviour. MATERIALS AND METHODS Tensile tests on 21 AAA thrombus specimens from six patients undergoing AAA repair and numerical evaluation of aneurysmal aortic wall stress and strain distribution. Parameters of the analysis were lumen eccentricity, thrombus Youngs Modulus and the aortic wall constitutive equation. RESULTS There was a linear stress/strain for all the thrombus specimens. The numerical analyses show the mechanical behaviour of AAA as a function of lumen eccentricity and biomechanical parameters. CONCLUSIONS Well organised thrombus reduces the effect of the pressure load on the aneurysmal aortic wall.

Aorto-oesophageal and aortobronchial fistulae following thoracic endovascular aortic repair: a national survey.

OBJECTIVE We evaluated the incidence of aorto-oesophageal (AEF) and aortobronchial (ABF) fistulae after thoracic endovascular aortic repair (TEVAR), and investigated their clinical features, determinants, therapeutic options and results. METHODS We conducted a voluntary national survey among Italian universities and hospital centres with a thoracic endovascular programme. RESULTS Thirty-nine centres were contacted, and 17 participated. Of the patients who underwent TEVAR between 1998 and 2008, 19/1113 (1.7%) developed AEF/ABF. Among indications to TEVAR, aortic pseudo-aneurysm was associated with the development of late AEF/ABF (P = 0.009). Further, emergent and complicated procedures resulted in increased risk of AEF/ABF (P = 0.008 and P < 0.001, respectively). Eight patients were treated conservatively, all of whom died within 30 days. Eleven patients underwent AEF/ABF surgical treatment, with a perioperative mortality of 64% (7/11). At a mean follow-up of 17.7 +/- 12.5 months, overall survival was 16% (3/19). CONCLUSIONS The incidence of AEF and ABF following TEVAR is not negligible, and is comparable to that following open repair. This finding warrants an ad hoc long-term follow-up after TEVAR, particularly in patients submitted to emergent and complicated procedures. Both surgical and endovascular treatment of AEF/ABF are associated with high mortality. However, conservative treatment does not appear to be a viable option.

Is Hybrid Procedure the Best Treatment Option for Thoraco-Abdominal Aortic Aneurysm?

OBJECTIVE Hybrid thoraco-abdominal aortic aneurysm (TAAA) repair, consisting in re-routing of abdominal aortic visceral branches followed by TAAA endograft exclusion has been shown to be a feasible strategy, especially appealing in high-risk patients. PATIENTS AND METHODS We analysed 31 high-risk patients who underwent hybrid TAAA repair in our centre with a variety of visceral re-routing configuration and of commercially available thoracic endografts. Twenty-three simultaneous (74.2%) and eight staged procedures (25.8%) were performed with a four-vessel re-vascularisation in 10 cases (32.3%), a three-vessel in six (19.4%) and a two-vessel in 15 (48.4%). We also performed a literature review of major single-centre series of TAAA hybrid repair. RESULTS No intra-operative deaths were observed in our series, with a technical success in endovascular TAAA repair of 100%, an overall perioperative mortality of 19.4% and a perioperative morbidity of 35.5%, including one case (3.2%) of permanent paraplegia. At a median follow-up of 11.9 months, we observed a visceral graft occlusion rate of 6.8%, one type II endoleak and one endograft migration. From the literature review, six other single-centre series with more than 10 hybrid TAAA repairs were found. From data available of 107 patients, we observed a mean perioperative mortality of 15.6%, the rate of primary endoleaks was 17.9%, paraplegia/paraparesis 7.2% and renal failure 9.9%, with other major perioperative complications reported in the 50.6% of cases. At the follow-up period visceral graft occlusion rate was 5.1%. CONCLUSION Typical complications of conventional TAAA open surgery have been not eliminated by hybrid repair and significant mortality and morbidity have been reported till date. The fate of visceral bypasses and incidence of endoleak and other endograft-related complications need to be carefully assessed. Hybrid TAAA repair should nowadays be limited as alternative to simple observation in patients unfit for the conventional open repair.

Three dimensional time-of-flight magnetic resonance angiography in carotid artery surgery: A comparison with digital subtraction angiography

Three dimensional time-of-flight magnetic resonance angiography (MRA) and intra-arterial digital subtraction angiography (DSA), considered the gold-standard technique, were compared for pre- and postoperative evaluation of the carotid bifurcation. Images of suitable quality of 194 bifurcations were available with both techniques. Percentage stenosis was graded into 5 groups: A = 0-29%, B = 30-59%, C = 60-89%, D = 90-99%, E = 100% (occlusion). Preoperative MRA (126 bifurcations) overgraded the stenosis in 14 cases and undergraded it in 11. The two techniques agreed in 101 cases and the extent of misgrading was never more than one category. Regression analysis showed a good correlation between the two methods. Severe ulceration was better identified by DSA. As far as the surgical indication was concerned, MRA had a sensitivity of 92.6% and a specificity of 98.3%. In 68 operated cases, postoperative MRA and intraoperative completion angiography showed a satisfactory endarterectomy with no residual stenosis in any of the cases. In conclusion, MRA seems an accurate modality for imaging of carotid bifurcations. Significant limitations still exist for an adequate demonstration of intracranial circulation.

Avidin and 111In-labelled biotin scan: A new radioisotopic method for localising vascular graft infection

OBJECTIVES To evaluate a new imaging technique, for diagnosis of prosthetic vascular graft infection. Avidin is a protein which accumulates nonspecifically at sites of inflammation or infection. Due to its extremely low dissociation constant with biotin sites of infection can be imaged, using avidin as a pre-target, followed by injection of 111In-labelled biotin. This technique is much simpler than the common scintigraphic methods which employ labelling of blood components and its target-to-background ratio is greater than the methods employing radiolabelled proteins. DESIGN Prospective clinical study. SETTING A single department of vascular surgery and one of nuclear medicine of a Northern Italian hospital. MATERIALS Between May 1993 and May 1994, 31 grafts in 26 patients were studied; the series included 23 men and three women with a mean age of 65.5 years (range 54-76 years). The prosthetic graft (Dacron -16, ePTFE -15) were: aortoaortic 5, aortobifemoral 15, aortoiliac 1, and femoropopliteal 10. Sixteen patients were suspected of having a vascular graft infection (Group A), the other 10 patients served as controls (Group B). 20 mg of Avidin were injected iv, followed 24 h later by i.v. injection of 500 micrograms of Biotin labelled with 74 MBq of 111In. CHIEF OUTCOME MEASURES Whole-body imaging was performed at 10 min and 2 h post-injection, along with SPECT imaging when indicated. Scan results were correlated with the traditional imaging modalities and the clinical outcome of the patients. MAIN RESULTS In Group A: two patients (three grafts) were excluded from the study, there were six true-positives, one false-positive and 11 true-negatives. Results in Group B: 10 true-negatives. The overall sensitivity was 100%, the specificity 95%, the accuracy 96%, the positive predictive value 86% and the negative predictive value 100%. CONCLUSIONS These data suggest that Avidin/111In-labelled Biotin scintigraphy is a useful non invasive diagnostic method for early diagnosis of suspected prosthetic vascular graft infection.

Aortic and Esophageal Endografting for Secondary Aortoenteric Fistula

The aorto-esophageal fistula is a well-recognized and potentially fatal complication of thoracic aortic surgery. Several strategies regarding its prevention and subsequent management have been described. We report the management of a large midthoracic fistula complicating redo thoraco-abdominal aortic surgery by the placement of covered stents in the aorta and esophagus to successfully exclude the lesion. While long term durability is uncertain, endografts and long-term antibiotics provide a therapeutic option for palliation in patients unfit for immediate surgery.

Thoraco-abdominal aorta

Thoraco-abdominal aorta , Thoraco-abdominal aorta , کتابخانه دیجیتالی دانشگاه علوم پزشکی و خدمات درمانی شهید بهشتی

Hybrid Procedures forThoraco-Abdominal Aortic Aneurysm

Thoraco-abdominal aortic aneurysm (TAAA) hybrid repair consists of rerouting of abdominal aortic visceral branches followed by TAAA endograft exclusion. In this chapter we report our single-center experience of 34 patients (28 males, median age 68.2 years, range 23 to 83 years) who underwent hybrid TAAA repair (13 type I, 4 type II, 7 type III, 3 type IV — Crawford classification — and 7 aneurysms of the visceral aortic patch) between 2001 and 2009. Patients’ data were prospectively collected in a computerized database. All patients were excluded from standard open surgery because of increased surgical risk and/or local technical concerns. Hybrid TAAA repair has been technically feasible in all cases undergoing TAAA exclusion, with a variety of operative strategies and materials. Typical complications of standard open surgery have not been eliminated by hybrid TAAA repair and there are still significant mortality and morbidity, and new threatening mid-term procedure-related complications have been reported. Larger series of hybrid TAAA repair with clear inclusion criteria and long-term follow-up are needed to establish a standardized operative technique and to make any statistically meaningful comparisons with standard open repair. Based on our experience with high-risk patients, hybrid TAAA repair should currently be limited as an alternative to simple observation in patients unfit for standard open repair.

Redo Open and Endovascular Procedures after Open Thoraco-Abdominal Aortic Aneurysm Repair

The outcomes of redo open repair for recurrent thoraco-abdominal aortic aneurysm (TAAA) are usually considered to be poorer when compared with the index procedure; for these reasons, less invasive strategies such as endovascular procedures are especially attractive. However, when the aneurysmal changes involve the visceral vessels such as in the case of visceral aortic patch (VAP) aneurysms, a conventional endovascular approach is not applicable. In this critical situation, a possible alternative to open regrafting is a hybrid treatment consisting of rerouting of visceral arteries, and aneurysm exclusion using commercially available thoracic aortic endografts. In this chapter, we compare the outcomes of our series of patients who, from 2001 to 2009, underwent redo VAP aneurysm open repair with a selected group of high-risk patients who underwent, in the same period, redo VAP aneurysm hybrid repair. We observed similar perioperative mortality and morbidity rates in the two groups of patients, with reduced surgical challenge in the hybrid group, allowing us to avoid redo-thoracotomy, retroperitoneal redissection, and previous thoracic graft reclamping. However, in the hybrid group, new medium-term specifically procedure-related complications have been observed and, until greater experience is available, a widespread use of this technique should currently be limited in this specific subset of high-risk patients.

Assessment of the Spinal Cord Vasculature with Computed Tomography

Knowledge of the spinal cord vascular supply is important in patients undergoing procedures that involve the thoracic and thoraco-abdominal aorta. However, the spinal cord vasculature has a complex anatomy, and teaching is often based only on anatomical sketches; historically, this has required a “leap of faith” on the part of aortic surgeons. Fortunately, this “leap of faith” is no longer necessary given recent breakthroughs in imaging technologies and post-processing software that have expanded the non-invasive diagnostic ability to determine a patient’s spinal cord vascular pattern, particularly in detecting the presence and location of the artery of Adamkiewicz. Computed tomography angiography fulfils the need of vascular surgeons for preoperative assessment of spinal cord anatomy, and planning of aortic interventions and procedures.