Endovascular aortic aneurysm repair by a multidisciplinary team: Lessons learned and six-year clinical update

Background: Endovascular aneurysm repair (EVAR) (using an Federal Drug Association-approved AneuRx® device) compared to conventional surgical repair of abdominal aortic aneurysm (AAA) previously rendered favourable outcomes regarding post-operative pain, avoidence of laparotomy, and rapid rehabilitation and hospital discharge in high-risk patients, including octagenarians. Objectives: To assess the safety, reduction in aneurysm-related deaths, and interim survival data up to 72 months after AAA exclusion by endoluminal endografts (EVAR). Design: We carried out an open, controlled, prospective, multidisciplinary EVAR study for the period 1998 to 2003 (six years). In the earlier part of the study, EVAR was compared with previously published results of conventional open aneurysmectomy surgery. Setting: Heart Unit, Panorama Medi-Clinic, Parow, South Africa. Participants: We recruited adult male and female patients presenting with AAA and fulfilling the inclusion criteria for endovascular repair, as recommended by the consensus 2003 meeting of the Vascular Association of South Africa (VASSA). All patients were offered open surgery as an alternative and were entered into the VASSA EVAR trial registry. Pre-operatively, AAA anatomy was assessed by spiral-computed tomography (CT), and selectively with conventional angiography and intravascular ultrasound (IVUS). Informed consent was obtained in accordance with the recommendations of the Senate of Surgery Paper 2, Ethical Guidelines, Great Britain and Ireland. Patients underwent EVAR by a multidisciplinary interventional team. Interventions: Two hundred and seven adult patient with AAA were assessed. Forty-four of the 207 (21.2%) were excluded from EVAR because of irreversible comorbid factors and complex aneurysm morphology. One hundred and sixty-three patients with a mean age of 70.7 years (range 60-91 years), underwent EVAR (1993-2003). Five patients were lost to follow-up (3%). Median AAA diameter was 56.9 mm and ASA ratings were I, 1.2%; II, 15.9%; III, 57%; IV, 22.6% and V, 2.4%. EVAR was performed in high- and low-risk categories of both sexes. Most patients were in ASA groups III and IV. Device deployed: EVAR was performed using a selection Of endografts over 72 months - AneuRx® (Medtronic) 47; Talent® (Medtronic) 49; Vanguard® three; Zenith® (Cook) one; Powerlink® (Endologix) 62; and other, one. Results: Thirty-day outcome: successful deployment 99%, primary stent patency 97%, surgical conversion 0.6%, procedural or intra-operative mortality 1.2%, 30-day mortality 4.3%, endoleaks 1.84%, and secondary intraprocedural endovascular interventions 24.5%. Peri-operative mortality was 3.1% (one aneurysm related). One patient had suspected endograft infection. Late mortality was 21.4% (35 patients due to co-morbidities, and one was aneurysm related). Follow-up was a median of 28.3 months (range 1-69 months). In 163 patients, two persisting endoleaks (1.2%) were detected. Endotension was detected in 3/163 (1.8% with average sac increase of 0.8 cm. Conversion to open surgery was needed in one patient (0.6%). Co-morbidities that contributed to late mortality included multi-organ failure, ischaemic heart disease (IHD), cardiomyopathy, renal failure, stroke and cancer. One procedural rupture was fatal (0.6%). Two late ruptures occurred; one was successfully endostented and the other patient died after a failed surgical intervention (0.6%). Endovascular repair of AAA is more expensive than conventional surgery. Introduction of the Endologix stent has reduced operative time from 120 to 60 minutes in uncomplicated patients. Newer-generation aortic stents allow better control of negative remodeling and stent migration. Conclusion: A multidisciplinary team can safely perform EVAR, with a low 30-day mortality rate in selected patients graded ASA II-IV and with favourable aortic aneurysm morphology. About 22% of patients with AAA are not suited for EVAR. Persisting late endoleaks occurred in 1.2% of the cohort study and were not device specific. Life-long follow-up post EVAR is a prerequisite to detect late device failure, endoleaks and aneurysm-sac enlargement, and to assure the durability of these mid-term results. Short-term aneurysm rupture prevention is a predictable outcome in high-risk groups.Revie

EVAR: Critical applied aortic morphology relevant to type-II endoleaks following device enhancement in patients with abdominal aortic aneurysms

Endovascular repair (EVAR) of abdominal aortic aneurysms (AAA) is an established alternative option to conventional surgery for AAA, provided optimal anatomical morphology of the aneurysm sac, neck and outflow exists. In most documented series of EVAR, type-II endoleak occurrence is a universal procedural drawback. This is referred to as the Achilles heel of EVAR. This morphological study, addressing predominantly non-aneurysmal aortic anatomy, reveals the dyssynchronous origins of the renal ostia, ectopia of the superior mesenteric artery and median sacral artery, variations in the length of the infrarenal abdominal aorta, multiple mainstem renal arteries, and the presence of accessory renal arteries (in 13% of cadavers). Such potential vascular anomalies need careful consideration pre-operatively prior to EVAR. In a prospective, clinical study of EVAR in 163 patients over 60 months, using four different aortic stent devices, we demonstrated an intraprocedural type-II endoleak rate, before exclusion, of 3% (5/163). Most were related to patent lumbar arteries. An active policy of intraprocedural aneurysm pressure sac measurement and angiography was used to demonstrate type-I and type-II endoleaks, focusing on the applied anatomy of aortic side branches and variations. Selective intraprocedural coli embolisation and thrombin injection into the sac was utilised to thrombose persisting and large lumbar arteries that predisposed to retroleaks. We recorded a low incidence of persisting type-II endoleaks using this proactive treatment strategy by addressing variant aortic morphology and patent lumbar arteries during EVAR. One aneurysm-related death (0.6%) was observed due to late rupture after EVAR, and a single intraprocedural death was related to unpredictable aneurysm rupture. In conclusion, comprehensive anatomical knowledge of the abdominal aorta and its main collateral side branches, including variations, is a fundamental prerequisite if satisfactory and predictable results are to be achieved after EVAR, especially regarding prevention, diagnosis and treatment of type-II endoleaks. Intraprocedaral aneurysm sac pressure monitoring, coil embolisation and the use of injection of thrombin into the aneurysm sac of selected patients is useful in reducing the incidence of post-EVAR type-II persisting endoleaks.Conference Pape

Carotid stenosis and carotid plaque analysis relevant to carotid endarterectomy and stent-assisted angioplasty

The primary objective of this cadaveric study was to review the morphological variations of the anatomy of the human carotid artery bifurcation relevant to carotid endarterectomy (CEA) and carotid artery stent-supported angioplasty (CSSA). We quantify carotid bifurcation plaque morphology. Results showed that the angle of deviation at the origin of the internal carotid artery (ICA), in relation to the common carotid artery (CCA), measured a mean of 21.8 degrees with a range from seven to 45 degrees. This anatomical finding is important for the interventionalist concerned with insertion of a carotid stent. The angle of the ICA origin may be an independent risk factor for early atherosclerotic changes at the ICA bulb. Carotid bifurcation plaque was observed in a small, random cohort of seven out of 13 cadavers, and contributed to a mean stenosis of 15.2% (range 5.0-34.8%). Plaque morphology (n = 7) showed haemorrhage (29%), superficial thrombosis (57%), calcification (71%), areas of focal necrosis (71%), neovascularisation (14%) and infiltrates (29%). Ulcerations were not detected. Although four out of 13 patients (31%) died of a cerebrovascular accident, the cause of cerebral apoplexy was thought not to be associated with the carotid bifurcation pathology. 'Re-boring' of occluding plaque, as in CEA, offers potential volumetric anatomical advantage over CSSA within the carotid bifurcation and bulb. In conclusion, precise and applied knowledge of carotid bifurcation anatomy is critical to reduce technical complications during CEA or CSSA. This information may reduce potential dangers of iatrogenic thrombo-embolism and ensuing neurologic deficits. Patients with low-grade carotid stenosis, evidence of focal plaque necrosis, are at risk of spontaneous plaque cap rupture, distal thrombo-embolism and stroke.Revie

All-optical signal processing for optical packet switching networks

We discuss how all-optical signal processing might play a role in future all-optical packet switched networks. We introduce a concept of optical packet switches that employ entirely all-optical signal processing technology. The optical packet switch is made out of three functional blocks: the optical header processing block, the optical memory block and the wavelength conversion block. The operation principle of the optical packet switch is explained. We show that these three functional blocks can be realized by using the nonlinearities of semiconductor optical amplifiers. Some technologies in these three functional blocks are described. The header processor is realized using a Terahertz Optical Asymmetric Demultiplexer. We also describe a header pre-processor to improve the extinction ratio of the header processor output. In the optical memory block, we show that an all-optical memory can be obtained by using two coupled lasers that form a master-slave configuration. The state of the optical memory is distinguished by the wavelength of the master laser. We extend the concept to an optical memory can have multiple states. In the wavelength conversion block, we demonstrate a 160 Gbit/s wavelength conversion using a single semiconductor optical amplifier in combination with a well-designed optical bandpass filter. The semiconductor optical amplifier has a gain recovery timegreater than 90 ps, which corresponds to a less than 20 GHz bandwidth for conventional wavelength conversion. We show that by properly using the optical bandpass filter, ultrafast dynamics in the semiconductor optical amplifier can be employed for wavelength conversion at ultrahigh bit-rates

All-optical signal processing for optical packet switching networks

We discuss how all-optical signal processing might play a role in future all-optical packet switched networks. We introduce a concept of optical packet switches that employ entirely all-optical signal processing technology. The optical packet switch is made out of three functional blocks: the optical header processing block, the optical memory block and the wavelength conversion block. The operation principle of the optical packet switch is explained. We show that these three functional blocks can be realized by using the nonlinearities of semiconductor optical amplifiers. Some technologies in these three functional blocks are described. The header processor is realized using a Terahertz Optical Asymmetric Demultiplexer. We also describe a header pre-processor to improve the extinction ratio of the header processor output. In the optical memory block, we show that an all-optical memory can be obtained by using two coupled lasers that form a master-slave configuration. The state of the optical memory is distinguished by the wavelength of the master laser. We extend the concept to an optical memory can have multiple states. In the wavelength conversion block, we demonstrate a 160 Gbit/s wavelength conversion using a single semiconductor optical amplifier in combination with a well-designed optical bandpass filter. The semiconductor optical amplifier has a gain recovery timegreater than 90 ps, which corresponds to a less than 20 GHz bandwidth for conventional wavelength conversion. We show that by properly using the optical bandpass filter, ultrafast dynamics in the semiconductor optical amplifier can be employed for wavelength conversion at ultrahigh bit-rates