Kak K. Yeung

A systematic review of endovascular treatment of extensive aortoiliac occlusive disease

OBJECTIVES Current multidisciplinary guidelines recommend to treat extensive aortoiliac occlusive disease (AIOD) by surgical revascularization. Surgery provides good long-term patency, but at the cost of substantial perioperative morbidity. Development of new technologies and techniques has led to increased use of endovascular therapy for extensive AIOD. We performed a systematic review of the literature to determine contemporary short- and long-term results of endovascular therapy for extensive AIOD. METHODS The Medline, Embase, and Cochrane databases were searched to identify all studies reporting endovascular treatment of extensive AIOD (TransAtlantic Inter-Society Consensus (TASC) type C and D) from January 2000 to June 2009. Two independent observers selected studies for inclusion, assessed the methodologic quality of the included studies, and performed the data extraction. Outcomes were technical success, clinical success, mortality, complications, long-term primary, and secondary patency rates. RESULTS Nineteen nonrandomized cohort studies reporting on 1711 patients were included. There was substantial clinical heterogeneity between the studies considering study population and interventional techniques. Technical success was achieved in 86% to 100% of the patients. Clinical symptoms improved in 83% to 100%. Mortality was described in seven studies and ranged from 1.2% to 6.7%. Complications were reported in 3% to 45% of the patients. Most common complications were distal embolization, access site hematomas, pseudoaneurysms, arterial ruptures, and arterial dissections. The majority of complications could be treated using percutaneous or noninvasive techniques. Four- or 5-year primary and secondary patency rates ranged from 60% to 86% and 80% to 98%, respectively. CONCLUSIONS Endovascular treatment of extensive AIOD can be performed successfully by experienced interventionists in selected patients. Although primary patency rates are lower than those reported for surgical revascularization, reinterventions can often be performed percutaneously, with secondary patency comparable to surgical repair.

Juxtarenal aortic aneurysm repair

OBJECTIVES Juxtarenal aortic aneurysms (JAA) account for approximately 15% of abdominal aortic aneurysms. Despite advances in endovascular aneurysm repair, open repair requiring suprarenal aortic cross-clamping is still the treatment of choice for JAA. We performed a systematic review of the literature to determine perioperative mortality and postoperative renal dysfunction after open repair for non-ruptured JAA. METHODS The Medline, Embase, and Cochrane databases were searched to identify all studies reporting non-ruptured JAA repair published between January 1966 and December 2008. Two independent observers selected studies for inclusion, assessed the methodologic quality of the included studies, and performed the data extraction. Study heterogeneity was assessed using forest plots and by calculating the between-study variance. Outcomes were perioperative mortality, postoperative renal dysfunction, and new onset of dialysis. Summary estimates with 95% confidence interval (95% CI) were calculated using a random effects model based on the binomial distribution. RESULTS Twenty-one non-randomized cohort studies from 1986 to 2008, reporting on 1256 patients, were included. Heterogeneity between the studies was low. The mean perioperative mortality was 2.9% (95% CI, 1.8 to 4.6). The mean incidence of new onset of dialysis was 3.3% (95% CI, 2.4 to 4.5). Incidence of postoperative renal dysfunction could be derived from 13 studies and ranged from 0% to 39% (median, 18%). In seven studies, cold renal perfusion during suprarenal clamping was performed in order to preserve renal function; however, based upon the included data, definitive conclusions regarding its efficacy could not be drawn. CONCLUSIONS Open repair of non-ruptured JAA using suprarenal cross-clamping can be performed with acceptable perioperative mortality; however, postoperative deterioration of renal function is a common complication. Preservation of renal function after JAA repair requires further investigation.

Geometric study of various chimney graft configurations in an in vitro juxtarenal aneurysm model.

Purpose To determine gutter size and stent-graft geometry in an in vitro juxtarenal aneurysm model using various chimney graft (CG) configurations. Methods Two silicone juxtarenal aortic aneurysm models were constructed combining different diameters of the aorta and renal artery. In a single-branched CG configuration, 2 sizes (23 and 28.5 mm) of Excluder stent-grafts were tested individually with 2 sizes of 2 types of CGs: Advanta balloon-expandable (BE) stent-grafts (6×59 and 12×61 mm) and Viabahn self-expanding (SE) stent-grafts (6×50 and 13×50 mm). All combinations were tested with a short (10-mm) and long (20-mm) sealing zone between the CG and main graft (total 16 configurations). Immediately after deployment, the CG configuration was scanned using a 64-slice computed tomography scanner. Gutter sizes were measured at different levels of the sealing zone. Results At the top of the sealing zone, the gutters were significantly larger in the BE CGs compared to SE CGs in combination with the 23-mm main graft (p=0.021). At the bottom of the sealing zone, there were no statistically significant differences (p=0.77). No significant differences were seen using the 28.5-mm main graft. Median gutter size was larger in the 6-mm CGs. The length of the sealing zone had no influence on gutter size. Significant compression of the main graft was found using 12 or 13-mm CGs compared to 6-mm CGs (p=0.001). Conclusion In this in vitro study, the CG configurations with BE stent-grafts show larger gutters than configurations with SE stent-grafts in small main grafts. Main graft compression is increased using wider CG stent-grafts.

Open surgical repair of ruptured juxtarenal aortic aneurysms with and without renal cooling: Observations regarding morbidity and mortality

OBJECTIVES Little is known about the outcome of ruptured juxtarenal aortic aneurysm (RJAA) repair. Surgical treatment of RJAAs requires suprarenal aortic cross-clamping, which causes additional renal ischemia-reperfusion injury on top of the pre-existing hypovolemic shock syndrome. As endovascular alternatives rarely exist in this situation, open repair continues to be the gold standard. We analyzed our results of open RJAA repair during an 11-year period. DESIGN Retrospective observational study. MATERIALS AND METHODS Between July 1997 and December 2008, all consecutive patients with RJAAs were included in the study. Part of these patients received cold perfusion of the kidneys during suprarenal aortic cross-clamping. Perioperative variables, morbidity, and 30-day or in-hospital mortality were assessed. Renal insufficiency was defined as an acute rise of >or=0.5 mg/dL in serum creatinine level. Multiple organ failure (MOF) was scored using the sequential organ failure assessment score (SOFA score). RESULTS A total of 29 consecutive patients with an RJAA, confirmed by computed tomography-scanning, presented to our hospital. In eight patients, the operation was aborted before the start of aortic repair, because no blood pressure could be regained in spite of maximal resuscitation measures. They were excluded from further analysis. Of the remaining 21 patients, 10 died during hospital stay. Renal insufficiency occurred in 11 out of 21 of the patients. Eleven out of 21 patients developed MOF postoperatively. In a subgroup of patients who received renal cooling during suprarenal aortic clamping, the 30-day or in-hospital mortality was two of 10 vs eight of 11 in patients who did not receive renal cooling (P = .03); renal insufficiency occurred in one out of 10 patients in the subgroup with renal cooling vs 10 out of 11 without renal cooling (P < .001) and MOF in two of 10 vs nine of 11, respectively (P = .009). CONCLUSIONS Open surgical repair of RJAAs is still associated with high mortality and morbidity. To our knowledge, this is the first report of cold perfusion of the kidneys during RJAA repair. Although numbers are small, a beneficial effect of renal cooling on the outcome of RJAA repair is suggested, warranting further research with this technique.

A Proof-of-Concept In Vitro Study to Determine if EndoAnchors Can Reduce Gutter Size in Chimney Graft Configurations

Purpose To investigate the feasibility of using endoanchor technology to reduce chimney graft–related gutter size in a juxtarenal aneurysm model. Methods In silicone juxtarenal aortic aneurysm models with two sizes of branch arteries and two sizes of aorta, single chimney graft (CG) configurations were constructed using 6-mm Atrium balloon-expandable stent-grafts in association with two sizes of Gore Excluder main grafts (23 and 28.5 mm). Configurations without Aptus EndoAnchors, with suprarenal placement of EndoAnchors, and with additional infrarenal placement of EndoAnchors were investigated. A total of 12 CG configurations were scanned using 64-slice computed tomography. Gutter volume and gutter areas at the top and bottom of the sealing zone were measured with image processing software. Results The combination of supra- and infrarenal placement of endoanchors led to a reduction in gutter volume compared to unanchored configurations. The same configurations also led to a decrease in gutter area at the bottom of the sealing zone. Conclusion It is feasible to reduce gutters in CG configurations with the use of endoanchors in an in vitro juxtarenal aneurysm model.

Direct videoscopic approach to the thoracic aorta for aortic endograft delivery: evaluation in a human cadaver circulation model.

Purpose: To examine the feasibility of a direct videoscopic approach to the descending thoracic aorta for branched endograft delivery to the aortic arch and abdominal aorta. Methods: Aneurysms were created in the aortic arch and pararenal aorta of 3 human cadavers, and pulsatile flow was established using a roller pump. Thoracoscopically, 2 double-felted purse-string sutures were placed on the thoracic aorta. Via the most distal trocar, an endoscopic needle was used to insert a stiff guidewire into the aorta through the center of the purse-string suture. Under direct videoscopic control, a 20-F sheath was advanced over the wire into the aorta. Switching to fluoroscopic control, a fenestrated endograft was deployed in the aortic arch followed by placement of a branch graft into the left subclavian artery. The delivery sheath was withdrawn from the aorta while simultaneously tightening the purse-string sutures. A similar procedure was performed in the same cadaver for antegrade branched endograft delivery to the pararenal aorta. Correct deployment of the branched endografts was evaluated by post implant angiography and autopsy. Results: The procedure was successfully completed in all cadavers. “Hemostasis” was obtained in all cadavers without aortic cross clamping. Median fluid loss was 165 mL. Autopsy proved all purse-string sutures to be adequately placed and all branched endografts to be deployed in the correct position. Conclusion: A direct videoscopic approach to the descending thoracic aorta proved a feasible technique for branched endograft delivery to the aortic arch and abdominal aorta in a human cadaver model.

In vitro feasibility of a sac-sealing endoprosthesis in a double chimney graft configuration for juxtarenal aneurysm.

Purpose: To investigate in an in vitro juxtarenal aneurysm flow model the feasibility and efficacy of using a sac-sealing endoprosthesis in a chimney graft configuration. Methods: In two experiments, a Nellix sac-sealing endoprosthesis was used as the main graft in a double-branched chimney graft configuration, using a self-expanding Viabahn stent-graft and a balloon-expandable Advanta V12 stent-graft in a pressurized silicone juxtarenal aneurysm flow model. In two consecutive experiments, the chimney graft balloons were inflated (1) at the beginning of and (2) to simulate varying renal ischemic times half-way through the injection of the sac-sealing polymer into the Nellix endobags. The balloons and were kept inflated until the endobags were filled and the polymer was cured. The aneurysm model was connected to a roller pump, pumping gelatin-water at a rate of 100 beats per minute. Before and after 24 hours of continuous flow, computed tomography (CT) scans were made using contrast injection. The CT scans were reconstructed and analyzed for gutter cross-sectional area, total gutter volume, chimney graft compression, and volume of space between the aneurysm wall and the endoprosthesis. Results: Differences in gutter size between both types of chimney grafts were minimal. Chimney graft compression exceeded 50% if the balloons were inflated in the chimney grafts halfway through polymer injection into the endobag. Twenty-four hours of flow did not influence chimney graft patency or gutter size. Conclusion: In a juxtarenal aneurysm flow model, we demonstrated the technical feasibility of a sac-sealing endoprosthesis in a chimney graft configuration. This early evidence suggests that balloon dilation of chimney grafts should occur over the entire period of polymer injection and curing to prevent considerable chimney graft compression.

Organ protection during aortic cross-clamping

Open surgical repair of an aortic aneurysm requires aortic cross-clamping, resulting in temporary ischemia of all organs and tissues supplied by the aorta distal to the clamp. Major complications of open aneurysm repair due to aortic cross-clamping include renal ischemia-reperfusion injury and postoperative colonic ischemia in case of supra- and infrarenal aortic aneurysm repair. Ischemia-reperfusion injury results in excessive production of reactive oxygen species and in oxidative stress, which can lead to multiple organ failure. Several perioperative protective strategies have been suggested to preserve renal function during aortic cross-clamping, such as pharmacotherapy and therapeutic hypothermia of the kidneys. In this chapter, we will briefly discuss the pathophysiology of ischemia-reperfusion injury and the preventative measures that can be taken to avoid abdominal organ injury. Finally, techniques to minimize the risk of complications during and after open aneurysm repair will be presented.

Therapeutic application of contrast-enhanced ultrasound and low-dose urokinase for thrombolysis in a porcine model of acute peripheral arterial occlusion

BACKGROUND The addition of local ultrasound (US) with a contrast agent to standard intra-arterial thrombolysis can accelerate the thrombolytic treatment of stroke and myocardial infarction. The contrast agent consists of microsized gas-filled bubbles that collapse when exposed to US, causing destabilization of the clot and making the clot surface more susceptible to fibrinolytics. In this study, we investigated the effect of additional US and microbubbles on standard low-dose intra-arterial thrombolysis in a porcine model of extensive peripheral arterial occlusion. METHODS Extensive arterial thrombosis was induced in 10 pigs in the 4-cm external iliac artery by clamping and injection of 100 IU of bovine thrombin. A transcutaneous laser Doppler flow probe and an ultrasonic perivascular flow probe assessed microcirculation and arterial flow respectively. The urokinase-only (UK) group (n = 4) received standard thrombolytic therapy: intra-arterial bolus injection of 500,000 IU, followed by a continuous low-dose urokinase (50,000 IU/h) infusion through an intra-arterial catheter and local intermittent application of US, 1 second on, 5 seconds off, to visualize vascular patency during the first hour of therapy and to ensure microbubbles replenished the proximal portion of the occluded artery. The urokinase plus microbubbles (UK+) group (n = 6) received the same urokinase therapy with a concomitant intravenous infusion of microbubbles and local intermittent application of US. The contrast infusion protocol consisted of a bolus of two vials of 5 mL in the first 15 minutes and then three times 5 mL slowly hand-injected continuously during the next 45 min. After 3 hours of therapy, the animals were euthanized, and thrombi were harvested and weighed. All organs were cut in thin slices and macroscopically inspected for potential (hemorrhagic) adverse events, and tissue samples were taken. RESULTS Median thrombus weights were 1.1 g (range, 0.8-1.3 g) in the UK+ group vs 1.6 g (range, 1.3-1.9 g) in the UK group (P = .01). Arterial blood flow increased in four of six pigs in the UK+ group by a mean 61% vs in one of four in the UK group, with 1%. Microcirculation and lower limb arterial pressure levels improved after the start of therapy in the UK+ group, contrary to a trend of decline in the UK group. No signs of bleeding complications were observed in either group. CONCLUSIONS In this experimental pilot study, the addition of contrast-enhanced US accelerated the thrombolytic effect of low-dose intra-arterial thrombolysis in peripheral arterial occlusions. Further clinical studies are warranted.

Infrarenal aortic-clamping after renal ischaemia aggravates acute renal failure

Eur J Clin Invest 2011; 41 (6): 605–615