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Stent graft therpy

Bariatric stent graft can reduce the rate of weight gain

Implanting a stent graft into an animal's small mesenteric artery led to chronic mesenteric ischaemia
Researchers claim the study offers a potential novel obesity therapy
Dr Timothy Brown who presented the data at ISET

Using a bariatric stent graft to limit blood flow to the gut after eating is associated with a reduction in the rate of weight gain, say researchers from the Department of Diagnostic Imaging, Rhode Island Hospital, Brown University. The study results, presented at the International Symposium on Endovascular Therapies, Miami, Florida, revealed that implanting a stent in a pig’s small mesenteric artery leads to chronic mesenteric ischaemia.

“This study demonstrates the feasibility and safety placing an adjustable lumen covered stent to mimic chronic mesenteric ischaemia, a clinical condition resulting in malabsorption and anorexia,” said Dr Timothy Murphy. “The results from the experimental animal study represent an exciting avenue of future research into a potential novel obesity therapy.”

Murphy and colleagues devised an experiment to induce a scenario similar to chronic mesenteric ischemia in pigs, in which blood flow is adequate at rest, but the flow limitation from the device prevents the required three-fold flow augmentation after meals, resulting in discomfort, malabsorption, and ultimately, behavioural modification.

Procedure

The researchers implanted Atrium Medical’s iCAST device, a stainless-steel strut, covered, balloon-mounted stent. It was partially deployed (over a 6-7Fr system and nominal stent diameters range to 10mm) and dilated only until the ends flared out to catch the arterial wall. The middle was left mostly compressed so the covered stent acted as a flow restrictor. Stents were placed in the proximal small mesenteric artery of three Yorkshire swine (named pig 989, pig 690 and pig 691) under fluoroscopic guidance, and the gastroduodenal artery, an anticipated source of collateral flow, was embolized if seen.

The animals were allowed to feed freely with a high caloric diet. Weight gain was recorded over a ten day period prior to the procedure and for at least 14 days following the procedure.

The investigators reported that the devices were well tolerated and there were no deaths or unplanned euthanasia. The device successfully limited blood flow in two pigs (690 and 691), but an angiography showed that blood continued to flow around the stent in the third (689). During the stent placement in the third pig (689), the small mesenteric artery itself was too large to accommodate the device, and the ileocolic and jejunal branches were stented independently. 

Results

The results showed that the pig 690 saw the least average weight gain per day. While the experiment was not controlled, pig 689, whose stent did not limit its blood flow, effectively acted as a control. The weight gain for all the pigs was less than published data for the species, ranging from approximately 0.6-0.7kg/day. However, Murphy acknowledged that there is variability depending on pig age, size, gender and feed.

Table 1: Weight gain summary

Pig

Weight at   arrival

Surgery wt

Final wt

Average   Kg/day

689

32.8

36

50.5

0.69

690

35.8

39.5

49.1

0.42

691

37.2

40.3

48.2

0.53

A single animal, pig 690, developed extenuating clinical signs and was kept alive a total of eight weeks for a more protracted weight-gain assessment, and a final angiogram was performed at the time of euthanasia.

An inferior mesenteric angiogram showed the stent graft succeeded in delaying blood flow to the collateral vessels, which supplied blood to the small mesenteric artery (see figure 1). The researchers believe that this delay may have had some effect on the prolonged treatment effect in pig 690.

Figure 1: Follow-up angiogram of the small mesenteric artery branch post stenting

“This study shows that placement of the covered stent in the pig model is safe and feasible, and can rapidly accommodate marked reduction in mesenteric arterial flow,” said Murphy. “Pig 690, with an appropriately positioned stent, demonstrated temporary signs related to gut ischaemia. We hope the results can offer some new insights into the future research to treat the obesity epidemic.”

Speaking to Bariatric News, Murphy said if the procedure was carried out in humans the stent graft would be permanently in place, but could be expanded to allow more flow if symptoms were present at rest.

“The biggest risk would be acute thrombosis, but it is possible that that outcome would be less frequent than death from the alternative treatment, gastric bypass, which is 1-2%,” he said. “All weight loss surgeries induce some discomfort with eating, and the stent graft would enable behavioural modification so people would learn to eat less and avoid over eating.

Murphy and colleague are currently seeking funding to conduct a larger study to confirm this study’s findings

The co-investigators on the study were Drs Tyler Harris, Bryan Jay, Christopher Hampson and Abdul Zafar.

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