Has the time arrived for endo mesenteric ischemia therapy?

ROBERT M. ZWOLAK, M.D., PH.D.

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Endo-therapy may be the best option for some patients.

While almost every experienced vascular surgeon has an anecdotal horror story about an unsuccessful or complicated percutaneous mesenteric intervention, advances in stent design, refinements in technique, and credible results from prospective series are silencing many skeptics. For chronic mesenteric ischemia, percutaneous therapy may be best for high-surgical-risk patients with advanced malnutrition and wasting. For acute mesenteric ischemia, retrograde open mesenteric stenting offers a new option to revascularize the superior mesenteric artery (SMA).

Open surgery has superior long-term revascularization patency, but is associated with greater mortality and morbidity. In 49 patients with surgical or endovascular treatment for chronic mesenteric ischemia at the Mayo Clinic in Jacksonville, Fla., those with surgery had more early complications (42% vs. 4%), longer hospital stay (11.6 days vs. 1.3 days), and higher overall mortality (31% vs. 4%) at 25 months (World J. Surg. 2007;31:562-8). Perioperative mortality with surgery has been reported at 10% or higher because of the frequent need for simultaneous aortic reconstruction. When up to 1 in 10 patients dies within 30 days of surgery, percutaneous intervention should at least be considered in all mesenteric disease patients.

There are no randomized trials directly comparing the two approaches. But when outcomes were pooled from 16 series involving 328 patients with chronic mesenteric ischemia treated endovascularly, technical success was achieved in 91%, clinical success in 82%, and late-clinical success in 75% (J. Endovasc. Ther. 2007;14:395-405). There were 11 deaths (3%) within 30 days. Restenosis occurred in 28% of patients at an average of 26 months follow-up, and repeat intervention was needed in 27%. These results are remarkable; patients with chronic mesenteric ischemia usually have multiple comorbidities and high rates of underlying coronary artery disease.

Proponents of open repair point to the higher rates of restenosis and repeat interventions reported in this and most every endovascular series as a chief reason to eschew endovascular therapy. For my patients, it is better to be alive with recurrent disease than to be dead. Still, the higher rates of restenosis demand close clinical follow-up. More work is needed to get an accurate sense of the optimal algorithm for use of these two complementary methods to treat mesenteric ischemia. The role of duplex ultrasound as an adjunct is not yet defined, but in a small series of five patients who had percutaneous mesenteric intervention, Doppler ultrasound identified recurrent stenosis in three asymptomatic patients (ANZ J. Surg. 2007;77:60-3).

Retrograde open mesenteric stenting (ROMS) is becoming an attractive alternative to emergent surgical bypass during open laparotomy for acute mesenteric ischemia. Since open laparotomy is typically required in this situation to explore and resect gangrenous bowel, ready access to the SMA may be obtained at the base of the transverse mesocolon for retrograde cannulation. Dr. Mark Wyers at our institution recently compared six patients with acute thrombotic mesenteric ischemia who underwent ROMS with five patients who underwent emergent mesenteric bypass graft (J. Vasc. Surg. 2007;45:269-75).

Technical success was 100%, even in five patients who had previous unsuccessful attempts to cross the SMA from a percutaneous antegrade approach. In-hospital mortality was 17% compared with 80% for emergent mesenteric bypass. Three patients died of unrelated causes during 1 year follow-up, while two were well. This small study allows only modest conclusions. Still, vascular surgeons should remember this option when treating patients with acute mesenteric ischemia

DR. ZWOLAK is a vascular surgeon at Dartmouth-Hitchcock Medical Center, Lebanon, N.H.

Open surgery is and should remain the standard.

Dr. Pearce Open surgical revascularization by bypass grafting remains the preferred method for treatment of both acute and chronic mesenteric ischemia. It results in low mortality and morbidity, and has excellent long-term patency. In acute mesenteric ischemia, proper construction of a retrograde bypass not only produces excellent long-term outcomes, but avoids an implant. Bare metal stents are not immune from infectious complication. Although such events are rare, the associated mortality and morbidity are significant (J. Vasc. Surg. 2007;46:813-20).

It has been hard to compare endovascular techniques with open surgery because the literature is consists of small case series, diverse patients, mixed surgical and endovascular approaches, and limited follow-up. However, in one of the largest series to date, Kruger et al. make a strong case for open mesenteric revascularization with their series from 1992 until 2006 of 39 consecutive patients who underwent 41 open procedures, comprising 67 bypass grafts (J. Vasc. Surg. 2007;46:941-5). There was one perioperative death and five cases of perioperative morbidity; primary graft patency was 92% at 5 years. In a series of 25 patients, no significant differences were noted at 36 months between late-patency rates of grafts for acute ischemia (92%) and chronic ischemia (89%) (J. Vasc. Surg. 1995;21:729-40). During a mean follow-up of 35 months, no one died of bowel infarction or needed revision for recurrent symptoms.

Mesenteric stenting is limited mainly by the high rate of recurrent stenosis. It has been suggested that restenosis may be higher in these patients because of the longer lesion length associated with complete occlusions. Angioplasty and stenting have been performed for both celiac and SMA stenosis, but the trend is toward their use only for SMA stenosis in the chronic setting. Most stents placed in the celiac artery will occlude, and celiac stenting is associated with median arcuate syndrome. Angioplasty and stenting of the SMA is not without risks, as it leaves the aorta at almost right angles to make a turn over the left renal vein. This may predispose the artery to dissection, making revascularization almost impossible or may have disastrous consequences.

Retrograde mesenteric stenting of the SMA with patch closure has been suggested as being faster than a venous bypass. However, the time savings are minimal given that the time needed to obtain radiographic images, place a stent, and patch the artery is the same as that required to perform an open bypass. This argument is particularly true when surgery is necessary in the off hours, when the proper equipment and personnel aren't readily within reach. Long-term outcomes are also rare.

Surgical revascularization continues to advance, with Foley et al. demonstrating that if the SMA is a suitable recipient vessel, multiple bypass grafts to other vessels are unnecessary (J. Vasc. Surg. 2000;32:37-47). In 49 patients with chronic and acute intestinal ischemia who had bypass grafting to the SMA alone, perioperative mortality was 3% in patients with chronic symptoms and 12% overall. Nine-year assisted primary graft patency was 79% and 5-year patient survival 61%. This work has shifted current practice, including our own, from multiple visceral artery revascularizations to single-vessel reconstructions in most cases.

Endovascular procedures may be a bridge to open surgery, and have a role in select patients. If patients are older than 80 years or have severely calcified arteries and no good venous conduit, one may want to consider retrograde stenting. These patients must be followed closely with angiography or duplex scanning because of the high risk of restenosis. The anatomy of the SMA is such that if a stent is put in the wrong place, one can actually occlude some of the side branch collaterals

DR. PEARCE is professor of vascular surgery at Northwestern University, Chicago.

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