Angioplasty and Stenting for Mesenteric and Renal Artery Disease

Etiology

The most common cause of CMI is atherosclerotic disease, accounting for over 90% of cases in most series. Atherosclerotic lesions usually affect the origin or the proximal 2 to 3 cm of the mesenteric arteries, frequently with associated plaque in the aorta and renal arteries. Nonatherosclerotic lesions can also affect the mesenteric arteries. The differential diagnosis includes vasculitis, systemic lupus, Buerger disease, spontaneous dissections, fibromuscular dysplasia, neurofibromatosis, radiation arteritis, coarctation, mesenteric venous stenosis or occlusion, and drug-induced arteriopathy from the use of cocaine or ergot.

In the resting state 20% of the cardiac output passes through the mesenteric arteries; but during the digestive process there is a hyperemic postprandial response and the output increases to 150%. Patients with mesenteric ischemia fail to provide the postprandial hyperemic response that is required to supply oxygen for the metabolic processes of digestion. The term “intestinal angina” was coined to describe postprandial pain after a meal, which is a direct analogy to angina pectoris, since the mechanism of pain is an imbalance between supply and demand of oxygen and metabolites. Because the mesenteric circulation has an extensive collateral network, symptoms usually start once obstructive lesions affect at least two or three visceral vessels ( Fig. 27.1 ). However, contrary to what has been described in many medical texts, some patients can suffer from CMI with a single diseased vessel. The clinical significance of ischemia correlates not only with the extent of disease but also with the adequacy of the collateral pathways, acuteness of symptoms, and presence of arterial steal.

Asymptomatic mesenteric stenosis tends to have a benign course, although 15% to 50% of patients with acute mesenteric ischemia from in situ thrombosis of preexisting lesions have no previous signs or symptoms. The prevalence of mesenteric stenosis or occlusion in male patients older than 65 years is 18% by duplex ultrasound. Most patients have single-vessel lesions and remain asymptomatic. Severe mesenteric artery disease was identified in 6% of patients submitted to aortography. In a small series of 15 patients with severe three-vessel disease, 4 (27%) developed symptoms, of whom 3 underwent successful revascularization and 1 died from acute ischemia.

Choice of Open Versus Endovascular Revascularization

Selection of the open versus the endovascular approach is based on careful review of preprocedure CTA and clinical risk. The superior mesenteric artery (SMA) is the primary target for revascularization; therefore the anatomy of the SMA is the most important determinant of choice of therapy. The ideal lesion for angioplasty and stenting is a short, focal stenosis or occlusion with minimal to moderate calcification or thrombus. Celiac axis (CA) angioplasty and stenting carries a higher risk of restenosis and should not be performed if there is active compression by the median arcuate ligament unless this has been surgically released.

The technical difficulty of endovascular procedures can be anticipated by the presence of severe eccentric calcification, flush occlusion, and in dealing with patients who have longer lesions, small vessels, and tandem lesions affecting branches. These anatomic features are associated with worse technical results, increased risk of arterial complications (e.g., distal embolization, dissection), and restenosis. Our preference in these patients is to offer open revascularization if the anatomy is unfavorable for angioplasty and stenting, particularly if the clinical risk is low. Open reconstruction has also been used in younger patients with nonatherosclerotic lesions and in those who have failed percutaneous intervention or have had multiple recurrent in-stent restenoses.

Preprocedure Evaluation

Preoperative evaluation should focus on a critical review of surgical risk, nutritional status, and anatomic factors that affect the choice of reconstruction. Optimization of clinical and nutritional status should be sought as long as no significant delay is caused. Evaluation and management are tailored to each patient. Optimal medical therapy in these patients ideally should include cessation of cigarette smoking, acetylsalicylic acid, beta-blocker, and lipid-lowering medication.

Revascularization should not be excessively delayed. Patients who present with deterioration of symptoms should be admitted, started on intravenous heparin, and treated urgently within 24 to 48 hours. Patients with iodinated contrast allergy should be premedicated with a steroid preparation. Those with chronic kidney disease who have a serum creatinine level above 1.5 to 2.0 mg/dL (133 to 177 mmol/L) should undergo intravenous hydration with sodium bicarbonate and oral acetylcysteine starting the day prior to intervention. Gentle bowel preparation may be used prior to open reconstruction but should be avoided in those with severe or subacute ischemia.

Technique of Endovascular Revascularization

Arterial access can be obtained using either the femoral or brachial approach, preferentially with ultrasound guidance and a micropuncture set. Choice of access is based on physician preference, the presence of mesenteric occlusion, and angle of origin. Diagnostic angiographies are usually done as part of the intervention and rarely indicated to establish the diagnosis. Brachial access offers more catheter support in patients with very acute origins and occlusions. To minimize risk of access-related complications, the authors' preference is to surgically expose the brachial artery with a small 1- to 2-cm incision under local anesthesia.

Initial arterial access is obtained with a 5 French sheath. Diagnostic angiography is done using a 5 French flush catheter positioned approximately at the level of T12. The patient is anticoagulated with intravenous heparin (80 UI/kg) prior to crossing the lesion for any intervention. Use of a low-osmolar contrast agent (e.g., Visipaque) minimizes the abdominal discomfort that occurs during selective injections. A complete diagnostic study should include an abdominal aortogram with anteroposterior and lateral views to define the location, severity, and extent of visceral artery involvement and to identify concomitant lesions in the aorta or the renal or iliac arteries. The optimal projection to display the proximal CA and SMA is a lateral view; for the origin of the inferior mesenteric artery (IMA), it is usually a 15-degree right-lateral-oblique view. Diagnostic angiography may not be needed if the preprocedure CTA has documented the extent of disease.

Mesenteric interventions are usually done using a 6 or 7 French sheath. If the brachial access is selected, a 90-cm hydrophilic sheath is positioned in the descending thoracic aorta. Choice of catheter shape for selective catheterization is dependent on access site, angle of origin, and individual preference. A multipurpose A (MPA) catheter is ideal for selective catheterization from the brachial approach, whereas a secondary curve catheter (e.g., SOS, VS1, or Simmons) can be used from the femoral approach. The initial selective angiography should demonstrate the area of stenosis and the distal runoff branches for comparison with postintervention views. In patients with questionable lesions, pressure gradients can be measured using pressure wire, “pull-back,” or a simultaneous pressure measurement technique. The target lesion is initially crossed using a 0.035-inch soft angled hydrophilic guidewire, which is exchanged for the interventional wire of choice. The tip of the guidewire should be visualized and positioned within the main trunk of the SMA rather than within small secondary branches, which are prone to perforate or dissect ( Fig. 27.2 ). Embolic protection may be useful in selected patients who present with acute or subacute symptoms, particularly those with occlusions, long lesions (>30 mm length), severe calcification, or thrombus. In these cases, the authors' preference is to use a 320-cm working-length 0.014-inch filter wire (Spider RX, Medtronic Covidien, Plymouth, MN). If a 0.035-inch stent is selected, a two-wire technique can be used by combining a 0.014-inch filter wire with a 0.018-inch “buddy wire.” Most recently, our practice has changed to covered stents (0.035-inch) in patients with lesions that do not involve side branches. Covered stents offer superior patency rates compared with bare metal stents. If a two-wire technique is used, the stent is introduced via both wires for better support and to facilitate subsequent retrieval of the embolic protection device ( Fig. 27.3 ). Predilatation is recommended only if there is tight stenosis, occlusion, or severe calcification, or to gauge the size of stents. A balloon-expandable stent with diameter from 5 to 8 mm is used in more than 95% of cases, allowing precise deployment and greater radial force. The stent should cover slightly more than the entire length of the lesion and should go 1 to 2 mm into the aortic lumen. Ideally the stent should be flared gently into the aorta to prevent missing the ostia and to facilitate recatheterization if needed. Occasionally a self-expandable stent is used if the treated segment is tortuous or long, extending across proximal jejunal branches.

The primary goal of percutaneous treatment is to restore antegrade flow into at least one of the three mesenteric arteries, preferentially the SMA. In most cases primary stenting is recommended because of elastic recoil and restenosis, which occurs with angioplasty of ostial lesions. Routine use of two-vessel stenting is not recommended, since it adds cost and potential risk of complications without any evidence of better outcomes.

Recanalization of chronic occlusions poses a special challenge. The technique requires a stiffer support system to cross the lesion and deliver the stent. A coaxial support system uses a 7 French sheath, 7 French MPA guide catheter, and 5 French MPA catheter ( Fig. 27.4 ). Attempting difficult recanalization from the femoral approach adds time, contrast, and catheter manipulations and is fraught with failure. The tip of the MPA catheter engages the stump of the occluded SMA, whereas the support system allows the lesion to be crossed using a straight-tipped hydrophilic, soft 0.035-in Glidewire. Occasionally, 0.018- or 0.014-in guidewires are needed. It is important to avoid the subintimal plane owing to the risk of dissection or disruption; it is best achieved using straight-tipped guidewires. A Quick-cross catheter (Spectranetics, Colorado Springs, CO), an alternative support catheter, or even a small coronary balloon may be needed to cross a tight lesion. Once the lesion has been crossed, access into the true lumen should be confirmed. Our preference has been to use an embolic protection device with a two-wire technique routinely in cases of total occlusion.

Following deployment and flaring of the stent, the embolic protection device is retrieved with careful attention to avoid entrapment into the stent. The basket is examined for debris. A formal completion angiography should be obtained, including a focal magnified view of the stent with the sheath in the aorta to demonstrate the vessel origin and a panoramic view of the entire SMA and its branches to rule out embolization or perforation. The stiff guidewire should be retracted and nitroglycerin may be administered via the sheath to minimize spasm or kinks caused by the guidewire tip.

A number of adjunctive techniques can be used to optimize results in complex lesions, but the authors acknowledge that these techniques are anecdotal. The presence of acute and subacute symptoms suggests fresh thrombus or a complicated plaque. In these cases local administration of tissue plasminogen activator (t-PA) into the diseased segment 20 to 30 minutes prior to stent placement may improve technical success. For eccentric, calcified lesions, percutaneous atherectomy has been used in very select cases. It is critical to have an appreciation for the limitations of this technique when it is applied as an off-label use in the mesenteric arteries.

Complications

The most commonly reported complications are access-related problems in 3% to 16%, renal insufficiency in 2% to 8%, acute bowel ischemia in 1% to 7%, gastrointestinal bleeding in 1% to 5%, cardiac events in 1% to 7%, and respiratory complications in 1% to 7% of cases. Mortality is usually related to cardiac events, gastrointestinal bleeding, and bowel ischemia. The last is typically associated with intraprocedural complications such as distal embolization, thrombosis, or dissection. Distal embolization occurs in 8% of patients treated by SMA stents without embolic protection, with higher rates among patients with subacute symptoms, occlusion, long lesions (>30 mm), and severe calcification.