Editorials
Current Treatment Strategy for Spontaneous Isolated Dissection of the Superior Mesenteric Artery
2016 Volume 80 Issue 6 Pages 1323-1325
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2016 Volume 80 Issue 6 Pages 1323-1325
Isolated arterial dissection can occur spontaneously in any part of the whole arterial system, but is uncommon.1 Spontaneous isolated dissection of the superior mesenteric artery (SMA) is also such a rare entity that there is not a definitive therapeutic guideline for it. In most cases, currently conservative treatment without any intervention is chosen as the first-line therapy, although open or endovascular interventions are attempted for a subset of persistently symptomatic or critical patients with ruptured SMA dissection or infarction of the bowels. However, the late outcome still remains unclear for lack of reports looking at it precisely, whether with conservative management or interventional treatment. Interestingly, the article published by Tomita et al2 in this issue of the Journal documents favorable early and late outcomes of initial conservative management for isolated SMA dissection in a relatively large series and clearly demonstrates some risk factors affecting long-term outcome by analyzing the detailed dimensions of the dissecting SMA on computed tomographic scans. Here, I will discuss the current therapeutic algorithm for this uncommon condition.
Article p 1452
This uncommon entity occurs mainly in middle-aged males with the risk factors of hypertension and smoking.3 In addition, segmental arterial mediolysis and arterial fibroelastic disease might be the fundamental arterial conditions related to this entity. Furthermore, shearing stress around the inferior edge of the pancreas because of differences in SMA fixation, 1.5–3 cm from the SMA origin, and at its maximum curved portion has been suggested as a significant anatomic factor in spontaneous isolated SMA dissection.4
Usually, this disease entity spontaneously occurs with sudden-onset abdominal pain, similar to aortic dissection. The following diagnosis is based on the findings of CT scans. In patients without clear abdominal pain, there is either no chance or some delay in its precise diagnosis. Subsequently, it is often recognized by chance in the chronic stage on CT scans performed for other reasons. In the past, angiography was carried out for the diagnosis, but currently this time-consuming and invasive examination is not performed routinely because of recent improvements in the imaging quality of CT scans including 3D images. In 2009, Yun et al5 categorized this entity according to their findings on angiography and/or CT scans for easy understanding of this rare condition: type I: patent true lumen (TL) and false lumen (FL) revealing entry and re-entry sites; type II: patent TL but no re-entry flow from FL, IIa: visible FL but not visible re-entry site (“blind pouch of FL”), IIb: no visible FL flow (thrombosed FL), which usually causes TL narrowing; type III: SMA dissection with occlusion of SMA. The appropriate treatment for each type should be chosen in consideration of its late outcome.
Treatment is still controversial, particularly for symptomatic SMA dissection in the acute phase. In general, recent first-line therapy has been conservative management, with or without antithrombotic treatment with antiplatelet and anticoagulant therapy to prevent TL occlusion by stabilizing the intimal flap (Figure,Table).3–11 For a subset of patients with persistent symptoms because of critical bowel ischemia or infarction caused by compression of the TL of the SMA or rupture of the dissecting SMA, endovascular treatment (EVT) with stents or open surgical repair (OSR) is indicated without delay.11 In the current shift towards EVT for aortic or peripheral arterial lesions,12 EVT predominates. In the report by Tomita et al, only one of 27 symptomatic patients required OSR for bowel infarction.2 Compared with OSR, less-invasive EVT has recently been attempted more since Leung et al first performed it using a Wallstent in 2000.13–15 However, there are also adverse sequelae of EVT such as stent thrombosis, intimal injury, and unavoidable closure of the multiple lateral branches of the SMA. Consequently, EVT is indicated preferably for localized segmental stenosis with some cautions.4,12–15 In addition, the long-term outcome of stent placement remains unclear, so younger patients should be excluded as candidates for prompt EVT. On the other hand, for cases of long segmental stenosis of the SMA and inadequate inflow of the SMA, OSR such as patch repair or arterial bypass is another option.4,12 Rupture is also an indication of the OSR. It is, however, rarely attempted because conservative management has been producing successful outcome for the past 2 decades.
Therapeutic algorithm for isolated SMA dissection. CT, computed tomography; EVT, endovascular treatment; OSR, open surgical repair; SMA, superior mesenteric artery.
| Authors | Year | Journal | No. of patients (symptomatic) |
Treatment (%) | First-line therapy | ||
|---|---|---|---|---|---|---|---|
| Medical | OSR | EVT | |||||
| Yun et al5 | 2009 | EJVEVS | 32 (22) | 87.5* | 3.0 | 3.1 | Conservative |
| Park et al3 | 2011 | JVS | 58 | 91.3* | 6.9 | 1.8 | Conservative |
| Cho et al6 | 2011 | EJVEVS | 30 | 76.7* | 3.3 | 16.7 | Conservative |
| Dong et al7 | 2013 | JVS | 14 (14) | 92.9* | 7.1 | 0 [64.3] | Conservative |
| Jibiki et al8 | 2012 | ST | 14 (8) | 92.3* | 7.1 | – | Conservative |
| Jia et al9 | 2013 | EJVEVS | 17 (17) | 82.4* | – | 17.6 | Conservative |
| Kim et al10 | 2014 | JVS | 27 (27) | 100* | – | – | Conservative |
| Garrett11 | 2014 | JVS | 6 (6) | 50.0* | 50.0 | – | Conservative |
| Li et al4 | 2014 | JVS | 42 (42) | 57.1 | 17.7 | 26.2 | Depending on morphologic classification |
| Pang et al14 | 2013 | EJR | 12 | 41.7 | – | 58.3* | EVT |
| Luan et al15 | 2013 | JVS | 18 (14) | 38.9 | – | 61.1* | EVT |
*Preferred or addressed therapy in each article. [ ], patient population undergoing EVT after initial medical therapy. EJR, European Journal of Radiology ; EJVEVS, European Journal of Vascular and Endovascular Surgery; EVT, endovascular treatment; JVS, Journal of Vascular Surgery; OSR, open surgical repair; ST, Surgery Today.
In their report, Tomita et al2 demonstrate favorable outcomes of initial conservative management for SMA dissection, and document 2 risk factors such as opened FL and aneurysmal formation affecting the long-term outcome. Remodeling was defined as an improvement in the SMA dissection, characterized by occlusion of the FL and/or improved stenosis in the TL. Complete remodeling was defined as morphological recovery of the SMA to its normal condition, without any aneurysm formation. Up to 64.0% of symptomatic patients who received conservative management showed complete remodeling within 2 years of the onset of SMA dissection.
In summary, for isolated SMA dissection, initial conservative management with or without antithrombotic treatment is promising with favorable early and long-term outcomes. For the subset of patients with persistent stenosis/occlusion of the TL of the SMA, bowel infarction or aneurysm formation, EVT or OSR without delay is recommended.
