Management Strategy and Radiologic Outcomes of Symptomatic Spontaneous Isolated Superior Mesenteric Artery Dissection Based on Angiographic Classification: The Follow-Up Experience in a Single Center

Abstract

Purpose:

To investigate the demographics, clinical features, radiologic measurement, treatment, and outcomes of symptomatic spontaneous isolated superior mesenteric artery dissection (SISMAD) according to computed tomography (CT) classification.

Methods:

This retrospective study included 201 patients diagnosed with symptomatic SISMAD from November 2014 to December 2020. Symptomatic spontaneous isolated superior mesenteric artery dissection was categorized into four types based on CT images by Yun’s angiographic classification. Their clinical characteristics, images features, treatment methods, and radiological outcomes were comparatively analyzed by CT angiographic types.

Results:

SISMADs were categorized into type I (13.9%) patent false lumen (FL) with both entry and re-entry; type IIa (37.3%), blind pouch of FL; type IIb (43.3%), thrombosed FL; and type III (5.5%), and the occlusion of superior mesenteric artery (SMA). Type IIb, the most common SISMAD, showed the largest true lumen (TL) residual diameter and the lowest percentage of TL stenosis. Type III positioned most proximally to SMA origin and had the maximum dissection length. Symptomatic spontaneous isolated superior mesenteric artery dissections underwent conservative (75.1%), endovascular (22.4%), and surgical (2.5%) treatment. Conservative treatment was more frequent in type I (85.7%) and type IIb (83.9%) than in type IIa (65.3%) and type III (45.5%). Endovascular intervention was more commonly utilized in type IIa (32.0%) and type III (36.4%) than in type I (14.3%) and type IIb (14.9%). Conservative patients achieved FL vanishment/shrinkage (57.8%), stabilization (26.6%), and enlargement (15.6%). After conservative treatment, type I showed angiographic FL stabilization; type IIa achieved FL shrinkage (48.1%), stabilization (22.2%), and enlargement (29.6%); type IIb exhibited FL vanishment/shrinkage (92.0%) and enlargement (8.0%). Cumulative rate of stent patency was 92.3% during 6-year follow-up.

Conclusions:

Conservative management with close follow-up is initially provided especially for types I and IIb. Morphological stabilization is more frequent in type I of patent FL with entry and re-entry. False lumen vanishment or shrinkage was more likely to occur in type IIb due to the thrombus absorption. Endovascular intervention has excellent long-term in-stent patency and is predominantly utilized in types IIa and III. Blood flow sustained into a blind-ending FL causes the TL compression and stenosis in type IIa. Type III with the occlusion of SMA has the high risk of bowel ischemia.

Clinical Impact

According to Yun’s angiographic classification of spontaneous isolated superior mesenteric artery dissection (SISMAD), type I (13.9%) has patent true and false lumen and the morphological pattern is maintained stable; type IIa (37.3%) possesses a patent blind-ending false lumen which might shrink, remain unchanged, or enlarge; and endovascular intervention is suggested when conservative treatment failed; type IIb (43.3%) recovers spontaneously due to the absorption of false lumen thrombus and conservative treatment is preferentially considered; type III (5.5%) with the occlusion of main trunk carries a high risk of bowel necrosis, early endovascular intervention is proposed, and open surgery might be necessary.

Keywords

spontaneous isolated superior mesenteric artery dissection management strategy conservative treatment angiographic classification endovascular intervention dissection remodeling

Introduction

Spontaneous isolated superior mesenteric artery dissection (SISMAD) is a rare vascular disease, but has been increasingly recognized as a result of advances in computed tomography¹ angiography (CTA). Symptomatic spontaneous isolated superior mesenteric artery dissection showed a relatively benign clinical course, and most patients were treated conservatively with or without anticoagulation therapy.² Endovascular intervention is indicated if patients have severe true lumen (TL) stenosis, large dissecting aneurysms, and persistent abdominal pain symptoms.³ Open surgery is indicated for patients with suspected bowel necrosis or arterial rupture. The majority of published studies focus on the basic profiles, imaging features, treatment strategies, clinical outcomes, and morphologic changes of SISMAD in Western and Asian population⁴ or in Chinese ethnicity.^5,6

Similar to aortic dissection, patients with SISMAD may have diverse types of dissection, progress with different results, and require differential management. The classification of SISMAD types has been demonstrated to be important for treatment decision and prognosis prediction.⁷ However, no quantitative evidence is available regarding the clinical profile, imaging characteristics, treatment option, natural course and long-term outcomes of SISMAD based on morphologic classification on initial computed tomography (CT) scan configuration. The present study aimed to compare the demographics, clinical features, images measurement, treatment, and long-term follow-up results according to angiographic types.

Patients and Methods

Study Subjects

We retrospectively examined the medical records of 201 consecutive patients who were diagnosed as SISMAD at our department between November 2014 and December 2020. The information collected, including age, sex, medical history, clinical manifestations, coexisting medical conditions, imaging features, treatment modalities, follow-up duration, remodeling outcomes, and prognosis, was retrospectively analyzed. All patients presented with acute onset abdominal pain. Asymptomatic patients were excluded from the study, as the disease onset was unclear and the condition was diagnosed incidentally on CT during an examination for other diseases. Patients with abdominal aortic dissection, superior mesenteric artery (SMA) thrombosis, or aneurysmal formation without dissection were excluded. The institutional review boards of Huazhong University of Science and Technology, and its affiliated Union Hospital approved the study.

Diagnosis of SISMAD by CT

Diagnosis of SISMAD was confirmed according to CTA findings, such as an intimal flap in the SMA and/or thrombosis of the false lumen (FL). The entry and re-entry sites of dissection, site of origin, presence of a patent FL, ulcer-like projection (ULP) and aneurismal formation were also evaluated on initial CTA. The length of dissection, distance between the SMA origin and dissection origin, TL residual diameter, adjacent normal SMA size, and SMA branching angle from aorta were measured on all CT images. The percentage of TL stenosis by FL was also measured at the point of most severe luminal narrowing compared with adjacent normal SMA size. We defined significant stenosis of the TL as more than 75% compared with adjacent normal SMA diameter. ULP was defined as a localized blood-filled pouch protruding from the TL into the thrombosed FL.

We categorized SISMAD into four types according to Yun’s classification.⁸ type I: patent TL and FL with both entry and re-entry; type IIa: patent TL but no re-entry flow from the FL (blind pouch of FL); type IIb: thrombosed FL; and type III: SMA dissection with the occlusion of main trunk. To determine the SISMAD angiographic type, various CT images were reviewed, including axial, coronal, and sagittal views. Reconstructed images were also reviewed. Two vascular attending surgeons (G.H. and J.W.) with 15 to 20 years of clinical experience, respectively, interpreted all CT scans. Differences in opinion were resolved by a discussion until a consensus was reached.

Treatment Protocol

Conservative, endovascular, or surgical treatments were selected based on the symptoms, signs, and the morphologic characteristics of SISMAD on CTA. For the patients with peritonitis, emergency surgery would be performed to resect necrotic bowels and restore the blood supply. For patients without peritonitis, conservative therapy included close observation for bowel ischemia, fasting, parenteral nutrition, control of blood pressure, and pain control with or without anticoagulation therapy. Patients undergoing anticoagulation treatment were provided with rivaroxaban 20 mg per day or low molecular heparin 4000 U twice per day. Anticoagulation therapy was selectively used only for patients showing an occlusion (type III) or severe compromised blood flow (type IIa) to the SMA. Oral anticoagulants were administered for 3 to 6 months after the acute onset of SISMAD. If symptoms were relieved, conservative therapy would be continued. If symptom persisted, endovascular intervention or open surgery would be performed. Endovascular intervention included self-expandable stent placement in the TL and coil embolization of the pseudoaneurysm in the dissected SMA.

Follow-Up Protocol

Patients were periodically followed up using CTA for up to 5 years after diagnosis. The frequency of performing CT depended on each patient. Morphological changes on follow-up examination were determined by comparing the initial baseline CTA images, and were classified according to the following: (1) positive remodeling: there was the shrinkage or vanishment of FL and the resultant expansion of TL; (2) neutral remodeling: FL remained patent and was maintained stable; and (3) negative remodeling: there was the enlargement of FL as well as the compression and stenosis of TL. Follow-up results were comparatively analyzed according to the angiographic types.

Statistical Analysis

All statistical analyses were performed using SPSS version software (SPSS Inc, Chicago, IL, USA). Categorical variables were recorded as number and the percentage of patients. Comparisons between groups were performed using Fisher’s exact test. Continuous variables were presented as mean±standard deviation with normal distribution, and comparisons were made using student t-test or one-way analysis of variance (ANOVA). Continuous variables were expressed as mean and range values in case of a non-parametric distribution, and comparisons were made using the Mann-Whitney U test and Kruskal-Wallis test. The cumulative rate of stent patency and freedom from intimal hyperplasia was calculated using a Kaplan-Meier curve generated with GraphPad Prism (GraphPad Software Inc, Lajolla, CA, USA). A p value<0.05 indicated a statistically significant difference.

Results

Clinical Characteristics

According to Yun’s angiographic classification, there were 13.9% type I, 37.3% type IIa, 43.3% type IIb, and 5.5% type III cases. Type IIb was the most common morphologic type. Patient demographics, clinical manifestations, co-morbidities, and laboratory findings according to the angiographic types are summarized in Table 1. Among 201 patients, 168 patients (83.6%) were male with a median age of 52.9±7.1 years. One hundred eighty-eight patients (93.5%) were complained of acute abdominal pain. Hypertension was detected in 85 patients (42.3%), smoking in 77 patients (38.3%), hyperlipidemia in 58 patients (28.9%), diabetes mellitus in eight patients (4.0%), coronary artery disease in two patients (1.0%), and history of abdominal surgery in 18 patients (9.0%). No statistically significant difference was found in age, sex ratio, clinical presentation, and co-morbidities between patients among four angiographic types.

Table 1.

Patient Demographics, Clinical Manifestations, Co-Morbidities, and Laboratory Findings of the Patients With Symptomatic SISMAD by Yun’s Angiographic Types.

Characteristics	All patients	Yun’s angiographic type				p value
Characteristics	All patients	Type I	Type IIa	Type IIb	Type III	p value
Patients, n	201 (100.0%)	28 (13.9%)	75 (37.3%)	87 (43.3%)	11 (5.5%)	NA
Age, years	52.9±7.1	55.3±6.6	53.8±7.5	52.1±6.8	53.4±6.8	0.176
Male (%)	83.6%	78.6%	84.0%	83.9%	90.9%	0.868
Clinical manifestation
Abdominal pain	188 (93.5%)	23 (82.1%)	71 (94.7%)	83 (95.4%)	11 (100.0%)	0.105
Nausea/vomiting	38 (18.9%)	6 (21.4%)	16 (21.3%)	13 (14.9%)	3 (27.3%)	0.616
Bloody stools	14 (7%)	1 (3.6%)	7 (9.3%)	4 (4.6%)	2 (18.2%)	0.207
Syncope	1 (0.5%)	0 (0%)	0 (0%)	1 (1.1%)	0 (0%)	1.000
Co-morbidities
Hypertension	85 (42.3%)	11 (39.3%)	32 (42.7%)	39 (44.8%)	3 (27.3%)	0.708
Tobacco use (current or ex-smoker)	77 (38.3%)	11 (39.3%)	27 (36.0%)	35 (40.2%)	4 (36.4%)	0.956
Hyperlipidemia	58 (28.9%)	7 (25%)	16 (21.3%)	32 (36.8%)	3 (27.3%)	0.178
Diabetes mellitus	8 (4.0%)	1 (3.6%)	3 (4.0%)	3 (3.4%)	0 (0%)	0.635
Coronary artery disease	2 (1.0%)	0 (0%)	1 (1.3%)	1 (1.1%)	0 (0%)	1.000
History of abdominal surgery	18 (9.0%)	5 (17.9%)	5 (6.7%)	6 (6.9%)	2 (18.2%)	0.144
Laboratory findings
White blood cells, 10⁹/L	6.8 (5.4; 8.6)	5.9 (4.4; 7.0)	6.4 (5.4; 8.7)	7.3 (5.7; 8.6)	8.2 (5.7; 14.8)	0.023
Erythrocyte sedimentation rate, mm/h	20.5±16.8	14.5± 9.2	21.3±16.5	11.3±5.3	42.0±31.1	0.545
C-reactive protein, mg/dL	38.1±52.4	15.8±15.6	29.4±31.7	25.8±29.8	97.1±122.3	0.489

Categorical data are presented as n (% of each group). Continuous data are presented as mean±standard deviation or median (first quartile; third quartile), according to the normality in distribution.

Abbreviations: NA, not applicable; SISMAD, spontaneous isolated superior mesenteric artery dissection.

The mean white blood cell was 6.8 (5.4; 8.6)×10⁹/L. The mean erythrocyte sedimentation rate (ESR) was 20.5±16.8 mm/h. The mean C-reactive protein (CRP) was 38.1±52.4 mg/dL. White blood cells were higher in type III than in types I, IIa, and IIb (p=0.023). Therefore, type III with the occlusion of SMA might be associated with inflammatory reaction initiated by bowel ischemia.

Imaging Features

Image measurements on initial CT at diagnosis according to the angiographic types are summarized in Table 2. The mean distance between the SMA origin and dissection origin was 10.6 (7.0; 21.0) mm. The mean dissection length was 70.1±35.7 mm. Distance between the SMA origin and dissection origin was significantly shorter in type III than in types I, IIa, and IIb (p=0.005). Dissection length was statistically longer in type III than in types I, IIa, and IIb (p=0.024). Thus, type III started at the most proximal SMA and affected a largest portion of SMA.

Table 2.

Computed Tomography Features at Diagnosis in the Patients With Symptomatic SISMAD by Yun’s Angiographic Types.

Characteristics	All patients(n=201)	Yun’s angiographic type				p value
Characteristics	All patients(n=201)	Type I (n=28)	Type IIa (n=75)	Type IIb (n=87)	Type III (n=11)	p value
Distance between SMA origin and dissection origin, mm	10.6 (7.0; 21.0)	14.0 (8.8; 32.6)	11.3 (8.1; 26.1)	8.8 (6.0; 15.4)	7.9 (5.3; 11.8)	0.005
The length of dissection, mm	70.4±35.3	61.8±33.9	63.0±33.1	77.1±36.6	86.7±30.0	0.024
True lumen residual diameter, mm	3.0 (1.9; 4.2)	2.3 (1.4; 3.6)	2.8 (1.8; 3.6)	3.3 (2.8; 5.1)	0	<0.001
Adjacent normal SMA size, mm	7.3±1.4	7.5±1.7	7.2±1.4	7.4±1.3	7.3±1.0	0.849
Percentage of true lumen stenosis, %	58.4 (44.6; 58.4)	63.0 (56.1; 81.1)	62.2 (47.8; 73.7)	60.1 (48.1; 71.0)	100	<0.001
SMA branching angle from aorta	112.6±20.7°	108.0±19.0°	114.6±21.3°	111.0±21.5°	123.2±11.1°	0.160

Continuous data are presented as mean±standard deviation or median (first quartile; third quartile), according to the normality in distribution.

Abbreviations: SISMAD, spontaneous isolated superior mesenteric artery dissection; SMA, superior mesenteric artery.

The mean TL residual diameter was 3.0 (1.9; 4.2) mm. The mean percentage stenosis of TL was 58.4% (44.6%; 58.4%). True lumen residual diameter was significantly larger in type IIb than in types I, IIa, and III (p<0.001). Percentage stenosis of TL was significantly lower in type IIb than in types I, IIa, and III (p<0.001). Thus, type IIb resulted in to a less extent the stenosis and compression of TL. The mean SMA branching angle from aorta was 112.6±20.7°, and did not differ among four angiographic types (p=0.160).

Treatment

Treatments and selection interventions according to the angiographic types are summarized in Table 3. The percentage of patients who underwent conservative, endovascular, and surgical treatments were 75.1%, 22.4%, and 2.5%, respectively. Conservative management was more frequently conducted in type I (85.7%) and type IIb (83.9%) than in type IIa (65.3%) and type III (45.5%) (p=0.003). Endovascular intervention was more prevalent in type III (36.4%) and type IIa (32.0%) than in type I (14.3%) and type IIb (14.9%) (p<0.001). Surgery was more commonly performed in type III (18.2%) than in type IIa (2.7%) and type IIb (1.1%) (p=0.027). Thus, conservative management with close follow-up should be considered firstly for the majority of patients with types I and IIb. Endovascular intervention might be reserved for type IIa patients with severe stenosis of TL (Figure 1) and type IIIpatients with TL occlusion (Figure 2).

Table 3.

Management Strategy, Endovascular, and Surgical Interventions of the Patients With Symptomatic SISMAD by Yun’s Angiographic Types.

	All patients(n=201)	Yun’s angiographic type				p value
	All patients(n=201)	Type I (n=28)	Type IIa (n=75)	Type IIb (n=87)	Type III (n=11)	p value
Treatment strategy
Conservative management	151 (75.1%)	24 (85.7%)	49 (65.3%)	73 (83.9%)	5 (45.5%)	0.003
Endovascular intervention	45 (22.4%)	4 (14.3%)	24 (32.0%)	13 (14.9%)	4 (36.4%)	<0.001
Open surgery	5 (2.5%)	0 (0.0%)	2 (2.7%)	1 (1.1%)	2 (18.2%)	0.027
Indications for endovascular intervention
Available	45 (22.4%)	4 (14.3%)	24 (32.0%)	13 (14.9%)	4 (36.4%)	<0.001
Severe stenosis of the true lumen>75%	24 (53.3%)	2 (7.1%)	14 (18.7%)	8 (9.2%)	0 (0.0%)	0.185
Persistent symptoms for 8 hours	20 (44.4%)	2 (7.1%)	9 (12.0%)	5 (5.7%)	4 (36.4%)	0.134
Dissecting aneurysm formation	1 (2.3%)	0 (0.0%)	1 (1.3%)	0 (0.0%)	0 (0.0%)	1.000
Indications for open surgery
Available	5 (2.5%)	0 (0.0%)	2 (2.7%)	1 (1.1%)	2 (18.2%)	0.027
Bowel infarction, necrosis, peritonitis	3 (60%)	0 (0.0%)	2 (2.7%)	0 (0.0%)	1 (9.1%)	0.600
Hematoma in abdominal cavity	2 (40%)	0 (0.0%)	0 (0.0%)	1 (1.1%)	1 (9.1%)	0.600

Categorical data are presented as n (% of each group).

Abbreviation: SISMAD, spontaneous isolated superior mesenteric artery dissection.

Indications for endovascular treatments included severe stenosis of the TL>75% (53.3%), persistent abdominal pain for 8 hours (44.4%), dissecting aneurysm (2.3%). The percentage of patients with severe TL stenosis and persistent abdominal pain did not differ statistically among types I, IIa, and IIb patients. All endovascular patients of type III suffered from persistent abdominal pain. Indications for open surgery comprised bowel necrosis and peritonitis in three patients (60.0%) and abdominal hematoma in two patients (40.0%).

Follow-Up Outcomes

Follow-up results of conservative or endovascular treatment according to the angiographic types are summarized in Table 4. During the follow-up period (mean, 16.6 months; range, 1.73–65.3 months), the 1-, 3-, 6-month, and 1-year follow-up were completed in 100% (64/64), 93.8% (60/64), 71.9% (46/64), and 45.3% (29/64) of patients, respectively. Of 64 conservative patients with completed follow-up, 37 patients (57.8%) achieved positive remodeling defined as the vanishment or shrinkage of FL, 17 patients (26.6%) experienced neutral remodeling defined as the stabilization of FL, and 10 patients (15.6%) had negative remodeling defined as the enlargement of FL. Positive remodeling was more frequent in type IIb (92.0%) than in type IIa (48.1%) and in type III (33.3%) (p<0.001). Neutral remodeling were more common in type I (100.0%) than in type IIa (22.2%) and in type III (66.7%) (p<0.001). Negative remodeling more frequently occurred in type IIa (29.6%) than in type IIb (8.0%), but the difference did not reach the statistical difference (p=0.308).

Table 4.

Follow-Up Computed Tomography Results of Conservative and Endovascular Treatment According to the Angiographic Findings.

	All patients(n=201)	Yun’s angiographic type				p value
	All patients(n=201)	Type I (n=28)	Type IIa (n=75)	Type IIb (n=87)	Type III (n=11)	p value
Conservative management
Available	64 (31.8%)	9 (32.1%)	27 (36.0%)	25 (28.7%)	3 (27.3%)	NA
Positive remodeling (FL vanishment/shrinkage)	37 (57.8%)	0 (0.0%)	13 (48.1%)	23 (92.0%)	1 (33.3%)	<0.001
Neutral remodeling (FL stabilization)	17 (26.6%)	9 (100.0%)	6 (22.2%)	0 (0.0%)	2 (66.7%)	<0.001
Negative remodeling (FL enlargement)	10 (15.6%)	0 (0.0%)	8 (29.6%)	2 (8.0%)	0 (0.0%)	0.308
Endovascular intervention
Available	32 (15.9%)	4 (14.3%)	16 (21.1%)	9 (10.3%)	3 (30.0%)	NA
Slight FL enhancement	7 (21.9%)	3 (75.0%)	4 (25.0%)	0 (0.0%)	0 (0.0%)	0.024
Intimal hyperplasia	9 (28.1%)	1 (25.0%)	3 (18.8%)	4 (44.4%)	1 (33.3%)	0.532
Severe re-stenosis	1 (3.1%)	0 (0.0%)	1 (6.3%)	0 (0.0%)	0 (0.0%)	1.000
Stent patency	31 (96.9%)	4 (100.0%)	15 (93.8%)	9 (100.0%)	3 (100.0%)	1.000
Complete FL obliteration	28 (87.5%)	3 (75.0%)	13 (81.3%)	9 (100.0%)	3 (100.0%)	0.465

Categorical data are presented as n (% of each group).

Abbreviations: FL, false lumen; NA, not applicable.

Patent TL and FL in type I are likely to be “no morphological change” (Figure 3). A blind-ending FL in type IIa might be narrowed (Figure 4), stabilized (Figure 5), or enlarged (Figure 6) depending on its configuration. Resolution of thrombus in type IIb was usually accompanied with FL vanishment, resulting in the complete recovery (Figure 7). When ULP was present in type IIb, the thrombosed FL in type was recanalized and TL was progressively dilated (Figure 8).

Of 32 endovascular patients who completed follow-up CT scan, 21.9% of patients showed the slight leakage of contrast agent into FL, which occurred in type I (75.0%) and type IIa (25.0%) (p=0.024). The median follow-up was 17.0 months, ranging from 2.23 to 49.6 months. The 1-, 3-, 6-month, and 1-year follow-ups were completed in 100% (32/32), 96.9% (31/32), 68.8% (22/32), and 53.1% (17/32) of patients, respectively. Focal mild intimal hyperplasia was found at the proximal end of stent in 28.1% of patients, which did not adversely affect stent patency. Cumulative freedom from intimal hyperplasia was 90.0% at 1 year, 64.0% at 2 years, 54.8% at 3 years, and 29.3% at 4 years (Figure 9A). One patient with two overlying stents suffered with severe intimal hyperplasia, which caused approximately 40% in-stent stenosis at 1-year follow-up. There was still dual-lumen configuration and the persistent presence of FL distal to the stent in four patients. Overall, during the average follow-up of 17.6 months, endovascular stenting exhibited 96.9% of stent patency and 87.6% of excellent remodeling efficacy. Kaplan-Meier analysis showed that the cumulative rate of stent patency was 92.3% during the 6-year follow-up (Figure 9B).

Discussion

The recent study summarized the demographic and clinical features of SISMAD in Chinese people in our institution. In our series, 83.6% of the patients were male, and the mean age of the patients was 52.9 years. Overall, 93.5% of patients presented with sudden-onset severe abdominal pain. Among various co-morbidities, hypertension and smoking might be the most common risk factors. Hypertension has been identified in approximately 42.3% in the recent study, which is similar to the 42.7% in previously reported review from the Chinese-language literature.⁵ Nearly, 38.3% of patients with SISMAD have a history of smoking, which is somewhat higher than the 17.2% that previously reported review from the Chinese-language literature.⁵ In laboratory tests, the elevated levels of leukocyte, CRP and ESR were revealed in type III patients. Type III has the complete occlusion of SMA and carries the highest risk of bowel ischemia or necrosis.

According to Yun’s classification, there were 13.9% type I, 37.3% type IIa, 43.3% type IIb, and 5.5% type III. Type IIb was the most common SISMAD type and had the maximum TL residual diameter and the minimum percentage stenosis of TL. Types IIa and I were the second and the third common types, respectively. There were no significant differences on the location of dissection origin, the length of dissection, and the extent of TL stenosis between types IIa and I. Type III was the less common type. We found that type III dissection was located most proximally to SMA origin and affected a longest portion of SMA. The average SMA branching angle was 112.6±20.7ºand did not differ among four Yun’s angiographic types, which was similar to that previously reported (115.3±23.3º).⁹

The aim of treatment for SISMAD is to limit the extension of dissection, to prevent the rupture of the FL, and to preserve the distal blood perfusion through TL. Currently available treatments for SISMAD include: conservative management, endovascular intervention, and open surgery based on CT scan findings and clinical presentation. Conservative treatment is non-invasive and does not leave foreign material in the artery. The relatively benign nature of SISMAD compared with SMA embolism supports conservative management as a first strategy.¹⁰ Endovascular intervention is generally recommended in cases of persistent abdominal pain, TL severe stenosis or occlusion, and aneurismal change of the arterial lesion.¹⁰ Open surgery remains the main approach when endovascular therapy fails or there are signs of bowel infarction or arterial rupture.¹⁰

In the present study, 201 patients with SISMAD were treated either conservatively (75.1%), or with endovascular intervention (22.4%), or by surgical procedure (2.5%). A recent survey of 622 Chinese patients with SISMAD demonstrated that they were managed with conservative (63.2%), endovascular (33.6%), and surgical (3.2%) treatments.⁵ Our study identified that 151 conservative patients consisted of type I in 24, type IIa in 49, type IIb in 73, and type III in 5. Conservative management was most frequently performed in type I (85.7%) and type IIb (83.9%), was secondly utilized in type IIa (65.3%), and was less underwent in type III (45.5%). Type I is characterized as patent FL and TL for the mesenteric blood supply, there is usually no severe bowel ischemia, and abdominal pain will be relieved after conservative management. As mentioned above, type IIb has thrombosed FL, maximum TL diameter, and minimum stenosis percentage among four angiographic types. Most patients with type IIb achieve symptom relief and radiological improvement due to the resolution of FL thrombus under observation treatment. Our study indicated that 45 endovascular patients comprised type I in 4, type IIa in 24, type IIb in 13, and type III in 4. Endovascular intervention was most frequent utilized in type III (36.4%), was secondly underwent in type IIa (32.0%), and was relatively less performed in type I (14.3%) and type IIb (14.9%). Type III dissection has the complete occlusion of SMA, bowel ischemia might occur in lack of collateral branches, and additional interventions besides medication are often needed. When type IIa has a long blind-end FL, the sustained flux in FL resulted in the compression and stenosis of TL. Forty-five endovascular patients belonged to the severe stenosis of TL (53.3%), persistent abdominal pain symptom (44.4%), and dissecting aneurysm (2.3%). If endovascular treatment fails or there are signs of bowel infarction or arterial rupture, then open surgery is indicated. Our study found that five surgical patients were due to bowel necrosis (60.0%) and abdominal hematoma (40.0%).

Serial follow-up CTA revealed positive remodeling (57.8%) explained as the vanishment or shrinkage of FL and the enlargement of TL, neutral remodeling (26.6%) explained as the stabilization of TL and FL, and negative remodeling (15.6%) defined as the enlargement of FL and the compression of TL in 64 conservative patients. A meta-analysis involving 43 studies reported conservative patients achieved complete remodeling (25.0%), incomplete remodeling (51.0%), and morphological progression (12.0%).² Vanishment or shrinkage of the FL (positive remodeling) was observed in 92.0% of type IIb with thrombosed FL. Thrombosis of the FL spontaneously resolved during the follow-up, and positive remodeling occurred.¹¹ Vascular positive remodeling was more likely to be achieved by thrombosis of FL in type IIb.¹¹ Stabilization of the TL and FL (neutral remodeling) belonged to 100% of patients with type I. Type I has patent SMA with patent entry and re-entry, and shows a propensity for no morphological change on follow-up angiogram.¹² In patients of type I with patent FL, a mean 17.1-month follow-up CTA did not demonstrate any definitive interval changes compared with the initial CT scan.¹³ Enlargement of the FL (negative remodeling) was obvious in 29.6% of type IIa. In patients with a blind-ending FL and without re-entry, the FL might enlarge, thus causing the compression of TL and compromised blood flow through the TL.¹³ Patent FL, especially without re-entry was a risk factor negatively affecting vascular remodeling.

Endovascular intervention should be considered for patients with persistent symptoms or severe stenosis or occlusion of the TL without bowel ischemia. Endovascular therapy is obviously less invasive than open surgery, and is associated with the high technical success rate and dissection remodeling rate.¹⁴ However, it still has potential concerns, such as stent thrombosis, intimal hyperplasia, and re-stenosis. Endovascular long-term results have yet to be determined. Of 32 patients who were followed up by serial CTA, 21.9% of patients had the slight leakage of contrast agent into the FL predominantly in types I and IIa patients, and focal mild intimal hyperplasia was identified at the proximal and middle segments of the stents in the 28.1% of patients, but it did not progress to in-stent stenosis. Our study found that all stents except one were patent and in-stent patency rate were 96.9% during a mean 17.1-month follow-up. Cumulative rate of stent patency was calculated to be 92.3% during the 6-year follow-up. One patient was treated with overlapping stents and encountered approximately 30% to 40% re-stenosis over 1 year. Of 10 patients who underwent stent placement, a median 53-month follow-up indicated that distal stent was occluded due to initial hyperplasia in one patient treated with two stents and long-term patency was 90%.³ Our study observed that 87.5% of endovascular patients showed the complete obliteration of the FL without compromise of major arterial branches. Four patient remained dual-lumen configuration distal to the stent, and did not achieve compete remodeling during the average follow-up of 17 months. Thus, endovascular stent placement might be a preferred treatment for suitable SISMAD patients due to the low-risk re-stenosis, excellent long-term patency, and satisfactory dissection remodeling efficacy. However, there is a possibility of stent stenosis when multiple stents are used to cover a long-segment dissection.³

There are several limitations in the present study. First, the treatment selection was up to the clinical judgment of each treating physician, even within one group, there was wide disparity between the use of endovascular stenting and anticoagulation therapy. Second, since this study is retrospective and that data are from a single institution, selection bias, and confounding factors were unavoidable. Third, the sample size was relatively small, and follow-up CTA could not be performed in all patients.

In conclusion, SISMAD may be managed by conservative, endovascular, and surgical treatments based on clinical manifestation, imaging appearance, and angiographic type. Type I has patent TL and FL for mesenteric blood supply, the symptoms usually resolve and morphological pattern is maintained stable under initial observation treatment. Type IIa possesses a patent blind-ending FL that might shrink, remain unchanged, or enlarge; and endovascular intervention is suggested in cases of failed conservative treatment. Type IIb recovers spontaneously due to the absorption of FL thrombus and conservative treatment should be preferentially considered. Type III with the occlusion of SMA carries a high risk of bowel necrosis, early endovascular intervention is proposed, and open surgery might be necessary when there are signs of bowel infarction or arterial rupture.

Supplemental Material

sj-docx-1-jet-10.1177_15266028221133700 – Supplemental material for Management Strategy and Radiologic Outcomes of Symptomatic Spontaneous Isolated Superior Mesenteric Artery Dissection Based on Angiographic Classification: The Follow-Up Experience in a Single Center

Supplemental material, sj-docx-1-jet-10.1177_15266028221133700 for Management Strategy and Radiologic Outcomes of Symptomatic Spontaneous Isolated Superior Mesenteric Artery Dissection Based on Angiographic Classification: The Follow-Up Experience in a Single Center by Zihui Yuan, Guofu Hu, Shi Sheng, Yun You and Jian Wang in Journal of Endovascular Therapy

Supplemental Material

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Supplemental material, sj-jpg-2-jet-10.1177_15266028221133700 for Management Strategy and Radiologic Outcomes of Symptomatic Spontaneous Isolated Superior Mesenteric Artery Dissection Based on Angiographic Classification: The Follow-Up Experience in a Single Center by Zihui Yuan, Guofu Hu, Shi Sheng, Yun You and Jian Wang in Journal of Endovascular Therapy

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was funded by the National Natural Sciences Foundation of China, grant number 81770277; the Natural Science Foundation of Hubei Province of China, grant number 2015CFB457; the Key Laboratory of Biological Targeted Therapy of Hubei Province, grant number 2021swbx020; and the Science Foundation of Wuhan Union Hospital, grant number 2021xhyn109.

ORCID iD

Jian Wang

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Supplemental material for this article is available online.

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