Isolated Abdominal Aortic Dissection With and Without Abdominal Aortic Aneurysm

Introduction

Aortic dissection usually affects the thoracic aorta, sometimes extending distally to the abdominal aorta; however, isolated abdominal aortic dissection (IAAD) is uncommon, with a reported incidence of 1-2% of all aortic dissections.^1,2 The anatomic and clinical characteristics of this entity differ from the typical dissection originating from the thoracic aorta, which is classified according to the thoracic location of the dissection with the Stanford or DeBakey classification; nevertheless, IAAD which refers to a dissection starting below the diaphragm, does not fit into any classification, differing from treatment strategies due to the scarce literature on the topic. ² Moreover, IAAD has also been associated with abdominal aortic aneurysm, iliac aneurysms, or aortic stenosis, supporting the fact that IAAD must be seen as a different disease.^3–5 The clinical presentation of symptomatic IAAD includes abdominal pain, lumbar pain, buttock pain, claudication, malperfusion, and acute limb ischemia, and the best treatment strategy remains undefined. ⁶ In 2019, a systematic review and meta-analysis of 491 patients with IAAD showed no differences between open surgery, endovascular therapy, or conservative management. ² One year later, another meta-analysis of 482 IAAD patients couldn’t compare clinical outcomes from different treatments due to a lack of data.^7,8

The aim of this study was to report the clinical presentation and treatment strategies of patients with IAAD seen in a single academic institution in South America.

Materials and Methods

This study was performed with prior consideration from the institution review board and ethics committee of the Pontifical Catholic University of Chile under number 231003003 and abides by the norms established in the Helsinki Conference of 1964 as well as its revision in 2012.

A retrospective review of all patients with IAAD diagnosed between January 2002 and December 2023 from a single academic hospital was performed. Data was collected from the vascular surgery department database of all operated patients, search strategy was done by using the terms “aortic dissection”, “abdominal dissection” “abdominal aortic dissection” “isolated abdominal aortic dissection”. Patients were scrutinized using hospital records, patients who had a thoracic aortic dissection (dissection above the diaphragm) or other thoracic diseases were excluded.

Variables gather included gender, age, diabetes mellitus (DM), systemic arterial hypertension (SAH), dyslipidemia, chronic renal failure, present or prior smoking history, type of symptoms, concomitant abdominal or iliac aneurysm, location of the dissection, treatment employed, treatment outcomes, and follow-up.

Conservative treatment included antithrombotic therapy with aspirin 100 daily, and blood pressure and heart rate control. Pain management and an infusion of labetalol or nitroprusside were started if the patient was hypertensive with a goal of systolic blood pressure of less than 110 mmhg and diastolic less than 70 mmhg. Heart rate target was less that 60 bpm. Preoperative diagnosis was established by contrast-enhanced angio-computed tomography (CTA) or angiography.

Patients were classified as chronic (>3 months), subacute (>14 days-3 months) or acute dissection (<14 days), according to the time from onset of symptoms to definitive treatment. Asymptomatic patients were classified as chronic dissections.

Indications for surgical or endovascular intervention included signs of aortic rupture, limb ischemia, persistent claudication, refractory abdominal pain, concomitant abdominal aortic aneurysms (AAA), or iliac aneurysms. The decision to perform open or endovascular surgery was left at the discretion of the operating surgeon. Operative complications and endoleaks were recorded. Demographics of patients with AAA and IAAD were compared with patients with IAAD and without AAA Figure 1.

OPEN IN VIEWER

Figure 1.

Computed tomography reconstruction. (A) Aneurysmal infrarrenal aorta with isolated abdominal aortic dissection. (B) Non dilated aorta with isolated abdominal aortic dissection.

Regular surveillance was done with a CT scan at six months, 12 months, and yearly after discharge or until complete resolution of the dissection.

Results

Eighteen patients with IAAD were seen during the study period. Thirteen (72.2%) were males, and 5 (27.7%) were females. Median age was 63 years (range: 43-88 years). Seven (38.8%) patients had diabetes mellitus, 13 (72.2%) had systemic arterial hypertension, seven (38.8%) had dyslipidemia, two (11.1%) were obese, and six (33.3%) were smokers. One (5.5%) patient had Marfan syndrome, one (5.5%) patient had antiphospholipid syndrome, and one (5.5%) patient had factor V deficiency. No patient had familiar history of aortic dissection or aneurysm. One (5.5%) patient had a right aortic arch and a Kommerel diverticulum.

Sixteen (88.8%) patients presented with symptoms; of them, ten (55.5%) presented with abdominal pain, three (16.6%) presented lumbar pain, and three (16.6%) patients presented buttock and thigh claudication. Two (11.2%) patients were asymptomatic.

Ten (55.5%) patients had concomitant abdominal aortic aneurysm (AAA), with a median size of the aneurysm of 49.5 mm (range: 44-66 mm). Of them, six had common iliac artery aneurysms (CIAA), four were bilateral, and two were unilateral. Two (11.1%) patients had unilateral isolated CIAA. One (5.5%) had a 21 mm popliteal artery aneurysm. The median size of the CIAAs was 30 mm (range: 25-45 mm). No differences were seen between patients with IAAD with and without AAA (Table 1).

OPEN IN VIEWER

Table 1.

Demographic Characteristics of Patients With Isolated Abdominal Aortic Dissection With and Without Abdominal Aortic Aneurysm.

	AAA + IAAD	IAAD	P =
	N = 10	N = 8
Age (years) [median (range)]	65 (51-77)	61 (43-88)	0.789
Male	9 (69.2%)	4 (30.8%)	0.118
Female	1 (20.0%)	4 (80%)
Diabetes mellitus	4 (57.1%)	3 (42.9%)	0.637
Hypertension	8 (61.5%)	5 (38.5%)	0.608
Obesity	1 (50.0%)	1 (50.0%)	1.000
Dyslipidemia	3 (50.0)	3 (50.0%)	1.000
Smoking	5 (83.3%)	1 (16.7%)	0.152
Chronic renal failure	1 (33.3%)	2 (66.7%)	0.559
Abdominal pain	6 (54.5%)	5 (45.5%)	0.819
Lumbar pain	2 (66.7%)	1 (33.3%)	1.000
Claudication	1 (50.0%)	1 (50.0%)	1.000

Anatomic zones of dissection varied between patients. Three (16.6%) patients presented IAAD in the suprarenal aorta and infrarenal aorta, five (27.7%) patients in the infrarenal aorta only, and 10 (55.5%) patients in the infrarenal aorta and the iliac arteries.

Seven (38.8%) patients presented chronic dissection, and 11 (61.1%) patients had acute dissection, and none had subacute dissection. The median time of onset of symptoms to treatment was 13.5 months (range: 3-24 months) and 14 days (1-14 days) in the chronic and acute groups, respectively.

From the chronic group, three patients were treated conservatively at first. Conservative treatment was given first in a patient with known AAA and recent IAAD, at 3 months of follow-up the aortic diameter had grown 5 mm. Open aortic repair was performed in this patient. (Figure 2) In another patient, at 24 months follow-up, right common iliac artery had dilated to 34 mm, from 20 mm, and in the other patient, the aortic diameter increased more than >10 mm in a year (from 41 mm to 54 mm); hence, EVAR was performed in both of them. In another patient with a 56 mm AAA and IAAD an EVAR was done six months after coronary bypass surgery. Two other patients were misdiagnosed with radiculopathy due to lumbar pain and claudication three months before a definitive diagnosis was made. In one of them, bare metal kissing stents were placed, and in the other patient with Marfan syndrome, open repair was performed. (Figures 3 and 4) In one patient, conservative treatment was given and at 15 years of follow-up the patient is asymptomatic with no changes seen in CT scan (Figure 5).

OPEN IN VIEWER

Figure 2.

53-year-old male patient with abdominal aortic aneurysm with subsequent isolated abdominal aortic dissection. (A) Initial CT scan. White arrow showing abdominal aortic aneurysm of 3.4 cm in diameter without dissection. (B) 3-year follow up CT scan. White arrow showing AAA of 4.7 cm with aortic dissection. (C) 3 months after “B” scan. White arrow showing the AAA which grew 5 mm, now measuring 5.2 cm. (D) CT scan 8 months after open aortic repair. White arrow showing the aortic graft.

OPEN IN VIEWER

Figure 3.

52-year-old female patient who presented buttock claudication due to isolated abdominal aortic dissection. (A) Angiography. White arrow showing aortic dissection. (B) Transoperative intravascular ultrasound, showing true lumen collapsed on the abdominal aorta. (C) Final angiography after kissing 8 mm × 80 mm Everflex ® (Medtronic, Santa Rosa, CA) stents placed.

OPEN IN VIEWER

Figure 4.

65-year-old male patient with Marfan syndrome with isolated abdominal aortic dissection and 49 mm abdominal aortic aneurysm. Asterisk showing dissection flap. P: proximal aorta, D: distal aorta.

OPEN IN VIEWER

Figure 5.

63-year-old female patient with isolated abdominal aortic dissection with conservative treatment. (A) Initial CT scan. White arrow showing abdominal aortic dissection. (B) 15-year follow-up CT scan. White arrow showing same abdominal aortic dissection without changed in aortic diameter.

Overall, definitive treatment included conservative, endovascular, or open approaches. Five (27.7%) patients, all except one, from the acute group were treated conservatively with blood pressure and pain control. Endovascular surgery was performed in eight (44.4%) patients and open surgery in five (27.7%) patients.

In the open surgery group, four patients underwent an aorto-biliac bypass, and one patient had an aorto-bihypogastric artery bypass with reimplantation of the external iliac arteries. The median operative time was 300 minutes (range: 150-480 min), and the median operative blood loss was 1200 mL (range: 800-3000 mL). One patient presented urinary retention on POD 6, treated with a Foley catheter. Another patient had melena 12 hours postoperatively due to jejunal diverticulosis treated with double balloon enteroscopy and sclerotherapy. The median length of stay was 7 days (range 3-9 days).

Seven patients of the endovascular group underwent endovascular aortic repair (EVAR), four with right hypogastric embolization. In one patient, kissing 8 mm × 80 mm Everflex ® (Medtronic, Santa Rosa, CA) stents were placed. Median operative time was 90 minutes (range: 50 min-150 min). There was one early post operative complication, on 6th post operative day, a femoral pseudoaneurysm was treated by femoral cutdown and repair, and there was one late postoperative complication, a type 3 endoleak 14 years after EVAR, treated with a Zenith, Spiral Z ® (Cook Medical, Bloomington, IN, USA) iliac limb. Median length of stay was 4 days (range: 1-7 days).

Overall, the complication rate was 22.2% (n = 4), and the mortality rate was 0%. Median follow-up was 36 months (range: 6-240 months). Complete remodeling was seen in all patients except two patients who underwent conservative treatment, who one had partial remodeling and the other one, no changed.

Discussion

The present study describes a single-center experience treating symptomatic or aneurysmal IAAD. IAAD is an uncommon disease, with the largest metanalysis composed of 482 patients. An estimated 91% of them occur spontaneously. ⁷ Other etiologies included traumatic and iatrogenic origins. ⁴ Moreover, IAAD has also been described secondary to Takayasu disease. ⁹ In the present study and similar to other published studies; a male predominance was seen.^6,10,11

Risk factors for IAAD include hypertension, smoking, and hyperlipidemia, all of which induce endothelial damage and permanent inflammatory reactions promoting atherosclerosis and, subsequently, aortic dissection.^3,12,13 In a study of 32 patients with IAAD, 69% of the patients had hypertension, 78% were smokers, and 81% had dyslipidemia. ⁸ Similarly, Zlatanovic et al. ⁵ reported a 90% rate of hypertension and a 60% rate of active smoking. Hypertension was present in more than two-thirds of our patients and smoking in one-third of them. It is worth noting that these two risk factors were more frequently encountered concomitantly in patients who presented with aneurysmal disease; however, no statistically significant difference was found.

The morphology of IAAD is different from the typical type B aortic dissection (TBAD), where the true lumen tends to collapse due to compression of the false lumen. ¹⁴ Li et al. ⁴ found an uncollapsed true lumen in patients with IAAD, describing true and false lumens of similar diameters. They hypothesized that since the abdominal aorta is distal to the heart, this segment is subject to lower blood pressure than the aortic arch and consequently, after the tear, perfusion of the false lumen is weaker than in the proximal aorta. In the present series 2 patients presented claudication due to true lumen collapsed and dynamic obstruction. On one patient, dynamic obstruction was confirmed using IVUS.

IAAD’s most common symptoms include abdominal or lumbar pain, and it is not uncommon for patients to present with claudication.^2,4 However, increase in imaging studies has led to many asymptomatic patients being incidentally diagnosed. Li et al, ⁴ Bockler et al, ⁶ and Faries et al ³ reported high rates of asymptomatic patients in their studies; 72.7%, 55%, and 67.6%, respectively. Also, in two metanalyses, there were 41% and 46% of asymptomatic patients.^2,7 On the contrary, in the present study, most patients were symptomatic, with abdominal pain as the most frequent symptom. Zlatanovic et al. ⁵ and Jawadi et al. ¹⁵ reported 90% and 62% rates of patients with abdominal pain, and in the IRAD registry, the authors found abdominal pain, mesenteric ischemia, and limb ischemia to be more common than in patients with TBAD. ¹ Claudication was present in 2 of the patients of the present series, and the two of them were wrongly diagnosed first as radiculopathies. Similarly, in other studies, between 10% and 20% of the patients with IAAD referred claudication.^3,4,7,16,17

Prior aortic dilatation, or AAA, has been previously described as a risk factor for IAAD. Sen et al. ¹¹ reported a 57% rate of previous aortic dilatation in patients with IAAD. Other authors have described this relationship to be present in 16.7%, 19%, 27.8%, and up to 48% of the patients with IAAD.^1,3,6,15,18 In the metanalysis of Liu et al., ⁷ a concomitant AAA was found in 28% of the cases. ⁷ Zlatanovic et al. ⁵ reported a concomitant AAA in half of their IAAD patients, all symptomatic and treated with aortobiliac bypass. Similarly, in the present study, 55.5% of the patients presented with AAA. Some patients had IAAD when the AAA diagnosis was made, and others developed IAAD several months after the initial AAA diagnosis. It remains unclear if dilatation of the arterial wall favors intimal rupture and consequently dissection, or if aortic dilatation is the consequence of the aortic dissection.^1,4,19 Some authors have stated that a concomitant AAA with IAAD indicates intervention since this coexistence can elevate the risk of aortic rupture.^1,10,20 Cambria et al. ²¹ published a case series of patients with IAAD and aortic aneurysms; five of them had an infrarenal aneurysms, and four of them died due to aortic rupture. In a study of 37 patients with IAAD, of whom 18 had a concomitant AAA, the mean diameter of the AAA was 43.8 mm, and EVAR was done in 10 of them. ³ Correspondingly, in the present study, the median diameter of AAA was 49.5 mm, and all of them were operated by either endovascular or open repair. Open and endovascular treatments have been proven effective for treating AAA with concomitant IAAD. Zlatanovic et al. ⁵ did open surgery on 10 patients with IAAD, of which 5 had a concomitant AAA. Open surgery is a valid option for young patients on whom the dissection tear is at the level of the renal arteries since securing the proximal segment of a dissected aorta with a suprarenal fixation graft might lead to retrograde dissection. Furthermore, Kalko et al. ²² successfully performed aorto-biliac bypass in 8 patients with IAAD and AAA. Likewise, EVAR has been reported in many IAAD series, with and without concomitant AAA.^1,3,15,23,24 Wang et al. ²⁵ did endovascular repair on 33 patients with IAAD and compared acute and chronic groups. They found that aortic remodeling was poorer in the chronic group and attributed this primarily due to the rigid and fibrotic intimal flap seen in chronic dissections.

EVAR in IAAD differs from common treatment for infrarenal AAA due to the different morphologies; for example, the aortic bifurcation is usually narrower in IAAD than in AAA; furthermore, the aorta in IAAD is more fragile, and post deployment balloon dilatation or excessive oversizing in these cases might increase the risk of retrograde dissections.^8,25

In the present series, one of the patients with IAAD and AAA who underwent a successful EVAR was intervened 14 years later due to a type 3 endoleak. It is known endovascular repair at long-term follow-up is not absent of complications, and close follow-up is mandatory. The best strategy for these patients depends on the expertise of each center, and drawing firm conclusions on which treatment is better is not feasible due to the small number of patients with this uncommon condition. We suggest open surgery in patients with unsuitable anatomy for endovascular repair, in young patients, or patients with known collagenopathies.

Indications for invasive treatment in patients with IAAD include acute aortic dilatation with impeding rupture, malperfusion, acute limb ischemia or persistent claudication, presence of unrelieved abdominal or back pain, or uncontrolled hypertension despite aggressive anti-impulse therapy.^1,5 Nowadays, conservative treatment is considered the initial treatment for most patients; however, intervention rates in this group of patients have been reported as high as 18%. ⁷ These patients must be monitored closely since persistent perfusion through the entry tear can lead to poor remodeling of the false lumen, consequently causing aneurysmal dilatation. ¹⁴ In the present study, two patients were intervened after conservative treatment due to aneurysmal dilatation, and one patient has been monitored for 15 years, without the need of any intervention. Our follow-up protocol includes CT scans in unoperated patients: at 1 month post-discharge, then at 3 months, 6 months, and 12 months, followed by yearly scans. For operated patients, CT scans are scheduled at 1 month, 6 months, and 12 months postoperatively, followed by yearly scans, as recommended by the American Heart Association in their 2022 scientific statement on aortic dissection. ²⁶ In asymptomatic patients, CT scan features may be assessed to predict the timing of dissection. Orabi et al. ²⁷ analyzed and compared imaging features of patients with acute and chronic dissections. They found statistically significant features of acute dissections, including periaortic confluent soft tissue opacity and a curved, highly mobile dissection flap. In contrast, chronic dissections typically showed a thick flap, a dilated false lumen, and calcification of the outer wall of the false lumen. Figure 6 displayes a proposed flowchart diagram for the management and follow up of patients with IAAD.

OPEN IN VIEWER

Figure 6.

Flowchart diagram for the management and follow-up of patients with isolated abdominal aortic dissection.

Aortic dissection might be misdiagnosed with an aortic ulcer or atherosclerotic aortic disease. ¹¹ Image studies can help differentiate these entities, such as CT angiogram, MRI, angiography, and IVUS. ⁸ The latter can help determine the true and false lumen when performing endovascular repair.^28,29 IVUS was used in one patient of the present series to confirm the correct position of the kissing stent within the true lumen.

Limitations include the study’s retrospective nature and the small sample size, which makes the possibility of performing multivariable analyses unfeasible. Furthermore, some other unoperated asymptomatic patients might have been followed in the outpatient clinic during the last two decades without a record.

Conclusion

Isolated aortic dissection of the abdominal aorta is an uncommon condition with different clinical presentations. Treatment should consist in conservative approach first and, if a concomitant AAA is encountered, symptoms persist, or aortic dilatation is seen; invasive treatment by open or endovascular approach might be considered. More studies describing the natural history of AAA and its association with IAAD are warranted, as well as further research reporting long-term outcomes on aortic remodeling after different treatment modalities.