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Interact CardioVasc Thorac Surg 2009;8:398-401. doi:10.1510/icvts.2008.198051 © 2009 European Association of Cardio-Thoracic Surgery
Spontaneous isolated dissection of the abdominal aorta: single-center experienceFirst Department of Thoracic and Cardiovascular Surgery, Aristotle University of Thessaloniki, AHEPA University Hospital, Thessaloniki, Greece Received 4 November 2008; received in revised form 13 December 2008; accepted 16 December 2008
*Corresponding author. Sakellaridi 25, 542 48 Thessaloniki, Greece. Tel.: +302310329729; fax: +302310329729.
Isolated abdominal aortic dissection is a rare clinical entity. We report a single-center experience with six patients with acute isolated abdominal aortic dissection managed during a period of seven years. The patients' median age was 62 years and they were predominantly male. All patients presented acutely with abdominal pain, one with hypovolemic shock due to aortic rupture, two with acute lower limb ischemia and one with buttock necrosis. Interestingly, one major symptom was astasia observed in four patients that resolved postoperatively. Computed tomography scan of the thoracic and abdominal aorta was the main diagnostic tool in all patients. Treatment consisted of open repair in three cases and endovascular repair with stent-graft deployment in the remaining three patients. One patient died postoperatively from multiorgan failure. Although natural history and treatment strategies of isolated abdominal aortic dissection have not been well defined, accurate clinical diagnosis and prompt management are essential to prevent adverse complications. Moreover, sudden development of astasia should alert the physician about this pathologic entity.
Key Words: Aortic dissection; Abdominal; Endovascular
Acute aortic dissection occurs when blood enters to the medial aortic layer through an intimal tear, resulting in separation of the layers of the aortic wall. This process most commonly involves the thoracic aorta and extends in an antegrade fashion to the abdominal aorta. Isolated dissection of the abdominal aorta (IAAD) is rare. It may be classified as iatrogenic, traumatic or spontaneous [1]. The anatomic and clinical features of this entity are different from the classical dissection originating from the ascending or descending thoracic aorta. Natural history and treatment strategy are poorly defined, based mainly on case reports and small series [2]. We report the experience of our institution in the diagnosis and management of spontaneous IAAD. Special emphasis is given on the clinical presentation of this rare entity and the treatment options that can be applied to in order to avoid adverse complications.
During a time period from January 2000 to December 2006 six patients were referred to our institution, which covers a population area of three million inhabitants, with IAAD. They were all Caucasian, predominantly male (5/6, 83.3%) with a median age of 62 years (range: 53–72 years). All patients experienced sudden onset of severe abdominal pain radiating to the back in four cases (66.7%) or the buttocks in two. Interestingly, four out of six patients developed astasia (disorder of gait and posture) associated with loss of function of the lower limbs. One patient presented in critical condition in hypovolemic shock from a ruptured dissecting aneurysm (Fig. 1), while another patient developed acute lower limb ischemia.
Hypertension was the most common potential predisposing factor present in five patients. Four patients were heavy smokers, two had coronary artery disease, while one patient had chronic pulmonary disease and one with a ruptured dissecting aneurysm had a history of necrotizing pancreatitis. Half of the patients were obese (BMI>40 kg/m2). On clinical examination no abdominal mass was identified even in patients with a dissecting aneurysm. One patient presented with stage IIIa ischemia of the right leg, absent femoral pulse and skin necrosis of the right buttock. Another patient had absent femoral pulses bilaterally without any associated ischemic lesions. Diagnosis of IAAD was established with contrast enhanced CT angiography of the thoracic and abdominal aorta in all cases, where the classic appearance of the ‘double- barreled’ abdominal aorta was identified (Fig. 2a). Aneurysm formation was evident in four patients with diameter ranging from 3.6 to 6.5 cm. In all cases dissection was limited at the abdominal aorta. No evidence of thoracic aortic involvement was identified (Fig. 2b). The dissection originated at the infrarenal aorta in four patients while the entry point was located at the level of the renal arteries in two (Fig. 3). In three patients dissection was extending bilaterally to the iliac arteries.
Open repair was the procedure of choice in half of the patients (3/6) in the early period of the study, while in the remaining an endovascular approach was applied. An aortobifemoral bypass with a synthetic 18/9 mm bifurcated polyester graft (Gelsoft, Sulzer Vascutek, Renfrewshire, Scotland) was performed in one patient who presented with clinical signs of acute limb ischemia. Embolectomy of the femoral artery was performed before completion of the distal anastomosis in order to establish flow to the affected limb. In another patient a straight Dacron 20 mm tube graft was used for infrarenal aorta replacement. In a female patient who presented with a 5-cm ruptured dissecting aneurysm an extra-anatomic axillobifemoral bypass was performed. She had a history of necrotizing pancreatitis with pseudocyst formation that required surgical debridement. The infrarenal abdominal aorta was ligated, supported with a flap of anterior longitudinal ligament and blood supply to the lower limbs was reestablished with an 8-mm axillobifemoral synthetic graft. In the endovascular group all three patients had an aorto-uniiliac stent graft (Endofit, LeMaitre Vascular Inc, Burlington, MA, USA) implanted through a groin incision. The proximal bare stent allowed for suprarenal fixation in all cases without occlusion of the renal arteries. Restoration of flow to the contralateral limb was achieved with a femoro-femoral crossover bypass with an 8-mm ringed ePTFE graft (Sulzer Vascutek, Renfrewshire, Scotland). Thirty-day mortality was 16.7% (1/6 patients). This was due to multiorgan failure on the fourth postoperative day in the setting of a ruptured dissecting aneurysm. Postoperative complications consisted of one case with acute renal failure that resolved conservatively without hemodialysis and one reoperation for above-knee ambutation in the patient who presented with acute lower limb ischemia. Disorder of posture and gait observed preoperatively resolved completely after surgical treatment in all patients.
Spontaneous IAAD is a rare clinical condition. In the International Registry of Acute Aortic Dissection (IRAD), 1.3% of the enrolled patients were identified as having IAAD [3]. The clinical experience on this condition is based on case reports and small case series, the largest of which is the IRAD cohort that consists of 18 patients. A review of the literature by Farber et al. in 2004 identified 51 cases in the English literature [4]. In our series six patients were identified with spontaneous IAAD in a 7-year period, accounting for about 4% of all patients diagnosed with acute aortic dissection in our department, which covers the area of Northern Greece. The usual mean age at presentation is at the fifth or sixth decade of life, which is similar to that observed in our series. The clinical form of presentation of acute IAAD is usually non-specific. The most common presenting symptom is sudden onset of abdominal pain radiating to the back and to the buttock [5]. This was recorded in all patients in our series. Interestingly, in the majority of our series, astasia was noticed that resolved after treatment of the dissection. It could be attributed to transient ischemic peripheral neuropathy or spinal cord stunning [6]. Acute lower limb ischemia and intermittent claudication are also encountered. In the reported case series one patient presented with critical limb ischemia. Other reported symptoms include hematuria, melena and hypovolemic shock, which are related with increased morbidity and mortality rates [7]. The majority of patients present in an acute setting, which conforms to all patients diagnosed with IAAD in our series. Acute aortic rupture is a serious complication associated with a reported mortality rate of 17–28% [3, 4]. In our series one patient who presented with major rupture died. The dissection entry site in IAAD is usually located between the renal arteries and the inferior mesenteric artery. Distal extent of dissection can be at the level of the aortic bifurcation or it may involve one or both common iliac arteries [2]. This was identified in half of our patients. Involvement of the iliofemoral segment increases the likelihood of ischemic complications of the distal extremities. Diagnostic studies include CT-scan, ultrasound, MRI and angiography [8, 9]. CT with IV contrast can be easily performed in the acute setting and can identify the characteristic double aortic lumen, patency of both lumens, aortic dilatation and the presence of calcification or possible extravasation of blood due to rupture. Evaluation of the thoracic aorta is important in order to exclude abdominal extension of a thoracic dissection. Angiography provides excellent information regarding visceral and limb perfusion as well as localization of an intimal tear that cannot be identified by CT. In our series diagnosis and appropriate treatment planning relied exclusively on CT angiography. With the increased availability of CT, angiography is not indispensable in diagnosing IAAD. When involvement of the suprarenal portion is suspected by non-invasive studies, angiography is advised for accurate definition of branch vessel involvement. Indications for operative intervention in patients with IAAD include aortic rupture, lower extremity ischemia, unremitting pain, associated aortic aneurysm and prevention of future aneurysmal degeneration [4]. Presence of IAAD and abdominal aortic aneurysm is an absolute indication for aortic repair due to the significant risk of rupture that has been noticed. Dissection weakens the integrity of the aortic wall and according to the law of Laplace increases wall tension applied on the abdominal aorta on the basis of both a reduction in the vessel wall thickness and increase in luminal radius. The optimal size of the aneurysm that requires intervention is poorly defined. However, the threshold for intervention should probably be lowered in patients at good risk. Farber et al. recommend considering all patients at good risk with IAAD and an aortic diameter exceeding 3 cm for elective repair [2]. Asymptomatic patients with a non-dilated aorta should be treated with antihypertensive medication. Annual imaging studies with abdominal CT-scan or MRI should be performed to evaluate possible aortic dilatation. Operative intervention includes open or endovascular repair of the abdominal aorta [10]. This decision is greatly influenced by anatomical conditions together with the surgeon's experience. As dissection may extend to the iliac arteries, aortobifemoral grafting is the operation of choice. Endovascular treatment of IAAD has been associated with a high rate of technical and clinical success with reduced morbidity and mortality rates in experienced centers [11]. Bifurcated and aortomonoiliac devices can be used, depending on the anatomic morphology of the aorta and iliac artery involvement. The choice for an aortomonoiliac stent-graft in our series was based on the experience gained with the use of the specific device, especially in short or conical proximal necks [12]. Conclusively, IAAD is a rare clinical condition that may have a number of clinical presentations with potential serious adverse effects. It should be considered in the differential diagnosis of any patient with an acute onset of abdominal pain radiating to the back and the buttocks together with presence or absence of a pulsatile abdominal mass or signs of limb ischemia. Moreover, as reported in our series, sudden development of astasia, even in the absence of the above-mentioned symptoms, should warn the physician about IAAD. Although the natural history of this process is not yet clearly described, early diagnosis and prompt initiation of treatment are key components in avoiding lethal complications.
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Abstract
1. Introduction
