Acute infrarenal aortic occlusion

Abstract

Acute aortic occlusion (AAO) is an uncommon but potentially devastating vascular emergency with reported perioperative mortality rates of up to 75%. We present the case of AAO in a 69-year-old woman who was transferred to our institution after presenting with sudden onset bilateral acute limb ischaemia. Imaging showed a completely obstructed aortoiliac segment with renal infarcts. She was treated successfully with aortoiliac over the wire thrombectomy.

Background

Acute aortic occlusion (AAO) is an uncommon vascular emergency which carries a high degree of morbidity and mortality. Previous studies report a 30-day mortality between 20% and 75% and major complication rates of 70%.^1–3

The most common causes of such aortic obstructions are either thrombotic, from in-situ thrombosis of severe atherosclerotic disease or abdominal aneurysm thrombosis or due to a large saddle embolism. Patients often present with sudden onset lower limb pain, sensory deficits, weakness and paralysis.⁴ AAO requires prompt recognition and intervention for revascularisation. Traditional methods have included open aortic surgery, extra-anatomic bypass, thrombolysis or thromboembolectomy. Increasing expertise and availability of endovascular techniques has led to a recent rise in employment of this modality.²

Due to the significant vascular compromise that occurs with AAO, it is an important condition to be recognised by any physician who may be responsible for assessing patients presenting with the above symptoms.

Case presentation

A 69-year-old woman was transferred to our institution from a peripheral hospital. She initially presented to the emergency department with new onset of bilateral leg pain and numbness commencing 1 hour previously. The patient’s medical history was significant for atrial fibrillation, rheumatic heart disease, hypertension, dyslipidaemia and nephrotic syndrome. She had also recently undergone a thoracentesis requiring a temporary discontinuation of her anticoagulant therapy.

Investigations\

At the peripheral hospital the patient had a computed tomography angiography which revealed a complete aortoiliac occlusion (figure 1) and bilateral renal infarcts (figure 2). On examination, the patient’s legs were cool, mottled and distal pulses were non-palpable.

Figure 1.

Acute infrarenal aortic occlusion visualised on coronal CT angiogram image.

Figure 2.

CT angiogram images demonstrating bilateral renal infarcts.

Treatment

An endovascular technique was chosen to treat the patient and she was taken to the operating room within 6 hours of initial presentation of symptoms. The patient received systemic heparinisation. Bilateral arteriotomies were performed on the common femoral arteries and no inflow was demonstrated. Under fluoroscopy guidance, guidewires were advanced bilaterally into the infrarenal aorta. Bilateral over wire Fogarty balloons were used to perform an embolectomy yielding copious thrombus (figure 3). This process was repeated for the profunda and superior femoral arteries bilaterally. Intraoperative angiogram confirmed that the clot had been grossly removed from the distal aorta, common and proximal external iliacs, and the inferior mesenteric artery remained patent. There remained some filling defect in the internal iliacs bilaterally. Following leg reperfusion distal pulses were present by Doppler bilaterally. Due to the short period of ischaemia, fasciotomies were not considered necessary.

Figure 3.

Bilateral over the wire Fogarty balloons visualised intraoperatively.

Outcome and follow-up

The patient’s recovery in hospital was generally uncomplicated. The only immediate perioperative issue was acute kidney injury due to the renal artery infarcts at presentation. Peak creatinine was 134 from 60 at triage, and the patient was initially anuric while in the operating room. The patient did not require haemodialysis and began making urine following fluid resustitution.

The pathology report from removed clot revealed remote and recent thrombus. The cause of the aortoiliac obstruction was believed to be multifactorial. Speculated contributing causes included to the recent temporary discontinuation of anticoagulation with underlying atrial fibrillation, nephrotic syndrome and vascular risk factors (hypertension, dyslipidaemia). Workup revealed no haematological hypercoagulable factors or malignancy. The patient remains on anticoagulation therapy.

At a follow-up visit 1 month after surgery, the patient was not experiencing any symptoms of leg claudication and the ankle–brachial index was 1.18 and 1.14 on the right and left, respectively. By 3 months postoperatively, the patient continued to do well with no major complications.

Discussion

AAO is a rare but life-threatening and limb-threatening vascular emergency. The pathophysiology of AAO differs from that of the more commonly seen chronic aortoiliac disease as a lack of collaterals precludes residual perfusion of the lower extremities. This creates a critical situation requiring a high degree of clinical suspicion by the evaluating physician for prompt intervention. However, due to the non-specific nature of some of neurological symptoms patients present with, including sensory deficits and weakness, AAO can be mistaken for a cerebrovascular accident or spinal pathology.¹ These misinterpretations have been noted to result in delays of diagnosis and appropriate therapy.^{3 5} In this case, there was appropriate recognition of the presenting symptoms at the external hospital with timely imaging, consultation to the vascular surgery service and transport to our centre. Because of this, the duration of time from the patient’s first symptom presentation to the operating room was under 6 hours.

Due to the rarity of the condition, prospective studies comparing the effectiveness of different treatment modalities are lacking, and no official guidelines exist to guide treatment. Recent retrospective studies have been unable to reach a consensus on the superiority of any given method.^{2 3} However, they note that with increased availability and expertise in endovascular techniques, there has been an increase in these procedures.² The most common methods for surgical revascularisation in these cases are major procedures such as axillary-bifemoral bypass or aortobi-iliacal/bifemoral bypass.² Endovascular treatments may offer certain advantages over open surgery including shorter recovery time and decreased length of hospital admission and therefore lower healthcare associated costs.⁶ Further, an endovascular approach may be more appropriate for certain patients such as those presenting with advanced age and greater burden of comorbidities, especially cardiovascular disorders.⁷

Beyond high rates of mortality, survivors of AAO interventions also incur major complications after treatment. One study reported major complications of cardiovascular disorders (34%), major amputation (15%), acute kidney injury (57%) with requiring haemodialysis (22%) and surgical site infection (6.2%). In this study, 42% of patients also required a second operation.³ In the presented case, the only perioperative complications included an acute kidney injury (AKI), not requiring dialysis.

The significance of a hypercoagulable state in precipitating AAO has been previously reported. One case series identified potential aetiologies for increased coagulability in 40% of patients, including antiphospholipid antibody syndrome and malignancy.¹ In this case, the patient presented with significant proteinuria and a serum albumin of 17 g/L. This, coupled with the discontinuation of anticoagulation therapy, potentially created a hypercoagulable state.

In conclusion, AAO is an uncommon but potentially deadly vascular condition which requires a high index of suspicion, timely identification and intervention.

Learning points.

• Acute aortic occlusion (AAO) is a rare vascular emergency that carries a high rate of morbidity and mortality.

• To provide the best opportunity for a good patient outcome following AAO, efficient recognition of the condition, transportation to an appropriate specialist and careful consideration of operative strategy are required.

• Endovascular interventions should be considered for patients presenting with AAO with advanced age and cardiovascular comorbidities.

• Nephrotic syndrome and hypoalbuminaemia should be considered as a possible mechanism that can contribute to a hypercoagulable state