An Unusual Case of Acute Thrombosis of Abdominal Aortic Aneurysm without Acute Limb Ischemia

Thrombosis in the pathogenesis of abdominal aortic aneurysm

Background

Abdominal aortic aneurysms (AAAs) are a relatively common vascular pathology of the elderly with high morbidity potential. Irreversible degeneration of the aortic wall leads to lethal rupture if left untreated. Nearly all AAAs contain intraluminal thrombus (ILT) to a varying degree, yet the mechanisms explaining how thrombosis is disturbed in AAA are relatively unknown. This review examined the thrombotic complications associated with AAA, the impact of thrombosis on AAA surgical outcomes and AAA pathogenesis, and the use of antithrombotic therapy in the management of this disease.

Methods

A literature search of the PubMed database was conducted using relevant keywords related to thrombosis and AAAs.

Results

Thrombotic complications are relatively infrequent in AAA yet carry significant morbidity risks. The ILT can impact endovascular aneurysm repair by limiting anatomic suitability and influence the risk of endoleaks. Many of the pathologic mechanisms involved in AAA development, including hemodynamics, inflammation, oxidative stress, and aortic wall remodeling, contain pathways that interact with thrombosis. Conversely, the ILT can also be a source of biochemical stress and exacerbate these aneurysmal processes. In animal AAA models, antithrombotic therapies have shown favorable results in preventing and stabilizing AAA. Antiplatelet agents may be beneficial for reducing risks of major adverse cardiovascular events in AAA patients; however, neither antiplatelet nor anticoagulation is currently used solely for the management of AAA.

Conclusions

Thrombosis and ILT may have detrimental effects on AAA growth, rupture risk, and patient outcomes, yet there is limited understanding of the pathologic thrombotic mechanisms in aneurysmal disease at the molecular level. Preventing ILT using platelet and coagulation inhibitors may be a reasonable theoretical target for aneurysm progression and stability; however, the practical benefits of current antithrombotic therapies in AAA are unclear. Further research is needed to demonstrate the extent to which thrombosis impacts AAA pathogenesis and to develop novel pharmacologic strategies for the medical management of this disease.

A poor outcome in non-occlusive thrombo-embolic limb ischaemia related to the dislocation of mural thrombus from an abdominal aortic aneurysm

Background

Acute thrombosis of an abdominal aortic aneurysm with acute limb ischaemia is an unusual complication and is associated with high mortality. Dislocation of the intrasaccular mural thrombus could be one of the mechanisms. For the most part, acute limb ischaemia presents with absent pulses, compatible with the clinical findings, which include pain, paraesthesia, and paralysis. Herein, we report a rare condition with detectable distal pulses in advanced limb ischaemia due to poor perfusion caused by the dislocation of mural thrombus from an abdominal aortic aneurysm.

Case presentation

A 74-year-old male patient with underlying hypertension and chronic renal disease presented at the emergency room with bilateral lower limb paralysis after falling on his back in the bathroom an hour prior. He reported numbness and weakness of his lower limbs, which was gradually worsening, over the past week. Physical examination showed cyanotic mottling of the lower limbs with paralysis. However, the dorsalis pedis pulse was intact. Computed tomography angiography showed a 7.3 cm abdominal aortic aneurysm containing highly irregular mural thrombus in the early phase, with slow perfusion of the contrast medium in the arteries below the bifurcation during the delayed phase. After traumatic spinal injury was excluded, an emergent endovascular aneurysm repair was performed. Although vital signs were initially stable post-surgery, both lower limbs were still paralysed and did not improve. He then experienced reperfusion injury with metabolic acidosis. There was no urine output despite intravenous hydration. Laboratory data included potassium 7.7 mEq/L, lactate 110 mg/dL, white blood cells 23,700/uL, and myoglobin 46,590 ng/mL. Even under critical medical care and continuous venovenous hemofiltration, his hemodynamic status worsened. He developed hypotension and needed endotracheal intubation because of loss of consciousness and respiratory failure. The patient finally died due to ventricular tachycardia even after several rounds of cardiopulmonary resuscitation with cardioversion.

Conclusion

The unusual clinical presentation of detectable lower limb pulses in advanced limb ischaemia showed that poor blood perfusion related to dislocation of mural thrombus in abdominal aortic aneurysm might mislead clinicians and delay accurate diagnosis and treatment.

Acute Thromboembolism from Trauma in a Patient with Abdominal Aortic Aneurysm

Case Presentation

A 64-year-old man with a history of a 5.5-centimeter (cm) abdominal aortic aneurysm (AAA) presented to the emergency department (ED) complaining of severe back pain after climbing over a fence and falling a distance of eight feet. Prior to arrival, the prehospital paramedics reported that the patient did not have palpable pulses in either lower extremity. The initial physical examination in the ED was significant for absent dorsalis pedis pulses bilaterally as well as absent posterior tibialis pulses bilaterally and cold, insensate lower extremities. Point-of-care ultrasound identified an approximate 7-cm infrarenal AAA with a mural thrombus present. After receiving several computed tomography (CT) studies including CT head without contrast and CT angiography of the chest, abdomen and pelvis, the patient was diagnosed with acute thrombosis of AAA and associated thromboembolic occlusion of both his right and left distal iliac vessels causing bilateral acute limb ischemia. He immediately received unfractionated heparin and was admitted to the hospital for embolectomy and intra-arterial tissue plasminogen activator.

Discussion

Acute thrombosis of AAA and subsequent thromboembolic events are a rare but significant complication that can occur in patients with a history of AAA. Thromboembolic events may occur spontaneously or in the setting of blunt abdominal trauma. Common presenting signs and symptoms include distal limb ischemia and absent femoral pulses. Timely management and recognition of this rare complication is vital as this condition can ultimately result in limb loss or death if not treated in a timely manner. Heparinization after confirmation of non-ruptured AAA as well as vascular surgery, and therapeutic and vascular interventional radiology consultations are key steps that should be taken to decrease patient morbidity and mortality.