Discussion

This case report illustrates the growing risk of thromboembolism from an AVF in ESRD patients. Risk factors for thromboembolism include a sedentary life-style, comorbidities such as atrial fibrillation, congestive heart disease, cancer, and predisposing factors such as the intrinsic renal disease itself, including nephrotic disorder and systemic lupus erythematosus.1 A significant number of these patients are the elderly and this number most predictably will increase.2
Traditionally, dialysis patients were believed to be protected by “uremic coagulopathy”, from developing VTE.3 Both a bleeding tendency as well as thrombotic events, such as AVF thrombosis, DVT and peripheral arterial occlusive disease have been noted in ESRD. More recent studies indicate that patients with CKD have a higher risk of developing VTE than those with normal kidney function.1 Factors established to be contributing to thrombotic events include hemodialyzer-induced platelet aggregation, increased release of Von Willebrand, thromboplastin, reduced protein C, increased plasminogen activator inhibitor-1, elevated oxidative stress, increased homocysteine, fibrinogen and activity of factors VII, VIII, and IX–XII.4 In addition, use of erythropoietin to correct anemia and/or blood transfusion has been shown to increase the risk of DVT.4 Frequent trauma from repeated AVF cannulation might be another cause for the development of thrombus in these patients.
Majority of dysfunctional fistulas including stenosis and thrombosis are treated by interventional approach. Currently the percutaneous modalities of treatment include mechanical thrombectomy, pharmaco-mechanical thrombolysis and infusion thrombolysis.5,6 These are invaluable alternatives to surgical thrombectomy with the advantage of being less invasive and reducing the patient’s venous reserve.7 However, the thrombi in the aneurysm can age and organize and may become resistant to both thrombolysis and percutaneous thrombectomy devices. Dilated endoluminal space restricts maneuverability during intervention and decreases the effectiveness of percutaneous thrombectomy devices. In order to overcome these issues and to better the technical success rate of recanalization, minimal venotomy with antegrade and retrograde milking has been introduced as an alternative.8
The volume of thrombus in a thrombosed AVF has been estimated to be less than 3-9 ml.9,10 The clinical implications, however, are influenced by other factors such as compromised cardiopulmonary reserve and release of various clinical mediators that initiate and perpetuate a systemic cascade of inflammation. In the general population, 6-month mortality rates in clinically stable patients with pulmonary embolism without major comorbidity are below 5%.11 Moreover, there is considerable concern with respect to sustaining even a small pulmonary emboli in patients with diminished cardiac and pulmonary reserve, a common entity in the dialysis patient population.4
Literature review revealed one case in which massive pulmonary embolism occurred following fistula thrombectomy in a patient with prior thromboembolic disease.12 Our patient had no previous history of VTE but her cardiac function appeared compensated in the background of moderate pericardial effusion. The pulmonary embolism in all likelihood tipped the balance in favor of decompensation.