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.