High-flow fistula: a problem not easy to handle


High-output cardiac failure is a well-known phenomenon of high-flow fistula in hemodialysis patients. The definition of “high flow” is varied and almost always connected to proximal arteriovenous fistulas (AVF).
High flow access is a condition in which hemodynamics is affected by a greater rate of blood flow required for hemodialysis and this can compromise circulatory dynamics, particularly in the elderly in the context of pre-existing heart disease.
High access flow is associated with complications like high output heart failure, pulmonary hypertension, massively dilated fistula, central vein stenosis, dialysis associated steal syndrome or distal hypoperfusion ischemic syndrome.
Although there is no single agreement about the values of AVF flow volume, nor about the definition of high‐flow AVF, there is no doubt that AVF flow should be considered too high if signs of cardiac failure develop.
The exact threshold for defining high flow access has not been validated or universally accepted by the guidelines, although a vascular access flow rate of 1 to 1.5 l/min has been suggested.
Moreover, even lower values may be indicative of relatively excessive blood flow, depending on the patient’s condition.
The pathophysiology contributing to this disease process is the shunting of blood from the high-resistance arterial system into the lower resistance venous system, increasing the venous return up to cardiac failure.
Accurate and well-timed diagnosis of high flow arteriovenous hemodynamics by monitoring of blood flow of fistula and cardiac function is required in order to stop this process prior to cardiac failure.
We present two cases of patients with high flow arteriovenous fistula with a review of the literature.

Keywords: Blood flow, cardiac failure, vascular access, hemodialysis

Sorry, this entry is only available in Italian.


Una insufficienza cardiaca ad alta gittata può essere la conseguenza di svariate condizioni patologiche quali anemia, sepsi, ipertiroidismo, beri beri. Un’altra causa nota, in alcuni pazienti emodializzati, può essere la presenza di una fistola arterovenosa (FAV) in relazione al notevole aumento del flusso dell’accesso vascolare con conseguente eccessivo carico di lavoro cardiaco, insufficienza cardiaca congestizia ed ipertensione polmonare [13].

Come è ben noto, la sindrome uremica è associata ad un aumento della morbilità e mortalità cardiovascolare; il rischio di morte in un paziente emodializzato con insufficienza cardiaca è del 33%, 46% e 57% rispettivamente a 12, 24 e 36 mesi dopo l’inizio della terapia dialitica secondo i dati del Renal Data System statunitense [4]. Un’insufficienza cardiaca congestizia può manifestarsi nel 25-50% dei pazienti emodializzati, in particolare nei pazienti con “fistola artero-venosa ad alto flusso”. 

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