Flowband Applications

The ability to precisely control band diameter allows one to optimally balance AV and downstream flow for each patient. While monitoring AV flow and distal perfusion (and heart rate, etc.), one can reduce AV flow to the range 500-900 ml/min in an incremental yet stable fashion. Observing the effect on distal perfusion and the heart, one can maximize distal perfusion and prevent over banding. 

  There is no need to operate a fistula wide open. Placing a midpoint band creates high- and low-pressure segments. This configuration reduces overall flow as well as the pressure returning to the right heart. This technique was first published as a solution to a low-flow steal scenario. (12)  

Central banding may also reduce the ischemic stunning experienced with dialysis. (13) The lower outlet pressure could also reduce pulmonary hypertension. 

The Flowband can gradually restrict a centrally placed band while monitoring upstream and downstream pressures to establish a patient-specific level of banding. 

Structural heart damage is proportional to AV flow. The LVM has been shown to increase by 2.1g per 100 ml access flow. (8) 

Median flows from 500-900 ml/min have been shown to induce reduce overall structural heart changes (8-10) Three studies divided flow values into groups to assess the cardiac impact. 

One study (8) divided the flow into 2 ranges, above and below the median flow of 906 ml/min.

The < 906 group had the same risk of LVH as the closed group. The > 906 group had 2.8x the

risk of LVH as the lower flow group.  

Another group (9) divided the flow into 2 ranges, with a median of 680 ml/min. The > 680 group had significant changes in right heart function and increased RAA. The < 680 group had a lower LVMI and RAA.

Another study (3) saw a graded increase in LVEDD with flow.

While flow reduction is very effective in relieving heart failure (14), the presence of fistula may be a predictor of HF in KT patients. (11). The incident rate of de novo HF after transplantation was 58/1000 person-years in AVF patients vs. 33/1000 person-years in non-AVF patients.

Controlled flow reductions are possible with Flowband. Reducing AV flow by only 300ml/min provides an additional 110 gallons of blood per day to the systemic circulation.

While access ligation has been shown to result in regression of LV hypertrophy, (15,16) significant and controlled flow reduction may also be expected to reverse some cardiac changes. 

The presence of a patent access has been shown to rob blood from transplanted kidneys. The perfusion of kidney grafts, as measured by the resistive index (RI), is increased by access closure or even temporary manual occlusion. (1,2)  The increased perfusion is proportional to the access flow. An increase in RI ≥10% over the first year was found to be an independent risk factor for graft loss with a hazard ratio of 6.2. (3) 

Closure of a patent access improves both kidney graft and cardiac function, with elevation of diastolic BP, reduced NT-proBNP levels, reduced LV and atrial dimensions, and stability of the eGFR slope.(4)  The presence of a fistula may also be a predictor of HF in KT patients. The incident rate of de novo HF after transplantation was 58/1000 person-years in AVF patients vs. 33/1000 for  non-AVF patients. (11)

The 5-year eGFR data of Weekers shows the detrimental effect of an open access on kidney graft function. (5) A 5-year graft survival study (open vs. closed accesses) confirms this: 60% with patent access, and 75% with closed accesses.(6) Also, the 5-year impact of ligation on cardiac structure shows a persistent regression of the LVM and LVM index. (17)

Flow Limitation – the Alternative to Ligation 

The work of Gkotsis and Jennings (7) demonstrated the benefit of reducing AV flow for KT patients. Twelve fistulas were banded to a flow of about 600 ml/min. All were patent at 19mo., and 2 of 12 were successfully reused after graft failure. 

To conveniently reduce flow to the 500-800 ml/min range, one needs to control the band diameter to less than 0.5mm.