Distensibility of forearm veins in haemodialysis patients on duplex ultrasound testing using three provocation methods.

OBJECTIVE: It is well-known that vasodilatator function is affected in patients with renal failure. We hypothesized impaired venous forearm distensibility in haemodialysis patients. The purpose of this study was to investigate which provocation method generated 'maximal' venous distensibility in the forearm of haemodialysis patients compared to healthy volunteers by using duplex ultrasound. DESIGN: The study group consisted of haemodialysis patients (n=30) and healthy volunteers (n=30). In each participant ultrasound measurements of the venous diameter were performed by using 3 different provocation methods. METHODS: The applied provocation methods were: 1) hydrostatic pressure, 2) venous congestion and 3) hydrostatic pressure and warmth. Significance of differences in mean diameter changes within the groups was assessed with the paired t-test. Significance of differences in mean diameter changes between the groups was compared by using multivariate regression analysis. RESULTS: In haemodialysis patients, the increase in mean diameter after the different methods was: 29% after methods 2 versus 1, 23% after methods 3 versus 2 and 59% after methods 3 versus 1. In healthy volunteers, the mean diameter increase was: 27% after methods 2 versus 1, 29% after methods 3 versus 2 and 64% after methods 3 versus 1. The greatest increase in the mean internal venous diameter among the haemodialysis patients and the healthy volunteers was after the provocation method which combined hydrostatic pressure with warmth (mean difference: 1mm, 95% CI: .57, 1.36; P<.001 and mean difference: 1.4mm, 95% CI: .88, 1.78; P<.001, respectively). After adjustment for the baseline variables, both groups demonstrated a non-significant mean diameter difference for each of the provocation methods. CONCLUSION: Hydrostatic pressure combined with warmth generates the greatest venous distensibility in the lower arm in haemodialysis patients in a sitting position and is not significantly different compared to healthy volunteers. Without the superior provocation method, venous diameters of haemodialysis patients can be assessed as false-negatives yielding that a primary radio cephalic arteriovenous fistula (RCAVF) at wrist level (the first choice) in these patients will be withheld.

A helical PTFE arteriovenous access graft to swirl flow across the distal anastomosis: results of a preliminary clinical study.

Intimal hyperplasia develops preferentially in regions where the blood flow is stagnant and wall shear stress low. The small amplitude helical geometry of the SwirlGraft was designed to ensure physiological-type swirling flow, and thus suppress the triggers. We report the first conceptual testing of the SwirlGraft. Primary, assisted primary and secondary patency rates at 6 months in 20 patients were 57.9+/-11.4%, 84.4+/-8.3% and 100+/-0.0%. There was angiographic evidence of reduction of helical geometry in a proportion of the grafts. The helical graft is associated with high assisted primary and secondary patency. Elaboration of the surgical implantation techniques and an improved SwirlGraft design can be expected to exploit the advantages of the helical concept.

End-to-end versus end-to-side distal anastomosis in femoropopliteal bypasses; results of a randomized multicenter trial.

OBJECTIVE: To compare end-to-side (ETS) and end-to-end (ETE) distal anastomoses for femoropopliteal bypasses. DESIGN: Prospective, randomized, multicenter trial. METHODS: Patients from 14 centers were randomized to either ETS or ETE distal anastomosis, with stratification according to center and four categories: venous and prosthetic above knee bypass, and venous and prosthetic below knee bypass. Follow-up, with history, physical examination, ankle-brachial pressure index and duplex scan was performed at 3 months, 6 months and every 6 months thereafter until 36 months postoperatively. RESULTS: A total of 328 femoropopliteal bypass operations were performed in 274 patients. Due to anatomical considerations at the time of surgery, 15 procedures (4.6%) were excluded from further analysis. Patient characteristics, cardiovascular risk factors, Rutherford classification and number of open run-off vessels were similar for both groups. Primary patency was 75 vs 74%, 65 vs 66% and 63 vs 55% for ETE vs ETS after 1, 2 and 3 years, respectively, (p = 0.26). During follow up major amputations were necessary in 20 ETE bypasses and in nine ETS bypasses (p = 0.028). CONCLUSION: ETE distal anastomosis infemoropopliteal bypasses does not improve patency compared to ETS anastomosis. Major amputations, after failure of the bypass, were required more frequently for ETE distal anastomoses.

[Diagnostic image (135). A woman with acute abdomen. Volvulus of the small bowel due to strangulation]. / Diagnose in beeld (135). Een vrouw met acute buik. Volvulus van de dunne darm ten gevolge van een streng.

In a 79-year-old woman with acute abdomen CT revealed a 'whirl sign' configuration, pathognomonic for volvulus of the small bowel.

Experimental evaluation of flow patterns in interposition vein cuff anastomosis. The influence of non-planarity of the inflow.

Clinical evidence suggests that the development of myointimal hyperplasia in prosthetic femorodistal bypass grafts may be reduced by the interposition of a cuff of autologous vein between the graft and the recipient artery. Previous experimental work has shown that some of the benefits may be attributed to the geometry of the cuffed anastomosis. Since the distal anastomosis in vivo is often non-planar we have carried out a preliminary study in a model where the graft is at an angle of 45 degrees to the anterior-posterior plane of the anastomosis. This out-of-plane angulation produces highly asymmetric flow patterns in the anastomosis with significant flow separation on the ipsilateral side of the cuff. In the proximal and distal outflow, however, the velocity vectors show significant helical motion with temporal instability in the distal outflow.

Harnessing haemodynamic forces for the suppression of anastomotic intimal hyperplasia: the rationale for precuffed grafts.

OBJECTIVES: Standardisation of cuff geometry by manufacturing prosthetic precuffed grafts (PCG) theoretically optimises haemodynamic forces. This study was designed in order to determine whether these beneficial flow patterns are replicated in vivo in PCG. PATIENTS AND METHODS: Flow visualisation and Doppler studies performed on anatomically accurate PCG models characterised in vitro anastomotic flow patterns. Thirty-two patients (median age 68 years) in whom autologous vein was unavailable, underwent bypass using PCG. Post-operative analysis included qualitative assessment of flow within the distal anastomosis using Doppler colour flow mapping. Cardiac gating techniques and assessment of velocity distribution were performed to gain additional information. These in vivo results were validated against the bench studies. RESULTS: A cohesive vortex was identified within the distal anastomosis of in vitro models and had an integral relationship with the cardiac cycle. This flow structure was also characterised using Doppler colour flow mapping in both longitudinal and transverse planes, confirming the location of the vortex within the body and proximal part of the anastomosis. Twenty-two patients (69%) undergoing bypass with a PCG underwent successful Doppler assessment one week post-operatively, of whom 17 (77%) had a vortical flow structure identified at the distal anastomosis, similar to that characterised in vitro. Cardiac gating verified the same integral relationship of the vortex with the cardiac cycle as that described in vitro. CONCLUSION: The geometric configuration of precuffed grafts induced vortices within the distal anastomoses in 17 out of 22 patients undergoing arterial reconstruction, thereby harnessing the haemodynamic forces that may suppress anastomotic hyperplasia and improve patency rates.

A comparison of distal end-to-side and end-to-end anastomoses in femoropopliteal bypasses.

OBJECTIVES: to compare end-to-side (ETS) and end-to-end (ETE) distal anastomoses. Design retrospective cohort study. METHODS: retrospective cohort study. Between 1988 and 1992, 204 femoropopliteal bypasses (188 patients) were performed for claudication (55%), rest pain (22%) and tissue loss (23%). One hundred and eighteen ETS were compared with 86 ETE in terms of patency or a mean (range) follow-up of 68 (0.5-120) months. RESULTS: overall patency was 86%, 66% and 57% at 1, 5 and 8 years, respectively. Multivariate analysis showed ETE anastomoses (p =0.04), and also knee bypass ( p =0.05) and venous conduit ( p =0.004) to be significantly associated with impaired patency. CONCLUSIONS: ETE may improve femoropopliteal bypass patency.

Vascular response in the femoropopliteal segment after implantation of an ePTFE balloon-expandable endovascular graft: an intravascular ultrasound study.

PURPOSE: To use intravascular ultrasound (IVUS) to document changes in vascular dimensions after placement of a balloon-expandable endograft. METHODS: Thirteen patients (9 men; mean age 62 years, range 47-75) treated with an investigational polytetrafluoroethylene endograft for obstructive disease of the femoropopliteal segment were studied with IVUS immediately after endograft implantation and at follow-up. Corresponding IVUS cross sections were analyzed for changes in lumen, vessel, and plaque areas seen inside the endograft, in the anastomotic segment, and in the remote arterial segment. RESULTS: A mean 6-month (range 1.5-9) follow-up was completed in 12 patients. Matched IVUS cross sections derived from within the endograft (n = 12) and at the endograft edges (n = 23) showed no change in lumen area (LA) in 17, reduction in 11, and dilatation in 7. Median changes within the endograft (+3%) were not significant (p = 0.28) and no neointima was found. Cross sections obtained at the anastomotic segment revealed a significant increase in LA (85%, p < 0.001), which was associated with a significant increase in both vessel area (VA) (42%, p < 0.001) and plaque area (PLA) (15%, p = 0.003) area. In the remote arterial segment, the change in LA was minimal (6%, p = 0.07), as were changes in the VA (9%, p = 0.04) and PLA (10%, p = 0.07). CONCLUSIONS: Following endograft placement, luminal changes within the endograft, at the endograft edges, and at the remote arterial segments were minimal. Intimal hyperplasia was not observed in the endograft. The distinct LA increase at the anastomotic segments was determined by the extent of VA and PLA change.