Effect of outflow level and maximum graft diameter on the velocity parameters of reversed vein bypass grafts.

OBJECTIVE: The objective of this study was to define a normal range of distal graft velocity (DGV) and peak systolic velocity (PSV) on the basis of outflow level and maximum graft diameter for infrainguinal reversed vein bypass grafting (RVG). METHODS: This study was designed as a prospective study of consecutive patients who underwent infrainguinal RVG from 1994 to 1997 in a university hospital and university-affiliated teaching hospital. All patients who underwent infrainguinal bypass grafting from 1994 to 1997 were placed in a prospective protocol with duplex scanning to better define the hemodynamics of normally functioning RVG. Graft revisions were performed for patients with velocity ratios of more than 2.5. One hundred twenty-one patients were entered into this protocol, and 114 were followed more than 3 months after RVG. Seven patients were excluded: five for death within 3 months, one for graft infection, and one for graft occlusion before the baseline duplex scanning. DGV and PSV were determined for each type of outflow (popliteal, crural, and pedal) and for ranges of maximum graft diameter. These then were correlated with subsequent graft occlusion or graft revision (graft failure). RESULTS: Grafts with larger diameters were associated with lower DGVs (P <.001), and more proximal outflow arteries were associated with higher DGVs (popliteal, 75 cm/s; crural, 50 cm/s; and pedal, 40 cm/s; P <.01).The mean PSVs were 150, 140, and 122 cm/s for popliteal, crural, and pedal grafts, respectively, but the difference was not statistically significant. The assisted primary patency rates for the grafts in this series were 99%, 92%, and 92% at 1, 2, and 3 years. CONCLUSION: Graft diameter and location of the distal anastomosis significantly affect the flow velocity in RVG. Other variables did not influence these parameters. Currently established criteria for arteriography or graft repair on the basis of graft velocity parameters may be improved if they can be modified depending on diameter and outflow.     

Arteriovenous graft with outflow in the proximal axillary vein

Arteriovenous access can result in complications including extremity ischemia and swelling. Use of the nondominant upper extremity is preferred because complications will result in less severe disability. The distal axillary vein in the axilla is usually considered to be the end point for arteriovenous access in the upper extremity. Vascular surgeons are familiar with exposure of the proximal axillary artery via an infraclavicular incision. The axillary vein is also easily exposed through this technique. Use of this vein for arteriovenous graft outflow can preserve the dominant arm for future use. Nine patients with arteriovenous grafts with venous outflow in the proximal arm for future use. All patients had exposure to the proximal axillary vein via an infraclavicular incision. There were six women and three men. All patients had multiple failed access in the ipsilateral extremity. One patient had a loop configuration graft, while the six others had a straight graft with arterial inflow via the brachial artery. One patient had a bovine mesenteric vein graft, while the remaining six had expanded polytetrafluoroethylene grafts. Six of the seven patients had ambulatory surgery, while one patient was admitted postoperatively with mental status changes. Patency rates were 78%, with mean follow-up of 16 months. One patient had early failure due to steal and one patient failed at 22 months. Six of seven patients are alive at current follow-up. Three patients required secondary procedures including venous angioplasty (n=2) and subclavian artery stenting (n=1). The infraclavicular axillary vein can be used as an effective outflow for arteriovenous grafts. This procedure can be done as an outpatient surgery with a low complication rate. This procedure can preserve the dominant arm for future access and provides a possible alternative to surgery on another extremity.     

A prospective study of the determinants of vein graft flow velocity: Implications for graft surveillance

Purpose: Serial monitoring of vein graft peak systolic flow velocity (PSFV) has been endorsed as a technique for vein graft surveillance with low values (<45 cm/sec) considered a marker for impending graft failure. Optimal application of this method requires an understanding of the factors affecting PSFV in normal grafts. A prospective evaluation of 46 consecutive elective infrainguinal vein grafts (6 popliteal/29 tibial/11 pedal) was undertaken to assess the major determinants of PSFV.Methods: Factors recorded for each patient included vein graft diameter (VGD), measured outflow resistance (MOR), conduit length, outflow level (popliteal/tibial/pedal), inflow level (femoral/popliteal), systolic blood pressure, cardiac ejection fraction, the presence of a patent plantar arch, and Society for Vascular Surgery/International Society for Cardiovascular Surgery resistance scoring. MOR was measured by occluding graft inflow and infusing saline solution through a proximal graft cannula at 60 cc/min while simultaneously recording the pressure at the distal anastomosis via a separate cannula. MOR was calculated by dividing the resultant pressure by the infusion rate. MORs were expressed in resistance units and were measured before and after the infusion of papaverine (MOR_(PAP)). PSFVs and VGDs were measured 4 to 6 cm from the distal anastomosis 3 weeks after surgery with duplex scanning (60 degree angle with midstream sample volume).Results: PSFVs ranged from 22 to 148 cm/sec and averaged 83.4 ± 4.8 cm/sec. Pedal bypass grafts had significantly lower PSFVs (64 ± 10 vs 89.5 ± 5 cm/sec, p = 0.02) and significantly higher MOR_(PAP)s (0.86 ± 0.15 vs 0.51 ± 0.05 resistance units, p = 0.05) than bypasses to the popliteal/tibial level. When subjected to univariate analysis the factors correlating with PSFV were MOR (r = -0.59, p = 0.0001), MOR_(PAP) (r = -0.69, p = 0.0001) VGD (r = -0.31, p = 0.06), the Society for Vascular Surgery/International Society for Cardiovascular Surgery score (r = -0.35, p = 0.04), inflow level (r = -0.47, p = 0.002), and outflow level (r = -0.35, p = 0.03). When subjected to multiple regression analysis, only MOR_(PAP) (r ² = 0.51, p = 0.001) and VGD (r ² = 0.14, p =0.001) contributed significantly to the overall model (r ² = 0.65, p = 0.0001) withMOR_(PAP)) eliminating the effect of the other variables. The multiple regression model predicts PSFV as follows: PSFV = 176 + VGD_(mm)( -11.7) + MOR_(PAP))( -63.4).Conclusions: Clinically successful and hemodynamically normal vein grafts have widely variable, yet predictable flow characteristics that are influenced primarily by outflow resistance and VGD. This wide variability suggests that no single lower threshold value for PSFV is universally applicable in identifying all grafts at risk for failure. Detection of focal areas of flow acceleration within the graft may be more accurate in identifying grafts at risk for failure. (J VASC SURG 1994;19:259-67.)     

The value of duplex scanning with venous occlusion in the preoperative prediction of femoro-distal vein bypass graft diameter.

The diameter of the long saphenous vein has been shown to affect the outcome of femoro-distal bypass. Many surgeons regard a vein with a diameter of less than 3 mm as being unsuitable. The long saphenous vein was studied in 35 patients undergoing femoro-distal bypass. Diameter measurements of the vein were performed using an ATL duplex scanner at the groin, mid-thigh and knee. Measurements were performed preoperatively both at rest and with a venous occlusion cuff to dilate the vein, and subsequently at 7 days and 2 months after implantation. The mean diameter of the vein at the mid-thigh was 4.1 mm non-dilated, 5.1 mm with occlusion, 5.0 mm 7 days postoperatively and 5.2 mm at 2 months (ANOVA, p less than 0.05). The mean diameter of the vein at the knee was 3.9 mm non-dilated, 4.8 mm with occlusion, 4.8 mm at 7 days and 4.9 mm at 2 months after operation (ANOVA, p less than 0.025). In all five patients whose preoperative resting vein diameter at the knee or mid-thigh was less than 3 mm, preoperative dilatation occurred, such that the diameter became greater than 3 mm. These results suggest that by using a technique of venous occlusion at the time of pre-operative vein mapping, the functional diameter of the vein can be predicted and vein utilisation may be increased.     

The effect of ejaculation time on varicose vein diameter and reflux level

The aim of this study was to investigate whether the time interval between ejaculation and scrotal Doppler ultrasonography affects the results of the varicose vein diameter and reflux time. Age, medication use, operation history, physical examination and semen analysis findings, varicose vein diameters and the presence of reflux and reflux time were evaluated prospectively in the patients older than 18 years of age who presented to the urology outpatient clinic with infertility and underwent scrotal Doppler ultrasonography and semen analysis. The time interval between the two scrotal Doppler ultrasonography for semen analysis was noted, the two results were compared. The patients were divided into four groups according to the time interval between ejaculation and scrotal Doppler ultrasonography. The study included 81 varicocele cases, with 57 left-sided and 12 bilateral varicocele. The varicose vein diameters were significantly larger after ejaculation than before ejaculation (p < .001). Similarly, the reflux time after ejaculation in all patients was significantly higher in scrotal Doppler ultrasonography performed before and after ejaculation at rest and during Valsalva manoeuvre (p < .001). In conclusion, the results of the present study suggest that a waiting time of at least 90 min must be allowed between ejaculation and scrotal Doppler ultrasonography.     

The significance of hepatic vein outflow volume in hepatic outflow insufficiency of living right liver graft evaluated by Doppler ultrasound

The color Doppler ultrasound has been used to evaluate hepatic vein (HV) outflow insufficiency based on flow velocity and waveforms. In our experience, some cases with flat waveforms are clinically asymptomatic. The parameters of HV flow velocity and waveforms are not always correlated with clinical problems. So, we proposed that total HV flow volume (HVFV) may be a more reliable index. From August 2001 to July 2003, 31 cases among 48 adult-to-adult living related transplants of a right liver graft had one HV anastomosis. HV velocity, waveforms, and HVFV were compared both before and after transplantation. We set the minimal HVFV ratio at 80% based on the original HVFV before graft retrieval. There was no significant difference in HVFV before liver graft retrieval between the 2 groups, but there was a significant change after transplantation. There were no cases of HV insufficiency among group A patients (>80%), whose HVFV ranged from 397 to 1181 mL/min with ratios from 75% to 180% (mean 115%). In group B, there were 4 complicated cases with prolonged severe ascites (<80%) with HVFV ratios from 56% to 76% (mean 66%). Fisher exact test showed a great significance (P < .001). Thus the preliminary criteria of 80% minimal HVFV ratio allows detection of HV insufficiency for further interventional management.     

Left trisegmentectomy with reconstruction of segment 6 hepatic venous outflow using cryopreserved vein graft

Liver resections that require hepatic vein reconstruction rarely occur. Options regarding venous reconstruction include primary end-to-end reconstruction, reimplantation into the vena cava, or the use of a variety of autologous or synthetic grafts. Cryopreserved vein grafts have recently become available for use. We describe a left trisegmentectomy with bile duct resection/reconstruction during which the segment 6 hepatic vein was reconstructed into the inferior vena cava using a cryopreserved vein graft.     

Reconstruction of the venous outflow using a vein graft in dural arteriovenous malformation associated with sinus occlusion

In some cases of dural arteriovenous malformations (dural AVMs) of the transverse-sigmoid sinuses, the presence of an occlusion or hypoplasia on the sinus contralateral to the affected side may significantly contribute to the development of intracranial hypertension. For these cases, closure of AV shunts or removal of the affected sinus may not be sufficient to improve intracranial hypertension. We encountered 2 cases of intracranial hypertension caused by dural AVMs at the transverse-sigmoid sinuses associated with disturbance of venous outflow contralateral to the lesion. Reconstruction of venous outflow using a saphenous vein graft was performed between the transverse sinus and the subclavian or external jugular vein after the dural AVMs were partially occluded by catheter embolization. Intracranial hypertension was relieved in both cases. In one case dural AVM was obstructed by both embolization and radical surgery after the bypass was confirmed unobstructed several weeks later. The bypass remained patent at the follow-up 4 months later. In the other case, patency of the bypass lasted only for approximately 1 month. In both cases clinical improvements were not remarkable. It is considered that the presence of AV shunt in the case of dural AVM may facilitate the patency of a graft placed between the venous systems. Reconstruction of the venous outflow may deserve further trial for the treatment of intracranial hypertension associated with some types of dural AVM.     

Detection and grading of femorodistal vein graft stenoses: duplex velocity measurements compared with angiography

Increasing recognition of the importance of vein graft stenoses in precipitating failure of femorodistal bypass procedures has stimulated an increasing interest in noninvasive postoperative surveillance. We have used duplex scanning, measuring relative changes in velocity throughout the entire length of the graft, to detect nonhemodynamic stenoses (i.e., stenoses without a significant change in ankle-brachial pressure indexes) as well as more severe lesions during the postoperative period. Seventy-five in situ vein grafts were assessed at three monthly intervals from operation with duplex scanning and intravenous digital subtraction angiography. Nineteen grafts (25%) had angiographically documented stenoses at a mean follow-up of 12 months. All 19 stenoses were detected independently by duplex velocity ratio criteria and 15 were correctly graded as mild, moderate, or severe. The results suggest that duplex-derived velocity ratio criteria are appropriate for graft surveillance and for determining the natural history of even minor stenoses to identify the optimal time of surgical intervention.     

Competitive flow between a vein and an arterial graft at transit-time flow measurement

We report the intraoperative finding, at a transit-time flow measurement, of competitive flow between a venous and an arterial graft in a 72-year old woman who underwent uncomplicated coronary artery bypass grafting 3. The blood flow in the left internal mammary artery (LIMA) improved only after temporary occlusion of the saphenous vein graft (SVG) anastomosed to the first diagonal (D1), demonstrating the presence of competitive flow from the SVG-D1 anastomosis into the LIMA-left anterior descending coronary artery (LAD) system. Interestingly the two target vessels suffered from separate critical lesions. The patient's haemodynamics remained stable throughout and no further action was taken. Her recovery was uneventful and the patient was discharged home on postoperative day 6. This case raised questions about the cost benefit of grafting a diagonal target even when it appeared to be disconnected from the LAD on a coronary angiogram.     

The value of vein graft surveillance in bypasses performed with small-diameter vein grafts

We assessed the impact of preoperative diameter of the venous conduit on reintervention rate and outcome following infrainguinal vein graft bypass. Consecutive infrainguinal vein bypasses between January 2001 and December 2006 were reviewed. All patients underwent preoperative measurement of vein graft diameter (VGD). Grafts were classified into those with VGD <3.5 mm and those with VGD > or =3.5 mm. All patients were enrolled in a duplex surveillance program. The association between VGD and reintervention rate was assessed. Graft patency and amputation rates were compared. There were 377 bypasses followed up for a median of 23 months (range 8-67). VGD was <3.5 mm in 139 grafts (36.9%) and > or =3.5 mm in 238 grafts (63.1%). A higher proportion of smaller vein grafts (32.3%) required reintervention to maintain graft patency compared with larger conduits (20.2%) (chi(2) = 7.7, p < 0.001). VGD (odds ratio [OR] = 2.87, 95% confidence interval [CI] 1.63-3.81; p < 0.001), smoking (OR = 1.83, 95% CI 1.39-3.20; p = 0.02), and type of bypass (OR = 1.86, 95% CI 1.49-2.47; p = 0.02) were variables associated with higher reintervention rate. There was no difference in graft patency (p = 0.13) or amputation rates (p = 0.35) between the two groups. Use of smaller vein grafts was associated with a higher reintervention rate. Provided that these grafts are surveyed and where necessary repaired, the use of smaller vein grafts is successful and expands the availability of autogenous conduit for infrainguinal arterial reconstruction.     

Comparison of functional results of nerve graft,vein graft,and vein filled with muscle graft in end-to-side neurorrhaphy

End-to-side neurorrhaphy is an alternative method in the situation where the proximal part of the nerve cannot be found. When the intact nerve is not close enough to perform end-to-side neurorrhaphy, it will be necessary to use a graft for transporting the regenerating axons. In this study, we tried to find out whether it is possible to use a graft in an end-to-side neurorrhaphy, and compared the nerve graft with possible alternative grafts, i.e., vein and muscle-filled vein grafts. Thirty male Sprague Dawley rats were used, with an average weight of 293 g (range, 250-350 g). All experiments were done on the right side. A 2-cm nerve graft, beginning 1 cm distal to the branching level, was sectioned from the peroneal nerve. A 1-mm epineural window was opened in the tibial nerve. In the first group, the proximal side of this graft was sutured to the tibial nerve side in an end-to-side fashion, and the distal side was sutured to the distal peroneal nerve stump in an end-to-end fashion. In the second group, the right 2-cm jugular vein was harvested, and was used to bridge the defect instead of the nerve graft used in the first group. In the third group, a 2-cm jugular vein filled with fresh skeletal muscle was used to bridge the defect. At 2, 4, 8, 12, 20, and 28 weeks, functional assessment of nerve regeneration was performed, using walking-track analysis. The numbers of myelinated fibers and fiber diameters were measured, and an electron microscopic evaluation was carried out. Based on walking-track analysis and fiber diameters, the differences of all three groups were statistically significant (P < 0.05). While the differences of myelinated fibers between the first and second groups were not significant, the differences between the rest (group 1-group 3 and group 2-group 3) were significant (P < 0.05). Our study showed that, in end-to-side neurorrhaphy, the use of a nerve graft is possible, and a vein graft is also a good alternative, but a muscle-filled vein graft is not.     

Donor graft outflow venoplasty in living donor liver transplantation.

Hepatic venous outflow reconstruction is a key to successful living donor liver transplantation (LDLT) because its obstruction leads to graft dysfunction and eventual loss. Inclusion or reconstruction of most draining veins is ideal to ensure graft venous drainage and avoids acute congestion in the donor graft. We developed donor graft hepatic venoplasty techniques for multiple hepatic veins that can be used in either right- or left-lobe liver transplantation. In left-lobe grafts, venoplasty consisting of the left hepatic vein and adjacent veins such as the left superior vein, middle hepatic vein, or segment 3 vein is performed to create a single, wide orifice without compromising outflow for anastomosis with the recipient's vena cava. In right lobe graft where a right hepatic vein (RHV) is adjacent with a significantly-sized segment 8 vein, accessory RHV, and/or inferior RHV, venoplasty of the RHV with the accessory RHV, inferior RHV, and/or segment 8 vein is performed to create a single orifice for single outflow reconstruction with the recipient's RHV or vena cava. Of 35 venoplasties, 2 developed hepatic venous stenoses which were promptly managed with percutaneous interventional radiologic procedures. No graft was lost due to hepatic venous stenosis. In conclusion, these techniques avoid interposition grafts, are easily performed at the back table, simplify graft-to-recipient cava anastomosis, and avoid venous outflow narrowing.