The use of arm veins in femoral-popliteal bypass grafts.

In view of the increasing debate as to the best alternative to saphenous vein for femoral popliteal bypass grafts, we present our experience with the use of arm vein grafts. Though there are many anecdotal reports, only one series has been previously published. Arm veins were used when saphenous vein was unavailable in 18 femoral popliteal or femoral tibial bypass grafts. Eighty-three per cent of the patients were diabetic. Ninety-four per cent of the patients were operated on for limb salvage, and in 67% the arteriograms showed only fair to poor run-off. Despite this, the one year patency rate was 82%, which is significantly better than the sixty-nine per cent one year patency rate reported by the senior author in an earlier series using cloth grafts. In view of these good results, we believe that autogenous vein remains the material of choice in femoral popliteal bypass grafts. We do not feel that expanded polytetrafluoroethylene grafts or umbilical vein grafts have yet been shown to be superior. We emphasize also the special techniques that are required when using arm veins.     

Patency of arm vein grafts used in aorto-coronary bypass surgery

Arm veins have been used in myocardial revascularisation procedures as a last resort bypass conduit because of their associated low patency. Nevertheless, leg veins and mammary arteries, which are the most commonly used, are sometimes not sufficient, leaving little choice as to the bypass conduit. To assess the properties of arm veins in bypass surgery, we compared a group of 28 patients that underwent an arm vein graft coronary bypass procedure with a matched group of patients in which leg veins were used. In 28 patients, 40 arm vein grafts with 77 distal anastomoses were used (mean 1.9 +/- 0.9; range 1-5). A cerebrovascular accident was the cause of the sole death (2%) during the study period. The mean follow-up was 4.6 years (Standard deviation, SD: 1.5 years). More antianginal medication was used in the arm vein group (P = 0.017). Additionally, the percentage of the expected maximal frequency during exercise testing was lower in the arm vein group as compared to the leg vein group. Digital subtraction angiography showed that the patency of the arm vein bypass grafts was 47% (70% confidence limits, CL: 32%-62%) while the patency of the leg vein grafts was 77% (CL: 64%-87%), which was statistically significant (P = 0.051). Comparison of these figures with the few published reports on arm veins used as coronary bypass grafts reveals similar results. We conclude that the arm vein as a coronary bypass graft is only to be used when mammary arteries and leg veins are not available.     

Prospective comparison of arm veins and greater saphenous veins as infrageniculate bypass grafts.

OBJECTIVES: to compare arm and saphenous veins for infrageniculate bypass grafting. DESIGN: prospective non-randomised study. MATERIALS: two hundred patients, of which 197 had ischaemic tissue loss or rest pain. METHODS: two hundred and eleven infrageniculate vein bypass procedures using 176 greater saphenous veins and 35 arm veins. RESULTS: the cumulative primary graft patency rate at 1-month and 2 years was 80% and 61% for saphenous vein and 89% and 42% for arm vein. The corresponding rates for secondary patency were 84.5% and 68%, and 91% and 57%, respectively. These results corresponded to a relative risk of secondary failure of 1.53 (95% CI 0.71, 3.31) for arm vein grafts. In subgroup analyses, this estimate was 0.93 and 2.1 for primary vs secondary bypasses and 0.38 and 2.06 for single-vein vs spliced-vein bypasses. Among arm veins, cephalic vein grafts performed better than basilic vein grafts. Early mortality was 14% for arm vein and 10% for saphenous vein. CONCLUSION: in the setting of infrageniculate bypass grafting, arm vein grafts are not equivalent to greater saphenous vein grafts, but contribute importantly to a policy of using autologous veins. The possibility of equivalence remains for the arm vein graft that uses a cephalic vein or is a primary procedure.     

Autogenous reversed vein bypass for lower extremity ischemia in patients with absent or inadequate greater saphenous vein

This report has presented the results of 329 reversed vein bypasses performed for lower extremity ischemia over a 6 3/4 year period. One hundred eighty-nine bypasses were formed from intact ipsilateral greater saphenous veins of adequate size and length. One hundred forty bypasses were formed in patients in whom the ipsilateral greater saphenous vein was absent or of inadequate size or length to complete the bypass. The grafts in these patients were accomplished using a variety of techniques including distal graft origin, use of arm veins and lesser saphenous veins, and use of vein splicing. The patency rates of these grafts were equivalent to those achieved using adequate intact ipsilateral greater saphenous vein. In view of these results, we conclude that the absence of a greater saphenous vein does not preclude successful autogenous lower extremity vein bypass and that prosthetic bypass is rarely justified.     

The use of arm vein conduits during infrageniculate arterial bypass.

To further examine the use of arm vein for bypass to the popliteal or infrapopliteal arteries, we retrospectively reviewed 43 patients undergoing infrageniculate arterial bypass by use of an arm vein as a conduit. Nine grafts were done to the below-knee popliteal artery and 34 to the infrapopliteal arteries. Six grafts were done by use of a single segment of an arm vein, whereas 37 grafts were composites of either multiple segments of arm vein (n = 19) or segments of saphenous and arm vein (n = 18). Mean follow-up time was 15 1/2 months. Initial (30-day) graft patency and limb salvage were 95%. Primary graft patency by life-table analysis was 67% at 1 year and 49% at 3 years. Follow-up examination detected graft stenosis before occlusion in six patients (all of whom were given anticoagulant medication) and three failing grafts were salvaged. This increased overall 3-year secondary graft patency to 64% and 3-year secondary patency for infrapopliteal bypasses to 66%. Eleven of 12 graft occlusions resulted in major amputations (eight were above the knee, and three were below the knee) so that limb salvage paralleled secondary graft patency (63% at 3 years). Thus arm veins provide an excellent alternative venous conduit for infrageniculate arterial bypass, even when composite venous grafts must be used.     

The fate of arm veins used for aorta-coronary bypass grafts

Arm veins have been a common second choice conduit for those patients having insufficient saphenous veins for coronary bypass operations. To define the patency and durability of arm vein grafts, we reviewed our patients with one or more arm vein grafts used for coronary revascularization between 1974 and 1982. A total of 59 patients required at least one arm vein graft and 51 are presently alive. Postoperative arteriograms were obtained in 28 patients. Of 56 arm vein grafts used, 32 (57%) were patent and 24 (43%) had failed at 2 years. Seven of the patent grafts had a localized area of stenosis. Sixteen internal mammary artery grafts also had been used in this group of patients, and 15 (93%) were patent. We conclude that arm vein grafts have a high failure rate and are not as dependable as saphenous vein grafts or internal mammary artery grafts.     

Arm veins for peripheral arterial reconstruction.

The ipsilateral saphenous vein has become accepted as the best available material for femoropopliteal bypass and for arterial patch grafts as well as for visceral and cardiac bypasses. However, in a few patients, nonavailability or nonsuitability of the saphenous vein forces use of some other material. We report an experience with 32 operations using arm veins. Among the 11 long vein grafts, seven composite vein-Dacron or vein-vein grafts, and 14 vein patch grafts during the past six years, there were no infections or aneurysms and only nine thrombotic failures have been detected to date, to our knowledge. Our present indications are (1) ipsilateral saphenous vein is not available or is not suitable, (2) only a short graft or patch is needed and the saphenous vein may therefore be saved for the future, (3) to join to a saphenous graft or to a Dacron composite graft for additional length, and (4) to reconstruct an arm artery. Our experiences using cephalic and basilic veins confirms them as a useful source of autogenous material for arterial reconstruction.     

Use of arm and lesser saphenous vein compared with prosthetic grafts for infrapopliteal arterial bypass: Are they worth the effort?

Purpose: Arm and lesser saphenous veins (ALSVs) are generally considered to be the best alternative for infrapopliteal arterial bypass grafts when greater saphenous vein is not available. The need for additional incisions and repositioning of the patient, along with occasional use of general anesthesia for arm vein harvesting, led to our perception that the use of ALSVs increased operative time and possibly patient discomfort. Therefore, we compared the outcome of ALSVs with that of prosthetic infrapopliteal arterial bypass procedures performed at our hospital. Methods: Between July 1, 1991, and Dec. 31, 1996, we performed 96 infrapopliteal arterial bypass procedures using 45 ALSVs (28 arm vein, 17 lesser saphenous) and 51 polytetrafluoroethylene (PTFE) grafts. Seventy grafts were single-length ALSV or PTFE bypass grafts, and 26 grafts were placed as the distal segment of a sequential or composite bypass graft. Every attempt was made to use ALSV and avoid the use of PTFE, even if a short segment of the vein graft measured less than 4.0 mm in diameter. There were no significant differences between patients with ALSV compared with PTFE grafts in terms of age, sex, indication for surgery, or number of previous revascularization procedures (2.1 vs 1.7), respectively (p > 0.05). However, ALSV grafts had more factors associated with an expected worse outcome: they were more commonly anastomosed to pedal arteries (17% [8 of 45] vs 0%; p = 0.0009), less commonly single-segment grafts (62% [28 of 45] vs 82% [42 of 51]; p = 0.03), had higher average runoff resistance values (2.3 vs 1.5; p = 0.001), and were less frequently treated with lifelong warfarin (65% [29 of 45] vs 95% [48 of 51]; p = 0.0001). Results: The hospital mortality rate was 3.1% (3 of 96; 3 PTFE). All deaths were cardiac-related. Despite the potential factors associated with worse patency rates for ALSVs, 2-year assisted primary patency rates tended to be higher for arm veins (46%) than for lesser saphenous veins (23%) and PTFE grafts (26%), although this difference was not statistically significant. Limb salvage rates were similar between ALSV and PTFE grafts (76% vs 71%, respectively). The average operative time was significantly longer for ALSV bypass procedures (mean, 6.2 hours) than for PTFE bypass procedures (mean, 4.9 hours; p = 0.003), and for single-length conduits when revision of previously placed grafts was not attempted, the operative time was 4.0 hours for ALSV grafts and 2.5 hours for PTFE grafts. Conclusion: In our experience ALSV bypass grafts to infrapopliteal arteries do not function as well as reported by some others. In spite of the extra effort involved, arm vein grafts are preferred over PTFE grafts for their likely higher assisted primary patency rates and equivalent, if not better, limb salvage rates. (J Vasc Surg 1997;26:919-27.)     

Experience with arm veins as aorto-coronary bypass grafts

In a series of 1,000 coronary bypass operations 15 patients received arm vein grafts. In these cases the saphenous veins were either absent or inadequate and the mammary arteries alone were not sufficient for multivessel coronary revascularization. Altogether, 34 coronary anastomoses were performed with 16 arm vein grafts; additional coronary endarterectomy was needed in four instances. Together with mammary artery or saphenous vein grafts these patients each had, on the average, 3.6 coronary anastomoses. There was no operative mortality and no complication related to the arm vein grafts. Postoperatively all the patients were free of angina pectoris. A follow-up angiogram (mean 1.4 years postoperatively) showed a patency rate of 87% for arm vein grafts. A frequent finding was an uneven diameter of the grafts. In three patients aneurysmal dilatation (of 8.3 to 9.8 mm in diameter) was revealed. Although the patency rate to date is satisfactory, our experience is too limited in time numbers to judge long term durability.     

Arm veins for arterial revascularization of the leg: arteriographic and clinical observations

The results of 160 infrainguinal bypasses with arm vein grafts were analyzed. Seventy-three arteriograms were reviewed to identify early and late graft defects; arteriographic findings paralleled those described for saphenous vein grafts. Intimal fibrosis during the first postoperative year, observed in 16 grafts, was the most common defect. Aneurysmosis and elongation were rare, resulting in two graft replacements. Patency and limb salvage rates were calculated for 88 single-length femorodistal bypass grafts; the other 72 were inflow (eight) or outflow (22) jump grafts, sequential (eight) and composite autogenous vein grafts (34). The primary and secondary patency rates for single-length grafts were 74% and 80% at 1 year and 51% and 57% at 5 years, respectively. The limb salvage rate at 5 years was 82%. The survival rate for all patients was 44% at 5 years. These findings reconfirm our use of arm veins as bypass grafts when the saphenous vein is unavailable.     

Infrainguinal Bypass for Peripheral Arterial Occlusive Disease: When Arms Save Legs

ObjectivesDetermine if arm veins are good conduits for infrainguinal revascularisation and should be used when good quality saphenous vein is not available.DesignRetrospective study.Materials and methodsWe evaluated a consecutive series of infrainguinal bypass (IB) using arm vein conduits from March 2001 to December 2006.We selected arm vein by preoperative ultrasound mapping to identify suitable veins. We measured vein diameter and assessed vein wall quality. We followed patients with systematic duplex imaging at 1 week, 1, 3, 6 and 12 months, and annually thereafter. We treated significative stenoses found during the follow-up.ResultsWe performed 56 infrainguinal revascularisation using arm vein conduits in 56 patients. Primary patency rates at 1, 2 and 3 years were 65%, 51% and 47%. Primary assisted patencies at 1, 2 and 3 years were 96%, 96% and 82%. Secondary patency rates at 1, 2 and 3 years were 92%, 88% and 88%. The three-year limb salvage rate was 88%.ConclusionsWe conclude that infrainguinal bypass using arm vein for conduits gives good patency rates, if selected by a preoperative US mapping to use the best autogenous conduit available.     

Use of the short saphenous vein in situ for popliteal-to-distal artery bypass

In the absence of a usable greater saphenous vein, the short saphenous vein has been relatively ignored for use as an arterial bypass conduit. In 36 patients, duplex ultrasound scanning was used for preoperative assessment of the short saphenous vein. The internal diameter of the vein ranged from 2.8 to 4.2 mm. The short saphenous vein was harvested for a free vein graft in 31 patients. In the remaining five patients, the short saphenous vein was used in situ for popliteal-to-distal artery bypass. In four patients, the distal anastomosis was performed to the distal anterior tibial artery and in one patient, to the distal posterior tibial artery. Valves were excised with valvulotomes and deep fistulas were easily ligated. A medial incision for vein exposure was the preferred approach. We suggest that the short saphenous vein be considered more often for use as an arterial bypass conduit when the greater saphenous vein is not available, before submitting to nonautogenous bypass or primary amputation.     

Angioscopy of arm vein infrainguinal bypass grafts

Between January 1988 and December 1990, 56 patients underwent 66 arm vein infrainguinal bypass grafts for limb salvage. Thirty-nine grafts were intraoperatively monitored by the standard methods of continuous wave Doppler alone (30) and arteriography (9). Twenty-seven grafts were prepared and monitored by intraoperative angioscopy. No significant findings requiring intraoperative revision or correction were noted in the grafts monitored by the standard methods. However, in those grafts prepared and monitored by angioscopy, intraluminal abnormalities of the arm veins were detected and corrected in 20/27 (74%). None of the grafts prepared or monitored by angioscopy occluded within 30 days, whereas, in those grafts monitored by continuous wave Doppler and arteriography, 7/39 failed within 30 days, a primary patency rate of 32/39 (82%) (x² with Yates correction, p=0.055). This study shows that angioscopic preparation and monitoring of arm vein bypass grafts allows the detection and correction of unsuspected intraluminal abnormalities, which appears to improve the early primary patency of arm vein infrainguinal bypass grafts.Presented at the Fifteenth Annual Meeting of the Peripheral Vascular Surgery Society, June 2, 1990, Los Angeles, California.     

Inadequacy of saphenous vein grafts for cross-femoral venous bypass

A mathematic model of unilateral iliac vein obstruction was used to establish the theoretic basis for selecting saphenous vein or a larger diameter prosthetic cross-femoral venous bypass graft for relief of obstructive venous hypertension. Common femoral vein resting and postexercise peak flows, and common femoral vein and saphenous vein diameters were measured in 18 healthy individuals and used to estimate the pressure gradient (dP) across 20 cm long cross-femoral venous bypass grafts of saphenous vein or 4, 6, 8, 10, and 12 mm prosthetic conduits, in the presence of a transpelvic venous collateral network of varied cross section. The upper limits of normal for the gradients in our model (dPstd) were set at 4 mm Hg for resting flows and 6 mm Hg after exercise. Mean saphenous vein diameter was 4.3 +/- 0.22 mm, which was 36.5% +/- 1.73% of common femoral vein diameter. When the saphenous veins of two thirds of the individuals in our study were used as theoretic cross-femoral venous bypass conduits, greater than 80% of postobstruction peak cross-femoral venous bypass graft flow had to be carried by collaterals to maintain a gradient less than or equal to dPstd. We demonstrated that 4.5 to 6.0 mm diameter saphenous cross-femoral venous bypass grafts would be hemodynamically efficacious in relieving venous hypertension, but only when implanted in parallel with an existing venous collateral network that limited the preoperative dP to 4.5 to 7.5 mm Hg at resting flows and 7.0 to 11.5 mm Hg after exercise; only 44% of saphenous veins were adequate for cross-femoral venous bypass grafts by these criteria.(ABSTRACT TRUNCATED AT 250 WORDS)     

Aorta--coronary artery revascularization with an expanded polytetrafluoroethylene vascular graft. A preliminary report.

Patients requiring coronary artery surgery may have had bilateral saphenous vein stripping, and the arm veins may not be adequate for use for coronary artery grafting. The internal mammary artery may not be long enough for use for the circumflex or right coronary artery anastomoses. A suitable substitute would be most welcome for these patients or for those with marked varicosities of the saphenous vein. Five patients received expanded polytetrafluoroethylene (PTFE) grafts (Gore-Tex vascular grafts) for coronary artery revascularization because veins of adequate size or length were not available at the time of operation. These five patients are alive 9 to 14 months after graft insertion. Four of the five grafts were patent at the time of restudy 3 to 6 months postoperatively. More follow-up studies for far longer periods of time will be necessary before Gore-Tex vascular grafts can be recommended as the ideal material for coronary artery bypass surgery.     

Preoperative saphenous venography in arterial reconstructive surgery of the lower extremity.

Preoperative saphenous venography was performed in 100 extremities in 60 patients to evaluate the saphenous vein for use as an arterial bypass graft. In 18 of the patients (30%), venography demonstrated vein abnormality, disease, or small size, which significantly influenced the management of the patient or the conduct of the operation. Good correlation was observed between venographically determined saphenous vein anatomy and diameter and those observed at operation in 52 patients. The average diameter of the saphenous veins on preoperative venograms was 3.4 mm (range, 1.0 to 6.0 mm). These veins dilated to an average diameter 73 +/- 5% greater than that observed venographically, so that the average diameter of harvested, dilated saphenous veins was 5.5 mm (range, 3.0 to 10.0 mm). All veins measuring 2.0 mm or more on the venograms dilated to 4.0 mm or more at operation and were suitable for femoropopliteal or small vessel bypass grafts. Four saphenous veins measuring 1.0 mm or more on the venograms dilated to 3.0 mm or more at operation and were suitable for small vessel bypasses. Thus preoperative saphenous venography can be of value in lower extremity arterial reconstructions. The procedure allows detection of anomalies and disease processes that would prevent the use of one or both saphenous veins as arterial bypass grafts and identifies the best available venous segment thereby obviating unnecessary incisions and minimizing operating time.     

Improvement in the visualization of superficial arm veins being evaluated for access and bypass

OBJECTIVES: Duplex ultrasound mapping of arm veins is being performed with increasing frequency. Unlike ultrasound testing in other areas, this has never been subjected to a gold standard invasive test to determine accuracy. Duplex mapping appears to have a good predictive value whenever large veins are demonstrated preoperatively, but its ability to accurately measure minimum-sized veins is unproven. In this study, we compared diameter measurements obtained under six different conditions and used the maximum diameter as the comparison gold standard. METHODS: A 12-MHz linear probe was used to measure the cephalic and basilic vein cross-sectional diameters at the wrist level in 24 normal volunteers under the following conditions: (1) resting supine with a room temperature of 23 degrees to 24 degrees C, (2) supine with a tourniquet inflated to 65 mm Hg, (3) sitting with the arm dangling, (4) sitting with a tourniquet, (5) sitting after a 2-minute immersion in warm water (44 degrees C), and (6) same with tourniquet. Half the subjects underwent the protocol in a different order. RESULTS: Vein diameters were significantly larger after submersion in warm water compared with supine (P < .05, pair-wise multiple comparison procedure, Student-Newman-Keuls method). Assuming the sitting position (from supine) resulted in a decreased arm vein diameter 58% of the time. In 25% of the normal subjects, the cephalic vein size was <2 mm, which increased to >2 mm after warming. All subjects had either a cephalic or a basilic vein at the wrist that was >3.1 mm after warming. CONCLUSION: Use of warm water immersion before vein diameter measurement in a sitting position, without a tourniquet, will result in significantly larger diameter findings in normal arm veins. These diameters are likely to more closely resemble the venous diameter after distension with arterial pressure. Further studies are needed to see if warming in patients could result in increased utilization of autogenous arm vein for dialysis access and bypass.     

Distal Venous Patch improves results in PFTE bypasses to Tibial arteries

In recent years, the management of limb-threatening ischemia has involved the use of distal bypasses to vessels beyond the popliteal trifurcation. Excellent patency rates and limb salvage data are achieved through the use of autologous long saphenous vein. However, an increasing number of patients in need of tibial bypass do not have adequate saphenous vein due to previous procedures, thrombophlebitis, or inadequate vein. In such cases alternative conduits have been proposed including lesser saphenous vein, arm vein, composite veins, composite vein with poly-tetrafluoroethylene (PTFE), and PTFE with or without a distal arteriovenous fistula. Unfortunately these alternative conduits have not resulted in equivalent results when used for distal bypass to tibial arteries. Several authors have reported upon the use of venous tissue at the distal anastomosis in the form of cuffs, collars, and boots to improve the results of prosthetic grafts in this challenging patient population. These techniques have been proposed as an option for revascu-larization in patients without adequate saphenous vein in an attempt to obtain limb salvage. The purpose of this review is to examine some of those techniques and focus on distal vein patch configuration with its perceived advantages and drawbacks.     

Distal venous patch improves results in PFTE bypasses to tibial arteries

In recent years, the management of limb-threatening ischemia has involved the use of distal bypasses to vessels beyond the popliteal trifurcation. Excellent patency rates and limb salvage data are achieved through the use of autologous long saphenous vein. However, an increasing number of patients in need of tibial bypass do not have adequate saphenous vein due to previous procedures, thrombophlebitis, or inadequate vein. In such cases alternative conduits have been proposed including lesser saphenous vein, arm vein, composite veins, composite vein with polytetrafluoroethylene (PTFE), and PTFE with or without a distal arteriovenous fistula. Unfortunately these alternative conduits have not resulted in equivalent results when used for distal bypass to tibial arteries. Several authors have reported upon the use of venous tissue at the distal anastomosis in the form of cuffs, collars, and boots to improve the results of prosthetic grafts in this challenging patient population. These techniques have been proposed as an option for revascularization in patients without adequate saphenous vein in an attempt to obtain limb salvage. The purpose of this review is to examine some of those techniques and focus on distal vein patch configuration with its perceived advantages and drawbacks.     

Diameter comparison of saphenous vein bypasses for popliteal aneurysm versus peripheral arterial occlusive disease in matched subjects

Previous research has suggested that arterial aneurysm might result from a systemic tendency to dilatation. This systemic effect would involve both arterial and venous dilatation. The authors investigated whether venous grafts implanted to bypass popliteal artery aneurysms (PAA) had larger diameters than those implanted to treat peripheral arterial occlusive disease (PAOD). They compared representative diameters of 20 vein grafts implanted for PAA with matched bypass grafts implanted for PAOD. Graft diameters were obtained by means of CVI-Q M-mode ultrasound imaging. Each PAA patient/graft was matched to an equivalent PAOD patient/graft based on the patient's gender and age and the vein graft type and distal anastomosis. Secondarily, graft proximal anastomosis was matched in 60% (12/20) of the cases. Age was matched if the difference was < or = 4 years. Average age at the time of surgery was 68 +/-12 years for PAA and 68 +/-13 for PAOD groups. There were 11 reversed greater saphenous vein (GSV), 2 nonreversed GSV, and 7 in situ GSV in each group. Distal anastomoses were at the popliteal (15), peroneal (3), posterior (1), and anterior tibial (1) arteries in each group. Matching was not possible for lesser saphenous and cephalic vein grafts or bypasses to the tibial-peroneal trunk. Graft diameters were significantly larger for the PAA group, 6.24 +/-0.66 mm (standard deviation), than for the PAOD group, 5.73 +/-0.69 mm (p < 0.02, Mann-Whitney U test). Of 10 bypasses with diameter >6.5 mm, 8 were implanted for PAA. If these 10 largest bypasses were eliminated from the calculations, the mean graft diameters were 5.82 +/-0.51 mm and 5.57 +/-0.52 mm for the PAA and PAOD groups, respectively (p = 0.28). Bypass grafts implanted in PAA patients had significantly greater diameters than grafts implanted in PAOD patients. This finding, however, was due to a subgroup of grafts with diameters >6.5 mm. Perhaps systemic abnormalities associated with PAA should be first studied in patients with large vein grafts or large original veins.