Valve replacement in the recanalized incompetent superficial femoral vein in dogs

Advances in Engineering Venous Valves: The Pursuit of a Definite Solution for Chronic Venous Disease

Native venous valves enable proper return of blood to the heart. Under pathological conditions (e.g., chronic venous insufficiency), venous valves malfunction and fail to prevent backward flow. Clinically, this can result in painful swelling, varicose veins, edema, and skin ulcerations leading to a chronic wound situation. Surgical correction of venous valves has proven to drastically reduce these symptoms. However, the absence of intact leaflets in many patients limits the applicability of this strategy. In this context, the development of venous valve replacements represents an appealing approach. Despite acceptable results in animal models, no venous valve has succeeded in clinical trials, and so far no single prosthetic venous valve is commercially available. This calls for advanced materials and fabrication approaches to develop clinically relevant venous valves able to restore natural flow conditions in the venous circulation. In this study, we critically discuss the approaches attempted in the last years, and we highlight the potential of tissue engineering to offer new avenues for valve fabrication. Impact statement Venous valves prosthesis offer the potential to restore normal venous flow, and to improve the prospect of patients that suffer from chronic venous disease. Current venous valve replacements are associated with poor outcomes. A deeper understanding of the approaches attempted so far is essential to establish the next steps toward valve development, and importantly, tissue engineering constitutes a unique toolbox to advance in this quest.

Prosthetic venous valves: Short history and advancements from 2012 to 2020

Chronic Venous Disease is estimated at 83.6% of the global population. Patients experience pain, discomfort and severe complications with few effective therapies being available. Current strategies for the treatment of malfunctioning venous valves are invasive with a high recurrence rate. A prosthetic venous valve replacement is imminent, possibly providing better outcomes and improved general quality of life. In this review, prosthetic venous valves history is presented and assesses the advantages and disadvantages of developed venous valves. Articles that discussed potential designs of prosthetic venous valves were examined. A systematic search produced thirty-five papers fitting the inclusion criteria. Our understanding of the ideal abilities required in prosthetic valves has evolved. Developed valves are reported for regurgitation, migration and leakage. Issues have been resolved, but we are still away from the ideal valve. Improvements within the last eight years provided information on the importance of sinuses and prosthetic to venous wall-size mismatch.

Surgical Treatment of Post Phlebitic Syndrome

Sequelae of deep vein thrombophlebitis, such as post phlebitic syndrome with or without ulceration, can be treated by direct surgery on the valve. Present surgical treatment of stasis ulcer includes removal of the incompetent communicating veins with excision of the ulcer and skin graft. This procedure is usually associated with a high incidence of leg ulcer among the patients with an incompetent deep venous system.

Experimental studies to restore venous valve function, such as autogenous vein valve transplant, valvoplasty, homologous vein transplant and synthetic valve procedures, have been tried. It has been shown that the patency rate with autogenous vein graft is higher than with other procedures.

The authors have operated on ten patients utilizing autogenous vein valve from the upper extremities to restore a normal functioning venous system of the distal leg. Data on pre- and post-operative, non-invasive, and ascending and descending venography with the results of surgery will be presented and discussed.

Percutaneous management of chronic deep venous reflux: review of experimental work and early clinical experience with bioprosthetic valve

Lower extremity chronic deep venous insufficiency (CDVI) is common and remains a major health problem worldwide. Selected patients benefited from direct deep vein valve surgical repair or valve transplantation. A major limitation of this approach is that most of the patients are not candidates for these procedures due to obstructions or residual thrombus throughout the vein. The past 15 years have witnessed experimental efforts at catheter-based management of CDVI. This review describes the initial designs and experimental evolution of a mechanical and bioprosthetic venous valve that can be implanted by using a transcatheter technique. These valves consisted of single, double, or triple cusp leaflets made of synthetic or biological materials attached to a carrier or frame. All described devices for percutaneous transcatheter valve placement rely on some form of a vascular stent for valve attachment.

Distal arteriovenous fistula to maintain patency of the venous drainage of a latissimus dorsi flap following subclavian vein repair

Successful reconstructive surgery with muscle flaps depends on adequate arterial supply and undisturbed venous drainage. Combining such surgery with reconstructive vascular surgery of a large-caliber vein that is responsible for the venous drainage of the flap poses an additional challenge--the repaired vein's susceptibility to thrombosis. Every attempt must be made to prevent venous outflow obstruction following muscle flap surgery. Data from the vascular surgery literature demonstrate a low success rate for subclavian vein repair. The success rate with venous reconstructive surgery has been greater when a distal arteriovenous fistula accompanied the repair. The present case described the use of a temporary distal cephalic-brachial arteriovenous fistula to maintain the patency of the venous drainage of a pedicled latissimus dorsi muscle flap, following subclavian vein repair, for one-stage coverage of a large chest wall defect.

Facts and fiction surrounding the discovery of the venous valves

Venous valves are delicate structures, the integrity of which is crucial for the normal function of the venous system. Their abnormalities lead to widespread disorders, ranging from chronic venous insufficiency to life-threatening thromboembolic phenomena. The discovery of the venous valves, however, has been the subject of hot controversy. Even though Fabricius ab Aquapendente is credited with the discovery by most historians, we demonstrate in this paper that other anatomists described them many years before Fabricius ab Aquapendente publicly demonstrated them in Padua in 1579. A thorough review of the historical literature surrounding the discovery of the venous valves was carried out from 1545 to the present under the supervision of the Medical History Department of our institution. Research was performed at the History of Medicine Division of the National Library of Medicine and through MEDLINE access to the medical literature. The Parisian Charles Estienne first mentioned the venous valves in his 1545 publication when he described "apophyses membranarum" in the veins of the liver. Lusitanus and Canano publicly demonstrated them in the azygos vein during cadaver dissections performed in Ferrera, Italy. The Parisian Jacques Sylvius described valves in the veins of the extremities in 1555. The work of these anatomists, however, could not achieve full recognition, because Andreas Vesalius, the leading anatomist at that time, was unable to confirm their findings and strongly denied the existence of venous valves. Vesalius's influence was so powerful that research on the subject was idle until 1579, when Fabricius ab Aquapendente "discovered" the venous valves. About the same time, the German Salomon Alberti published the first drawings of a venous valve (in 1585). William Harvey, a disciple of Fabricius ab Aquapendente, finally postulated the function of the venous valves, providing anatomical support for one of the greatest discoveries in medicine: the blood circulation. Therefore, our investigations revealed that Estienne and Canano discovered the venous valves in the 1530s. Fabricius ab Aquapendente's achievement was their full recognition 64 years later. However, it was not until 1628 that their function was fully understood, with the discovery of the blood circulation by William Harvey.

A multicenter, phase I evaluation of cryopreserved venous valve allografts for the treatment of chronic deep venous insufficiency

PURPOSE

A phase I feasibility study was conducted to determine whether cryopreserved venous valved segments would remain patent/competent in a short-term period (6 months).

METHODS

The target group consisted of 10 patients (C(4-6), E, A(D), P(R)). The exclusion criteria included untreated superficial/perforator venous disease, significant venous or arterial obstruction, hypercoagulability or coagulopathy, and significant preexisting medical conditions. Required preoperative tests were venous duplex, ascending/descending venography, and a physiologic study (eg, APG, blood typing, an ankle/brachial index, and if post-thrombotic, a hypercoagulability work-up). A single-valve transplant was placed below all reflux, aided by anticoagulation with or without a distal arteriovenous fistula. Postoperative assessment included duplex scanning/clinical examination (at 1, 3, and 6 months), descending venogram (at 1 month), and physiologic study (at 1 and 6 months). The primary end point was valve patency/competence, with clinical outcome as a secondary end point. Adverse events were recorded.

RESULTS

After eliminating protocol violations, nine patients with superficial femoral (5) or popliteal (4) vein valve transplants were studied. Six-month actuarial results show a patency rate of 67% +/- 16% and 78% +/- 13%, respectively, a primary and secondary competency rate of 56% +/- 17% and 67% +/- 16%, respectively, and a 100% patient survival rate. Clinical outcome averaged 1.1, with healing and/or freedom from ulcer recurrence, in six of nine patients. A postoperative risk of seroma formation (3) and cellulitis (1) exists.

CONCLUSION

In patients with few remaining therapeutic options, one can achieve a 6-month assisted patency and competency rate of 78% and 67%, respectively, with an improved clinical outcome.

Animal models for the study of lower extremity chronic venous disease: lessons learned and future needs

The purpose of this review is to define animal models of chronic venous disease and to demonstrate how animal studies can impact our understanding and treatment of this disorder. To this end an extensive literature search was conducted highlighting potential animal models of chronic lower extremity venous disease. Scientific investigations using animals to study particular aspects of this disease are also reviewed. This review was conducted by members of the Committee on Research of the American Venous Forum to help provide direction for future venous research endeavors. Useful models of chronic venous occlusive disease involve controlled ligation of a major lower limb vein and multiple tributaries. Such a model can provide sustained venous hypertension and studies using this model have confirmed that an isodiametric graft can provide early hemodynamic relief. Models of primary, postphlebitic, and isolated chronic deep venous insufficiency are available for study. Valve repair or transplantation can positively impact the insufficiency observed in these models. Investigations into valve substitutes have generally been disappointing or are undergoing early evaluation. In conclusion, animal models for the study of some aspects of chronic venous disease do exist and have already affected our clinical approach to patients. The scientific study of basic pathophysiology, diagnostics, end-organ response, and long-term surgical treatments of this disorder in well-controlled animal experiments have not been conducted.

The deep venous system and reverse flow flaps

The deep venous system of the upper and lower extremities was injected with a lead oxide mixture in 2 fresh human cadavers, dissected, radiographed and the sites of the venous valves located. These studies confirmed that the macrovenous connections between the venae comitantes of the distributing arteries were insufficient in number to bypass the venous valves in conventional, distally based reverse flow flaps (e.g. radial, ulnar, peroneal) but revealed an alternative microvenous interconnecting pathway which surrounds the artery as the venae arteriosa. This pathway was investigated in a series of distally based reverse flow saphenous flaps in dogs, comparing flaps where the microvenous connections were left intact (non-skeletonised) with those where these vessels were disconnected with the operating microscope (skeletonised). All non-skeletonised flaps survived subtotally or totally whereas total necrosis was observed in 70% of the skeletonised flaps. Finally a series of haemodynamic studies was performed to test valve competency including extrinsic pressure on the valves. It is concluded that the macrovenous and microvenous pathways, coupled with the variable anatomy of the venous valves, are major factors in determining the survival of reverse flow flaps.

Repair and replacement of deep vein valves in the treatment of venous insufficiency

Venous insufficiency is a widespread condition, the prevalence of venous ulceration being 0.5-1.0 per cent in Western populations. A principal abnormality causing venous insufficiency is deep venous reflux, usually resulting from post-thrombotic valve destruction. Patients undergoing treatment for venous insufficiency should have all venous abnormalities investigated, defined and corrected where possible. Although treatment for superficial and communicating vein incompetence is available, correction of deep vein reflux has been neglected until recently. Deep vein valve physiology, the selection of patients for deep vein valve surgery and methods of valve repair and replacement are reviewed.

Canine model for surgical correction of chronic venous hypertension

A chronic model of venous hypertension was created by iliofemoral venous ligation in the left hindlimb of eight greyhounds (right limb control). Prior to ligation, immediately postligation (T0), and at 2, 4, 6, and 15 weeks postligation (T2-T15), bilateral hindlimb venous pressures were measured at rest. At T2-T15, exercise pressures were measured for 5 min after hindlimb muscle contraction induced under sedation by tetanic (20 sec, 50 Hz, 8 mA) stimulus (S30-S300 sec). Resting and exercise pressures were significantly higher in the ligated hindlimb at all time intervals (resting, P less than 0.001 at T0, T2, T4, T6, and P less than 0.025 at T15; exercise, P less than 0.001 for S30-S300 at T2-T15). In five of the animals at 15 weeks, a cross-femoral venous bypass (CFB) with adjacent adjuvant arteriovenous fistula (AVF) was constructed using autologous external jugular vein. Venous pressures were measured at 2 and 6 weeks post-CFB both at rest and after tetanic muscle stimulation. At 2 weeks, venous pressure in the ligated limb was significantly higher than that in control only after exercise (P less than 0.025 at S30-S120; P less than 0.05 at S150-S180; NS at S240-S300). At 6 weeks, venous pressures were not significantly different at rest or with exercise. All five grafts were patent at 6 weeks. Three of five dogs then successfully underwent ligation of the AVF. At 2 weeks post-AVF ligation there was no difference in resting or exercise venous pressure in the ligated limb compared to control. At 6 weeks post-AVF ligation only two dogs remained for monitoring and in these there was no trend toward venous hypertension in the ligated hindlimb. Graft patency was maintained despite AVF ligation.

Surgical treatment of post-phlebitic syndrome

The post-phlebitic syndrome which succeeds deep vein thrombophlebitis may be treated by various surgical interventions. Removal of incompetent perforating veins and excision of any concomitant skin ulcer with grafting is a usual course of therapy. However, if the skin ulceration and symptoms are actually due to deep venous incompetence then a more direct approach should be attempted. Numerous procedures have been advocated, such as valvoplasty, homologous vein transplant, synthetic valve procedures and autogenous vein valve transplant. It has been demonstrated that autogenous vein valve transplant yields a satisfactory haemodynamically stable result with high valve competency rates. The authors have operated on 10 patients utilizing an autogenous vein valve with good results. Pre- and postoperative data including ascending and descending venography indicate that valvular competence is restored and ulcers heal.

Influence of heparin and low molecular weight dextran on the patency of autogenous vein grafts in the venous system

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Experimental venous thrombectomy

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