Venowave

Venowave is a specific application of the the wave generating application developed in collaboration with Dr Jack Hirsh, McMaster University and the associated teaching hospitals in Hamilton, Ontario. It is a small wave generator that can be worn under clothes in the area of the calf. It acts like a peristaltic pump, pushing blood through the lower leg towards the heart.

Venowaveis a battery-powered, biomechanical device (0.3 kgs), consisting of a rotating gearmotor that is attached to a flexible sheet via a patented wave generating linkage (dimensions 22 x 11 x 4 cm) (see figure), that generates a repetitive wave-form that moves in one direction along the length of the sheet at speeds of ~2 cm per second. This results in a peristaltic pump action with volumetric displacement of 16 cm³/sec (1 cm amplitude x 8 cm width x 2 cm/sec). Venowave, which is attached firmly to the calf with a velcro support cuff, applies a moving wave of pressure to the underlying tissues and promotes continuous emptying of the leg veins (i.e., pushes blood back towards the heart). The device can be worn while resting or active (e.g., under clothing). There is no other such device currently available.

Venowave is currently being clinically tested and validated for treatment of the postthrombotic syndrome (PTS). PTS occurs after deep vein thrombosis and is characterized by leg pain, heaviness, swelling and skin ulceration. About 250,000 patients have deep vein thrombosis in Canada and the US each year, of which 50% develop PTS and 15% develop severe PTS. PTS is a disabling condition that interferes with activities of daily living, reduces quality of life and can prevent employment. In addition to being important to affected patients, PTS is a major burden to society. It is responsible for a large proportion of venous ulcers for which direct medical costs are estimated at about $500 million per year, and which lead to the loss of about two million workdays per year in the US.

Fasten the VW3 to the back of the calf of the leg with the white dot on the switch (left hand side of unit) pointing upwards toward the knee. (See photo opposite side of page) The unit may be worn with or without a compression stocking. Adjust the strap tension so that there is firm pressure on the back of the calf. Turn unit on. Warning: To prevent injury from moving parts keep fingers away from the underside of the machine and only turn machine ON when it is covered with soft goods.

Use 6 x AA batteries. Rechargeable alkaline batteries are recommended however any AA batteries may be used including NiCad or NiMih. Average battery life varies depending on the battery type. Alkaline cells typically provide 20 hrs of continuous use. To replace batteries lift cover to expose batteries (Note: Pull back cover 90 degrees only. Pulling it too far back may damage cover), remove and replace with freshly charged or new batteries.

Soft goods (Part # V3-SG00) consist of 2 velcro straps securing a fabric wrap and a non slip pad (Part #V3-SG01). The longer strap goes on top (White dot on switch points to top). The VW3 slides into a sleeve sewn on to the fabric (See photo). The non slip pad is placed with the white surface against the back of the calf. Only use soft goods supplied for use with this machine.

If unit does not operate check batteries and make sure that they are fully charged and properly installed.If unit slows down or stops, check batteries. If batteries are OK then reduce pressure on Velcro straps.

9 Volts DC, 1 watt VW3 is made in Canada by Saringer Research Inc.US Pats #6,029,294, #6,269,500 B1 + other pats pending

Treatment of Post Thrombotic Syndrome with Venowave: Overview of studies performed to date

The main mechanism for development of PTS is destruction of the valves of the deep veins of the leg by the thrombosis. This leads to high venous pressures in the lower leg, and poor blood flow (“venous stasis”), while patients are standing or walking. Venowave, by promoting venous blood flow, can reverse these effects. We have performed the following studies to evaluate ability of Venowave to successfully treat PTS. First, in 10 patients with chronic limb edema, we demonstrated that wearing Venowave produces an 88% increase in blood flow at the common femoral vein as measured with doppler ultrasound (p=0.03) Second, we demonstrated that Venowave resulted in a substantial clinical improvement in symptoms in 4 of 6 subjects with severe, intractable post-thrombotic syndrome. (see appendix #3) Third, based on the positive findings of the two previous studies, we performed a larger placebo-controlled trial to definitively determine if Venowave is an effective treatment for patients with severe PTS (see appendix #4). Severity of PTS symptoms and health-related quality of life were measured using validated scales in 32 patients from McMaster and McGill universities while patients were using 1) Venowave, and 2) an Inactive Venowave device (altered so as not to deliver a wave of pressure, therefore, acting as a placebo). Marked improvement in PTS occurred with Venowave in 12 patients and occurred with the Inactive device in 6 patients (2 patients had improvement during both treatment periods). Severity of PTS symptoms was less, and health-related quality of life was better, with Venowave that with the Inactive device; both of these differences were highly statistically significant (P=0.004). The findings of the first 2 studies were presented at the Scientific Meetings of the American Society of Hematology (2002) and the International Society on Thrombosis and Haemostasis (2003), and the third study is will be presented at this year’s American Society of Hematology meeting in December; these organizations are the premier international scientific meetings in this field. As the only other treatment for PTS is use of graduated compression stockings (modestly efficacy), and as Venowave can be used in addition to such stockings, there is great clinical demand for a new treatment for PTS and Venowave has the potential to meet that need.

To date, Venowave has only been evaluated as a treatment for the PTS. Venowave is also expected to be an effective way to preventing deep vein thrombosis after surgery, as venous stasis is the main mechanism of thrombosis in such patients. Venowave could supplant blood-thinning therapies for this purpose as, unlike such drugs, Venowave will not cause bleeding, and it is also easy to use after patients leave hospital. Prevention of venous thrombosis is a very large market; for example, considering major orthopaedic surgery alone, about 60,000 hip and knee replacements are performed in Canada each year.

Effects of a Novel Venous-return Assist Device ("Venowave") on Lower Limb Venous Flow

Authors: Martin O’Donnell MB, Jeff Ginsberg MD, John Saringer, Clive Kearon MB PhD Debbie Magher, Jim Julian MMath, Jack Hirsh MD

Introduction: Post-thrombotic syndrome (PTS) is a chronic, often debilitating, complication of deep vein thrombosis that is usually characterised by swelling, pain and varicose eczema of the affected limb. Venous hypertension and valvular incompetence are believed to be the main factors responsible for the development of PTS. To date, evaluated therapies have primarily focused on countering increased venous hydrostatic pressure using intermittent compression pumps and/or graduated compression stockings (GCS). Although compression pumps provide symptomatic relief in most patients, they are expensive and inconvenient. GCS are convenient but are effective in only a minority of patients. The "Venowave", a lower limb venous-return device, may be an effective treatment for the PTS Objective: To determine if the Venowave increases peak venous flow in normal subjects and patients with the PTS. Device: The Venowave consists of a flexible planar sheet which is placed longitudinally on the posterior aspect of the calf and attached firmly about the leg with an adjustable support cuff. A battery operated rotating motor generates a peristaltic wave-form motion on the flexible planar sheet. It is designed to increase venous flow by upward volumetric displacement. It may be used with compression stocking and may be worn when mobile. Methods: The effect of Venowave on peak venous flow (PVF) in the common femoral and popliteal veins was evaluated in 10 normal subjects and 9 patients with PTS. PVF was calculated from ultrasound measurements of peak venous velocity and vein diameter. In control subjects we estimated PVF at; 1) Baseline; 2) Venowave device alone; 3) GCS (25mmHg) alone and; 4) Venowave device with GCS. In subjects with PTS, we estimated PVF at 1) Baseline; 2) Venowave device after 2 minutes of use; and 3) Venowave after 50 minutes of use. Analysis was performed using repeated measures ANOVA (main effects model) on the log transformed data (data distribution was skewed). Results: Normal subjects: Baseline mean PVF was 0.273 l/min at popliteal vein and 0.887 l/min at common femoral vein. Venowave resulted in a 32% increase in popliteal PVF (p=0.004) and a 15% increase in common femoral PVF (p=0.081). GCS resulted in a 40% increase in popliteal PVF (p=0.025) and a 20% increase in common femoral vein PVF (p=0.007). There was no evidence of interaction between Venowave and GCS. PTS subjects: Baseline mean PVF was 0.329 l/min at popliteal vein and 0.989 l/min at common femoral vein. Venowave resulted in a 64% increase in popliteal PVF (p=0.001) but did not significantly increase common femoral PVF at time 2 minutes. However, Venowave resulted in an 88% increase in common femoral vein PVF (p=0.029) at 50 minutes. There was no significant increase in PVF at popliteal vein at 50 minutes. Conclusions: Venowave increased PVF in controls and patients with PTS. This device has potential as a treatment for PTS and as a method to prevent venous thrombosis in high-risk patients.

Evaluation of a Venous-return Assist Device (Venowave) to Treat Post-thrombotic Syndrome: A Pilot Study

Martin O'Donnell, MB ¹*, Jeff Ginsberg, MD ², John Saringer ³*, Clive Kearon, MB PhD ⁴, Deborah Magier, RN ²*, and Jack Hirsh, MD ¹. ¹Henderson Research Centre, McMaster University, Hamilton, Ontario, Canada, L8V 1C3; ²Chedoke Thromboembolism Unit, McMaster University, Hamilton, Ontario, Canada; ³Saringer Research Inc, Stouffville, Ontario, Canada, L4A 7X5 and ⁴Thromboembolism Unit, Dept of Medicine, McMaster University, Hamilton, Onatrio, Canada, L8V 1C3.

Background: Graduated compression stockings and pneumatic compression pumps are used to treat Post-thrombotic syndrome (PTS) but both have limitations including uncertain efficacy and lack of portability, respectively. Venowave, a new compact mechanical device, consists of a flexible planar sheet attached to a battery-operated motor that generates a peristaltic wave-form motion. When worn firmly attached to the back of the calf, the Venowave results in upward volumetric displacement and increase venous flow. Consequently, Venowave has the potential to be an effective treatment for the PTS that can be worn under clothing while active. Objective: To determine if daily use of the Venowave for 4 weeks reduces symptoms, improves quality of life (QOL), and improves ability to perform activities of daily living (ADL) in patients with PTS and/or other causes of chronic leg edema. Methods: Ten subjects with chronic lower limb edema (7 with PTS, 2 with primary lymphedema and 1 with pre-tibial myxedema) were studied. Subjects were asked to wear Venowave for at least 2 hours per day for 4 weeks. The VEINES-questionnaire (a validated, disease-specific QOL instrument) was completed at baseline and 4 weeks. In addition, a 7-point Likert Scale, designed to measure change in symptoms, ADL, and perceived QOL, was completed at 4 weeks. At the end of the 4-week period, patients that had improvement in leg discomfort and swelling, and also had improvement in ability to perform ADL or improved QOL, were considered ‘treatment successes'. Results: 'Treatment success' occurred in 5/10 subjects [95%CI 18 to 81%], including 4/7 [95%CI 18 to 90%] with PTS. All 4 patients with severe PTS responded to use of the Venowave. Conclusions: Venowave shows promise as a new therapy for PTS.

Evaluation of a Venous-return Assist Device (Venowave^TM) to Treat Severe Post-Thrombotic Syndrome (VENOPTS): A Randomized Controlled Trial

O’Donnell M, McRae S, Kahn SR, Julian J, MacKinnon B, Magier D, Strulovitch C, Kearon C, Lyons T, Hirsh J, Ginsberg JS.

Severe post-thrombotic syndrome (PTS) is responsible for considerable disability, reduced quality of life and increased health care costs.Current therapies are limited and often ineffective. Methods: We performed a two-center, randomized, cross-over controlled trial to evaluate Venowave^TM, a novel lower-limb venous return assist device, for the treatment of severe PTS. Eligible subjects were allocated to receive, in randomized order, Venowave^TM for 8 weeks and control-device for 8 weeks. Participants were crossed-over after a 4-week (wash-out) period. The primary outcome measure was a clinical success, defined as; 1) reported benefit from the device; 2) moderate or greater improvement in symptoms of PTS; and 3) willingness to continue using the device. Secondary outcome measures included venous disease-specific quality of life (QOL) (measured by VEINES-QOL questionnaire; higher scores indicate better QOL) and PTS severity (measured by Villalta PTS scale; higher scores indicate more severe PTS). The study was registered with ClinicalTrials.gov (NCT00182208). Results: Thirty-two patients were enrolled. Of these, 26 (80%) were also using graduated compression stockings. Twenty-six participants completed both trial periods. The primary outcome measure occurred in 10 participants receiving Venowave and 4 participants receiving the control-device (P=0.1). Two participants reported a clinical success with both devices. Mean Villalta scale score at the end of treatment period was significantly lower for Venowave^TM (12.2; SD 6.3) compared to control (15.0; SD 6.1)(P=0.004). Mean VEINES-QOL score at the end of treatment period was significantly greater for Venowave^TM (52.5; SD 5.8) compared to control (50.2; SD 6.2). (P=0.004) Conclusions: Venowave^TM is a very promising new therapy for patients with severe PTS, which may be used alone or in combination with graduated compression stockings. In our study population of patients with severe PTS, refractory to standard therapies, almost one-third of patients reported clinical improvement with Venowave^TM.

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