Electrical Foot Stimulation: A Potential New Method of Deep Venous Thrombosis Prophylaxis

James J. Czyrny; Robert E. Kaplan; Gregory E. Wilding; Christopher H. Purdy; Jack Hirsh

Disclosures

Vascular. 2010;18(1):20-27. 

In This Article

Discussion

The relative risk reduction of DVT of approximately 60% by IPC is well established.[1,16–19] This includes a recent meta-analysis of over 2,200 postoperative patients in 15 studies.[20]

Our study indicates that electrical foot stimulation is at least as effective as IPC in increasing venous blood flow velocity in the popliteal and femoral veins during the study period. The compact electrical foot stimulation device used in this study requires only a 9-volt battery power source and therefore does not interfere with ambulation and other activities of daily living. A rechargeable 9-volt lithium battery power source could be used for days at a time.

The electrical foot stimulation device has a mechanism of action similar to that of existing intermittent pneumatic foot pumps. Both increase flow velocity in the popliteal and femoral veins by rapidly discharging blood from the plantar venous plexus. Increased blood flow velocity reduces stasis in the venous sinuses and around the valve cusps. This is particularly important in the venous systems of the gastrocnemius and soleus muscles, where deep vein thromboses originate. The foot pump achieves this effect by intermittently compressing the veins in the plexus by external mechanical compression, whereas the electrical foot stimulation device does so by stimulating the intrinsic foot muscles to contract and thus compress the plantar venous plexus. Given that the intermittent pneumatic foot pump has been shown to reduce the risk of venous thrombosis, it would be reasonable to expect that the electrical foot stimulation device would also be effective clinically, although a study comparing the two modalities in terms of actual VTE prevention is necessary.

Traditional intermittent leg or foot pneumatic compression devices require an AC power source, which tethers the patient and limits mobility. Portable battery- powered IPC devices are now available.[21] These devices are still cumbersome and allow a patient limited mobility and are therefore practical only in the acute hospital setting. Additionally, pneumatic compression devices are difficult to use correctly in a sustained fashion. In one study, only 23% of patients were correctly using a foot compression device on the fifth postoperative day following hip or knee arthroplasty.[22]

Electrical foot stimulation has advantages over electrical calf stimulation. The anatomic variation of the sole of the foot is much less than that of the calf. The range of voltage amplitude required is also less with foot stimulation compared with calf stimulation. This simplifies the design and use of the device.

Our device can be used as long as the plantar foot muscles are accessible to placement of the electrodes and a muscle contraction to the electrical stimulation can be obtained. The most important contraindication to electrical stimulation is the presence of a cardiac pacemaker. Skin lesions affecting the sole of the foot may also be a contraindication. Severe peripheral polyneuropathy, or trauma to the tibial nerve, which innervates the plantar muscles, might prevent muscle contraction from occurring. Finally, pregnancy should be considered a contraindication.

The American College of Chest Physicians in July 2008 published the eighth edition of their evidence-based clinical practice guidelines for antithrombotic and thrombolytic therapy.[23] They recommend that mechanical methods of thromboprophylaxis be used in patients with a high risk of bleeding or as an adjunct to anticoagulant therapies. The guidelines emphasized that careful attention to the use of and optimal adherence to these methods are important. The new guidelines also recommend continued thromboprophylaxis after discharge for hip fracture and total hip and total knee replacement up to 35 days after surgery. Our device has the advantage of being portable and is therefore particularly well suited for prolonged DVT prophylaxis.

Long-term use of electrical foot stimulation will have to address the issue of comfort. The degree of discomfort noted by the subjects in this study should be analyzed in view of the fact that subjects sat continually for 4 hours in rather cramped conditions and that half of the subjects were obese. Furthermore, in our initial study, subjects did not find electrical foot stimulation uncomfortable and two subjects found foot stimulation pleasurable.[11]

Electrical conductive fabrics presently exist that eliminate the need for adhesive electrodes such as those used in our study. Additionally, these soft electrodes, contained within the conductive sock fabric, would not cause increased friction or pressure on the skin surface. This should reduce discomfort, avoid skin breakdown, and enhance compliance.

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