Increased incidence of deep venous thrombosis in ALS

I agree that the real incidence of DVT in ALS patients is underestimated, particularly when considering the following conditions of ALS: muscular weakness and atrophy in the legs leads to decreased muscle- pump activity which facilitates blood congestion; reduced fluid intake in ALS with bulbar palsy may induce dehydration and thrombosis; and hypoxemia leads to endothelial cell damage, the production of oxygen-derived free radicals, and venous wall relaxation--causing decreased flow velocity and stasis.

We reported the case of a 61-year-old man with ALS who developed acute respiratory failure from PE which can masquerade as respiratory failure due to progression of ALS. [2] The key in the diagnosis of PE was the blood gas findings for hypoxemia and hypocapnia at admission, which were incompatible with the type II respiratory failure seen in the terminal stage of ALS.

This patient regularly worked for 8 hours in a sitting position using his small wheelchair. Deep-vein echography disclosed marked thrombosis in the right popliteal vein, suggesting that popliteal vein entrapment is a complication of using small wheelchairs with greater restrictions of joint movement. Venous stasis from extended sitting in the wheelchair may enhance the formation of DVT and subsequent PE similar to Economy Class Syndrome which describes air travel-related DVT and PE due to the compression of vessel lesions while sitting in a cramped position during long-distance flights with low aircraft cabin oxygen pressure. [3]

Long-term use of wheelchairs may be related to the occurrences of DVT and PE. Is it possible that patients with DVT and/or PE who had lower %VC and lower leg strength were wheelchair users? In addition, was DVT located in the proximal or distal portion of the popliteal vein in these cases?

The frequency of DVT for individuals undergoing stroke rehabilitation is higher in wheelchair-bound patients than in bedridden patients. [4] From a public health standpoint, Wheelchair Economy Class Syndrome offers a warning not only for long-term wheelchair users with ALS, but also for other immobile patients.

References

1. Qureshi MM, Cudkowicz ME, Zhang H, Raynor E. Increased incidence of deep venous thrombosis in ALS. Neurology 2007 68: 76-77.

2. Kimura F, Ishida S, Furutama D, et al. Wheelchair Economy Class Syndrome in Amyotrophic Lateral Sclerosis. Neuromuscul Disord 2006 16:204-207.

3. Symington LS, Bryan RS. Pulmonary thromboembolism after travel. Br J Dis Chest 1977 71:138-140.

4. Oczkowski WJ, Ginsberg JS, Shin A, Panju A. Venous thromboembolism in patients undergoing rehabilitation for stroke. Arch Phys Med Rehabil 1992 73:712-716.

Disclosure: The author reports no conflicts of interest.

We thank Dr. Kimura for his correspondence regarding our article. [1] We read his paper [2] and have re-analyzed our data to address the queries. The walking scores for the Ayotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS) of the eleven ALS patients, who suffered from DVT, revealed the following walking status at the time of enrollment into the trials (baseline visit):

Non-ambulatory functional movement - two patients

Early ambulation difficulties - three patients

Walks with assistance - five patients

Normal - one patient

It can be postulated that the patients with ALS who suffered from DVT were likely to be immobile at baseline and may have ambulated using wheelchairs. However, we do not have specific data regarding wheelchair usage or ultrasound findings in these patients.

References: The authors report no conflicts of interest.