Venous thromboembolism (VTE) is a common and potentially avoidable cause of death and illness in hospitalized patients. Each year in the United States, it has been estimated that about 300,000 cases of VTE occur. Mortality can be as high as 3.8 percent in patients with deep vein thrombosis (DVT) and 38.9 percent in those with pulmonary embolism (PE). VTE is associated with a high risk of death in the United States and Europe, with an estimated incidence rate of one in 1,000 patients. VTE is particularly common after a stroke. Approximately 20 percent of hospitalized immobile stroke patient will develop DVT and 10 percent a PE.1

There is a need for clinical practice to change and to reduce mortality and morbidity. As researchers wrote in “Venous Thromboembolism After Acute Stroke:”

Treatment for established venous thromboembolism (VTE) is highly effective in preventing morbidity and mortality, yet pulmonary embolism (PE) accounts for up to 25% of early deaths after stroke. There is little evidence to support the notion that DVT prophylaxis reduces mortality. Identifying VTE risk factors in a patient that has had a stroke should identify the appropriate treatment depending on the high-risk nature inherent in the stroke patients. This is because the current diagnostic paradigm is reactive rather than proactive: the clinician responds to VTE when it becomes symptomatic, in the expectation that initiation of treatment will prevent progression to more serious manifestations. This approach is flawed, because sudden death from PE is frequently unheralded and nonfatal symptomatic pulmonary emboli are often unrecognized or misdiagnosed.

Consequently, the Clots 3 study led by Martin Dennis, MD of University of Edinburgh, Western General Hospital may change the clinical practice to prevent DVT in stroke patients.

The Clots 3 study was a large multi-center randomized controlled trial using thigh length Intermittent Pneumatic Compression IPC). It showed that use of IPC was associated with a one third reduction in the risk of proximal DVT and additionally a 14 percent increase in survival within six-months. The study’s purpose was to evaluate the effectiveness of IPC in decreasing the risk of proximal DVT in patients who have had a stroke.

We interviewed Dr. Dennis about this landmark study and its implications for clinical practice:

How do you think the Clots 3 study will change clinical practice?

CLOTS 3 showed for the first time that thigh-length IPC reduces the risk of DVT after stroke, and moreover improved survival. Therefore, I would expect its use to increase rapidly. Certainly in the UK there are national programs to introduce IPC into all stroke units; national stroke audits are monitoring its use.

During the study, what were the procedures for monitoring the patients skin in those wearing IPC?

We advised that the nurses should check patients three times per day. They should ensure that the patient’s legs are not marking, that the skin appears healthy and the IPC is actually applied properly and switched on.

Were the stroke patients also fitted with thigh length graduated compression stockings (GCS) to wear under theIPC sleeves?

No, given the evidence from the CLOTS 1 trial that GCS do not reduce the risk of DVT after stroke and cause some skin breaks we did not recommend them.

What do your think are the broader implications of your study on the treatment practices for stroke patients?

For immobile patients admitted to hospital after a stroke we think that they should be offered IPC. However, where patients have had very severe strokes which are likely to lead to a very poor quality of life, if they survive, the appropriateness of using treatments like IPC which only aim to increase survival need to be discussed with patients and their families.

During the 6-month follow up period in your study, were you able to identify any increased or decreased readmission rate for the stroke patient? If yes, what factors were identified?

No, we did not measure this. However, I doubt whether there was any difference.

Your study focused on DVT prevention and reduction in mortality. Are your able to identify other possible benefits for IPC?

No, those are the main effects we observed.

Your trial focused on stroke patients. As a result of your study are you able to identify any possible possible implications for other patient populations at high risk for VTE?

It seems very likely that IPC would reduce the risk of DVT in other groups of high risk patients. Indeed there is already quite good evidence for its effect in patients undergoing surgery. However, IPC has not been shown to improve survival in other groups of medical patients, so further studies are needed to demonstrate whether this is the case. After all, the main purpose of DVT prophylaxis is to prevent patients from dying from pulmonary embolism.

What do you foresee for future study in terms of VTE prevention or follow up on the Clots 3 study?

We are planning a large trial to establish whether VTE prevention with IPC and/or anticoagulants reduce the risks of dying amongst medical patients at high risk of VTE. Many clinicians using VTE prophylaxis are unaware that the trials have so far not shown improved survival with current methods of prophylaxis.


For greater patient safety, and to reduce the incidence of DVT in stroke patients, the Clots 3 study shows the effectiveness of using thigh length IPC devices, whereas graduated compression stockings have been shown to be ineffective in stroke patients. This is a new validated approach to prophylaxis for this high-risk patient population both in terms of proximal VTE reduction but more significantly in the reduction of mortality.

To help standardize practice and encourage the use of IPC devices, Dr. Dennis is a member of a panel of healthcare experts from the US and around the world. This panel is developing concise recommendations to help clinicians caring for stroke patients to provide consistent, safe and effective VTE prophylaxis The draft Stroke VTE Safety Recommendations encompass a user friendly four step process for clinicians, shown in Table 1.

In addition, in the United States, according to the OECD, US hospitals stays are shorter and discharges are more costly compared with other industrialized countries. This suggests the need for continued care in the home after hospital discharge or transfer to step down units providing ongoing rehabilitation and care, with the following points to be considered:

  • Ensure the patient is assessed for thigh length intermittent pneumatic compression, not graduated compression stockings continuing into the home or transition of care.
  • Ensure the patient, significant other or caregiver knows the meaning of the patient’s VTE risk and the rationale for continuing thigh length intermittent pneumatic compression post discharge if indicated and warranted by the ordering clinician. This is critical in terms of preventing an avoidable readmission for VTE treatment in the stroke patient.
  • Ensure the patient’s primary care provider has effectively communicated with the next health care team caring for the patient to ensure that the patients continue to receive effective VTE prophylaxis where appropriate.
  • Provide follow through communication regarding the patient’s post discharge plan or care, synopsis of patient’s VTE risk and necessity for early follow up appointment about five days after discharge from the acute hospital.
  1. Kelly J, Rudd A, Lewis R, Hunt BJ. Venous thromboembolism after acute stroke. Stroke. 2001 Jan;32(1):262-7.