Optional vena cava filters: indications, management, and results

In vivo evaluation of a new vena cava filter

Background

Pulmonary embolism is an important cause of cardiovascular death. Inferior vena cava filters have been shown to be effective for prevention of this condition.

Objectives

To determine the safety, performance and efficacy of a new inferior vena cava filter in an ovine model.

Methods

BKone1 filters are self-centering with over-the-wire deployment, have three filtering regions and are made from nickel-titanium alloy. Eight of these filters were implanted in 8 sheep. The sheep were divided into 4 groups of two animals (A and B) and the number of clots injected differed by group. Two clots were injected in group 2, four in group 3, eight in group 4 and zero clots in group 1. A animals underwent euthanasia soon after the procedure and B animals were observed for 30 days and then euthanized after a control cavography. All inferior vena cavas were processed for histological examination. Clots were prepared in a metal mold, sectioned and then radiopaque markers were inserted. Clot capture was analyzed by identifying the radiopaque marker on fluoroscopy.

Results

No clot migration was observed during follow-up. Control cavographies showed patent inferior vena cavas. Pathological examination indicated little inflammatory tissue response. All clots were captured in the condition with 2 clots, only one clot was missed in the group injected with 4 clots and in the condition of 8 clots, they were partly captured.

Conclusions

The filters were deployed safely. There was a reduction in efficacy as the number of blood clots increased.

The diagnosis and treatment of acute pulmonary embolism

BACKGROUND

Pulmonary embolism (PE) is a cardiovascular emergency with high morbidity and mortality.

METHODS

Review of relevant literature retrieved by a selective Medline search, including current guidelines.

RESULTS

Hemodynamically unstable patients are considered to have high-risk PE, whereas hemodynamically stable patients are considered to have non-high-risk PE. After classification into one of these two risk groups, patients undergo further diagnostic evaluation for PE according to the appropriate risk-adapted algorithm. Patients who are in cardiogenic shock or have persistent arterial hypotension (high-risk PE) should undergo multidetector computed tomography (MDCT) or echocardiography at once, so that a PE, if present, can be treated immediately by thrombolysis. For hemodynamically stable patients with non-high-risk PE the proper diagnostic strategy is determined by the clinical probability of PE, which can be calculated with the aid of validated scoring systems and is based on both MDCT and D-dimer levels. For further risk stratification in hemodynamically stable patients, tests are performed to detect right ventricular dysfunction or myocardial injury, either of which indicates intermediate-risk PE. In addition to specific therapy, patients with high-risk PE, patients at high risk for hemorrhage and these with severe renal insufficiency should be anticoagulated with unfractionated heparin. All other patients should be treated with low-molecular-weight heparin or fondaparinux. Thereafter, long-term oral anticoagulation with vitamin K antagonists is recommended.

CONCLUSION

Modern algorithms have considerably simplified the diagnosis and treatment of acute PE. It would be desirable for these algorithms to be rapidly implemented in routine practice, because speedy diagnosis and immediate treatment can lower the morbidity and mortality associated with PE.