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Recommended reporting standards for vena caval filter placement and patient follow-up☆☆☆★★★♢

Presented at the Vena Caval Filter Consensus Conference, Chicago, Ill, April 13–14, 1998.

Received 8 September 1998; accepted 3 May 1999.

Article Outline

• PATIENT ASSESSMENT

• DEVICE ASSESSMENT

• PROCEDURAL ASSESSMENT

• PLACEMENT PROBLEMS

• TECHNICAL SUCCESS/FAILURE

• FOLLOW-UP ASSESSMENT

• TEMPORARY AND OPTIONAL DEVICES

• CONCLUSION

• APPENDIX I. PARTICIPANTS IN THE VENA CAVAL FILTER CONSENSUS CONFERENCE

• COMPETITIVE INTERESTS

• References

• Copyright

The use of vena caval filters has increased significantly since the introduction of percutaneous placement techniques and the development of reduced-profile devices. The literature contains hundreds of reports of immediate and long-term outcomes for patients in whom these devices have been placed, but the reports do not use consistent standards, definitions, or techniques, making it difficult to compare outcomes and determine the relative efficacy and safety of the available devices.1, 2, 3

Successful deployment of a vena caval filter fundamentally requires a patent filter, properly positioned within the vena cava in a manner that protects against pulmonary embolism. With this premise, reporting standards have been developed to assess caval filter placement, function, and other outcome parameters. They are applicable to all vena caval filters, regardless of other reportable aspects: basic design, manufacturer, the specialty of the clinician placing the device, the indications for which it was placed, and whether it was intended for permanent or temporary use. These data should be evaluated with rigorous statistical methods to allow unbiased comparisons that should lead to improved outcomes for patients. Extensive literature citations have been included, either to highlight the significance of each standard or to provide examples of typical reports.

PATIENT ASSESSMENT

General patient information, including age, sex, underlying disease and level of severity, and current use of anticoagulation (type and level), should be noted.4, 5 Patient informed consent and institutional review board approval, when appropriate, should be documented. Because outcomes are related to the underlying venous disorder, the presence or absence of venous thromboembolism (pulmonary embolism [PE], deep venous thrombosis [DVT], or both) should be described, along with the extent of DVT involvement for correlation with subsequent status of the limb. PE should be objectively documented with available imaging studies, including radionuclide ventilation/perfusion scans using the Prospective Investigation on Pulmonary Embolism Diagnosis (PIOPED) criteria,6 pulmonary angiography, echocardiography, contrast-enhanced spiral computed tomography (CT), or gadolinium-enhanced magnetic resonance (MR) angiography.7, 8, 9, 10, 11, 12 The presence of DVT should be documented by means of contrast venography, duplex ultrasound scanning, CT, or MR venography.13, 14, 15 The proximal extent of thrombus and the percent of greatest luminal narrowing should be identified (Table I).

Table I.

Staging deep venous thrombosis


	Extent of thrombus	Grading of occlusion
	Calf
	Popliteal
	Femoral	0 = Clear
		1 = Partial occlusion
	Iliac	2 = 0ccluded
	Vena cava (inferior or superior)
	Axillary/subclavian

The patient’s risk factors for venous thrombosis should be identified (Table II).

Table II.

Classification of risk factors for thromboembolism


	Factors
	History of deep venous thrombosis
	Immobilization
	Postoperative status
	Age
	Malignancy and tissue type
	Cardiac disease
	Limb trauma
	Prothrombotic state
	Hormonal therapy
	Pregnancy and postpartum
	Obesity

Based on Porter JM, Moneta G, and International Consensus Committee on Chronic Venous Disease. J Vasc Surg 1995;21: 635-45.

This is especially important when the filter is placed for prophylaxis in the absence of thromboembolism.16, 17, 18, 19, 20

The indications for filter placement should be identified (Table III).

Table III.

Categorical indications for filter placement

	1. Contraindication to anticoagulation (absolute or relative)
	2. Complication of anticoagulation
	a. Failure: objectively documented extension of existing deep venous thrombosis or new deep venous thrombosis or pulmonary embolism while therapeutically anticoagu- lated
	b. Hemorrhage: major or minor
	c. Thrombocytopenia
	d. Skin necrosis
	e. Drug reaction
	f. Evidence/probability of poor compliance
	3. Prophylaxis: no thromboembolic disease90
	4. Prophylaxis with thromboembolism in addition to anticoagulation
	5. Failure of previous device to prevent pulmonary embolism; central extension of thrombus through an existing filter or recurrent pulmonary embolism
	6. In association with another procedure: thrombectomy, embolectomy, lytic therapy91, 92, 93, 94

21, 22, 23, 24, 25 Multiple indications may be present, but only the primary one should be used for group analyses.3, 26 Normal and abnormal factors related to successful filter placement should be described. These include: (1) the transverse caval diameter at the level of desired placement, corrected for magnification; (2) caval anomalies, such as duplication or renal vein anomalies; (3) spinal deformities; and (4) the patency of the planned access site (graded according to Table I).

DEVICE ASSESSMENT

The manufacturer and type of filter should be recorded, as should the specific information concerning the delivery system, such as the size of the introducer system and use of a guidewire. The reason for device selection should be noted (Table IV).

Table IV.

Justification for device selection

	1. Device routinely available at the institution
	a. Clinician preference
	b. Clinical research study
	c. Training
	d. Cost
	2. Specific choice
	a. Diameter of the vena cava
	b. Upper extremity access95
	c. To be positioned above the renal vein
	d. Short period of thromboembolic risk (temporary or optional)
	e. Ease of deployment
	f. Access vein problem (tortuosity, thrombosis, compression, etc)
	g. Freedom from magnetic susceptibility artifact

The intended duration of placement, either permanent, temporary (requiring removal), or optional (may be removed) should be indicated.

PROCEDURAL ASSESSMENT

The training background and specialty of the physician placing the filter (such as interventional radiologist, surgeon, interventional cardiologist, or pulmonologist) should be identified, and the level of experience of the physician should be characterized as either trainee or staff. The timing of the procedure should be classified as elective, urgent (within 24 hours of decision), or emergent (as soon as possible).

The location in which the procedure was conducted (such as the operating room, radiology suite, cardiac catheterization laboratory, bedside, or other) should be identified.27, 28, 29, 30 Any anesthesia other than local should be indicated.

The method by which the vena cava was evaluated before placement of the device, ie, contrast venography or intravascular ultrasound scanning, should be provided.31, 32, 33, 34 When venography is used, the type of contrast and the degree and method of correcting for magnification should be included.35 Identification of the renal veins should be reported.

The site of insertion should be identified by name and location, such as left or right femoral or jugular vein, an upper-extremity vein, the external jugular vein, or by direct vena caval access. This is important because the route of insertion has been shown to affect performance in some cases.36, 37, 38, 39, 40 The method of access should be described as being either percutaneous or venotomy. If ultrasound scanning guidance was used to identify the vessel, this should also be reported. The intended site for deployment should be recorded as infrarenal or suprarenal vena cava, iliac vein, or the superior vena cava.41

PLACEMENT PROBLEMS

The characteristic steps of successful placement are listed in Table V and should be referred to when reporting placement problems.

Table V.

Criteria for successful placement

	1. The delivery system was advanced to the intended placement level
	2. The filter was deployed and fixed at the intended position
	a. No migration (> 20 mm) or embolization of the filter
	b. No extravascular penetration of guidewire or device
	3. The filter configuration was consistent with protection from pulmonary embolism
	a. Complete opening42
	b. Adequate distribution of filtering mechanism (no additional device was placed)96
	c. Alignment with the axis of the vena cava (eg, tilting; record degree)

Problems should be identified by and, in larger series, stratified by these levels or steps and whether clinical sequelae developed as a result.

TECHNICAL SUCCESS/FAILURE

Technical success requires proper placement of the filter. Each filter placement that is attempted should be included in the total number of filter placements reported, following the intent-to-treat rule. Failures occur when the filter cannot be placed as intended and a second attempt is made with a different filter.42, 43, 44, 45, 46, 47

Procedural complications are not the same as technical failures, but both should be reported. Insertion site thrombosis or hemorrhage, infection or the development of an arteriovenous fistula, or positioning that requires placing an additional filter or correcting the placement of an existing filter are considered to be complications and should be identified as such.39, 48, 49 Insertion site thrombosis should be graded as being either occlusive or non-occlusive, and the method of diagnosis should be reported.50, 51, 52 Complications that require additional procedures, prolong hospitalization, or result in death are considered to be major. Events that occur within 24 hours are considered to be early, as compared with those occurring after 24 hours.

FOLLOW-UP ASSESSMENT

Patients with permanently implanted devices deserve routine follow-up.53, 54, 55, 56, 57, 58 When this follow-up is reported, the number of patients observed should be compared with the total number of filters placed at each institution during the period of the report. Censored patients should be indicated as having been lost to follow-up or being dead. The cause of death and method of ascertainment should be identified. The time between filter placement and follow-up should be given as a mean with the standard deviation and median, but in an intermediate or long-term study, success rates should be reported with classic life table or Kaplan-Meier plots.59 Clinical success is defined as a technical success without subsequent pulmonary embolism, significant filter migration or malpositioning, symptomatic caval thrombosis, or other complication requiring removal or invasive intervention.

The preferred method for following up with patients is by clinical examination and objective testing. The clinical examination should include venous duplex examination of the lower extremities for recurrent DVT, chronic venous insufficiency, or both.50, 52, 60, 61, 62 Edema, other post-thrombotic skin changes or ulceration, the current use of anticoagulants,63, 64 any complications resulting in discontinuation of anticoagulant therapy, and the occurrence of suspected or proven PE should be reported. When PE is reported, the method of diagnosis and treatment received should be included. Minimum objective testing should include evaluation of the stability and patency of the filter. Patency of the filter and vena cava should be determined by means of vena cavography, ultrasound scanning, CT, or MR scanning. The findings should be accompanied by statements concerning the adequacy of the examination.65, 66, 67, 68, 69, 70 The report should indicate whether there was thrombus within the vena cava, its location, and whether it was occlusive.

The stability of the filter can be documented by means of orthogonal plain films. From these, the location of the filter relative to its original position at placement in both the horizontal and vertical dimensions should be determined. Change in vertical position and the direction (proximal vs. distal) can be measured and documented.71, 72, 73, 74, 75, 76, 77 The diameter at the base of the filter should be measured. A reduction in diameter of the cone-shaped filters may suggest caval stenosis or occlusion, and expansion can be indicative of extracaval extension of the anchoring devices; therefore, both should be reported.78 More specific tests, such as CT scans, cavography, intravascular ultrasound scans, or MR studies may be indicated to document penetration and/or impingement on an adjacent organ or caval occlusion. Finally, any deformation of the filter, ie, fracture or collapse, should be reported.79, 80, 81, 82, 83, 84, 85

Outcome data should be based on samples of sufficient size to support clinical conclusions. Actual numbers, not just percentages, should be included. Many literature reports are based on small case series or even case reports that make it difficult to determine the magnitude of the problem. Data should be obtained from primary contacts, which are less subject to the bias found in chart reviews or telephone contacts.

TEMPORARY AND OPTIONAL DEVICES

Currently, there are no approved temporary (must be removed) or optional (may be removed) vena caval filters in the United States. However, there is great interest among many physicians in evaluating the efficacy and safety of these devices.86, 87, 88, 89 Clinical studies are currently in progress, and we urge that study results be reported according to these recommendations to facilitate fair evaluation. Reports for these devices should include all the information listed herein and also those factors particular to these devices (Table VI).

Table VI.

Additional reporting criteria for temporary and optional filters

	1. Description of the device, including the materials
	2. Recommendation for duration of placement
	3. Whether it was used in conjunction with another procedure
	4. Whether it was removed and the length of time it was in place
	5. Complications related to removal of the device, ie, inability to remove according to directions, infection, or trapped embolus within the filter, and its fate97
	6. How complication was treated
	7. Need for a permanent filter

CONCLUSION

These recommendations are based on current practice patterns and are subject to change as our knowledge improves, technology changes, and practice develops. However, adherence to these guidelines, which are summarized in Table VII, will allow the combination of reports from multiple sites and provide a better level of evidence on which to base future recommendations.

Table VII.

Summary of reporting standards and level of recommendation


	Required	Highly recommended	Recommended
Patient assessment
Age	✓
Sex	✓
Underlying disease	✓
Anticoagulation use	✓
DVT (diagnosed)	✓
PE (diagnosed)	✓
Risk factors			✓
Indications for placement	✓
Filter placement
IVC transverse diameter	✓
IVC/RV abnormality	✓
Spinal deformity		✓
Access site patency		✓
Device assessment
Device identification	✓
Guidewire use	✓
Reason for selection		✓
Intended duration of placement	✓
Procedural assessment
Physician specialty		✓
Physician training level		✓
Location of procedure			✓
Type anesthesia	✓
Method of IVC evaluation	✓
Insertion site	✓
Method of access	✓
Use of ultrasound scanning	✓
Deployment site	✓
Technical success rate	✓
Clinical sequelae	✓
Follow-up assessment
% patients observed	✓
Patient status	✓
Cause of death			✓
Time to death or failure			✓
Venous duplex		✓
Postphlebitic symptoms		✓
Anticoagulation	✓
Complication of anti-coagulation	✓
Suspected/proven PE	✓
Diagnosis of PE		✓
Treatment of PE			✓
Filter stability	✓
IVC patency	✓
Method of determining patency	✓
Outcomes reported as raw numbers and %	✓
Source of data	✓

DVT, Deep venous thrombosis; PE, pulmonary embolism; IVC, inferior vena cava; RV, renal vein.

APPENDIX I. PARTICIPANTS IN THE VENA CAVAL FILTER CONSENSUS CONFERENCE

Dr Joseph Bonn, Department of Radiology, Thomas Jefferson University; *Dr Kyung J. Cho, Department of Radiology, University of Michigan; Dr Mark Cipolle, Department of Surgery, Lehigh Valley Hospital; Dr Ernest Ferris, Department of Radiology, University of Arkansas; Dr Stuart Geller, Department of Radiology, Massachusetts General, Harvard University; Dr Clement Grassi, Department of Radiology, Harvard Medical School; *Dr Lazar J. Greenfield, Department of Surgery, University of Michigan; Dr Michael Lilly, Department of Surgery, University of Maryland; *Dr Timothy C. McCowan, Department of Radiology, University of Nebraska; *Dr David McFarland, Department of Radiology, University of Arkansas; Dr Stephen Okhi, Department of Radiology, Hartford Hospital; Dr S. Osher Pais, Department of Radiology, University of Maryland; *Ms Mary C. Proctor, Department of Surgery, University of Michigan; Dr John-Baptiste Ricco, Department of Surgery, University of Poitiers; Dr Robert B. Rutherford; Dr Morris Simon, Department of Radiology, Beth Israel Deaconess, Harvard University; Dr Anthony Venbrux, Department of Radiology, Johns Hopkins University; Dr Robert Vogelzang, Department of Radiology, Northwestern University.

COMPETITIVE INTERESTS

Dr Greenfield has funding for laboratory research at the University of Michigan provided by Boston Scientific Corporation; Ms Proctor owns shares of Boston Scientific stock; Dr Bonn is a paid consultant for Boston Scientific Corporation in his role as principal investigator for their FDA-sponsored Symphony Iliac Stent clinical trial; Dr Simon is a paid consultant, part-time scientific director, board member, and shareholder of Nitinol Medical Technologies, manufacturer of the Simon Nitinol filter, and he has a royalty agreement on certain patents assigned to the company.

This article also will appear in the September issue of the Journal of Vascular and Interventional Radiology (published by Lippincott-Raven).

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Ann Arbor, Mich

☆ From the Department of Surgery, University of Michigan (Dr Greenfield), and the Department of Surgery, University of Colorado.

☆☆ Supported by grants from The Lifeline Foundation, The American Venous Forum Foundation, and the Cardiovascular and Interventional Radiology Research and Education Foundation of The Society of Cardiovascular and Interventional Radiology.

★ J Vasc Surg 1999;30:573-9.

★★ Reprint requests: Lazar J. Greenfield, MD, Department of Surgery, University of Michigan Hospitals, 2101 Taubman Center/Box 0346, 1500 E Medical Center Dr, Ann Arbor, MI 48109-0346.

♢ 0741-5214/99/$8.00 + 0 24/1/10053

NO LABEL *Members of the Organizing Committee

PII: S0741-5214(99)70088-1

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