CLINICAL STUDY
Improving Inferior Vena Cava Filter Retrieval Rates with the Define, Measure, Analyze, Improve, Control Methodology Patrick D. Sutphin, MD, PhD, Stephen P. Reis, MD, Angie McKune, RN, BSN, Maria Ravanzo, MPAS, Sanjeeva P. Kalva, MD, and Anil K. Pillai, MD
ABSTRACT Purpose: To design a sustainable process to improve optional inferior vena cava (IVC) filter retrieval rates based on the DMAIC methodology of the Six Sigma process improvement paradigm. Materials and Methods: DMAIC, an acronym for Define, Measure, Analyze, Improve, and Control, was employed to design and implement a quality improvement project to increase IVC filter retrieval rates at a tertiary academic hospital. Retrievable IVC filters were placed in 139 patients over a 2-year period. The baseline IVC filter retrieval rate (n ¼ 51) was reviewed through a retrospective analysis, and two strategies were devised to improve the filter retrieval rate: (a) mailing of letters to clinicians and patients for patients who had filters placed within 8 months of implementation of the project (n ¼ 43) and (b) a prospective automated scheduling of a clinic visit at 4 weeks after filter placement for all new patients (n ¼ 45). The effectiveness of these strategies was assessed by measuring the filter retrieval rates and estimated increase in revenue to interventional radiology. Results: IVC filter retrieval rates increased from a baseline of 8% to 40% with the mailing of letters and to 52% with the automated scheduling of a clinic visit 4 weeks after IVC filter placement. The estimated revenue per 100 IVC filters placed increased from $2,249 to $10,518 with the mailing of letters and to $17,022 with the automated scheduling of a clinic visit. Conclusions: Using the DMAIC methodology, a simple and sustainable quality improvement intervention was devised that markedly improved IVC filter retrieval rates in eligible patients.
ABBREVIATIONS CPT = Current Procedural Terminology, DMAIC = Define, Measure, Analyze, Improve, Control, FDA = Food and Drug Administration, IVC = inferior vena cava, PDSA = Plan, Do, Study, Act, QI = quality improvement, RVU = relative value unit
In August 2010, the U.S. Food and Drug Administration (FDA) released a communication on the removal of retrievable inferior vena cava (IVC) filters and issued the From the Division of Interventional Radiology, Department of Radiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390. Received August 19, 2014; final revision received and accepted November 21, 2014. Address correspondence to P.D.S.; E-mail: [email protected] From the SIR 2014 Annual Meeting. P.D.S. is inventor on patent applications owned by the Board of Trustees of Leland Stanford Jr. University and Auckland Uniservices Limited. S.P.K. is a paid consultant for CeleNova BioSciences, receives royalties from Elsevier and Amirsys, and is an investor in AltheaHealth, Inc. None of the other authors have identified a conflict of interest. Appendices A and B are available online at www.jvir.org & SIR, 2015 J Vasc Interv Radiol 2015; XX:]]]–]]] http://dx.doi.org/10.1016/j.jvir.2014.11.030
following recommendation: “FDA recommends that implanting physicians and clinicians responsible for the ongoing care of patients with retrievable IVC filters consider removing the filter as soon as protection from PE [pulmonary embolism] is no longer needed” (1). In May 2014, the FDA updated the communication to include reference to a mathematical model that suggests if the patientʼs risk of pulmonary embolism has resolved, the risk/ benefit profile begins to favor removal of the IVC filter between 29 and 54 days after IVC filter placement (2,3). A systematic literature review of retrievable IVC filters by Angel et al (4) confirmed that most (93%) complications associated with retrievable IVC filters occurred with long-term use (4 30 d). Several reports have found high rates of IVC penetration with Celect (Cook, Inc, Bloomington, Indiana) (22%–93%) and Günther Tulip (Cook, Inc) (22%–78%) IVC filters (5–7) associated with longer dwell times. IVC filter fractures are the most common complication reported in the Manufacturer and
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User Facility Device Experience database with a rate up to 16% in the literature (6,8–11). A Kaplan-Meier survival analysis by Tam et al (9) estimated a 40% fracture rate at 5.5 years for the Bard Recovery filter (Bard Peripheral Vascular, Tempe, Arizona). IVC filter retrieval rates are heterogeneous across institutions and patient populations. Estimated IVC filter retrieval rates in the Medicare population were 1.2%–5.1% for the 65,041 filters placed in 2008 (12). A systematic review of the literature reported retrieval rates of 12%–45% with a mean of 34% and an average retrieval time of 72 days (4). Retrieval rates with dedicated follow-up have been reported to approach 60% (13,14). Given the risk of adverse events with the long-term use of retrievable IVC filters and the FDA recommendations, we initiated a quality improvement (QI) project with a goal to increase the retrieval rate in eligible patients at our institution to 35% within 1 year of placement. The design of the QI project was based on the DMAIC methodology. DMAIC is an acronym for Define, Measure, Analyze, Improve, and Control. DMAIC is a core tool in the Six Sigma paradigm developed in industry for process improvement with the aim to reach a level of quality 6 SDs above the average, equivalent to 3.4 defects of per 1 million opportunities. DMAIC has been successfully implemented over a wide range of disciplines and has previously been adopted in the health care setting (15–18).
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mined the success of the program. Secondarily, the percentage of patients seen in the clinic after filter placement was used as a measure of patient follow-up. Analyze the Process. The existing filter placement and retrieval process was evaluated (Fig 2). The IVC filter placement process began with a request from the referring physician. An IVC filter was subsequently placed, and instructions on how to arrange for IVC filter removal were placed at the end of the dictation if the filter was retrievable (Fig 2). The multidisciplinary team reviewed the process and discussed the strengths and weaknesses and brainstormed to identify barriers to IVC filter removal over multiple sessions. The barriers to removal were grouped into four categories: provider, patient, clinical, and systems. The barriers were further classified into controllable (Fig 3a) and uncontrollable
MATERIALS AND METHODS DMAIC Methodology as Applied to the Current Project This institutional review board–approved, Health Insurance Portability and Accountability Act–compliant QI project with retrospective and prospective components was conducted as part of a clinical safety and effectiveness project. The core team included a lead interventional radiologist, nurse coordinator, internal medicine nurse navigator, and QI facilitator. Additional members of the multidisciplinary team included interventional radiologists, interventional radiology physician assistants, a pulmonologist, and a hematologist. The DMAIC methodology set a framework for process improvement, and it was applied sequentially as detailed subsequently and in Fig 1. Define the Problem. IVC filter complications occur with long-term use often after the risk of pulmonary embolus has subsided. The presence of an IVC filter after the indication for placement has resolved was defined as the problem. In addition, after initiating the improvement process, it was recognized that poor clinical followup of patients with IVC filters was a major contributing factor and was defined as a secondary problem. Measure the Problem. The IVC filter retrieval rate in eligible patients was the measure that ultimately deter-
Figure 1. DMAIC methodology. Graphic representation of the DMAIC model of process improvement. (Available in color online at www.jvir.org.)
Figure 2. Existing IVC filter placement process. Flow diagram of the existing filter placement process reveals that the referring physician (MD) determines when the filter is no longer indicated and requests filter removal.
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(Fig 3b) barriers. Key barriers in the provider category were provider knowledge and communication; patient knowledge and follow-up after the procedure were key barriers in the patient group. In addition, barriers in the clinical and systems categories included lack of a formal patient database and shortage of permanent filters in stock for patients in whom a permanent filter was desired. Improve the Process. To improve the filter placement and retrieval process, new workflows were designed to address the controllable barriers (Fig 4). After 3 months of planning, the multidisciplinary group devised two workflows. The first workflow was designed for patients in whom an IVC filter had already been placed between September 2012 and April 2013 (Fig 5). In this group, a letter was sent to the primary physician or hospitalist and
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patient to schedule a clinic visit with a lower extremity venous ultrasound study. The ultrasound study was performed to (i) detect failure of anticoagulation and (ii) check for new development of lower extremity thrombus if none was previously reported. If a response was not received at 2 weeks, a second letter was mailed, and the process was repeated until three letters were sent. “No response” was documented in the electronic medical record, and no further follow-up was performed. A second workflow was designed for patients who were to have an IVC filter placed during May 2013 or later. This workflow consisted of automatic scheduling of a clinic visit and lower extremity venous ultrasound 4 weeks after IVC filter placement if the patient was an outpatient or at 4–6 weeks after discharge if the patient was an inpatient. The extended inpatient follow-up
Figure 3. Barriers to IVC filter removal from the multidisciplinary team brainstorming sessions are shown in fishbone diagrams and are divided into (a) controllable and (b) uncontrollable barriers. PT ¼ patient; pt ¼ patient.
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Figure 4. Action items for improvement. Fishbone diagram demonstrating the actionable items based on controllable barriers to filter removal.
scheduling was done to account for the variable course of convalescence after discharge (Fig 5). The purpose of the clinic visit was to educate the patient on IVC filters and to determine patient candidacy for filter retrieval.
Control the Process. An IVC filter database was created and maintained by a physician assistant, and any clinic “no shows” were investigated and documented. In addition, the referring physician was notified to improve provider education and buy-in. The process was reviewed monthly by the core team. Quarterly meetings of the multidisciplinary team were held to evaluate the outcome of this QI project and to determine if adjustments were needed.
Patient Cohorts Between January 2012 and December 2013, retrievable IVC filters were placed in 139 patients (71 men and 68 women; average age, 64 y; range, 21–98 y). These patients were divided into three groups based on the time period when the IVC filters were placed. Patients who had a filter placed in the 8-month period extending from January 2012 to August 2012 made up the “baseline” group (n ¼ 51). This group was used to calculate the baseline IVC filter retrieval rate. Patients who had an IVC filter placed in the 8-month period between September 2012 and April 2013 made up the “letters” cohort (n ¼ 43). The patients in this group and the referring physicians were retrospectively contacted by letters (Appendices A and B, available online at www. jvir.org) beginning on May 22, 2013, to schedule a clinic visit to evaluate for filter retrieval. The “prospective” group comprised patients (n = 45) who had an IVC filter placed in the 8-month period between May 2013 and December 2013. Patients in the prospective group were scheduled for a clinic visit at the time of filter placement.
Statistical Methodology IVC filter retrieval rate is expressed as a percentage and calculated based on patients who are eligible for retrieval. The retrieval rate is calculated as follows: (%) Retrieved = IVC filters retrieved/(total IVC filters placed (patients ineligible for filter retrieval)) * 100. The clinic visit was used to determine eligibility for retrieval, and the filter retrieval rate was calculated independently of the clinic visit rate. Patients were considered ineligible for filter retrieval only if they were evaluated in the clinic or by phone and found to have any contraindication to or a failure of anticoagulation and required continued mechanical prophylaxis. Deceased patients were also considered ineligible for retrieval. Patients who did not have clinical follow-up or failed to keep their appointment remained in the pool of eligible patients. In the baseline group, 15 of 51 patients were categorized as ineligible owing to death. In the letters group, 18 of 43 patients were ineligible for retrieval (6 deaths and 12 patients with persistent contraindication to anticoagulation). In the prospective group, 16 patients were considered ineligible for retrieval (12 deaths, 3 patients with persistent contraindication to anticoagulation, and 1 patient with failure of anticoagulation). Three patients in the letters group and one patient in the prospective group continued their care elsewhere and were included in the equation as eligible for retrieval. Statistical comparison was made between the retrieval rates of the baseline group and the letters group and the baseline group and the prospective group using Fisher exact test (R statistical computing software [http:// www.R-project.org]). A P o .05 was considered significant.
RESULTS Follow-up Clinic Visits None of the patients in the baseline cohort (n = 51) of patients had clinic visits. The introduction of letters mailed retrospectively (ie, letters group) to the primary care
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Figure 5. Modified workflow for IVC filter placement and removal. Flow diagram demonstrating the modified workflow for patients with an IVC filter. A retrospective workflow was designed for patients who had an IVC filter placed between September 2012 and April 2013 where letters were mailed to the referring physician and patient (letters cohort). A prospective workflow was also designed for IVC filters placed between May 2013 and December 2013 where a clinic visit was prospectively scheduled (prospective cohort). EMR ¼ electronic medical record; LE ¼ lower extremity.
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physician or hospitalist and patient raised the percentage of patients seen in the clinic to 19% (n = 43). Automated scheduling of a clinic visit (ie, prospective group) further improved the percentage of patients seen in the clinic to 49% (n = 45) (Fig 6).
Filter Retrieval Rates The increased number of patients seen in the clinic was associated with an improved IVC filter retrieval rate. Our baseline cohort of patients had an 8% (n ¼ 51) IVC filter retrieval rate in eligible patients, which increased to 40% (n ¼ 43) in the letters group and 52% (n ¼ 45) in the prospective group (Fig 6). The retrospective letter–based workflow and the prospective workflow resulted in a statistically significant increase in the filter retrieval rate relative to the baseline group based on Fisher exact test with P ¼ .03 and P ¼ .007, respectively. The average time of retrieval was 64 days (range, 58–70 d) in the baseline group, 137 days (range, 36–265 d) in the letters group, and 59 days (range, 0–199 d) in the prospective group. Across all groups, 28 IVC filters were retrieved. Although two patients required three attempts to remove the IVC filter, all IVC filters in patients who presented for retrieval were ultimately removed.
Improved Retrieval Rates Increase Revenue Financial gains of this QI project resultant from the increased number of clinic visits and improved retrieval rate were assessed. Revenue for a clinic visit was calculated based on the Medicare reimbursement of $51.76 (Current Procedural Terminology [CPT] code 99213) for a clinic visit at our institution plus the Medicare reimbursement for a bilateral lower extremity ultrasound scan of $35.79 (CPT code 93970). The reimbursement for a clinic visit with imaging was $87.55. Medicare
Figure 6. Modified workflow increases clinic visits and retrieval rate. Bar graphs represent the percent of patients seen in the clinic and IVC filter retrieval rates in the period before intervention (baseline, January 2012–August 2012), in the period after the mailing of letters (letters, September 2012–April 2013), and after the implementation of a formal clinic-based process (prospective, May 2013–December 2013). Percent seen in clinic was calculated using the following formula: Percent clinic ¼ ([clinic visit þ pending clinic visit]/total IVC filters placed) 100.
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reimbursement for IVC filter retrieval was $382.25. Based on these values, the revenue per 100 IVC filters placed was $2,249 for the baseline cohort, $10,518 for the letters cohort, and $17,022 for the prospective cohort (Fig 7). Relative value units (RVUs) were also calculated for each group and were as follows: baseline, 43 RVUs; letters, 202 RVUs; and prospective, 327 RVUs.
DISCUSSION We undertook a QI project to increase the IVC filter retrieval rate using the DMAIC methodology of the Six Sigma process improvement adopted from industry. DMAIC is a systematic sequential framework for longterm process improvement that decomposes process improvement into five simple elements: define, measure, analyze, improve, and control. It is ideal for an established workflow that is not meeting expectations. A poor IVC filter retrieval rate was defined as the problem at the start of the QI project with a goal to improve the filter retrieval rate to 35%. A new workflow was designed that emphasized at the time of IVC filter placement the requirement of a clinic visit after the procedure, which improved the IVC filter retrieval rate to 52% in eligible patients. Other process improvement paradigms have been used in the health care setting. Kaizen (Japanese word meaning to “make better”) uses the PDSA (Plan, Do, Study, Act) or Deming cycle framework. It is an iterative improvement cycle that emphasizes quick and early failure by making improvements on a small scale or trial basis. First, a Plan is made and implemented on a
Figure 7. Estimated revenue per 100 IVC filters. Bar graph represents the estimated revenue production in the baseline period (January 2012–August 2012), after the mailing of letters period (letters period, September 2012–April 2013), and after the implementation of a formal clinic-based prospective period (May 2013–December 2013). Clinic visit revenue ¼ Medicare reimbursement of $51.76 for clinic visit (CPT code 99213) plus Medicare reimbursement average for bilateral lower extremity venous ultrasound of $35.79 (CPT code 93970). Removal revenue ¼ Medicare reimbursement of $382.25 for IVC filter removal (CPT code 37193).
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small scale in the Do phase. The results of the trial are evaluated in the Study phase and are adopted, adapted, or abandoned in the Act phase (19). The iterative nature of the improvement cycle with small changes often takes several iterations to arrive at a manageable process. PDSA and DMAIC share common elements, including planning, process evaluation, and correction phases. However, DMAIC is a linear, long-term continuous QI methodology, whereas PDSA is a rapid, cyclic, shortterm process. PDSA is best employed when an established workflow is absent or baseline data do not exist and frequent changes have to be made to create a new process. Our project was suited for the DMAIC methodology because there was a process, although inefficient, in place. DMAIC also emphasizes sustaining improvements, and to this end, monthly reviews of follow-up and retrieval rates were performed as well as quarterly multidisciplinary meetings. Other methodologies include root cause analysis and failure mode and effect analysis. Root cause analysis can be a part of the DMAIC process or a standalone methodology that asks “5 whys” to determine the root cause of a problem. Failure mode and effect analysis is a systematic method to evaluate a process and identify where and how it might fail to identify parts of a process that are most in need of change. Several other groups have reported strategies to improve the filter retrieval rates. Minocha et al (14) found that IVC filter retrieval rates were significantly improved from 29% to 60% after the creation of a comprehensive database and a dedicated IVC filter clinic. Another approach is to contact patients directly via mail at regular time intervals after IVC filter placement based on review of the electronic medical record using a database designed specifically for IVC filter follow-up. Lynch (13) found that this approach improved filter retrieval rates from 24% to 59%. Another small study of a radiology-led system for IVC filter removal did not significantly improve retrieval rates. The filter retrieval attempt rate in that study was already 50% at baseline and increased only slightly to 55% (20). The DMAIC framework is a linear, long-term process of continuous improvement that is best suited for underperforming processes with definable and measurable endpoints. Other potential applications in interventional radiology include improving patient preparation before the procedure to minimize procedure room downtime, central line placement procedures to reduce central line– associated bloodstream infections, and work-up of patients with gastrointestinal bleeding to maximize yield of mesenteric angiography. This study has several limitations. The historic retrieval rate in the baseline cohort was a control for new workflow implementations. Because this patient cohort received no dedicated IVC filter clinical followup, it was difficult to designate patients as ineligible for filter removal. Patients were considered ineligible for
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retrieval based only on patient death, likely underestimating the filter retrieval rate in this group of patients. The retrieval rate may also be underestimated in the letters group because these patients were contacted in some cases only several months after filter placement, which may have resulted in fewer patients seen in the clinic. Direct comparison between the letters group and prospective group based on retrieval rates is not fair because the associated workflows were implemented under different time periods and circumstances. Nevertheless, we favored the scheduling of the clinic visit at the time of IVC filter placement based on ease of implementation versus mailing of letters. Although the QI project focused on retrievable filters, another limitation is the ill-defined role of permanent IVC filters in our practice. During the 2-year study period, six permanent filters were placed on an inconsistent operator-dependent basis. Additional permanent filters may have been placed, but a lack of inventory of permanent IVC filters forced substitution with retrievable filters. In conclusion, the DMAIC methodology was used to review systematically the current IVC filter placement and retrieval process and restructure the workflow to improve clinical follow-up and IVC filter retrieval. The existing filter removal process placed the burden of filter removal on the referring physician, whereas the restructured workflow increased the role of the interventional radiologist in deciding when the filter is no longer indicated. DMAIC process improvement significantly increased our filter retrieval rates and revenue associated with filter retrieval.
REFERENCES 1. FDA. Removing retrievable inferior vena cava filters: initial communication. 2010. Available at: http://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/ucm221676.htm. Accessed October 30, 2014. 2. FDA. Removing retrievable inferior vena cava filters: FDA safety communication. 2014. Available at: http://www.fda.gov/MedicalDevices/Safety/ AlertsandNotices/ucm396377.htm. Accessed October 30, 2014. 3. Morales JP, Li X, Irony TZ, Ibrahim NG, Moynahan M, Cavanaugh KJ. Decision analysis of retrievable inferior vena cava filters in patients without pulmonary embolism. J Vasc Surg Venous Lymphat Disord 2013; 1:376–384. 4. Angel LF, Tapson V, Galgon RE, Restrepo MI, Kaufman J. Systematic review of the use of retrievable inferior vena cava filters. J Vasc Interv Radiol 2011; 22:1522-1530. e3. 5. Sangwaiya MJ, Marentis TC, Walker TG, Stecker M, Wicky ST, Kalva SP. Safety and effectiveness of the Celect inferior vena cava filter: preliminary results. J Vasc Interv Radiol 2009; 20:1188–1192. 6. McLoney ED, Krishnasamy VP, Castle JC, Yang X, Guy G. Complications of Celect, Gunther tulip, and Greenfield inferior vena cava filters on CT follow-up: a single-institution experience. J Vasc Interv Radiol 2013; 24:1723–1729. 7. Durack JC, Westphalen AC, Kekulawela S, et al. Perforation of the IVC: rule rather than exception after longer indwelling times for the Gunther Tulip and Celect retrievable filters. Cardiovasc Intervent Radiol 2012; 35: 299–308. 8. Nicholson W, Nicholson WJ, Tolerico P, et al. Prevalence of fracture and fragment embolization of Bard retrievable vena cava filters and clinical implications including cardiac perforation and tamponade. Arch Intern Med 2010; 170:1827–1831. 9. Tam MD, Spain J, Lieber M, Geisinger M, Sands MJ, Wang W. Fracture and distant migration of the Bard Recovery filter: a retrospective review
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of 363 implantations for potentially life-threatening complications. J Vasc Interv Radiol 2012; 23:199-205. e1. Vijay K, Hughes JA, Burdette AS, et al. Fractured Bard Recovery, G2, and G2 express inferior vena cava filters: incidence, clinical consequences, and outcomes of removal attempts. J Vasc Interv Radiol 2012; 23:188–194. Andreoli JM, Lewandowski RJ, Vogelzang RL, Ryu RK. Comparison of complication rates associated with permanent and retrievable inferior vena cava filters: a review of the MAUDE database. J Vasc Interv Radiol 2014; 25:1181–1185. Duszak R Jr, Parker L, Levin DC, Rao VM. Placement and removal of inferior vena cava filters: national trends in the Medicare population. J Am Coll Radiol 2011; 8:483–489. Lynch FC. A method for following patients with retrievable inferior vena cava filters: results and lessons learned from the first 1,100 patients. J Vasc Interv Radiol 2011; 22:1507–1512. Minocha J, Idakoji I, Riaz A, et al. Improving inferior vena cava filter retrieval rates: impact of a dedicated inferior vena cava filter clinic. J Vasc Interv Radiol 2010; 21:1847–1851.
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15. Antony J, Downey-Ennis K, Antony F, Seow C. Can Six Sigma be the “cure” for our “ailing”. NHS? Leadersh Health Serv 2007; 20: 242–253. 16. DuPree E, Martin L, Anderson R, et al. Improving patient satisfaction with pain management using Six Sigma tools. Jt Comm J Qual Patient Saf 2009; 35:343–350. 17. Leaphart CL, Gonwa TA, Mai ML, et al. Formal quality improvement curriculum and DMAIC method results in interdisciplinary collaboration and process improvement in renal transplant patients. J Surg Res 2012; 177:7–13. 18. Smith C, Wood S, Beauvais B. Thinking lean: implementing DMAIC methods to improve efficiency within a cystic fibrosis clinic. J Healthc Qual 2011; 33:37–46. 19. Tamm EP, Szklaruk J, Puthooran L, Stone D, Stevens BL, Modaro C. Quality initiatives: planning, setting up, and carrying out radiology process improvement projects. Radiographics 2012; 32:1529–1542. 20. Lee L, Taylor J, Munneke G, Morgan R, Belli AM. Radiology-led followup system for IVC filters: effects on retrieval rates and times. Cardiovasc Intervent Radiol 2012; 35:309–315.
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APPENDIX A Dear [Patient Name]: Our records show that you had a temporary inferior vena cava (IVC) filter placed at XXXXXX Hospital on [date]. These filters require continuous follow-up by Interventional Radiology. Please contact our office at XXX-XXX-XXXX to schedule a clinic appointment to discuss management of your IVC filter. Sincerely, Interventional Radiology
APPENDIX B [Your Name] [Street Address] [City, State, ZIP Code] [Date] [Recipient Name] [Title] [Company Name] [Street Address] [City, State, ZIP Code] Re: Patient Name/MRN Dear [Recipient Name]: Our records show that your patient had a temporary inferior vena cava filter placed at XXXXXX on [date]. Although these filters serve a purpose in protecting a patient against pulmonary embolus, they are not without complications. Hence, these filters require continuous follow-up by Interventional Radiology. Please contact our office at XXX-XXXXXXX to schedule your patient for an appointment in the Interventional Radiology Clinic. Sincerely, [Your Name] [Title]
Improving Inferior Vena Cava Filter Retrieval Rates with the Define, Measure, Analyze, Improve, Control Methodology Patrick D. Sutphin, MD, PhD, Stephen P. Reis, MD, Angie McKune, RN, BSN, Maria Ravanzo, MPAS, Sanjeeva P. Kalva, MD, and Anil K. Pillai, MD
ABSTRACT Purpose: To design a sustainable process to improve optional inferior vena cava (IVC) filter retrieval rates based on the DMAIC methodology of the Six Sigma process improvement paradigm. Materials and Methods: DMAIC, an acronym for Define, Measure, Analyze, Improve, and Control, was employed to design and implement a quality improvement project to increase IVC filter retrieval rates at a tertiary academic hospital. Retrievable IVC filters were placed in 139 patients over a 2-year period. The baseline IVC filter retrieval rate (n ¼ 51) was reviewed through a retrospective analysis, and two strategies were devised to improve the filter retrieval rate: (a) mailing of letters to clinicians and patients for patients who had filters placed within 8 months of implementation of the project (n ¼ 43) and (b) a prospective automated scheduling of a clinic visit at 4 weeks after filter placement for all new patients (n ¼ 45). The effectiveness of these strategies was assessed by measuring the filter retrieval rates and estimated increase in revenue to interventional radiology. Results: IVC filter retrieval rates increased from a baseline of 8% to 40% with the mailing of letters and to 52% with the automated scheduling of a clinic visit 4 weeks after IVC filter placement. The estimated revenue per 100 IVC filters placed increased from $2,249 to $10,518 with the mailing of letters and to $17,022 with the automated scheduling of a clinic visit. Conclusions: Using the DMAIC methodology, a simple and sustainable quality improvement intervention was devised that markedly improved IVC filter retrieval rates in eligible patients.
ABBREVIATIONS CPT = Current Procedural Terminology, DMAIC = Define, Measure, Analyze, Improve, Control, FDA = Food and Drug Administration, IVC = inferior vena cava, PDSA = Plan, Do, Study, Act, QI = quality improvement, RVU = relative value unit
In August 2010, the U.S. Food and Drug Administration (FDA) released a communication on the removal of retrievable inferior vena cava (IVC) filters and issued the From the Division of Interventional Radiology, Department of Radiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390. Received August 19, 2014; final revision received and accepted November 21, 2014. Address correspondence to P.D.S.; E-mail: [email protected] From the SIR 2014 Annual Meeting. P.D.S. is inventor on patent applications owned by the Board of Trustees of Leland Stanford Jr. University and Auckland Uniservices Limited. S.P.K. is a paid consultant for CeleNova BioSciences, receives royalties from Elsevier and Amirsys, and is an investor in AltheaHealth, Inc. None of the other authors have identified a conflict of interest. Appendices A and B are available online at www.jvir.org & SIR, 2015 J Vasc Interv Radiol 2015; XX:]]]–]]] http://dx.doi.org/10.1016/j.jvir.2014.11.030
following recommendation: “FDA recommends that implanting physicians and clinicians responsible for the ongoing care of patients with retrievable IVC filters consider removing the filter as soon as protection from PE [pulmonary embolism] is no longer needed” (1). In May 2014, the FDA updated the communication to include reference to a mathematical model that suggests if the patientʼs risk of pulmonary embolism has resolved, the risk/ benefit profile begins to favor removal of the IVC filter between 29 and 54 days after IVC filter placement (2,3). A systematic literature review of retrievable IVC filters by Angel et al (4) confirmed that most (93%) complications associated with retrievable IVC filters occurred with long-term use (4 30 d). Several reports have found high rates of IVC penetration with Celect (Cook, Inc, Bloomington, Indiana) (22%–93%) and Günther Tulip (Cook, Inc) (22%–78%) IVC filters (5–7) associated with longer dwell times. IVC filter fractures are the most common complication reported in the Manufacturer and
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User Facility Device Experience database with a rate up to 16% in the literature (6,8–11). A Kaplan-Meier survival analysis by Tam et al (9) estimated a 40% fracture rate at 5.5 years for the Bard Recovery filter (Bard Peripheral Vascular, Tempe, Arizona). IVC filter retrieval rates are heterogeneous across institutions and patient populations. Estimated IVC filter retrieval rates in the Medicare population were 1.2%–5.1% for the 65,041 filters placed in 2008 (12). A systematic review of the literature reported retrieval rates of 12%–45% with a mean of 34% and an average retrieval time of 72 days (4). Retrieval rates with dedicated follow-up have been reported to approach 60% (13,14). Given the risk of adverse events with the long-term use of retrievable IVC filters and the FDA recommendations, we initiated a quality improvement (QI) project with a goal to increase the retrieval rate in eligible patients at our institution to 35% within 1 year of placement. The design of the QI project was based on the DMAIC methodology. DMAIC is an acronym for Define, Measure, Analyze, Improve, and Control. DMAIC is a core tool in the Six Sigma paradigm developed in industry for process improvement with the aim to reach a level of quality 6 SDs above the average, equivalent to 3.4 defects of per 1 million opportunities. DMAIC has been successfully implemented over a wide range of disciplines and has previously been adopted in the health care setting (15–18).
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mined the success of the program. Secondarily, the percentage of patients seen in the clinic after filter placement was used as a measure of patient follow-up. Analyze the Process. The existing filter placement and retrieval process was evaluated (Fig 2). The IVC filter placement process began with a request from the referring physician. An IVC filter was subsequently placed, and instructions on how to arrange for IVC filter removal were placed at the end of the dictation if the filter was retrievable (Fig 2). The multidisciplinary team reviewed the process and discussed the strengths and weaknesses and brainstormed to identify barriers to IVC filter removal over multiple sessions. The barriers to removal were grouped into four categories: provider, patient, clinical, and systems. The barriers were further classified into controllable (Fig 3a) and uncontrollable
MATERIALS AND METHODS DMAIC Methodology as Applied to the Current Project This institutional review board–approved, Health Insurance Portability and Accountability Act–compliant QI project with retrospective and prospective components was conducted as part of a clinical safety and effectiveness project. The core team included a lead interventional radiologist, nurse coordinator, internal medicine nurse navigator, and QI facilitator. Additional members of the multidisciplinary team included interventional radiologists, interventional radiology physician assistants, a pulmonologist, and a hematologist. The DMAIC methodology set a framework for process improvement, and it was applied sequentially as detailed subsequently and in Fig 1. Define the Problem. IVC filter complications occur with long-term use often after the risk of pulmonary embolus has subsided. The presence of an IVC filter after the indication for placement has resolved was defined as the problem. In addition, after initiating the improvement process, it was recognized that poor clinical followup of patients with IVC filters was a major contributing factor and was defined as a secondary problem. Measure the Problem. The IVC filter retrieval rate in eligible patients was the measure that ultimately deter-
Figure 1. DMAIC methodology. Graphic representation of the DMAIC model of process improvement. (Available in color online at www.jvir.org.)
Figure 2. Existing IVC filter placement process. Flow diagram of the existing filter placement process reveals that the referring physician (MD) determines when the filter is no longer indicated and requests filter removal.
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(Fig 3b) barriers. Key barriers in the provider category were provider knowledge and communication; patient knowledge and follow-up after the procedure were key barriers in the patient group. In addition, barriers in the clinical and systems categories included lack of a formal patient database and shortage of permanent filters in stock for patients in whom a permanent filter was desired. Improve the Process. To improve the filter placement and retrieval process, new workflows were designed to address the controllable barriers (Fig 4). After 3 months of planning, the multidisciplinary group devised two workflows. The first workflow was designed for patients in whom an IVC filter had already been placed between September 2012 and April 2013 (Fig 5). In this group, a letter was sent to the primary physician or hospitalist and
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patient to schedule a clinic visit with a lower extremity venous ultrasound study. The ultrasound study was performed to (i) detect failure of anticoagulation and (ii) check for new development of lower extremity thrombus if none was previously reported. If a response was not received at 2 weeks, a second letter was mailed, and the process was repeated until three letters were sent. “No response” was documented in the electronic medical record, and no further follow-up was performed. A second workflow was designed for patients who were to have an IVC filter placed during May 2013 or later. This workflow consisted of automatic scheduling of a clinic visit and lower extremity venous ultrasound 4 weeks after IVC filter placement if the patient was an outpatient or at 4–6 weeks after discharge if the patient was an inpatient. The extended inpatient follow-up
Figure 3. Barriers to IVC filter removal from the multidisciplinary team brainstorming sessions are shown in fishbone diagrams and are divided into (a) controllable and (b) uncontrollable barriers. PT ¼ patient; pt ¼ patient.
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Figure 4. Action items for improvement. Fishbone diagram demonstrating the actionable items based on controllable barriers to filter removal.
scheduling was done to account for the variable course of convalescence after discharge (Fig 5). The purpose of the clinic visit was to educate the patient on IVC filters and to determine patient candidacy for filter retrieval.
Control the Process. An IVC filter database was created and maintained by a physician assistant, and any clinic “no shows” were investigated and documented. In addition, the referring physician was notified to improve provider education and buy-in. The process was reviewed monthly by the core team. Quarterly meetings of the multidisciplinary team were held to evaluate the outcome of this QI project and to determine if adjustments were needed.
Patient Cohorts Between January 2012 and December 2013, retrievable IVC filters were placed in 139 patients (71 men and 68 women; average age, 64 y; range, 21–98 y). These patients were divided into three groups based on the time period when the IVC filters were placed. Patients who had a filter placed in the 8-month period extending from January 2012 to August 2012 made up the “baseline” group (n ¼ 51). This group was used to calculate the baseline IVC filter retrieval rate. Patients who had an IVC filter placed in the 8-month period between September 2012 and April 2013 made up the “letters” cohort (n ¼ 43). The patients in this group and the referring physicians were retrospectively contacted by letters (Appendices A and B, available online at www. jvir.org) beginning on May 22, 2013, to schedule a clinic visit to evaluate for filter retrieval. The “prospective” group comprised patients (n = 45) who had an IVC filter placed in the 8-month period between May 2013 and December 2013. Patients in the prospective group were scheduled for a clinic visit at the time of filter placement.
Statistical Methodology IVC filter retrieval rate is expressed as a percentage and calculated based on patients who are eligible for retrieval. The retrieval rate is calculated as follows: (%) Retrieved = IVC filters retrieved/(total IVC filters placed (patients ineligible for filter retrieval)) * 100. The clinic visit was used to determine eligibility for retrieval, and the filter retrieval rate was calculated independently of the clinic visit rate. Patients were considered ineligible for filter retrieval only if they were evaluated in the clinic or by phone and found to have any contraindication to or a failure of anticoagulation and required continued mechanical prophylaxis. Deceased patients were also considered ineligible for retrieval. Patients who did not have clinical follow-up or failed to keep their appointment remained in the pool of eligible patients. In the baseline group, 15 of 51 patients were categorized as ineligible owing to death. In the letters group, 18 of 43 patients were ineligible for retrieval (6 deaths and 12 patients with persistent contraindication to anticoagulation). In the prospective group, 16 patients were considered ineligible for retrieval (12 deaths, 3 patients with persistent contraindication to anticoagulation, and 1 patient with failure of anticoagulation). Three patients in the letters group and one patient in the prospective group continued their care elsewhere and were included in the equation as eligible for retrieval. Statistical comparison was made between the retrieval rates of the baseline group and the letters group and the baseline group and the prospective group using Fisher exact test (R statistical computing software [http:// www.R-project.org]). A P o .05 was considered significant.
RESULTS Follow-up Clinic Visits None of the patients in the baseline cohort (n = 51) of patients had clinic visits. The introduction of letters mailed retrospectively (ie, letters group) to the primary care
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Figure 5. Modified workflow for IVC filter placement and removal. Flow diagram demonstrating the modified workflow for patients with an IVC filter. A retrospective workflow was designed for patients who had an IVC filter placed between September 2012 and April 2013 where letters were mailed to the referring physician and patient (letters cohort). A prospective workflow was also designed for IVC filters placed between May 2013 and December 2013 where a clinic visit was prospectively scheduled (prospective cohort). EMR ¼ electronic medical record; LE ¼ lower extremity.
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physician or hospitalist and patient raised the percentage of patients seen in the clinic to 19% (n = 43). Automated scheduling of a clinic visit (ie, prospective group) further improved the percentage of patients seen in the clinic to 49% (n = 45) (Fig 6).
Filter Retrieval Rates The increased number of patients seen in the clinic was associated with an improved IVC filter retrieval rate. Our baseline cohort of patients had an 8% (n ¼ 51) IVC filter retrieval rate in eligible patients, which increased to 40% (n ¼ 43) in the letters group and 52% (n ¼ 45) in the prospective group (Fig 6). The retrospective letter–based workflow and the prospective workflow resulted in a statistically significant increase in the filter retrieval rate relative to the baseline group based on Fisher exact test with P ¼ .03 and P ¼ .007, respectively. The average time of retrieval was 64 days (range, 58–70 d) in the baseline group, 137 days (range, 36–265 d) in the letters group, and 59 days (range, 0–199 d) in the prospective group. Across all groups, 28 IVC filters were retrieved. Although two patients required three attempts to remove the IVC filter, all IVC filters in patients who presented for retrieval were ultimately removed.
Improved Retrieval Rates Increase Revenue Financial gains of this QI project resultant from the increased number of clinic visits and improved retrieval rate were assessed. Revenue for a clinic visit was calculated based on the Medicare reimbursement of $51.76 (Current Procedural Terminology [CPT] code 99213) for a clinic visit at our institution plus the Medicare reimbursement for a bilateral lower extremity ultrasound scan of $35.79 (CPT code 93970). The reimbursement for a clinic visit with imaging was $87.55. Medicare
Figure 6. Modified workflow increases clinic visits and retrieval rate. Bar graphs represent the percent of patients seen in the clinic and IVC filter retrieval rates in the period before intervention (baseline, January 2012–August 2012), in the period after the mailing of letters (letters, September 2012–April 2013), and after the implementation of a formal clinic-based process (prospective, May 2013–December 2013). Percent seen in clinic was calculated using the following formula: Percent clinic ¼ ([clinic visit þ pending clinic visit]/total IVC filters placed) 100.
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reimbursement for IVC filter retrieval was $382.25. Based on these values, the revenue per 100 IVC filters placed was $2,249 for the baseline cohort, $10,518 for the letters cohort, and $17,022 for the prospective cohort (Fig 7). Relative value units (RVUs) were also calculated for each group and were as follows: baseline, 43 RVUs; letters, 202 RVUs; and prospective, 327 RVUs.
DISCUSSION We undertook a QI project to increase the IVC filter retrieval rate using the DMAIC methodology of the Six Sigma process improvement adopted from industry. DMAIC is a systematic sequential framework for longterm process improvement that decomposes process improvement into five simple elements: define, measure, analyze, improve, and control. It is ideal for an established workflow that is not meeting expectations. A poor IVC filter retrieval rate was defined as the problem at the start of the QI project with a goal to improve the filter retrieval rate to 35%. A new workflow was designed that emphasized at the time of IVC filter placement the requirement of a clinic visit after the procedure, which improved the IVC filter retrieval rate to 52% in eligible patients. Other process improvement paradigms have been used in the health care setting. Kaizen (Japanese word meaning to “make better”) uses the PDSA (Plan, Do, Study, Act) or Deming cycle framework. It is an iterative improvement cycle that emphasizes quick and early failure by making improvements on a small scale or trial basis. First, a Plan is made and implemented on a
Figure 7. Estimated revenue per 100 IVC filters. Bar graph represents the estimated revenue production in the baseline period (January 2012–August 2012), after the mailing of letters period (letters period, September 2012–April 2013), and after the implementation of a formal clinic-based prospective period (May 2013–December 2013). Clinic visit revenue ¼ Medicare reimbursement of $51.76 for clinic visit (CPT code 99213) plus Medicare reimbursement average for bilateral lower extremity venous ultrasound of $35.79 (CPT code 93970). Removal revenue ¼ Medicare reimbursement of $382.25 for IVC filter removal (CPT code 37193).
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small scale in the Do phase. The results of the trial are evaluated in the Study phase and are adopted, adapted, or abandoned in the Act phase (19). The iterative nature of the improvement cycle with small changes often takes several iterations to arrive at a manageable process. PDSA and DMAIC share common elements, including planning, process evaluation, and correction phases. However, DMAIC is a linear, long-term continuous QI methodology, whereas PDSA is a rapid, cyclic, shortterm process. PDSA is best employed when an established workflow is absent or baseline data do not exist and frequent changes have to be made to create a new process. Our project was suited for the DMAIC methodology because there was a process, although inefficient, in place. DMAIC also emphasizes sustaining improvements, and to this end, monthly reviews of follow-up and retrieval rates were performed as well as quarterly multidisciplinary meetings. Other methodologies include root cause analysis and failure mode and effect analysis. Root cause analysis can be a part of the DMAIC process or a standalone methodology that asks “5 whys” to determine the root cause of a problem. Failure mode and effect analysis is a systematic method to evaluate a process and identify where and how it might fail to identify parts of a process that are most in need of change. Several other groups have reported strategies to improve the filter retrieval rates. Minocha et al (14) found that IVC filter retrieval rates were significantly improved from 29% to 60% after the creation of a comprehensive database and a dedicated IVC filter clinic. Another approach is to contact patients directly via mail at regular time intervals after IVC filter placement based on review of the electronic medical record using a database designed specifically for IVC filter follow-up. Lynch (13) found that this approach improved filter retrieval rates from 24% to 59%. Another small study of a radiology-led system for IVC filter removal did not significantly improve retrieval rates. The filter retrieval attempt rate in that study was already 50% at baseline and increased only slightly to 55% (20). The DMAIC framework is a linear, long-term process of continuous improvement that is best suited for underperforming processes with definable and measurable endpoints. Other potential applications in interventional radiology include improving patient preparation before the procedure to minimize procedure room downtime, central line placement procedures to reduce central line– associated bloodstream infections, and work-up of patients with gastrointestinal bleeding to maximize yield of mesenteric angiography. This study has several limitations. The historic retrieval rate in the baseline cohort was a control for new workflow implementations. Because this patient cohort received no dedicated IVC filter clinical followup, it was difficult to designate patients as ineligible for filter removal. Patients were considered ineligible for
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retrieval based only on patient death, likely underestimating the filter retrieval rate in this group of patients. The retrieval rate may also be underestimated in the letters group because these patients were contacted in some cases only several months after filter placement, which may have resulted in fewer patients seen in the clinic. Direct comparison between the letters group and prospective group based on retrieval rates is not fair because the associated workflows were implemented under different time periods and circumstances. Nevertheless, we favored the scheduling of the clinic visit at the time of IVC filter placement based on ease of implementation versus mailing of letters. Although the QI project focused on retrievable filters, another limitation is the ill-defined role of permanent IVC filters in our practice. During the 2-year study period, six permanent filters were placed on an inconsistent operator-dependent basis. Additional permanent filters may have been placed, but a lack of inventory of permanent IVC filters forced substitution with retrievable filters. In conclusion, the DMAIC methodology was used to review systematically the current IVC filter placement and retrieval process and restructure the workflow to improve clinical follow-up and IVC filter retrieval. The existing filter removal process placed the burden of filter removal on the referring physician, whereas the restructured workflow increased the role of the interventional radiologist in deciding when the filter is no longer indicated. DMAIC process improvement significantly increased our filter retrieval rates and revenue associated with filter retrieval.
REFERENCES 1. FDA. Removing retrievable inferior vena cava filters: initial communication. 2010. Available at: http://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/ucm221676.htm. Accessed October 30, 2014. 2. FDA. Removing retrievable inferior vena cava filters: FDA safety communication. 2014. Available at: http://www.fda.gov/MedicalDevices/Safety/ AlertsandNotices/ucm396377.htm. Accessed October 30, 2014. 3. Morales JP, Li X, Irony TZ, Ibrahim NG, Moynahan M, Cavanaugh KJ. Decision analysis of retrievable inferior vena cava filters in patients without pulmonary embolism. J Vasc Surg Venous Lymphat Disord 2013; 1:376–384. 4. Angel LF, Tapson V, Galgon RE, Restrepo MI, Kaufman J. Systematic review of the use of retrievable inferior vena cava filters. J Vasc Interv Radiol 2011; 22:1522-1530. e3. 5. Sangwaiya MJ, Marentis TC, Walker TG, Stecker M, Wicky ST, Kalva SP. Safety and effectiveness of the Celect inferior vena cava filter: preliminary results. J Vasc Interv Radiol 2009; 20:1188–1192. 6. McLoney ED, Krishnasamy VP, Castle JC, Yang X, Guy G. Complications of Celect, Gunther tulip, and Greenfield inferior vena cava filters on CT follow-up: a single-institution experience. J Vasc Interv Radiol 2013; 24:1723–1729. 7. Durack JC, Westphalen AC, Kekulawela S, et al. Perforation of the IVC: rule rather than exception after longer indwelling times for the Gunther Tulip and Celect retrievable filters. Cardiovasc Intervent Radiol 2012; 35: 299–308. 8. Nicholson W, Nicholson WJ, Tolerico P, et al. Prevalence of fracture and fragment embolization of Bard retrievable vena cava filters and clinical implications including cardiac perforation and tamponade. Arch Intern Med 2010; 170:1827–1831. 9. Tam MD, Spain J, Lieber M, Geisinger M, Sands MJ, Wang W. Fracture and distant migration of the Bard Recovery filter: a retrospective review
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of 363 implantations for potentially life-threatening complications. J Vasc Interv Radiol 2012; 23:199-205. e1. Vijay K, Hughes JA, Burdette AS, et al. Fractured Bard Recovery, G2, and G2 express inferior vena cava filters: incidence, clinical consequences, and outcomes of removal attempts. J Vasc Interv Radiol 2012; 23:188–194. Andreoli JM, Lewandowski RJ, Vogelzang RL, Ryu RK. Comparison of complication rates associated with permanent and retrievable inferior vena cava filters: a review of the MAUDE database. J Vasc Interv Radiol 2014; 25:1181–1185. Duszak R Jr, Parker L, Levin DC, Rao VM. Placement and removal of inferior vena cava filters: national trends in the Medicare population. J Am Coll Radiol 2011; 8:483–489. Lynch FC. A method for following patients with retrievable inferior vena cava filters: results and lessons learned from the first 1,100 patients. J Vasc Interv Radiol 2011; 22:1507–1512. Minocha J, Idakoji I, Riaz A, et al. Improving inferior vena cava filter retrieval rates: impact of a dedicated inferior vena cava filter clinic. J Vasc Interv Radiol 2010; 21:1847–1851.
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15. Antony J, Downey-Ennis K, Antony F, Seow C. Can Six Sigma be the “cure” for our “ailing”. NHS? Leadersh Health Serv 2007; 20: 242–253. 16. DuPree E, Martin L, Anderson R, et al. Improving patient satisfaction with pain management using Six Sigma tools. Jt Comm J Qual Patient Saf 2009; 35:343–350. 17. Leaphart CL, Gonwa TA, Mai ML, et al. Formal quality improvement curriculum and DMAIC method results in interdisciplinary collaboration and process improvement in renal transplant patients. J Surg Res 2012; 177:7–13. 18. Smith C, Wood S, Beauvais B. Thinking lean: implementing DMAIC methods to improve efficiency within a cystic fibrosis clinic. J Healthc Qual 2011; 33:37–46. 19. Tamm EP, Szklaruk J, Puthooran L, Stone D, Stevens BL, Modaro C. Quality initiatives: planning, setting up, and carrying out radiology process improvement projects. Radiographics 2012; 32:1529–1542. 20. Lee L, Taylor J, Munneke G, Morgan R, Belli AM. Radiology-led followup system for IVC filters: effects on retrieval rates and times. Cardiovasc Intervent Radiol 2012; 35:309–315.
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APPENDIX A Dear [Patient Name]: Our records show that you had a temporary inferior vena cava (IVC) filter placed at XXXXXX Hospital on [date]. These filters require continuous follow-up by Interventional Radiology. Please contact our office at XXX-XXX-XXXX to schedule a clinic appointment to discuss management of your IVC filter. Sincerely, Interventional Radiology
APPENDIX B [Your Name] [Street Address] [City, State, ZIP Code] [Date] [Recipient Name] [Title] [Company Name] [Street Address] [City, State, ZIP Code] Re: Patient Name/MRN Dear [Recipient Name]: Our records show that your patient had a temporary inferior vena cava filter placed at XXXXXX on [date]. Although these filters serve a purpose in protecting a patient against pulmonary embolus, they are not without complications. Hence, these filters require continuous follow-up by Interventional Radiology. Please contact our office at XXX-XXXXXXX to schedule your patient for an appointment in the Interventional Radiology Clinic. Sincerely, [Your Name] [Title]
