Referral patterns for catheter-directed thrombolysis for iliofemoral deep venous thrombosis

Abstract

Objectives

Post thrombotic syndrome (PTS) is a serious complication of deep venous thromboses (DVTs). PTS occurs more frequently and severely following iliofemoral DVT compared to distal DVTs. Catheter directed thrombolysis (CDT) of iliofemoral DVTs may reduce PTS incidence and severity.

We aimed to determine the rate of iliofemoral DVT within our institution, their subsequent management, and compliance with NICE guidelines.

Methods

Retrospective review of all DVTs diagnosed over a 3-year period was conducted. Cases of iliofemoral DVT were identified using ICD-10 codes from patient notes, and radiology reports of Duplex scans. Further details were retrieved, such as patient demographics and referrals to vascular services. NICE guidance was applied to determine if patients would have been suitable for CDT. A survey was sent to clinicians within medicine to identify awareness of CDT and local guidelines for iliofemoral DVT management.

Results

225 patients with lower limb DVTs were identified. Of these, 96 were radiographically confirmed as iliofemoral DVTs. The median age was 77. 67.7% of iliofemoral DVTs affected the left leg. Right leg DVTs made up 30.2% and 2.1% were bilateral DVTs. Of the 96 iliofemoral DVTs, 21 were deemed eligible for CDT. Only 3 patients (14.3%) were referred to vascular services, and 3 received thrombolysis.

From our survey, 95.5% of respondents suggested anticoagulation alone as management for iliofemoral DVT. Only one respondent recommended referral to vascular services. There was a knowledge deficiency regarding venous anatomy, including superficial versus deep veins.

Conclusions

CDT and other mechanochemical procedures have been shown to improve outcomes of patients post-iliofemoral DVT, however a lack of awareness regarding CDT as a management option results in under-referral to vascular services. We suggest closer relations between vascular services and their “tributary” DVT clinics, development of guidelines and robust care pathways in the management of iliofemoral DVT.

Keywords

Deep vein thrombosis DVT catheter-directed thrombolysis referral iliofemoral

Introduction

Acute deep venous thrombosis (DVT) is a serious condition with an incidence of 1 in 2000 per annum.¹ Deep venous thromboses can lead to several complications such as pulmonary embolism and post thrombotic syndrome (PTS). The basis of treatment for DVT is anticoagulation to prevent thrombus extension, pulmonary embolism, and recurrence. However, despite anticoagulation approximately 50% of patients with proximal DVT will develop PTS within 2 years.² This syndrome is characterised by itching, pain, swelling, and later ulceration of the legs. Several studies have demonstrated the negative effects of PTS on quality of life^3,4 and a significant healthcare cost implication.^5,6

Iliofemoral DVT is defined as a complete or partial thrombosis of an iliac vein and/or common femoral veins, with or without concomitant distal DVT.⁷ PTS occurs more frequently and can be more severe following an iliofemoral DVT compared to a more distal DVT.^4,8,9 Catheter directed thrombolysis (CDT) and pharmacomechanical methods have been investigated to restore flow in the iliofemoral segment and thereby reduce incidence and severity of PTS. A meta-analysis of studies has shown thrombolysis of any kind improved venous patency, complete clot lysis rates and reduced rates of PTS in intermediate (6 months to 5 years) and long term follow up (>5 years).¹⁰

In 2012, the National Institute for Health and Clinical Excellence (NICE) amended guidelines for the management of iliofemoral DVT to recommend the use of CDT in selected patients.¹¹ A few studies have demonstrated that a significant proportion of iliofemoral DVT would be suitable for CDT^12,13 however, in one of these studies only 15% of eligible patients were treated with CDT.¹³ Following NICE recommendation, major vascular centres in the UK developed regional guidelines and care pathways to facilitate the management of iliofemoral DVT across the hub & spoke model.

We aimed to determine the rate of iliofemoral DVT within our institution, a district general hospital in North West London, examine the features and management of these cases, and assess compliance with NICE guidelines. We also aimed to determine the rate of referrals made to a tertiary vascular centre for CDT, and the level of knowledge and awareness of iliofemoral DVT management, including NICE guidance and CDT as a management option. Finally, we sought to evaluate the care pathways currently in place within the region.

Methods

A retrospective review of all DVTs diagnosed over a 3-year period (January 2017 to December 2019) was conducted at Hillingdon Hospital. This district general hospital provides healthcare services to a population of 350 000 and has a catchment area that encompasses London Heathrow Airport. The hub and spoke model for vascular services includes Hillingdon Hospital and Ealing Hospital as the spoke sites and Northwick Park Hospital as the hub.

Most patients investigated for DVT at Hillingdon Hospital attend an ambulatory medical clinic to undergo assessment by physicians. Referrals to this clinic can be from the Emergency Department, General Practitioners, and Radiology. Referrals can be made to the vascular surgery team at Northwick Park Hospital if required. A DVT guideline, generated by local haematologists, is available on the hospital intranet to guide management.

Cases of DVT were identified by interrogating our health informatics systems using ICD-10 codes. The following codes were used to identify all potential cases of DVTs:

I80 (0–9)

I82 (0–9)

I87 (0–9)

The patient list generated by these codes was then examined and confirmed cases of DVTs were selected for further analysis. From these cases, the radiology reports were studied independently by 3 authors (KP (Vascular Surgery), AT (General Medicine), AZ (General Medicine)) to determine the extent of thrombosis, and to select all cases of iliofemoral DVTs. In keeping with the CaVenT, ATTRACT and CAVA trials, and the American Heart Association Consensus Statement, we defined an iliofemoral DVT as a complete or partial thrombosis of an iliac vein and/or common femoral vein, with or without distal DVT.^14–17

For the patients with iliofemoral DVT, the following information was extracted from their discharge summaries, blood reports and medical notes: patient demographics, acuity of symptoms, co-morbidities, history of venous thromboembolism (VTE), cause of DVT, contraindications to thrombolysis, functional status, and whether the patient was referred on to vascular services.

To determine if a patient would have been suitable for CDT, the NICE guidance was applied to all iliofemoral DVTs.¹¹ Suitability for CDT was determined by 2 independent clinicians, and discrepancies were adjudicated by a third clinician.

Contraindications to CDT were determined using the following specific criteria as guided by NICE guidelines and Saunders et al.:^11,13

Age greater than 80

Evidence of, or suspected disseminated malignancy

Contraindications to thrombolysis¹⁸

Symptoms greater than 14 days

Poor patient functional status, determined as a WHO performance status greater than 2

To identify whether staff members were aware of CDT and local management practices of iliofemoral DVTs, a survey was sent out to staff members of all grades working in medical specialities, particularly those working in the ambulatory medical clinic. An online survey platform was utilised to develop and disseminate the survey via an email link. The survey questions are detailed in Appendix 1 (Supplementary material).

Finally, we interrogated the regional vascular hub records (Northwick Park), to determine the number of patients who underwent CDT from each of its spoke hospitals in the same time frame. We also accessed each hospital’s local guidelines regarding DVT management.

Ethical Approval was not required for this quality improvement and audit project following the principles outlined in the Declaration of Helsinki. Accordingly, this project was registered at our local audit department (Audit Registration number 999).

Results

The median age of patients with iliofemoral DVTs was 77 (range 22–103). Female patients comprised 57.3% of iliofemoral DVTs, and males comprised 42.7%. The majority of iliofemoral DVTs affected the left leg (67.7%). Right leg DVTs made up 30.2%, and bilateral DVTs accounted for 2.1% of cases.

Following interrogation of our health informatics system using ICD10 codes, 657 patients with potential DVTs were identified between January 2017 and December 2019. Of these, a total of 225 patients with a lower limb DVT were identified, the proximal extent of these DVTs are demonstrated in Table 1. A total of 96 DVTs were radiographically confirmed as iliofemoral DVTs who could have potentially been referred to vascular services for further assessment. Of these 96 cases, there were 26 patients who had a history of previous DVT. Of the 96 iliofemoral DVT cases, 66 were deemed to be provoked DVTs. The causes of the provoked DVTs are outlined in Table 2.

Table 1.

Proximal extent of thrombosis.

Proximal extent of DVT	Number of patients (%)n = 225
Inferior vena cava	2 (0.9)
Iliac vein	33 (14.7)
Common femoral vein	60 (26.7)
Superficial femoral vein	54 (24.0)
Popliteal vein	30 (13.3)
Below knee vein	46 (20.4)

Table 2.

Causes of provoked iliofemoral DVT.

Causes of provoked DVT	Number of patients (%)n = 66
Cancer	29 (43.9)
Immobility – admission related	15 (22.7)
Chronic immobility	5 (7.6)
Intravenous drug use	4 (6.1)
Recent long-haul journey	4 (6.1)
Post-operative	3 (4.5)
Immobility – bedbound	2 (3.0)
Ankle fracture	1 (1.5)
Oral contraceptive pill	1 (1.5)
Fibroids	1 (1.5)
Post-partum	1 (1.5)

Out of the 96 patients with iliofemoral DVT, 21 were deemed to be eligible for CDT. Only 2 of these 21 cases had a history of previous DVT. For those where CDT was not indicated, the reasons are stated in Table 3. Of the 21 deemed eligible, only 3 patients (14.3%) were referred on to vascular services and all 3 received thrombolysis (Figure 1).

Table 3.

Contraindications to thrombolysis for patients with iliofemoral DVT.

Reason not for thrombolysis	Number of patients (%) n = 75
Age >80	34 (45.3)
Disseminated malignancy	13 (17.3)
Poor functional status	6 (8.0)
>14 days since symptom onset	5 (6.7)
Intracranial neoplasm	3 (4.0)
Groin sepsis	1 (1.3)
Imminent deportation	1 (1.3)
Intracranial haemorrhage	1 (1.3)
Post-operative	1 (1.3)
Unspecified duration of symptoms	10 (13.3)

Figure 1.

Flowchart demonstrating patient eligibility and referral for CDT.

From the survey conducted, we received 23 responses. The respondents included: 2 consultants, 5 registrars, 10 SHOs and 6 Foundation level doctors. Specialities of respondents were as follows: Acute medicine (65.2%), Geriatrics (17.4%), Respiratory (8.7%), Neurology (4.3%), and Cardiology (4.3%).

In a question exploring the management strategy that each individual would implement for a patient with an iliofemoral DVT, 22 (95.7%) respondents opted for anticoagulation alone, whereas only 1 (4.3%) respondent opted to anticoagulate and refer on to vascular services for consideration of IVC filter.

To determine whether the respondents understood what constitutes a deep vein, we asked respondents to identify whether certain veins were superficial or deep. Results are presented in Figure 2. Of the 23 respondents, 14 (60.9%) identified the external iliac vein, 23 (100%) the common femoral vein, 7 (30.4%) the superficial femoral vein, 17 (73.9%) the profunda femoral vein, and 8 (34.8%) the peroneal vein, as deep veins. In addition, 3 (13.0%) respondents identified the saphenous vein as a deep vein.

Figure 2.

Bar chart demonstrating physician knowledge on deep and superficial venous anatomy.

Discussion

We explored compliance with the management strategies and referral patterns of patients with iliofemoral DVTs in Hillingdon Hospital, a district general hospital.

The study results demonstrated that 21 patients were potentially eligible for CDT, however only 3 (14.3%) patients were referred for CDT. Some studies have shown the advantage of CDT over routine anticoagulation in the treatment of iliofemoral DVT.^14,15,19 The CaVenT trial indicated that at 5-year follow-up, there was a significant reduction in cases of PTS in patients who had received CDT compared to standard anticoagulation.¹⁵ From this trial the number needed to treat (NNT) was 4 to prevent 1 case of PTS.¹⁵ Using this NNT, over the 3-year period examined, a total of 4–5 possible further cases of PTS could have been prevented.

There may be several reasons why clinicians did not refer these patients for CDT. These include consideration of CDT bleeding risks, lack of clinician knowledge of management options and their availability, limitations to the NICE guidance, and the presence of conflicting evidence regarding the benefit of CDT.

Thrombolysis in general increases the risk of bleeding. Although there is a reduced dose of thrombolytic agents used in CDT and its associated mechanical and ultrasound assisted techniques, it is not without risk. CDT has an associated major bleeding risk of approximately 1–5% and intracranial bleed rate of 0–1%.^{15,17,20–22} As a result, careful patient selection is required to ensure that only those with a low bleeding risk and high PTS risk are offered intervention. Some physicians may avoid referral for thrombolysis if they feel that there is a low chance of benefit from intervention, and that any benefit may be outweighed by the risk of bleeding.

The survey results highlighted medical teams were unaware of CDT as a management option for iliofemoral DVT. 95.5% of respondents opted for purely pharmacological treatments, and only 4.5% of respondents suggested a referral to vascular services. The survey results demonstrate that most clinicians proposed management plans for iliofemoral DVTs that deviate from NICE guidance. Of concern, the survey results also demonstrated a lack of understanding amongst medical staff regarding venous anatomy. Only 60.9% of respondents identified the external iliac vein as a deep vein, and only 30.4% recognised the superficial femoral vein as a deep vein. This lack of knowledge may contribute to the under referral and mismanagement of DVTs within our institution and may reflect that of practice in general.

NICE guidance regarding the use of CDT in iliofemoral DVT is relatively general, leaving room for interpretation by clinicians. NICE recommends that patients with symptoms less than 14 days, a good functional status, low bleeding risk, and a life expectancy of greater than 1 year should be considered for CDT.¹¹ However, a good functional status can be subjective. What one clinician views as a good functional status may not meet the surgical threshold of what is required for CDT. Furthermore, patients between 65-80 years old may fit the NICE criteria for CDT, however the ATTRACT trial demonstrated that patients over the age of 65 had worse safety and PTS prevention efficacy than younger patients.¹⁴ This may deter clinicians from referral of patients within this age bracket for CDT. Despite these cautions, acute medical physicians should still refer patients meeting NICE criteria for assessment by a specialist who can then decide whether the benefits of CDT outweigh the risks for those individual patients.

Conflicting results from the CaVeNT, CAVA and ATTRACT trials have created uncertainty regarding the benefit of CDT. The CaVeNT trial observed the effects of purely pharmacological CDT on patients with DVT down to the mid-thigh. They found a risk reduction of PTS incidence at 2 years and 5 years, but no improvement in difference of quality of life (QOL) between the 2 arms. ATTRACT on the other hand observed the effects of pharmacomechanical CDT on acute proximal DVT (including femoropopliteal veins). No difference in PTS incidence was observed in the iliofemoral group up to 2 years. However, there was a reduction of severity of PTS in the CDT arm at 6, 12, 18 and 24 months, with improvement in QOL at 24 months. Subgroup analyses of the ATTRACT trial demonstrated that patients with iliofemoral DVT treated with CDT methods had significantly reduced clot burden which correlated to a reduced 2-year PTS severity.²³ The differences between ATTRACT and CaVeNT trials may be explained by the fact that in the CaVeNT trial, there was no way to distinguish between iliofemoral or femoropopliteal veins. In addition, the use of different methods of clot dissolution may have also been a contributing factor. Most recently, the CAVA trial observed the effect of ultrasound accelerated CDT on iliofemoral DVT. At 1 year, there was no difference observed in incidence or severity of PTS, or improvement in QOL. It is worth noting that the CAVA trial utilised venous stenting in the CDT arm, with 10% of patients having in-stent thrombosis subsequently. This may have affected the results of the trial. Given this uncertainty again, physicians may avoid referring patients for a therapy of which the effects have not fully been confirmed.

Our results demonstrate that our single centre may only refer approximately 7 eligible cases of iliofemoral DVT a year for consideration of CDT if the guidance from NICE is adhered to. An increase in caseload will add opportunity to develop surgical experience and may subsequently improve outcomes from these vascular centres, mirroring other vascular pathologies such as abdominal aortic aneurysms, carotid stenosis and lower limb arterial disease.^24–27 This moderate rise in workload for vascular services may be negated by the burden already created due to patients returning with complications of DVT, such as PTS. The subsequent treatment for these patients generates a significant burden on healthcare finances and nursing care at present.^5,6,28

Within our regional network, Northwick Park and Ealing Hospital have local guidelines which specify the need for referral to vascular services for iliofemoral DVT, however our hospital (Hillingdon) does not currently have this specified within local guidelines. Despite Ealing Hospital having a smaller population and level of services compared to Hillingdon Hospital, the higher number of their patients receiving CDT may be the result of more comprehensive guidelines. Meanwhile, the presence of on-site vascular services and a robust care pathway at Northwick Park Hospital (Vascular hub) appears to promote an even higher number of patients receiving CDT.

The data obtained within our study spanned the last 3 years, providing up to date information on iliofemoral DVT management. However, being a single centre study there was potentially a biased snapshot of the general population. Despite this, our results have corroborated with previous studies of larger regions. Our results were similar to that found in a 2013 study based at a Nottingham vascular hub, covering a population of 800,000. In this study, only 15% of eligible iliofemoral DVTs were referred for CDT.¹³ Our results alongside other UK and international studies show that CDT is currently underutilised due to a lack of referral of eligible cases.^13,29

With this being a retrospective review of case notes, there were problems with incomplete data due to poor clinical documentation and archiving of records. Consequently, some records with unknown data were included within our analysis. Furthermore, potential DVT cases were identified through use of ICD-10 codes and interrogation of the health informatics system. Despite a range of codes being used to capture all potential DVT cases, this method may have resulted in missing cases due to incorrect coding. To mitigate this, we verified with the vascular hub the number and which patients underwent CDT from our hospital, to ensure accuracy.

Although the results of the survey are enlightening, there is a risk that the responses may not be a true representation of the entire population of medical practitioners dealing with DVTs, due to the sample size. Furthermore, there was a skew of more junior doctor respondents compared with consultants. However, patients in ambulatory medical clinics will often be assessed and managed according to local guidelines by these junior doctors, with input from senior advice when requested.

A study in North West England examining DVT management revealed uncoordinated care pathways that often differed from NICE guidelines, suggesting that this may be the case across the country.³⁰ Our data supports the finding of a lack of coordinated services for DVT management and at present there is no defined pathway for the management of iliofemoral DVTs in our trust. This demonstrates the need for a local and national standardised programme, which would lead to more consistent protocols for the management of DVTs, as suggested by the study in North West England.³⁰

Whilst examining our local guidelines for treatment of DVTs, it was noted that these guidelines were produced by our haematologists, with no clear input from our regional vascular team. Consequently, these guidelines are based purely on anticoagulation management of all DVTs. Alongside this, the lack of insight into NICE guidance regarding iliofemoral DVT management, as demonstrated by our survey results, has potentially led to the under referral of eligible patients for CDT.

High volume centres have been shown to have a positive effect on morbidity and mortality in several vascular pathologies.^24–26 With centralisation of vascular services, a lack of cooperation can develop between centralised vascular hubs and their referring hospitals. This can lead to under referral of patients that may benefit from management by vascular teams, leading to poorer outcomes.

With these issues highlighted, multiple strategies can be implemented to aid referral to vascular services. Locally, one strategy may be the revision of Trust guidelines and care pathways with input from the regional vascular services, adhering to NICE guidance and local service capability. Another strategy may include targeted education of the NICE guidance and revised local guidelines regarding the endovascular options for iliofemoral DVT management. This may be supported by prompting of physicians to make vascular referrals and highlighting the finding of an iliofemoral DVT by radiologists and sonographers within radiology reports.

Although evidence for CDT is currently conflicting, it is likely still beneficial in carefully selected patients. This being the case, high levels of non-adherence to NICE guidelines may expose ourselves from a medicolegal perspective. Having identified this issue, local clinical governance units have a duty to assess and monitor this. Governance units need to take an active role in identifying these changes in NICE guidelines and adapting local pathways to reflect these changes.

We have identified serious failings in the management of iliofemoral DVTs, non-compliance with NICE guidelines, and a lack of knowledge and awareness of this complex condition. Whether this problem is a local or national problem needs to be ascertained with a national survey. The changes in NICE guidelines to reflect the role of CDT in management of iliofemoral DVT occurred in 2012. In light of new evidence, there is an urgent need for review of NICE guidelines or development of a consensus statement in the management of iliofemoral DVT.

Conclusion

CDT has been shown to improve outcomes of patients post iliofemoral DVT. However, there is a significant lack of awareness regarding the availability of CDT as a management option amongst professionals dealing with DVTs daily. As a result, there is an under referral of these iliofemoral DVT cases for CDT from these practitioners to vascular services. We suggest closer relations between vascular services and their “tributary” DVT clinics to manage iliofemoral DVT.

Supplemental Material

sj-pdf-1-phl-10.1177_0268355520977281 - Supplemental material for Referral patterns for catheter-directed thrombolysis for iliofemoral deep venous thrombosis

Supplemental material, sj-pdf-1-phl-10.1177_0268355520977281 for Referral patterns for catheter-directed thrombolysis for iliofemoral deep venous thrombosis by Kirtan D Patel, Alison YY Tang, Ashik DJ Zala, Rakesh Patel, Kishan R Parmar and Saroj Das in Phlebology

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Ethical approval

Guarantor

SD acts as guarantor for this project

Contributorship

KDP, AYYT and ADJZ were responsible for the initial plan, study design and first draft of the manuscript. KDP, AYYT, ADJZ and RP were responsible for data collection and extraction. All authors were involved in data analysis, interpretation, and critical revision of the manuscript. All authors were reviewed and approved the final draft. RP, KRP and SD provided overall supervision for the study. The corresponding author attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted.

ORCID iD

Kirtan D Patel

Supplementary material

Supplementary material is available is for this article.

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