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Institution of Surgical Sciences, Department of Vascular Surgery, Uppsala University, Uppsala, SwedenDepartment of Surgery, Blekinge Hospital, Karlskrona, Sweden
To compare practice in lower limb bypass surgery in nine countries.
Design
A prospective study amalgamating and analysing data from national and regional vascular registries.
Methods
A table of data fields and definitions was agreed by all member countries of the Vascunet Collaboration. Data from January 2005 to December 2009 was submitted to a central database.
Results
32,084 cases of infrainguinal bypass (IIB) in nine countries were analysed. Procedures per 100,000 population varied between 2.3 in the UK and 24.6 in Finland. The proportion of women varied from 25% to 43.5%. The median age for all countries was 70 for men and 76 for women. Hungary treated the youngest patients. IIB was performed for claudication for between 15.7% and 40.8% of all procedures. Vein grafts were used in patients operated on for claudication (52.9%), for rest pain (66.7%) and tissue loss (74.1%). Italy had the highest use of synthetic grafts. Among claudicants 45% of bypasses were performed to the below knee popliteal artery or more distally. Graft patency at 30 days varied between 86% and 99%.
Conclusions
Significant variations in practice between countries were demonstrated. These results should be interpreted alongside the known limitations of such registry data with respect to quality and completeness of the data. Variation in data completeness and data validation between countries needs to be improved for useful international comparison of outcomes.
This is the largest international series of infrainguinal bypass operations to be published and gives insight into variations in practice across the globe. The paper provides information on surgery in different countries, the proportions performed for claudication and critical ischaemia, the types of graft used, risk factors, demographics and outcomes.
Introduction
Infrainguinal bypass (IIB) surgery is one of the most common procedures in vascular surgery and has been well described and studied for decades. One might expect practice and outcomes to be uniform throughout the world. In the last few years the members of several large national vascular registries have collaborated to compare vascular procedures at a national level through the Vascunet Committee of the European Society of Vascular Surgery.
Vascunet was originally formed by a group of enthusiasts as a working group within the European Society for Vascular Surgery to exchange ideas and promote discussion between those responsible for the National Registries and other interested individuals in Europe.
have demonstrated that amalgamation and analysis of vascular outcome data is possible at an international level and important geographical differences in demographic data have been highlighted. For this type of international comparison to be valuable however it is necessary to ensure a common dataset so that data comparison between countries is valid. With this in mind further work has been undertaken since the initial publications to define a standardised dataset across all the countries taking part in the collaboration.
This paper presents the analysis of amalgamated data on IIB from nine contributing countries in Europe and Australasia. Data from over 32,000 vascular patients have been analysed making this the largest database of its kind. In order to improve the validity of comparisons and ensure contemporary data, we have restricted the analysis to the last five years.
Methods
The dataset to be collected was agreed between all the participating countries. The aims of this were to keep the dataset to a minimum whilst providing useful comparative data, but also to include data fields which are collected by the majority of countries in the collaboration. It was accepted that due to the national variations in vascular data registries that not all countries would be able to contribute data in all fields. It was agreed however that national audit committees would be encouraged to adapt their own datasets in the future to include the minimum international dataset, a process that has been ongoing since 2005. Data collected was combined data from years prior to the commencement of this study and prospective data following the inception of the study up to 31st December 2009.
The defined dataset is shown in Table 1, and is available via the Vascunet website (www.esvs.org/social/vascunet). Interventions on existing bypasses were not included but repeat bypass grafts in patients who had had some other previous intervention were included.
Table 1Dataset with numbers of responses for each datafield by country.
Australia
Denmark
Finland
Hungary
Italy
Norway
Sweden
Switzerland
UK
Age
2384
3962
1848
1358
10,279
1445
4793
1787
4236
Gender
2386
3962
1845
1363
10,279
1445
4793
1790
4235
Admission date
2385
3954
1848
0
10,279
1445
0
1741
4236
Admission mode
2379
3944
1710
1363
10,279
1445
4673
0
4220
Diabetes
2294
3935
1794
0
10,279
1445
4676
1790
3752
Cardiac history
0
3928
1781
0
10,279
1445
4624
1790
3788
Current smoker
2268
3884
1594
0
10,279
1445
4070
1790
3063
Pulmonary history
0
3929
1773
0
10,279
1445
4603
1790
0
Cerebrovascular event history
0
3922
1776
0
0
1445
4580
1790
0
Hypertension history
2291
3909
1787
0
10,279
1445
4590
1790
0
Indication
2386
3962
1848
1360
10,279
1445
4793
1790
3824
Side of operation
2374
3962
1824
0
10,279
1445
4790
1719
3706
ABI
0
2969
533
0
0
776
3521
772
1627
Previous ipsilateral intervention
0
3957
1847
1363
0
1445
0
1790
3265
Operation date
2386
3962
1847
1363
10,279
1445
4793
1790
4203
Proximal anastomosis site
2243
3962
1846
1363
0
1445
4585
1772
3701
Distal anastomosis site
2386
3962
1835
1362
0
1445
4625
1541
3701
Graft type
2386
3962
1848
1363
10,279
1445
4793
1790
4236
Graft type further detail
2025
2619
1074
562
1037
0
738
1152
0
Additional open procedure
2386
0
1847
1363
0
0
1141
0
2435
Additional endovascular procedure
0
0
1847
1363
0
0
1141
0
0
Wound complication
0
3905
408
1363
0
1445
4043
1790
2823
Haemorrhage
40
3900
1790
1363
0
1445
4043
1790
3171
Compartment syndrome
0
3912
124
0
0
1445
4044
1790
0
Graft patent at discharge
0
3916
1381
1342
0
1346
0
1569
0
Graft patent at 30 days
2384
0
1845
0
0
812
4606
1569
0
Amputation
2384
3962
1781
1363
0
1431
4718
1790
3212
Post treatment ABI
0
2358
323
0
0
775
2830
0
0
Acute coronary event
186
3912
1133
1363
0
1445
4041
1790
3111
Major stroke
52
3912
1135
253
0
113
4041
1790
2786
Discharge date
2386
3917
1828
0
0
1445
0
1747
3829
Died within 30 days of surgery
2386
3951
1778
1363
10,279
1445
3687
1395
4232
Date of death
0
1305
85
0
86
28
1394
47
145
Is post op data based on hospital discharge or 30 days?
Following definition of the dataset a data entry template was provided to each participating country and this was used for submission of national data to the international database. Data was submitted for patients admitted between 1st January 2005 and 31st December 2009.
Once the data was received from each country this was sorted and amalgamated into a single spreadsheet for analysis. The datasheet was then returned to each country for error checking and validation in order to ensure that no errors had occurred during data amalgamation. Further validation was performed on the data to look for data errors (e.g. an impossible date of birth), missing data and unexpected responses and any perceived data issues were checked back again with the referring country.
External validation of the registries
Some of the registries have performed external validation procedures to assess the proportion of operated cases that were not entered into the registries. The Swedvasc compared the data in the Registry with the Inpatient Registry (IR) used for reimbursement,
and the Population Registry, where all deaths are registered. They were granted permission to cross-match using the personal identity code that is unique for each citizen and identifies the patients in all registries. The external validity was 93.0% regarding infrainguinal bypass procedures. Five hospitals (three non-participating) accounted for 35% of the procedures missed in Swedvasc, only 5 of 33 centres registered fewer than 80% of their infrainguinal bypass procedures. There was no statistical difference in 30 day mortality (2.9%) between registered and unregistered patients. In Denmark data validation has been performed and published in the Annual Report 2010.
The overall data completeness for index cases (AAA, CEA, IIB) was 99.0% for the period 2001–2010. This figure is calculated as a comparison between the Danish Vascular Registry and the national Hospital Episodes Statistics. For IIB the rate of missing data for wound complications was 6.8% and 7.1% for surgical wound infection. In Australia internal validation has demonstrated a data accuracy error rate of between 6.5% and 11.9%. Public hospital data was externally validated using State Health Department data and although not available in the public domain the estimated agreement between the 2 data sources was 85%. Private data was externally validated using Medicare data. In the UK direct external validation of all IIB data was not performed. However a comparison between Hospital Episode Statistics and Hospital surgeon reported data for the year 2008 demonstrated a median discrepancy between these of 3 cases per centre with an interquartile range of 0–12.
In Hungary, Norway, Finland, Switzerland and Italy there was no independent external validation performed.
Statistical analysis
Analysis of the data was done using the SPSS Program package, version 18. Categorical variables were compared with Chi-2-test and continuous variables with ANOVA or Mann–Whitney-U test depending on the distribution of the variable. All tests were two tailed and level of significance set at p < 0.01.
Results
Initial data amalgamation produced a total of 44,059 cases. This included 22,254 cases from Italy. Following further checking of Italian registry data it was agreed to exclude cases where a type of graft was not specified due to concern that some of these cases were not open infrainguinal bypass cases. There were 10,279 cases in Italy where a type of graft was specified. After having excluded the other cases there were a total of 32,084 cases for analysis. There was a wide variation in the number of cases from each country, with Italy contributing the highest number of cases overall (Table 2). The rate of reported IIB surgery for each country also varied, from 2.3 per 100,000 inhabitants in the UK to 24.6 per 100,000 in Finland (Table 3). This calculation was not done for Italy due to uncertainties regarding the precise population base.
Table 2Number of IIB operations reported, per year and country.
The proportion of women undergoing infrainguinal bypass varied from 25 % to 43.5 % (Table 4), and was higher in the Scandinavian countries and Switzerland. The age at surgery shows a more uniform picture with a median age for men of 70 and of 76 for women (Fig. 1). Hungary differs though, with a median age of 62 for men and 67 for women.
Table 4Percentage of females among patients undergoing IIB surgery.
There are also differences in the indications for surgery (Fig. 2). Bypasses for patients suffering from claudication constitute between 15.7% and 40.8% of reported procedures for leg ischaemia. It is notable that these extremes are found in two neighbouring Scandinavian countries, Denmark and Norway.
Figure 2Indications for bypass grafting (data on indication not available from Italy). The number of cases reported is shown with the name of each country.
Data was not available on the number of primary and secondary bypasses, however 77.7% of cases were “primary” to the extent that the individual had only one procedure recorded in the database.
Not all participating countries record all suggested pre-operative risk factors (Fig. 3). Diabetes was present in 21.1%–47% of cases. Cardiac disease was found in 36.4%–58.2%, lung disease in 15.2%–20.7%, hypertension in 51.9%–83.2% and a history of cerebrovascular events in 9.5%–16%. All these differences (between the highest and lowest incidence) in risk factors between countries are highly significant (p < 0.0001). Current smoking was reported in 17.7%–58.4%.
The choice of vein as the conduit used for bypass differed according to indication. The types of graft used by each country are shown in Fig. 4 (the data on indication was not available for Italy). Vein grafts were used increasingly with increasing degree of ischaemia: in claudication 52.9%, in rest pain 66.7% and with tissue loss 74.1%. The practice between countries differed however, which is clearly shown in Fig. 5. Overall Italy had the highest use of synthetic grafts and the lowest use of vein grafts.
It may be expected also that the site of the distal anastomosis would be influenced by the degree of ischaemia. Fig. 6 shows that this indeed was the case, with more distal bypass cases being performed for critical limb ischaemia (CLI). It is also of note that 45% of bypasses for claudication were performed to the below knee popliteal artery or a more distal vessel, with 9.6% being attached to the crural vessels. The relationship between graft type and distal anastomosis for patients with claudication, rest pain, and tissue loss is shown in Fig. 7.
Figure 6Distal anastomosis according to indication.
Figure 7Graft type related to site of distal anastomosis for (a) all patients (b) patients with claudication (c) patients with rest pain (d) patients with tissue loss.
There are considerable national differences when distal anastomosis site is plotted against country for a specific indication (Fig. 8a and b). In cases with tissue loss, the most advanced degree of ischaemia, above knee anastomosis is used in between 8.7% and 39% of cases.
Figure 8(a) Distal anastomosis in infrainguinal bypass for claudication. (b) Distal anastomosis in infrainguinal bypass for critical ischaemia.
Post-operative complications are reported in Table 5 for in hospital stay for Australia, Hungary, Denmark, UK, and Switzerland, and up to 30 days for Sweden, Finland and Norway.
Table 5Post-operative complications by indication (%).
The reported graft patency varies according to graft material but differences are small during the short term follow-up available in the present data (Table 6). The degree of ischaemia seems to influence patency more than graft material.
Graft patency was reported by seven countries, this was at the time of discharge by six and at 30 days by one other, and at both by two (Table 7). One-year follow-up data was available from so few countries that it was not included in the common database. Swedish data for 2008–09, however, demonstrated at 1-year follow-up a 12% mortality rate, and a 16.1% major limb amputation rate. 84.2% of patients had improved leg function at 1 year and 64.1% were mobile outdoors without support.
Registry data collection is not subject to the rigours of external validation associated with data collection in randomised trials, and is often criticised as a result. Nevertheless it does represent real clinical practice without the selection criteria applied to randomised trials.
Useful information can be gained from this type of data and some general conclusions can be legitimately drawn from the data. Some of the analyses have provided support to the conclusions of randomised trials and other areas have revealed differences in outcome that deserve further investigation.
The number of bypasses performed per 100,000 population varies considerably between countries, being highest in Finland and lowest in the UK. This may reflect the prevalence of peripheral vascular disease or a variation between countries as to how intermittent claudication is managed. In Finland the proportion of bypasses done for claudication is low compared to many other countries and the figures may also be explained by a very active management of CLI by infrainguinal bypass. Other factors may also play a part in this, for example the availability and use of endovascular surgery. In addition in some countries (the UK for example) it is known that the national database does not capture all cases of femoropopliteal bypass grafting and the low figure may represent under-reporting. Indeed a study of Hospital Episode Statistics in the UK over a 4-year period between 2002 and 2006 identified 21,675 femoropopliteal bypasses and 3458 femorodistal bypasses.
It is not clear from the literature what constitutes best practice in relation to the number of bypasses that should be expected, the current average from our data is 10.3 per 100,000 population.
There is also a variation in the male to female ratio between countries with a higher proportion of females in the Scandinavian countries. Previous studies have shown that between 64% and 98% of patients undergoing this type of bypass are male.
The proportion of patients treated for CLI or claudication is an important confounding factor when studying gender distribution. Patients with CLI more often have diabetes and are women than the claudicants who are more often smokers and men.
The median age of the patients undergoing this type of bypass is remarkably consistent between countries (overall 70 in men and 76 in women) and is higher than in many previous reports in which the majority of patients were below the age of 70.
This is likely to represent an increasingly elderly population across all the countries. The only exception to this was in Hungary where the patients were almost ten years younger. This may be due to a high incidence of smoking in this country and a shorter life expectancy, relatively poor health education and possibly the overall structure of the healthcare systems.
The indication for surgical bypass is not uniform across the countries studied. Overall approximately one quarter of grafts are performed for claudication. However there is considerable variation with the extremes being Denmark (15.7%) and Norway (40.8%). This information was unfortunately unavailable for Italy which contributed the highest number of cases overall, although the high use of synthetic grafts in this country suggests that the majority of cases may have been done for claudication. The reason for this variation needs further examination along with examination of the outcomes in the claudication group. Italy should be encouraged to collect this data on indication in order to provide it's surgeons with meaningful comparative audit. Possible explanations for this variation include different selection attitudes for bypass surgery in peripheral arterial disease and also the use of endovascular solutions compared to open surgical bypass but this finding may also indicate a variation in the management of claudication with some countries favouring a more interventional approach over conservative management. This Vascunet study did not examine the use of endovascular treatments, but future international data comparison might usefully study this.
The recording of pre-operative risk factors is notoriously difficult and this is an area prone to missing data.
Diabetes is a major risk factor for peripheral vascular disease and previous studies have demonstrated a wide variation in the rate of diabetes between 17%
In this data there was less variation with most countries reporting rates between 30% and 47%. Norway reported a low rate of diabetes of 21.1% perhaps indicating different attitudes to active intervention for vascular disease in diabetics. As might be expected hypertension and cardiac disease remain the most common pre-operative risk factors in these patients, with some countries reporting hypertension in over 75% of cases. The data also show a wide variation in current smoking. However it should be noted that there are differences in the definition of smoking between countries which partly explains this variation. For example the Swedvasc registry record smoking as smoking within the previous 5 years.
Patients undergoing peripheral bypass grafting are at risk of post-operative complications as a result of their pre-existing comorbidities. The incidence of some of the reported complications is high with 0.4% of claudicants requiring subsequent amputation and between 1.7% and 5.9% having an acute coronary event. In addition it is likely that there is some under-reporting of complications and therefore these rates may be an underestimation. Therefore the incidence of many of these complications including wound complications, haemorrhage, perioperative coronary events and death should be of considerable concern for all surgeons involved, with a mortality rate approaching 5% for patients with critical ischaemia and tissue loss.
Although there was a greater use of autologous vein in patients with critical ischaemia, the use of synthetic grafts varied between 15.7% in Australia and 46.8% in Hungary. A Cochrane review has demonstrated that there is a clear primary patency benefit of autologous vein over synthetic grafts for above knee femoropopliteal bypass.
A further review also demonstrated that the patency of venous bypasses was superior to PTFE bypasses at all times and recommended that a venous bypass should always be chosen if possible.
In an investigation from the Swedvasc registry patients operated on for CLI with a bypass to the popliteal artery above knee had equal results during the first year, but then the curves separated showing only half the patency with PTFE bypass after five years.
The reasons why synthetic grafts were used so often were not explored in depth in this international comparison, and therefore the precise reason for this finding is not clear. In addition the presence of varicose veins, previous use of the vein for coronary artery bypass, and unsuitability of the vein were reasons cited. The data would suggest however that there is potential for increasing the use of vein over prosthetic bypass in many countries. Traditionally infrapopliteal bypass is preserved for patients with critical limb ischaemia, but this study demonstrates that bypasses are performed to below the knee popliteal artery or a more distal artery in up to half of all cases done for claudication, and this is true of all the countries studied. This practice however is supported by Bryne et al.
who demonstrated primary and secondary patency rates of 77% and 81% at 4 years for infrainguinal arterial reconstruction to the below knee popliteal artery for disabling claudication. Indeed in some countries such as Denmark infrapopliteal bypass with vein is used preferentially on the basis that the approach to the infrapopliteal artery is considered in that country to be technically easier and has similar patency to above knee bypass.
One of the main outcomes of infrainguinal bypass surgery is graft patency. It is therefore surprising and disappointing that only a few countries record this as a mandatory outcome field. Similarly most of the countries in this study were not able to provide data on the incidence of major amputation following lower limb bypass surgery. Table 6 shows that seven countries make some assessment of graft patency but only three record graft patency at 30 days. The Vascunet group recommend that the recording of graft patency at the very minimum of 30 days, but ideally for longer, should become a mandatory requirement for each of the national vascular registries. Discharge patency rates vary from 91% to 99% in patients with tissue loss. This graft occlusion rate of up to 9% reinforces the need to monitor these patients for graft patency prior to hospital discharge and to record the outcome of this assessment. Sweden has one of the most robust data collection systems and in this country 8% of grafts occlude by 30 days in patients with claudication. This is in keeping with published data; a recent study of femoropopliteal bypass grafting for occlusive superficial femoral artery disease and stenting demonstrated a primary patency of 76% at 12 months for PTFE grafts.
Four-year randomized prospective comparison of percutaneous ePTFE/nitinol self-expanding stent graft versus prosthetic femoral-popliteal bypass in the treatment of superficial femoral artery occlusive disease.
These findings need to stimulate debate about the management and recording of outcomes in this group of patients internationally.
Limitations of study
This study uses registry data to compare practice between countries. It is well known that registries have limitations in respect to the quality and completeness of data and therefore the results of this study should be considered against this background. It was not possible, for example to ensure that each country used precisely the same definition for all of the variables collected, for example risk factors such as hypertension. The data presented here represent data from several countries, but we know that some countries have a more robust system of data capture than others and in some countries such as Sweden and Denmark data collection is compulsory and therefore more complete as a result. Other countries have voluntary registries and therefore cannot be sure of complete coverage of all cases, and we know that some of the registries included were regional. One of the difficulties of comparing infrainguinal bypass surgery between countries is that we do not know how variation in decision making affects the use of bypass surgery, and the employment of endovascular techniques which might influence the use of bypass grafting is not known. This may act as a confounder in the analysis of some of the data. In addition to this, whilst some countries have systems for internal validation of data we have not yet conducted any validation of the data at an international level. This is the next stage of the process of international vascular audit and an external international validation programme is now being undertaken.
In conclusion, we have demonstrated that international vascular audit is feasible, providing a large volume of data and allowing thought-provoking international comparisons to be made. With the fast pace at which vascular surgery is developing, and in particular the endovascular treatment options, the advantage of being able to report contemporary data is of particular importance, and an advantage over randomised and other prospective trials. This study raises many unanswered questions such as the clinical impact and outcome of bypass surgery and how this might be improved, but it is the first stage in trying to provide robust evidence of the indications, techniques and outcomes from infrainguinal bypass across countries. Further work is being undertaken to ensure that data comparison between countries is robust, data are complete, and a process for validation of data is put in place. Recommendations for national registries for standardisation of key data to allow international comparisons are required.
Acknowledgements
The Vascunet Committee work is supported by the European Society of Vascular Surgery which funds the expenses of the Committee.
The committee would also like to thank all the surgeons in the contributing countries for their diligence in collection of audit and outcome data on their patients.
Conflict of Interest
The authors have no conflict of interest to declare.
Funding
The Vascunet Committee is funded by the European Society of Vascular Surgery.
References
Björck M.
Gibbons C.
Jensen L.P.
Laustsen J.
Lees T.
Moreno-Carriles R.
et al.
Vascular registries join and create the common European dataset on AAA surgery.
Four-year randomized prospective comparison of percutaneous ePTFE/nitinol self-expanding stent graft versus prosthetic femoral-popliteal bypass in the treatment of superficial femoral artery occlusive disease.
This issue of the Journal features a vitally important paper which, hopefully, heralds a new era of complementary reporting of vascular care. The VASCUNET Committee, a group of National vascular registry representatives supported by the European Society for Vascular Surgery (ESVS), presents its first peer-reviewed report on surgical practice pattern for peripheral arterial occlusive disease (PAOD) within nine countries across Europe and Australia.1 The sheer size of more than 32,000 analyzed peripheral bypass procedures warrants a powerful voice to its findings that cannot be ignored.
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