Short-term patency of iliofemoral to tibial bypass with vascular allografts in a minority population: A retrospective analysis of a single center acute care facility

Introduction

Chronic limb threatening ischemia (CLTI) is a commonly described vascular surgical problem and requires revascularization efforts in order to avoid major morbidity or amputation. ¹ Treatment options typically involve some combination of systemic anticoagulation, thrombolytic agents, thrombo-embolectomy, or surgical bypass.

There have been many advancements in treatment strategies, especially with the popularization of endovascular techniques; despite these, surgical bypass is indicated in many cases. The recent BEST-CLI clinical trial, for example, indicates an essential role for surgical bypass, and in some clinical scenarios as a first line effort. ² There exist several options for bypass conduit, including autogenous, prosthetic, cryopreserved saphenous vein (CSV) grafts, and other less commonly used alternatives. ³

Surgical bypass operation remains a frequently performed procedure for CLTI but has some obstacles for certain patient populations. Surgical bypass and ensuing hospital course remain an expensive undertaking, evidenced by several studies including sub-analyses of the BASIL trial.^3,4 This cost increases further with varying types of conduits, and not all options may be covered by all insurance types, potentiating a variability in treatment options regarding patients’ socioeconomic status. In Lee MH et al. (2022), ⁵ we see that not only do patients in lower socio-economic cohorts present with a higher incidence of CLTI, but that they are typically treated at lower volume vascular centers with less revascularization options and have higher rates of post-revascularization amputation.

Minority populations and those without traditional insurance plans may be less frequently recipients of these expensive revascularization options (CSV) due to the nature of healthcare disparities. At our acute care facility serving a minority population, we are provided the opportunity to report findings on patients in this understudied cohort who underwent lower extremity bypass procedures for the diagnosis of CLTI, with CSV allografts.

Methods

This study was a retrospective analysis of all patients at a single center acute care facility (Harlem Hospital Center, Harlem, New York) undergoing ilio-tibial or femoral-tibial bypass between 1^st March 2020 and 23^rd April 2022. Institutional Review Board waiver of approval was obtained. A total of 20 bypass grafts were done during this time period, nine were either with native vein or synthetic graft, and the remaining 11 were performed with CSV. CSV was selected for use in these patients for CLTI with each patient having had one or several failed prior revascularization attempts, with with surgeon determination that cryopreserved graft was the most suitable conduit available. All cases were performed using RestoreFlow great saphenous vein (GSV) allografts. On 23^rd April 2023 (exactly 1 year after inclusion period), data was collected to include all notable perioperative events and significant findings at all follow-up visits for as long as documented in the medical record.

Inclusion criteria for this study was all patients who underwent bypass with CSV during the aforementioned time frame for CLTI, with indications mentioned above. Under this bracket, there were no exclusion criteria.

Patient information for clinical and demographic variables including comorbidities (hypertension, diabetes mellitus, chronic obstructive pulmonary disease, and congestive heart failure), smoking history, blood groups, body–mass index, and others were collected. Specific vascular surgery history was obtained including indications for surgery, type of bypass performed, surveillance details and complications, including need for salvage procedures as well as amputations. All patients who underwent bypass with CSV in this study were found to have either Medicare or Medicaid insurance or were uninsured. For this reason, a control group of patients with alternative insurance options was not identified. Additionally, patients were offered CSV without physician knowledge of insurance status, in attempts to mitigate selection bias as it relates to high cost of graft. Insurance status was only known after retrospective review.

Primary endpoints examined were primary and cumulative patency rates of CSV grafts. Secondary endpoints included target limb revascularization (TLR) and amputation free survival (AFS).

Baseline characteristics are analyzed in Tables 1 and 2, and patency rates were demonstrated using line graphs (Figures 1 and 3) and a life table (Figure 2) with associated standard errors.

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Table 1.

Patient characteristics and comorbidities.

Parameter	Incidence	SD
Gender		-
- Male	1 patient (9.1%)
- Female	10 patients (90.9%)
Mean age (years)	69.2 (59–78)	6.08
Mean BMI	27.15 (19.07–41.7)	6.03
Blood types		-
- A	2 patients (18.2%)
- B	3 patients (27.3%)
- O	6 patients (54.5%)
- AB	0 patients (0%)
Mean # prior vascular procedures	3 (1–7)	1.97
Mean duration followed for (months)	10.8 months	6.9
Type of bypass done		-
- EIA-ATA	1 patient (9.1%)
- EIA-PTA	1 patient (9.1%)
- CFA-ATA	2 patients (18.2%)
- CFA-PTA	1 patient (9.1%)
- SFA-ATA	2 patients (18.2%)
- SFA-PTA	4 patients (36.4 %)
Smoking history		-
- Current	5 patients 45.4%
- Former	3 patients 27.3%
- Never	3 patients 27.3%
Comorbidities		-
- Diabetes	90.9%
- Hypertension	90.9%
- Hyperlipidemia	36.4%
- COPD	27.3%
- CKD	27.3%
- Obesity (BMI >30)	27.3%
- Cardiac disease a	63.6%
Prior contralateral limb revascularization	2 patients (18.2%)	-

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Table 2.

Patient socioeconomic data.

Parameter	Incidence (%)
Race/Ethnicity	African American 90.9
	Hispanic 9.1
Religion	Catholic 45.5
	Baptist 9.1
	Pentecostal 9.1
	7th Day adventist 9.1
	Other 27.3
Language	English 90.9
	Spanish 9.1
ZIP code address	10469—9.1
	10468—18.2
	10037—9.1
	10035—27.3
	10031—9.1
	10030—18.2
	10027—9.1

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Figure 1.

Primary patency.

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Figure 2.

Life table showing cumulative primary patency rates and associated standard errors.

Results

Patient characteristics and data on comorbidities are documented in Table 1. Average age of patients included was 69.2 (range = 59–78) years. Of the eleven bypass procedures studied, male patients made up 9.1% (n = 1) of the study with females making up the other 90.9%. Each patient had a mean of 3 (range = 1–7, SD = 1.97) prior revascularization procedures performed on ipsilateral extremity. ABO blood groups were also assessed, without any notable contribution to outcomes. All patients in this study had undergone an iliofemoral origin to tibial bypass with CSV. The most used proximal vessel was the superficial femoral artery (SFA) in 54.5% of cases, and the most common distal target was posterior tibial artery (PTA) in 54.4% of cases, with SFA-PTA performed the most frequently in 36.4% of cases (summarized in Table 1). Also listed in Table 1 are comorbidities such as diabetes, hypertension, hyperlipidemia, cardiac disease, obesity, chronic obstructive pulmonary disease (COPD), chronic kidney disease (CKD), obesity, and smoking history. This noted 90% of included patients having clinically significant diabetes and hypertension, 63.6% of patients having some form of cardiac disease and 72.7% of patients having either current or former history of smoking.

Table 2 demonstrates data used to crudely assess socioeconomic background of participants.

Figure 1 demonstrates the primary patency for the eleven cases performed. Primary patency rates at 1, 6, and 12 months were 72.7%, 36.4%, and 27.3%, respectively. Secondary patency rate was not described as there were no successful graft interventions noted in this series.

Figure 2 represents a life table, constructed to examine cumulative patency of the bypass grafts to adjust for lost to follow-up patients. This provided corresponding rates at 1, 6, and 12 months of 72.7%, 54.5%, and 40.9% with standard errors of 11.5, 16.5, and 18.2, respectively, and is further demonstrated in Figure 3 where we see these values superimposed onto Figure 1.OPEN IN VIEWER

At the mean of 10.8 months follow-up, TLR was calculated to be 36.4%, and AFS calculated at 72.7% (total major amputations performed; n = 3).

Discussion

CSV grafts remain an expensive revascularization option and demonstrate inferior patency to many alternate options, thus is widely regarded as a last resort for lower extremity bypass. ⁶ We acknowledge the shortcomings identified in the literature and present our results to demonstrate consideration of this technique prior to amputation in minority populations. At acute care facilities, limited options and resources exist for complex revascularization efforts. In all cases, CSV was used as there was no suitable autogenous vein present, and synthetic graft was not desirable due to infrapopliteal targets; we believe that alternative treatments within the scope of a small acute care facility were exhausted. The use of cephalic vein grafts and complex endovascular treatments were not feasible options at this facility. Cryopreserved arterial grafts were not used due to inadequate length for infrapopliteal targets (our proximal and distal targets were at least 50 cm apart requiring a conduit no shorter than 55 cm in length; see Table 1 for list of bypass procedures performed). Had the length allowed or if a shorter conduit was needed, cryopreserved artery would have been considered. CSV were a viable and available conduit for in lieu of other alternatives for limb salvage and were a fortunate commodity to possess with such liberality of use in an acute care center.

In our study we noted significant comorbidities burden on the patients. All with at least two significant cardiac risk factors, with over 90% of participants having clinically significant diabetes and hypertension. 63.6% of patients had some form of cardiac disease, with 72.7% of patients either being current smokers at time of bypass or former smokers. Relative to the available literature on CSV, this study notes a high proportion of these co-morbid conditions, representative of the population served at our acute care facility.

We reviewed ABO blood types to determine clinical relevance. There has been little research done on blood type matched to cryopreserved graft patency. ⁷ In this review, no notable differences in patency were observed between blood groups, with relatively similar patency noted in each.

Minority populations and those within low socioeconomic cohorts tend to have higher incidences of CLTI and therefore increased need for revascularization procedures, but often are managed at lower volume vascular surgery centers with less resources for revascularization and inferior post-revascularization outcomes. ⁵ Table 2 outlines socioeconomic data points used to illustrate the minority population treated and reviewed in this paper. Using data extrapolated from the United States census of 2000, ⁸ we noted that approximately 63.6% of the studied patients are from zip codes with over 40% living below that year’s poverty level. Despite the paucity of data regarding demographics of recipients of CSV, we maintain this is likely an understudied patient population. This is especially likely due to the high expense of these grafts compared to effectiveness relative to polytetrafluoroethylene (PTFE) and other options. On discussion with a representative from the company (Lemaitre), based on their internal data, the cost of CSV grafts used in this study range from approximately $9000 to around $13,000, with the price mostly dependent on size, geographic location and surgeon/hospital volume. In a cost-effective analysis done by Barshes NR et al. (2013), ⁹ they note less cost effectiveness of CSV as compared to alternative allograft or synthetic grafts. They further elaborate to advocate that CSV remains a more cost-effective treatment than primary amputation for those who are candidates for limb preservation, despite previous studies arguing otherwise. Due to historical debates and controversy regarding cost–benefit relationship of this revascularization option, patients within minority populations and having medicare/Medicaid insurance (or lack of insurance) are rarely recipients of CSV.

The selection of proximal and distal target vessels for bypass were based on prior angiographic studies and remaining patent vessels. The most used proximal vessel was the superficial femoral artery (SFA) in 54.5% of cases, and the most common distal target was posterior tibial artery (PTA) in 54.4% of cases. Notably, of the 36.4% of grafts patent at 6-month follow-up, 75% used SFA as the proximal target and similarly 75% had the PTA as the distal target. We note this finding with the understanding that due to the small sample size we may not be able to extrapolate clinical significance from this result.

Figure 1 shows a line graph demonstrating primary patency of CSV. In this study we noted limitations regarding follow-up of patients. In a study by Jasinski PT et al. (2017), ¹⁰ evaluating potential factors affecting patient non-compliance after complex vascular surgery, the authors identified minority population, multiple comorbidities and lack of health insurance as variables associated with decreased follow-up; characteristics comparable to those of the patient population in this review. To attempt to adjust for the limitation of follow-up compliance, a life table was created showing cumulative primary patency rates at 1, 6, and 12 months of 72.7%, 54.5%, and 40.9% with standard errors of 11.5, 16.5, and 18.2, respectively. The primary patency noted within this study falls within the average short-term patencies noted in Zehr BP et al. (2011), ⁷ which summarizes the results and conclusions of several larger studies on CSV seeking a similar primary outcome.

Short-term Target limb revascularization rate (TLR) at the mean follow-up time of 10.8 months was calculated to be 36.4%, with overall incidence of major amputation of 27.3% with total amputation free survival (AFS) of 66.7%. We note the findings of O'Banion LA et al. (2017), ¹¹ with AFS at 1 year of 63% in all cryopreserved bypasses performed and 53% in patients undergoing bypass with the tibial (or pedal) artery as the distal target vessel. In this small study, the only complications noted were graft thrombosis—addressed as primary patency, and the only salvage procedures needed were major amputation, described in the form of AFS.

The authors identify that a potential limitation of this study is that there was a wide range of interventions performed on patients prior to CSV (mean = 3; range = 1–7; SD 1.97). Despite a relatively small SD, there remains the possibility that this range may have contributed to varied outcomes after bypass.

The primary patency of prosthetic conduits for similar target vessels demonstrates considerable range in current literature, from 34% to 69% 1-year cumulative primary patency in some studies.^12,13 The cumulative primary patency rate of 40.9% observed in this study falls within this range, even considering that many of these studies exclude redo bypasses which may further decrease observed patency rates. Comparative analyses between the two would be needed to determine superiority.

As a small acute care facility, the small sample size limits the generalizability of these results. Authors Johnston LE et al. (2017) ¹⁴ acknowledge that surgeon volume plays a major role in primary patency and major adverse outcomes after bypass surgery, with the institution volume itself having less effect on outcomes. This is even more relevant in smaller acute care facilities, where only one or two vascular surgeons may be performing all revascularization procedures.

This points to the potential for improved outcomes in similar patient populations if the surgeons at these smaller acute care facilities had increased patient volume for CSV interventions. With many lacking the infrastructure necessary to support more complex revascularization options, there is great potential for benefit if more acute care facilities were able to offer the option of CSV.

Conclusions

The outcomes of minority patients undergoing bypass with CSV were analyzed with creation of a life table and calculation of patency rates, TLR and AFS. The results of the primary and short-term patency rates and post-operative complications remain relatively comparable to larger studies in non-minority cohorts. These short-term results suggest that larger studies as well as prospective analyses and randomized controlled trials in this patient cohort and demographic are needed, as well as comparative data for minority populations versus non-minority populations. With results of this study relatively comparable to those of the general public as seen in other similar studies, we advocate for the above to improve optimal selection of patients and to determine true clinical implications.