Long-term postplacement cost after endovascular aneurysm repair

Cost analysis 

Institutional costs incurred directly from patient care were accessed through OCF’s cost accounting database (Eclipsys, Boca Raton, Fla). Costs of preoperative evaluation, and initial endograft placement with hospitalization, were not part of the present study.

The steps in our cost accounting system are briefly described here. Direct expenses are first consolidated monthly at a departmental (cost center) level and then are classified by the cost components of labor, supply, equipment, and facility. Next, components are divided into fixed expenses independent of patient volume and variable expenses dependent on patient volume. Individual patients are assigned cost codes for every chargeable service or supply item. Departmental managers and Hospital Decision Support then develop allocation statistics (relative value units) for each component of every cost code so that a final cost can be assigned. Individual patient costs are the sum of costs from each department utilized. The average cost calculations from January to June 2006 were used to adjust prior years’ costs for the sake of data uniformity.

Professional fees were calculated by using department-specific cost-to-charge ratios and were adjusted according to the average January to June 2006 costs. Costs for outpatient appointments were determined by using a time-based formula. Patient appointments were categorized as 10, 20, and 30 minutes according to Evaluation and Management codes. Outpatient department expenses were then allocated by the time coded for the follow-up appointment.

Overhead costs for the institution were added to the direct costs by a factor of 30% for each patient. This factor has been uniformly decided on by Hospital Decision Support and varies 1% to 2% monthly. This method allows for equitable distribution among patients: those patients with higher overall cost absorb more overhead cost. Overhead expense includes costs from departments not directly involved in patient care (eg, housekeeping, computer technology, finance), equipment and facility depreciation, and interest expense on borrowings.

All costs incurred after discharge from the original EVAR were included in this study and will heretofore be referred to as postplacement costs. These postplacement costs were subdivided into outpatient visits, radiologic studies, laboratory tests, secondary procedures, and hospital readmissions for complications of EVAR that did not require a secondary procedure (eg, ischemic colitis). Radiologic costs consisted of CT scans, abdominal radiographs, duplex ultrasonography, and vascular laboratory studies.

A secondary procedure was defined as any intervention (including diagnostic angiograms) performed due to the original aneurysm or for a complication of EVAR during the follow-up period. Secondary procedure costs were further broken down into cost of operating/interventional suite (anesthesia, operating room time, professional fees, nonendovascular surgical supply), endovascular supply, room and board (recovery room, outpatient surgery, floor/intensive care), pharmacy/laboratory, medical supply (nonoperative supply costs), radiology, and miscellaneous (respiratory care, dialysis, physical therapy, occupational therapy).

Endoleak was defined as persistent blood flow outside the endograft identified on an imaging study during follow-up. The types of endoleak have been previously reported.14, 15 Indications for secondary interventions for endoleak were the presence of a type I or type III endoleak, or a type II endoleak with significant aneurysm sac expansion (>5 mm). Translumbar glue embolization has been favored for treatment of type II endoleaks in recent years, although previously coil microembolization was used. Migration was determined as ≥10-mm caudal movement of the endograft or any amount of migration resulting in symptoms or a secondary procedure.

Statistical analysis 

The data are expressed as mean ± standard error. Cost comparisons between groups with and without secondary interventions or endoleaks were made with the Wilcoxon two-sample test. P < .05 was considered statistically significant. Statistical analysis was performed by using SAS 8.2 software (SAS Institute Inc, Cary, NC).

Patient cohort 

Of 259 completed EVARs included in the study period, 136 patients were included in the final cost analysis. Reasons for exclusion were death in 35 patients, <1 year since EVAR in 33, 28 were lost to follow-up, 15 had follow-up at another institution, and 12 patients refused further treatment.

Complete follow-up with all required outpatient visits and surveillance imaging was attained in 61 of the 136 included patients. An additional 60 patients missed one or more outpatient visits or imaging studies during their follow-up period, completing 81.1% of outpatient visits, 75.9% CT or duplex ultrasonography, and 75.1% of abdominal radiograph sets. The remaining 15 patients had an interval of ≥1 years (mean 1.3 ± 0.2 years) without follow-up, after which they resumed normal surveillance.

Baseline characteristics 

The mean age of the patients (87.5% men) was 73.2 ± 0.6 years. Comorbidities included the presence of coronary artery disease (58.8%), hypertension (57.4%), peripheral vascular disease (30.1%), chronic obstructive pulmonary disease (27.9%), diabetes mellitus (13.9%), and chronic renal insufficiency (12.5%). Spinal/regional anesthesia was used in 80.9% of EVAR.

Modular bifurcated endografts were deployed in 130 patients. Endograft types were Zenith (Cook, Bloomington, Ind) in 75, AneuRx (Medtronic/AVE Inc, Santa Rosa, Calif) in 50, and Excluder (W.L. Gore & Assoc, Flagstaff, Ariz) in five. The other six patients were treated with endocuffs (AneuRx, n = 5; Zenith, n = 1) alone for saccular aneurysms (n = 4) and pseudoaneurysms (n = 2).

Postplacement costs 

The mean follow-up was 34.7 ± 1.8 months. During the first postplacement year, patients averaged 3.7 ± 0.1 outpatient visits, 2.7 ± 0.1 CT scans, and 2.5 ± 0.1 complete sets of abdominal radiographs. For the subsequent years 2 through 5 of follow-up, the number of yearly outpatient visits, CT scans, and abdominal radiograph sets averaged 1.2 ± 0.04, 1.0 ± 0.04, and 1.0 ± 0.03, respectively. Ultrasound studies (n = 18) were used selectively in place of surveillance CT scans in 10 patients with renal insufficiency.

Mean postplacement cost was $2768 ± $556, $1435 ± $428, $2205 ± $706, $1710 ± $610, and $3233 ± $1687 at 1, 2, 3, 4, and 5 years, respectively. Overall, the cumulative 5-year cost per patient was $11,351 (Table I). Postplacement cost consisted of secondary procedures (57.4%), radiologic studies (32.5%), outpatient visits (7.6%), related hospital readmissions (2.1%), and laboratory costs (0.4%). In the first year of follow-up, the largest cost component was radiologic studies (Fig 1). For years 2, 3, 4, and 5, secondary procedures accounted for most of the expenses.

Table I. Five-year cumulative postplacement cost

	Follow-up year	All patients⁎		No secondary procedure⁎		Secondary procedure⁎
		No.	Mean cost	No.	Mean cost	No.	Mean cost
	1	136	$2768±$556	109	$1635±$131	27	$7340±$2608†
	2	98	$1435±$428	75	$499±$21	23	$4490±$1695†
	3	65	$2205±$706	47	$458±$25	18	$6767±$2254
	4	47	$1710±$610	33	$523±$52	14	$4506±$1884†
	5	33	$3233±$1687	22	$553±$77	11	$8593±$4796
	Cumulative cost		$11,351		$3668		$31,696†

⁎ Data are mean ± standard error. † Statistically significant (P < .05) vs no secondary intervention group.

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Fig 1. Yearly postplacement cost components. Laboratory costs were <0.6% for all years.

Secondary procedures 

Fifty-one secondary procedures were performed in 27 patients (19.9%; Table II). The mean time to secondary procedures was 25.4 ± 1.0 months. Patients who underwent a secondary procedure at any point during follow-up were also analyzed as a separate group. Patients with secondary procedures had an 8.6-fold increase in postplacement cost (Table I) compared with patients not needing an additional intervention (P < .05). Cost components for secondary procedures were operating/interventional suite (41.1%), room and board (21.1%), endovascular supply (18.2%), pharmacy/laboratory (10.2%), medical supply (3.0%), radiology (1.5%), and miscellaneous (4.9%).

Table II. Secondary procedures

	Procedure	No.	Mean cost⁎
	Endograft explant/EAB†	2	$57,681±$6464
	Iliac limb placement/EC‡	1	$29,479
	Open conversion (delayed)	4	$21,382±$3130
	Aortouniiliac device	1	$20,983
	Iliac endocuff	6	$13,042±$2274
	Endocuff	4	$8722±$2041
	Femoral-femoral bypass	1	$8217
	Laparoscopic IMA ligation	1	$8021
	Thrombolysis	1	$7437
	PTA±stent	2	$5153±$334
	Translumbar glue embolization	3	$4850±$769
	Coil microembolization	4	$4640±$458
	Diagnostic angiogram	20	$2677±$378
	Abscess drainage	1	$1507

EAB, Extra-anatomic bypass; EC, endocuff; IMA, inferior mesenteric artery; PTA, percutaneous transluminal angioplasty.

⁎ Data are mean ± standard error. † One procedure was staged, with the costs of both procedures combined. ‡ Staged placement of iliac limb after the initial endograft device malfunctioned.

The most common secondary procedure was a diagnostic angiogram (n = 20), performed in 13 patients (Fig 2, A). Indications for these angiograms were aneurysm growth (n = 13), endoleak identification (n = 6), and endograft limb thrombosis (n = 1; Table III). The remaining 31 secondary procedures were performed for therapeutic reasons (Table II). Proximal (n = 4) and iliac (n = 6) endocuffs were placed for cases of endoleak (n = 6), migration (n = 2), or both endoleak/migration (n = 2). The mean cost of an iliac endocuff procedure was $13,042 ± $2274 compared with $8722 ± $2041 for a proximal endocuff procedure. The use of additional supplies with iliac endocuffs was responsible for the increased expense of this procedure.

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Fig 2. A, Secondary procedures by frequency (%). B, Secondary procedures by cost (%). PTA, Percutaneous transluminal angioplasty.

Table III. Diagnostic angiograms

	Patient	Indications	Findings	Additional treatment
	1	AAA growth	None
		AAA growth	None
		AAA growth	None	Delayed OC
	2	EL identification	None	None
	3	Endograft limb thrombosis	Limb occlusion	Femorofemoral bypass
	4	AAA growth	Type II EL	None
	5	EL identification	Type I EL	EC
	6	AAA growth	Type II EL	Embolization
	7	AAA growth	None	Delayed OC
	8	AAA growth	None
		AAA growth	None	Delayed OC
	9	EL identification	Type II EL	Embolization
	10	AAA growth	Type II EL	Embolization
		AAA growth	Type III EL	Iliac endocuff
	11	AAA growth	None	Iliac endocuff
		AAA growth	None
		AAA growth	Infection	Endograft explant/EAB
	12	EL identification	Type II EL
		EL identification/attempted embolization	Type II EL	Laparoscopic IMA ligation
	13	EL identification	Type II EL	Embolization

AAA, Abdominal aortic aneurysm; OC, open conversion; EL, endoleak; EC, endocuff; IMA, inferior mesenteric artery; EAB, extra-anatomic bypass.

Six delayed open conversions were required. Conversions were due to endoleaks alone (type I, type III) in 2 patients, for endograft infection in 2, migration and endoleak (type I) in 1, and aneurysm expansion (endotension) in 1. Both open conversions for infection were managed with extra-anatomic bypass and endograft explantation. The mean cost of open conversion alone was $21,382 ± $3130, and the mean cost for open conversion with extra-anatomic bypass was $57,681 ± $6464, the highest for any of the secondary procedures. These six conversions accounted for 41% of the secondary procedure expense (Fig 2, B).

Related hospital admissions 

Two patients required a hospital readmission not associated with a secondary procedure. One was admitted for ischemic colitis 5 days after EVAR. The colitis resolved without operative intervention, and the patient was discharged on hospital day 8 for a total cost of $12,264. The other patient was admitted on two separate occasions with incisional postoperative wound infections. The first occurred after EVAR and the second after a delayed open conversion. The patient was released from the hospital in good condition on both occasions, with respective readmission costs of $1979 and $3650.

Endoleaks 

During the follow-up period, 27 patients (19.9%) had 29 endoleaks (type I, n = 5; type II, n = 17; type III, n = 7). In 14 patients, 14 endoleaks were seen on the 1-month postplacement CT; the remaining 15 endoleaks were detected later in follow-up. Eight endoleaks (type II) were monitored without any secondary procedure, and seven have resolved to date at a mean of 7.7 ± 1.1 months. In patients with endoleaks, 5-year cumulative post-placement costs were 4.7-fold higher (Table IV) than for patients without endoleak ($26,739 vs $5706; P < .05).

Table IV. Postplacement costs in patients with no endoleak versus patients with endoleak

	Follow-up year	Patients with no endoleak⁎		Patients with endoleak⁎
		No.	Mean cost	No.	Mean cost
	1	109	$2297±$615	27	$4668±$1253†
	2	77	$569±$74	21	$4607±$1851
	3	50	$1715±$698	15	$3836±$1986
	4	35	$567±$59	12	$5043±$2171
	5	22	$558±$77	11	$8585±$4797
	Cumulative cost		$5706		$26,739†

⁎ Data are mean ± standard error. † Statistically significant (P < .05) vs no endoleak group.

Secondary procedures 

A secondary procedure was required in 19.9% of the cohort (n = 27), and open conversions were necessary in 4.4% (n = 6). These values are within the range reported in recent literature, with rates as high as 27% for secondary procedures and 9% for open conversion.11, 17 In addition, to capture all costs, we counted diagnostic angiograms as secondary procedures, which is not uniformly done in the published reports. Similarly, our 19.9% incidence of endoleaks corresponds with previously reported values.22, 23 These comparable results confirm that the frequency of our largest cost generators is representative of the general post-EVAR population.

Endoleaks alone or in conjunction with migration were the driving force behind 56.9% of the secondary interventions (n = 29). Significant differences in long-term follow-up cost between patients with and without secondary intervention ($31,696 vs $3668) and endoleak ($26,739 vs $5706) stress the monetary impact of late complications. Costly late conversions comprised 12% of secondary procedures yet accounted for 41% of late expense (Fig 2). The procedural components, operative/interventional suite, and endovascular materials generated 59.3% of cost of the secondary procedures.

Radiologic studies 

Diagnostic radiologic studies for endograft surveillance were responsible for >30% of the long-term follow-up expense and comprised the second largest cost component. Although surveillance schedules vary, our protocol is a common one. Our 2006 costs were $350 for a CT of the abdomen and pelvis, $70 for duplex ultrasound imaging, and $51 for four-view abdominal radiographs. Although the cost per study is not large, expenses accumulate rapidly due to volume. A decrease in the frequency of postplacement CT or use of a different modality could reduce this large radiology expense. However, safe minimization of post-EVAR imaging will first require a reduction in complications and secondary interventions. Alternative methods of postprocedure monitoring provide another avenue for cost reduction.

Although color flow duplex ultrasound lacks the sensitivity of CT in endoleak detection,24 contrast-enhanced ultrasound imaging may provide improved detection.25 Unfortunately, the expense of ultrasound contrast agents and the inability to evaluate migration potentially limits its use. Remaining cost components contributed 10.1% of the total follow-up expense. The largest of these, outpatient visits (7.6%), coincided with the frequency of surveillance imaging.

It is apparent that long-term follow-up adds considerable expense to the global hospital cost of EVAR. However, this does not mean EVAR lacks societal cost-effectiveness. Patel et al,26 and Bosch et al,27 using Markov decision analysis models, found EVAR to be a cost-effective alternative to open repair. Both of these analyses included cost of follow-up. Critical to societal cost-effectiveness is maintenance of low morbidity and mortality rates26 and long-term failure and rupture rates.27

Study limitations 

This study has certain limitations. First, most patients did not have complete follow-up in which all outpatient visits and surveillance imaging occurred according to the strict surveillance protocol. Therefore, the calculated cost does not reflect all of the potential postplacement expenses that could be incurred in a “model” patient. Our data more accurately represent a realistic cross-section of postplacement follow-up, and therefore, our determined costs are potentially less than those obtained when follow-up is complete.

Second, the absence of those patients lost to follow-up should not affect the results. All costs were given as per patient with follow-up. Thus, there should be no change in mean per patient costs, unless those patients had a different postplacement history.

As a single institution costing analysis, costs such as overhead and labor may vary regionally or be hospital specific. As a retrospective study, follow-up practice patterns and expenses included in the early experience with endografts, such as surveillance ankle-brachial indices, are no longer used. As a consequence, current yearly postplacement costs are potentially lower. It is also possible that our use of diagnostic angiograms was more aggressive in our earlier experience. Nonetheless, most angiograms yielded a positive result, and furthermore, with exclusion of the first 50 patients in our series, it is unlikely that a learning curve issue was a significant factor in the cost differences. Our study did not compare long-term postplacement costs of EVAR with open repair. Follow-up costs of open repair may be less, as late graft-related complications are less frequent13 and long-term surveillance is not typically required.

Finally, there are limitations to the cost data. The assigned institutional overhead cost factor is an estimated fluctuating value that varies a percentage or two monthly. In addition, the cost of professional fees was determined by using a cost-to-charge ratio. Although this is a well-characterized method of estimating costs, it is ultimately based on charges, not underlying cost. These potential areas of subtle cost alterations are unlikely to have affected the larger trends and values seen in our cost analysis.