Comparison of 30-day readmission rates and risk factors between carotid artery stenting and endarterectomy

From the Society for Vascular Surgery

Comparison of 30-day readmission rates and risk factors between carotid artery stenting and endarterectomy Hanaa Dakour Aridi, MD, Satinderjit Locham, MD, Besma Nejim, MBChB, MPH, and Mahmoud B. Malas, MD, MHS, FACS, Baltimore, Md

ABSTRACT Objective: The aim of this study was to analyze the rates, reasons, and risk factors of 30-day readmission, both planned and unplanned, after carotid revascularization as well as to evaluate major outcomes associated with those readmissions. Methods: Using the Premier Healthcare database, we retrospectively identified patients undergoing carotid endarterectomy (CEA) and carotid artery stenting (CAS) between 2009 and 2015. The primary outcome was 30-day all-cause readmission. Secondary outcomes included mortality and overall cost associated with readmissions. Univariate and multivariate analyses were used and further validated using coarsened exact matching on baseline differences between CEA and CAS patients. Results: A total of 95,687 patients underwent carotid revascularization, 13.5% of whom underwent CAS. Crude 30-day readmission rates were 6.5% after CEA vs 6.1% after CAS (P ¼ .10). Stroke, bleeding, pneumonia, and respiratory failure were the most common reasons for readmission after both CEA and CAS (6.7% vs 8.3%, 6.9% vs 5.3%, 3.4% vs 2.4%, and 4.4% vs 3.9%; all P > .05). Myocardial infarction and wound complications were more likely to be an indication for readmission after CEA (4.1% vs 2.5% and 4.1% vs 1.5%, respectively; P < .05). On the other hand, readmissions due to vascular or stent-related complications were more likely after CAS compared with CEA (5.8% vs 3.8%; P ¼ .003). On multivariate analysis, CEA was found to be associated with 41% higher odds of readmission than CAS (adjusted odds ratio, 1.41; 95% confidence interval, 1.29-1.54; P < .001). Age, female gender, emergency/urgent procedures, concomitant cardiac procedures, rural hospitals, and Midwest region were significantly associated with 30-day readmission. Other risk factors included major preoperative comorbidities (diabetes, congestive heart failure, renal disease, chronic obstructive pulmonary disease, peripheral vascular disease, and history of cancer) as well as the occurrence of postoperative stroke and renal complications during the index admission and nonhome discharge. Coarsened exact matching between CEA and CAS patients also yielded higher adjusted rates of readmission after CEA (6.2% vs 4.9%; P < .001). On the other hand, patients readmitted after CAS had a longer length of hospital stay (5 days vs 4 days; P ¼ .001), increased readmission mortality (6.2% vs 2.8%; P < .001), and higher rehospitalization costs ($8903 vs $7629; P ¼ .01) compared with those readmitted after CEA. Conclusions: Our results show that CAS is associated with lower 30-day readmission rates compared with CEA. However, CAS readmissions are more complex and are associated with higher mortality and costs. We have also identified patients who are at high risk of readmissions, which can help focus attention on interventions that can improve the management of these patients and reduce readmission rates. (J Vasc Surg 2017;-:1-13.)

Carotid revascularization has been shown to effectively reduce the risk of ischemic stroke in selected patients with severe carotid artery stenosis.1 Prior studies have focused on the safety and efficacy of carotid From the Johns Hopkins Bayview Medical Center. Author conflict of interest: none. Presented as a poster at the 2017 Vascular Annual Meeting of the Society for Vascular Surgery, San Diego, Calif, May 31-June 3, 2017. Additional material for this article may be found online at www.jvascsurg.org. Correspondence: Mahmoud B. Malas, MD, MHS, FACS, Johns Hopkins Bayview Medical Center, 4940 Eastern Ave, Bldg A/5, Ste 547, Baltimore, MD 21224 (e-mail: [email protected]). The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest. 0741-5214 Copyright Ó 2017 by the Society for Vascular Surgery. Published by Elsevier Inc. http://dx.doi.org/10.1016/j.jvs.2017.05.097

endarterectomy (CEA) and carotid artery stenting (CAS).2-8 However, reducing readmission has become an important measurable quality outcome and an area of active research because of the increased pressure placed on hospitals and the planned monetary penalties to be imposed on centers with higher than expected readmission rates. This has been established through the Hospital Readmissions Reduction Program and the Patient Protection and Affordable Care Act.1,9-15 Between 2009 and 2011, nearly 10% of Medicare patients who underwent carotid revascularization returned to the hospital within 30 days of discharge.1 CEA has been considered the surgical procedure with the third highest readmission rate.16 However, a study published in the Journal of the American College of Cardiology found that CAS was associated with higher 30-day readmission rates compared with CEA. 1

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With the continuous improvement of revascularization techniques, we sought to evaluate 30-day readmission, including causes and risk factors, after CEA and CAS using a large nationwide database. This can offer insight into clinical decision-making and can guide effective strategies that can reduce readmission and improve the quality of care of patients undergoing carotid revascularization.

METHODS Data source. A retrospective study using the Premier Healthcare database (PHD) between 2009 and 2015 was performed and approved by the Institutional Review Board. The PHD is a large, U.S. hospital-based, servicelevel, all-payer database that contains information on inpatient discharges, primarily from geographically diverse nonprofit, nongovernmental, community and teaching hospitals and health systems from rural and urban areas. The PHD is a dynamic database that is updated weekly. To date, the PHD maintains cumulative information from >700 hospitals with >80 million inpatient admissions since 2011 (approximately 20% of annual inpatient discharges in the United States).17 The PHD offers deidentified, Health Insurance Portability and Accountability Act-compliant data from standard hospital discharge billing files. These data include demographics and disease states; admission and discharge diagnoses; information on billed services, including costs and charges at the departmental level; and patient disposition and discharge health status. For most data elements, <1% of patient records have missing information; and for key elements, such as demographics and diagnostic information, <0.01% have missing data. Data are subject to an extensive validation process occurring during implementation and with each monthly data submission by the hospital to ensure accurate and complete reporting. Subjects. Patients who underwent carotid revascularization (CAS or CEA) were identified using admission and primary procedure-specific codes from the International Classification of Diseases, Ninth Revision, Clinical Modification for CAS (00.63) and CEA (38.12). Patients with concomitant contralateral or ipsilateral carotid revascularization (0.12%), length of stay >30 days (0.35%), and death during the index hospital stay (0.6%) were excluded from the analysis. The need for informed consent of the patients was waived because the data are deidentified data and not considered human subjects research under federal guidelines. Outcomes. The primary outcome of interest was 30day readmission. Using a unique masked identifier, patients were tracked across the inpatient settings to assess consecutive admissions to the index hospital in a chronologic order as well as the cumulative number of days since the previous admission. Secondary outcomes

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ARTICLE HIGHLIGHTS d

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Type of Research: Retrospective analysis of the prospectively collected Premier Healthcare database Take Home Message: Of 95,687 patients who underwent carotid revascularizations, carotid artery stenting patients had lower 30-day readmission rates but more complex readmissions with higher mortality and costs than carotid endarterectomy patients. Recommendation: This study suggests that readmissions after carotid artery stenting, although less frequent, are more complex and have higher mortality rates and costs than readmissions after carotid endarterectomy.

included medical and surgical complications during both the initial hospitalization and the readmission stay. These were identified using secondary diagnosis and procedure codes provided in Supplementary Table I (online only). Device-related complications included stent occlusion, CEA patch infection, and occlusion of the carotid artery. Furthermore, in-hospital outcomes in readmitted patients including mortality, complications, and total hospitalization costs were analyzed. Costs are those reported by the hospital. They are not the charge to a payer or the amount reimbursed to the hospital. Currency data were presented as medians, adjusted for inflation for 2015 U.S. dollars using the Consumer Price Index Inflation Calculator from the U.S. Department of Labor. Symptomatic status was defined as presenting with transient cerebral ischemia, carotid artery stenosis with cerebral infarction, stroke, or transient limb paralysis as well as retinal vascular occlusion or retinal ischemia. Statistical analyses. Student independent t-tests and Wilcoxon rank sum tests were used to analyze continuous variables, and c2 tests were used to compare categorical variables. Multiple logistic regression models were used to study the association between 30-day readmission and patients’ demographics, comorbidities, symptomatic status, and discharge destination as well as hospital teaching status and provider regions. Variables included in the final models were chosen on the basis of clinical relevance or a P value # .20 on initial bivariate analysis. C statistics and the Hosmer-Lemeshow test evaluated the models’ predictive ability and goodness of fit, respectively. Regression models were also checked for multicollinearity using variance inflation factors for each covariate (mean variance inflation factor, 1.13; maximum, 1.56). The analysis was validated using coarsened exact matching (CEM) described by Iacus et al18 to ensure valid evaluation of patients within each procedure and to avoid selection bias. Matching was performed on baseline characteristics that were significantly different

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Table I. Baseline characteristics of patients undergoing carotid endarterectomy (CEA) and carotid artery stenting (CAS) CEA No. of patients Age, years, mean (SD)

P value

CAS

82,817 (86.5) 12,870 (13.5) 71.9 (8.3)

71.7 (8.5)

Female

34,562 (41.7)

5009 (38.9)

Male

48,246 (58.3)

7861 (61.1)

Race White

3450 (4.2)

604 (4.7)

Others

10,959 (13.2)

1899 (14.7)

Insurance type Medicare

64,679 (78.5)

9893 (77.6)

Medicaid

2359 (2.9)

509 (4.0)

13,406 (16.3)

2031 (15.9)

1978 (2.4)

315 (2.5)

66,504 (80.3)

8707 (67.7)

Other Elective Emergency Urgent Others

5870 (7.1)

1773 (13.8)

10,008 (12.1)

2317 (18.0)

435 (0.5)

73 (0.6) 3548 (27.6)

<.001

Teaching hospitals

34,966 (42.5)

7675 (59.8)

<.001

Rural

11,128 (13.5)

892 (7.0)

Urban

71,189 (86.5)

Midwest

<.001 11,948 (93.1) <.001 15,202 (18.5)

2631 (20.5)

10,511 (12.8)

2173 (16.9)

South

44,878 (54.5)

6478 (50.5)

West

11,726 (14.2)

1558 (12.1)

10,591 (12.9)

2334 (18.5)

<.001

Diabetes

28,658 (34.6)

4427 (34.4)

.65

Old MI

10,573 (12.8)

1723 (13.4)

.05

CHF

7047 (8.5)

1701 (13.2)

<.001

Renal disease

9488 (11.5)

1727 (13.4)

<.001

20,134 (24.3)

3120 (24.2)

.87

1770 (2.1)

186 (1.5)

<.001

North-East

Comorbidities Symptomatic

COPD Connective tissue disease Peptic ulcer disease Paraplegia/hemiplegia Liver disease Peripheral vascular disease

531 (0.6) 1593 (1.9)

72 (0.6) 755 (5.9)

.28 <.001

694 (0.8)

104 (0.8)

.73

20,790 (25.1)

4067 (31.6)

<.001

1471 (1.8)

315 (2.5)

P value

I

30,834 (37.2)

4474 (34.8)

<.001

II

26,717 (32.3)

3757 (29.2)

III

13,024 (15.7)

2148 (16.7)

IV

6714 (8.1)

1277 (9.9)

V

3260 (3.9)

650 (5.1)

VI

2268 (2.7)

564 (4.4)

between CEA and CAS patients, including age, gender, race, insurance type, admission type (elective, emergency, and urgent), concomitant cardiac procedures, teaching status, region (rural vs urban), provider area, symptomatic status, medical comorbidities (old myocardial infarction [MI], congestive heart failure [CHF], renal disease, connective tissue disease, paraplegia/ hemiplegia, peripheral vascular disease, and cancer), and comorbidity index. Some of the advantages of CEM over standard matching approaches, such as propensity score matching, are that it requires fewer postestimation assumptions about how to define a match, automatically balances treatment and control populations, and has superior computational properties for large data sets. Analysis was performed using Stata version 14.1 (StataCorp, College Station, Tex). Significance tests were two sided with a .05 significance level.

18,948 (22.9)

Provider area

CAS

<.001

Concomitant cardiac procedures Region

CEA Charlson Comorbidity Index

<.001

<.001

Admission type

Table I. Continued.

CHF, Congestive heart failure; COPD, chronic obstructive pulmonary disease; MI, myocardial infarction; SD, standard deviation. Values are reported as number (%) unless otherwise indicated.

68,408 (82.6) 10,367 (80.6)

Black

Private insurance

.06 <.001

Gender

Cancer

3

-

<.001

(Continued)

RESULTS A total of 95,687 patients underwent carotid revascularization between 2009 and 2015: 82,817 CEA (86.5%) and 12,870 (13.5%) CAS. Of those, 6118 (6.4%) were readmitted within 30 days of discharge (CEA, 6.5%; CAS, 6.1%; P ¼ .10). Comparison of baseline characteristics between the two groups is shown in Table I. Occurrence of more than one readmission was more common after CAS than after CEA (31% vs 25%; P < .001). Compared with patients not readmitted within 30 days, those readmitted were older (73 6 8.6 years vs 71.8 6 8.3 years; P < .001), were more often women (43.4% vs 41.2%; P < .001) and African Americans (5.6% vs 4.1%; P < .001), and were mostly covered by Medicare (81.7% vs 78.1%; P < .001; Table II). Moreover, they were more likely to be readmitted after emergency or urgent index procedures (36.2% vs 19.9%; P < .001) or with concomitant cardiac procedures (34.2% vs 22.8%; P < .001). Readmitted patients were more likely to be symptomatic on initial presentation (21.4% vs 13.1%; P < .001) and had a higher prevalence of comorbid conditions, such as diabetes (40.9% vs 34.2%), history of MI (15.5% vs 12.7%),

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Table II. Comparison of baseline characteristics and in-hospital complications between patients readmitted and those not readmitted within 30 days of carotid revascularization Not readmitted

Readmitted

89,569 (94.6)

6118 (6.4)

CEA

77,479 (86.5)

5338 (87.3)

CAS

12,090 (13.5)

780 (12.7)

No. of patients

P value

71.8 (8.3)

.10

73.0 (8.6)

<.001 <.001

Gender Male

52,642 (58.8)

3465 (56.6)

Female

36,918 (41.2)

2653 (43.4)

Race White

73,823 (82.4)

4952 (80.9)

3712 (4.1)

342 (5.6)

Others

12,034 (13.4)

824 (13.5)

69,598 (78.1)

4974 (81.7)

2666 (3.0)

202 (3.3)

<.001

Private insurance Other

<.001

Emergency Urgent Others

IV

7234 (8.1)

757 (12.4)

V

3422 (3.8)

488 (8.0)

VI

2378 (2.7)

454 (7.4)

6563 (7.3)

699 (11.4)

<.001

31 (0.5)

<.001

Hemorrhage or bleeding

135 (0.15)

Cardiac (MI, CHF, arrhythmia)

5178 (5.8)

615 (10.1)

<.001

<.001

326 (5.3)

<.001

160 (0.2)

44 (0.7)

<.001

71,345 (79.7)

3866 (63.2)

<.001

7046 (7.9)

597 (9.8)

Infectious (wound, sepsis, others)

10,709 (12.0)

1616 (26.4)

Ileus

99 (0.1)

29 (0.5)

<.001

Venous thromboembolic (DVT, PE)

66 (0.07)

14 (0.2)

<.001

1 (1-3)

3 (1-8)

<.001

469 (0.5)

39 (0.6) 2094 (34.2) 2710 (44.5)

<.001 .66

Length of stay, days, median (IQR) Discharge destination

11,218 (12.6)

802 (13.2)

77,855 (87.4)

5282 (86.8)

16,569 (18.6)

1264 (20.8)

.18

West

12,477 (14.0)

807 (13.3)

<.001

11,632 (13.1)

1293 (21.4)

<.001

30,585 (34.2)

2500 (40.9)

<.001

11,346 (12.7)

950 (15.5)

<.001

7703 (8.6)

1045 (17.1)

<.001

9991 (11.2)

1224 (20.0)

<.001

21,453 (24.0)

1801 (29.4)

<.001

1805 (2.0)

151 (2.5)

.02

550 (0.6) 1903 (2.1) 735 (0.8)

53 (0.9)

Home Home under home health care

Comorbidities

Liver disease

1176 (19.2)

424 (6.9)

824 (13.5)

Paraplegia/hemiplegia

1671 (27.3)

13,996 (15.6)

1077 (1.2)

3189 (52.4)

Peptic ulcer disease

28,803 (32.2)

III

2304 (2.6)

11,860 (13.3)

Connective tissue disease

II

Stroke

48,167 (54.1)

Renal disease

<.001

Renal (AKI, UTI, others)

South

COPD

1572 (25.7)

146 (2.4)

North-East

CHF

33,736 (37.6)

2147 (2.4)

Provider area

Old MI

I

<.001

39,931 (44.8)

Symptomatic

<.001

287 (4.7)

Teaching hospitals

Diabetes

192 (3.1)

1382 (1.5)

Region

Midwest

1594 (1.8)

Cancer

Respiratory (pneumonia or respiratory failure)

20,402 (22.8)

Urban

<.001

765 (12.6)

Concomitant cardiac procedures

Rural

P value

1812 (29.6)

14,672 (16.5)

Admission type Elective

Readmitted

23,045 (25.7)

Peripheral arterial disease

Vascular or stent complication

Insurance type Medicaid

Not readmitted

In-hospital complications

Black

Medicare

Table II. Continued.

Charlson Comorbidity Index

Procedure

Age, years, mean (SD)

2017

.02

445 (7.3)

<.001

63 (1.0)

.08

(Continued)

General hospital

77,265 (86.6)

3720 (61.2)

6792 (7.6)

687 (11.3)

462 (0.52)

<.001

52 (0.9)

Skilled nursing facility

3041 (3.4)

585 (9.6)

Other rehabilitation or hospice

1672 (1.9)

1036 (17.0)

AKI, Acute kidney injury; CAS, carotid artery stenting; CEA, carotid endarterectomy; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; DVT, deep venous thrombosis; IQR, interquartile range; MI, myocardial infarction; PE, pulmonary embolism; SD, standard deviation; UTI, urinary tract infection. Values are reported as number (%) unless otherwise indicated.

CHF (17.1% vs 8.6%), chronic obstructive pulmonary disease (COPD; 29.4% vs 24.0%), and peripheral vascular disease (29.6% vs 25.7%), compared with patients who were not readmitted within 30 days (all P < .001). Readmitted patients experienced more stroke (5.3% vs 1.2%), hemorrhage/bleeding (11.4% vs 7.3%), cardiac complications (including acute MIs, CHF, and arrhythmias; 10.1% vs 5.8%), and more respiratory (4.7% vs 1.5%) and renal

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30

25

Percentage

CEA

CAS

20

15

10

5

0

Fig. Most common readmission indications after carotid endarterectomy (CEA) and carotid artery stenting (CAS). GI, Gastrointestinal.

(6.9% vs 2.6%) complications during the index admission compared with patients not readmitted (all P < .001). Median index length of stay was significantly higher in readmitted patients (median [interquartile range], 3 [1-8] vs 1 [1-3] days; P < .001). A significant portion of readmitted patients were not discharged home initially, with 10.5% transferred to a general hospital or a skilled nursing facility and 11.3% discharged home under a home health service organization. Causes of readmission. A total of 7153 readmissions occurred, mostly 1 week after discharge from the hospital. Other than nonspecific complaints such as fatigue, fever, headache, syncope, and admission for physical therapy, most common indications of these readmissions (n ¼ 7153) were related to cardiac, neurologic, infectious, and respiratory complications (Fig). Stroke was one of the most common reasons for readmission after both CAS and CEA (8.3% vs 6.7%; P ¼ .07), followed by hemorrhage/shock/bleeding (5.3% vs 6.9%; P ¼ .06), pneumonia (2.4 vs 3.4%; P ¼ .12), and respiratory failure (3.9% vs 4.4%; P ¼ .5). MI and wound complications were more

likely to be an indication for readmission after CEA compared with CAS (4.1% vs 2.5% [P ¼ .02] and 4.1% vs 1.5% [P < .001], respectively; Table III). On the other hand, readmissions due to vascular or stent-related complications were more likely after CAS than after CEA (5.8% vs 3.8%; P ¼ .003). Predictors of 30-day readmission. After multivariate adjustment, CEA was found to be associated with 41% higher odds of readmission compared with CAS (adjusted odds ratio [aOR], 1.41; 95% confidence interval [CI], 1.29-1.54). Advanced age (aOR, 1.01; 95% CI, 1.00-1.01), female gender (aOR, 1.09; 95% CI, 1.03-1.16), emergency and urgent procedures (aOR, 1.43 [95% CI, 1.32-1.55] and 1.14 [95% CI, 1.03-1.26], respectively), and concomitant cardiac procedures (aOR, 1.18; 95% CI, 1.11-1.26) were significantly associated with higher odds of readmission (P < .05). Other risk factors included hospitals’ location (rural and Midwest areas had higher odds of readmission); major comorbidities, such as diabetes, CHF, renal disease, COPD, peripheral arterial disease, and a history of cancer; and nonhome discharge. The model

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was able to predict only 8.8% of variability in 30-day readmission (R2 ¼ 8.8%; C statistic ¼ 69.5%). Further including in-hospital complications did not significantly improve predictability (R2 ¼ 8.9%; C statistic ¼ 69.6%). Among in-hospital complications, stroke increased the odds of 30-day readmission by 40% (aOR, 1.40; 95% CI, 1.20-1.64; P < .001) and renal adverse events by 14% (aOR, 1.14; 95% CI, 1.01-1.30; P ¼ .04; Table IV). Subgroup analysis: CEM. Exact one-to-one matching was performed on the basis of baseline characteristics that were shown to be significantly different between CEA and CAS patients, including age, gender, race, insurance coverage, admission type, presence of concomitant cardiac procedures, region (urban vs rural), provider area, hospital teaching status, and medical comorbidities that make up the Charlson Comorbidity Index (history of MI, CHF, connective tissue disease, paraplegia/hemiplegia, peripheral arterial disease, and renal disease). This yielded two comparison groups each with 8966 patients (Supplementary Table II, online only). Comparison of the two groups showed higher adjusted 30-day readmission rates after CEA compared with CAS (6.2% vs 4.9%; P < .001). Secondary outcomes that are significantly different between CEA and CAS were in-hospital stroke (1.8% vs 1.2%; P < .01), arrhythmia (4.9% vs 6.7%; P < .001), hemorrhage/bleeding (8.6% vs 7.4%; P < .01), acute kidney injury (1.8% vs 1.5%; P ¼ .05), and discharge disposition (Table V). We further controlled for in-hospital postoperative complications, and readmission was still 35% higher after CEA compared with CAS (aOR, 1.35; 95% CI, 1.18-1.54; P < .001). Outcomes of readmitted patients. Patients readmitted after CAS had a longer length of hospital stay (5 days vs 4 days; P ¼ .001) and significantly higher readmission mortality (6.2% vs 2.8%; P < .001) compared with those readmitted after CEA. Adjusted readmission mortality was two times higher in patients readmitted after CAS vs CEA (aOR, 2.0; 95% CI, 1.5-2.8; P < .001). Throughout the readmission, patients were also subject to various adverse events complicating the course of their rehospitalization after CEA and CAS. These included bleeding (4.8% after CEA vs 3.1% after CAS; P ¼ .02), cardiac (6.7% vs 6.1%; P ¼ .53), respiratory (3.5% vs 5.0%; P ¼ .03), and renal (5.3% vs 6.7%; P ¼ .10) complications. The median total, fixed, and variable costs of readmission were higher if the readmission occurred after CAS compared with CEA ($8903, $4313, and $4390 vs $7629, $3762, and $3651, respectively). Adjusted rehospitalization costs after CAS were higher by around U.S. $700 compared with those after CEA (Table VI).

DISCUSSION Carotid revascularization is a high-volume procedure with significant readmission rates. The likelihood that the Centers for Medicare and Medicaid Services will

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penalize readmissions after vascular procedures in the future is high; thus, reducing unplanned readmissions has become of prominent importance to improve quality of care and to reduce significant expenses both to the health care system and to the patient.19 The overall 30-day readmission rate in our study was around 6.4%, which is comparable to that reported using other large population databases.20-22 Al-Damluji et al1 reported a much higher unadjusted 30-day readmission rate (9.6%). For CEA, overall reported readmission rates are around 6.5%15,20,22,23 but can be as high as 9.4%.24 On the other hand, reported readmission rates after CAS range between 9.7%22 and 11.11%,25 which is higher compared with our study (6.1%). Our study shows an association between CEA and increased all-cause readmission rates after risk adjustment (aOR, 1.41; 95% CI, 1.29-1.54; P < .001) as well as after exact matching (6.2% vs 4.9%; P < .001). This is in contrast to two previous studies that demonstrated higher adjusted risk of readmission after CAS compared with CEA.1,25 Galinanes et al25 used the Centers for Medicare and Medicaid Services Medicare Provider Analysis and Review file between 2005 and 2009 and showed increased odds of readmission in patients undergoing CAS compared with those undergoing CEA within 30 days (aOR, 1.21; 95% CI, 1.15-1.26; P < .0001), 60 days (aOR, 1.34; 95% CI, 1.29-1.39; P < .0001), and 90 days after discharge (aOR, 1.36; 95% CI, 1.31-1.40), with coronary artery disease being the most common reason for readmission. In addition, Al-Damluji et al1 showed 13% higher adjusted risk of readmission after CAS (aOR, 1.13, 95% CI, 1.08-1.18; P < .001) using Medicare beneficiaries from 2009 to 2011 with the same relationship holding true in a propensity-matched cohort (OR, 1.18; 95% CI, 1.07-1.23) regardless of symptomatic status, age, sex, and race. An important finding by the authors was that the variation in proportional use of CAS was not associated with differences in hospital risk-standardized readmission rates. Thus, hospitals with more frequent CAS use will not necessarily be disadvantaged when hospitals with higher than expected readmissions are penalized. However, an editorial comment on that study cautioned that the poorer performance of CAS might be due to selection bias, which could not be adjusted for, and that the small difference in readmission rates between the two procedures might not be meaningful as it could be a potential artifact of the study’s large sample size.26 The lower readmission rates after CAS in our study might be explained by several factors, such as the use of different databases and different time frames as well as the continuous decline in 30-day major adverse events after CAS due to the refinement in CAS techniques, development of better stents and protection devices, better selection of patients for each procedure, and increased expertise of operators over time. Unlike the cited studies that examined Medicare data between

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Table III. Most common indications for 30-day readmission after carotid endarterectomy (CEA) and carotid artery stenting (CAS)

No. of readmissions More than one readmission Time to readmission, days (IQR)

CEA

CAS

6205 (86.7)

948 (13.3)

1552 (25.0)

293 (30.9)

6 (1-16)

7 (1-17)

P value

Total 7153

<.001 .89

1845 (25.8) 6 (1-16)

Hemorrhage/shock/bleeding

428 (6.9)

50 (5.3)

.06

478 (6.7)

Vascular or stent complication

235 (3.8)

55 (5.8)

.003

290 (4.1)

MI

255 (4.1)

24 (2.5)

.02

279 (3.9)

Heart failure

212 (3.4)

33 (3.5)

.92

245 (3.4)

Chest pain

221 (3.6)

34 (3.6)

.97

255 (3.6)

Arrhythmia

240 (3.9)

35 (3.7)

.79

275 (3.8)

16 (0.3)

1 (0.1)

.37

17 (0.2)

Cardiac

Other cardiac Respiratory Pneumonia

211 (3.4)

23 (2.4)

.12

234 (3.3)

Respiratory failure

272 (4.4)

37 (3.9)

.50

309 (4.3)

Other

433 (7.0)

56 (5.9)

.22

489 (6.8)

Renal or urologic Acute kidney injury Others

151 (2.4)

21 (2.2)

.68

172 (2.4)

180 (2.9)

21 (2.2)

.23

201 (2.8)

417 (6.7)

79 (8.3)

.07

496 (6.9)

Neurologic Stroke Paraplegia Other neurologic

5 (0.1) 485 (7.8)

0

.38

5 (0.1)

92 (9.7)

.05

577 (8.1)

Infectious Wound complication

254 (4.1)

14 (1.5)

<.001

268 (3.7)

Sepsis

184 (3.0)

36 (3.8)

.17

220 (3.1)

5 (0.5)

.91

36 (0.5)

.01

185 (2.6)

.73

19 (0.3)

UTI/pyelonephritis Other infection

31 (0.5) 173 (2.8)

12 (1.3)

Gastrointestinal Bowel obstruction Bowel ischemia

16 (0.3) 5 (0.1)

3 (0.3) 0

1.0

5 (0.1)

Venous thromboembolic Deep venous thrombosis

13 (0.2)

3 (0.3)

.46

16 (0.2)

Pulmonary embolism

44 (0.7)

5 (0.5)

.67

49 (0.7)

Other venous

5 (0.1)

0

1.0

5 (0.1)

Reoperation Carotid revascularization

17 (0.3)

3 (0.3)

.74

20 (0.3)

Other vascular reoperation

74 (1.2)

16 (1.7)

.20

90 (1.3)

183 (3.0)

33 (3.5)

.37

216 (3.0)

58 (0.9)

5 (0.5)

.21

63 (0.9)

78 (1.3)

9 (1.0)

.42

87 (1.2)

Other abdominal Cancer Nonspecific/others Headache Nausea/vomiting/dysphagia

128 (2.1)

12 (1.3)

.10

140 (2.0)

Syncope/collapse

183 (3.0)

23 (2.4)

.37

206 (2.9)

Fever

79 (1.3)

11 (1.2)

.77

90 (1.3)

120 (1.9)

14 (1.5)

.33

134 (1.9)

Physical therapy

1065 (17.2)

199 (21.0)

.004

1264 (17.7)

Unknown

1360 (21.9)

213 (22.5)

.70

1573 (22.0)

Fatigue

IQR, Interquartile range; MI, myocardial infarction; UTI, urinary tract infection. Values are reported as number (%) unless otherwise indicated.

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Table IV. Bivariate and multivariate logistic regression models of the predictors of 30-day readmission after carotid revascularization Unadjusted OR (95% CI)

P value

Adjusted OR (95% CI)

P value

Procedure CAS CEA Age

1.0 (reference)

1.0 (reference)

1.07 (0.99-1.15)

.097

1.41 (1.29-1.54)

<.001

1.02 (1.01-1.02)

<.001

1.01 (1.00-1.01)

<.001

<.01

1.09 (1.03-1.16)

Gender Male Female

1.0 (reference) 1.09 (1.04-1.15)

1.0 (reference) <.01

Race White

1.0 (reference)

1.0 (reference)

Black

1.37 (1.22-1.54)

<.001

1.09 (0.97-1.24)

.16

Others

1.02 (0.95-1.10)

.60

0.98 (0.90-1.06)

.60

Insurance type Medicare

1.0 (reference)

1.0 (reference)

Medicaid

1.06 (0.92-1.23)

.43

1.06 (0.90-1.24)

Private insurance

0.73 (0.67-0.79)

<.001

0.94 (0.85-1.02)

.51 .15

Other

0.95 (0.80-1.13)

.57

1.08 (0.90-1.31)

.40

Admission type Elective

1.0 (reference)

1.0 (reference)

Emergency

2.78 (2.62-2.96)

<.001

1.43 (1.32-1.55)

Urgent

1.56 (1.43-1.71)

<.001

1.14 (1.03-1.26)

.01

Others

1.53 (1.11-2.13)

.01

1.26 (0.88-1.79)

.20

1.76 (1.67-1.86)

<.001

0.99 (0.94-1.04)

.66

Concomitant cardiac procedures Teaching hospitals

1.18 (1.11-1.26) d

<.001

<.001 d

Region Rural Urban

1.0 (reference) 0.95 (0.88-1.02)

1.0 (reference) .18

0.88 (0.81-0.96)

<.01

Provider area Midwest

1.0 (reference)

1.0 (reference)

North-East

0.91 (0.83-0.99)

.04

0.83 (0.76-0.92)

<.001

South

0.87 (0.81-0.93)

<.001

0.92 (0.85-0.98)

.02

West

0.85 (0.77-0.93)

<.001

0.94 (0.85-1.03)

.20

Symptomatic

1.81 (1.70-1.93)

<.001

1.06 (0.98-1.14)

.17

Diabetes

1.33 (1.26-1.40)

<.001

1.15 (1.09-1.22)

<.001

Old MI

1.27 (1.18-1.36)

<.001

1.06 (0.98-1.14)

.16

CHF

2.19 (2.04-2.35)

<.001

1.47 (1.36-1.60)

<.001

Renal disease

1.99 (1.86-2.13)

<.001

1.39 (1.29-1.50)

<.001

COPD

1.32 (1.25-1.40)

<.001

1.17 (1.10-1.25)

<.001

Connective tissue disease

1.23 (1.04-1.46)

.02

1.10 (0.92-1.31)

.31

Peptic ulcer disease

1.41 (1.07-1.88)

.02

1.07 (0.79-1.45)

.66

Paraplegia/hemiplegia

3.61 (3.25-4.02)

<.001

1.02 (0.89-1.17)

.75

Liver disease

1.26 (0.97-1.63)

.08

1.06 (0.80-1.40)

.69

Peripheral arterial disease

1.21 (1.15-1.29)

<.001

1.11 (1.04-1.18)

Cancer

1.79 (1.54-2.08)

<.001

1.52 (1.29-1.79)

Comorbidities

<.01 <.001

Discharge destination Home Home under home health care

1.0 (reference) 2.10 (1.93-2.29)

1.0 (reference) <.001

1.59 (1.45-1.74)

<.001

(Continued on next page)

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Table IV. Continued. P value

Adjusted OR (95% CI)

P value

General hospital

2.34 (1.75-3.12)

<.001

1.41 (1.03-1.93)

.03

Skilled nursing facility

4.00 (3.64-4.39)

<.001

2.60 (2.3-2.89)

12.9 (11.8-14.0)

<.001

9.2 (8.26-10.2)

Hemorrhage/shock/bleeding

1.63 (1.50-1.77)

<.001

1.06 (0.97-1.17)

.20

Vascular or stent

3.37 (2.28-4.99)

<.001

1.33 (0.84-2.09)

.22

Cardiac

1.82 (1.67-1.99)

<.001

1.03 (0.92-1.14)

.59

Respiratory

3.14 (2.76-3.58)

<.001

1.12 (0.97-1.31)

.13

Unadjusted OR (95% CI)

Other rehabilitation or hospice

<.001 <.001

In-hospital complications

Renal (AKI, UTI, others)

2.82 (2.53-3.14)

<.001

1.14 (1.01-1.30)

.04

Stroke

4.62 (4.07-5.25)

<.001

1.4 (1.20-1.64)

<.001

Infectious

4.05 (2.90-5.66)

<.001

1.18 (0.80-1.74)

.39

Ileus

4.30 (2.84-6.52)

<.001

1.32 (0.81-2.13)

.27

3.11 (1.75-5.54)

<.001

0.81 (0.39-1.71)

.59

Venous thromboembolic

AKI, Acute kidney injury; CAS, carotid artery stenting; CEA, carotid endarterectomy; CHF, congestive heart failure; CI, confidence interval; COPD, chronic obstructive pulmonary disease; MI, myocardial infarction; OR, odds ratio; UTI, urinary tract infection.

2005 and 2009 and between 2009 and 2011, our results represent more recent real-world outcomes and include private insurance data in addition to Medicare data. The most common indications of readmission in our cohort were stroke, cardiac, infectious, and respiratory complications, which are more likely to develop in CEA patients after hospital discharge compared with the immediate complications of CAS.20,27,28 In the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST), the majority of CAS strokes occurred on day 0 after the procedure, whereas CEA strokes were distributed evenly over 30 days postoperatively. This could explain increased readmission after CEA due to stroke despite lower overall stroke rates compared with CAS.27 A recent study by our group using the American College of Surgeons National Surgical Quality Improvement Program database and another by Greenleaf et al using the Pennsylvania Health Care Cost Containment Council database showed that the risk of 30-day readmission was not procedure related but rather determined by symptomatic status and comorbidities.22,24 In our analyses, readmission remained significantly higher after CEA than after CAS even after adjusting for patients’ comorbidities and symptomatic status. These findings add to the benefits and cost-effectiveness of the less invasive CAS in highrisk patients who are not candidates for surgery. However, the lower readmission rates of CAS are opposed by the high mortality associated with these readmissions. As evident in Table VI, patients readmitted after CAS have a longer hospital stay compared with patients readmitted after CEA (5 days vs 4 days; P ¼ .001), higher crude mortality (6.2% vs 2.8%; P < .001), and increased respiratory complications (5.0 vs 3.5%; P ¼ .03), reflecting a more difficult rehospitalization course in the high-risk CAS patients compared with CEA patients. This leads to

significantly higher adjusted readmission costs for CAS patients by around $700 (Table VI). Identifying preventable causes of readmission after carotid revascularization is a complex task, especially given that vascular surgery patients are usually older and have multiple comorbidities compared with patients in other surgical specialties. Readmission in this population of patients is thus highly related to their medical illnesses and comorbidities rather than to the index procedure. On the other hand, many readmissions in vascular surgery are planned.25,29 A significant portion of patients in our study were readmitted for nonspecific or nonrelated causes, such as cancer/chemotherapy, abdominal surgeries, and nonspecific complaints, such as fatigue, fever, headache, syncope, and physical therapy (Table III). The key to reducing preventable readmissions is better perioperative planning and comorbidity management in high-risk patients. Older patients and those with major preoperative comorbidities (diabetes, renal disease, COPD, peripheral arterial disease, and cancer) are reported to have increased risk of adverse events leading to higher hospital readmissions. These may require a more intense preoperative maximization of the patient and close postoperative follow-up.25,30 Another prominent risk factor associated with increased readmission was nonhome discharge, mainly to skilled nursing facilities, rehabilitation centers, and hospice care. Among patients who were readmitted from those facilities, 16.8% had prior CAS compared with 11.2% who were readmitted from home (P < .001). Moreover, they had significant comorbidities, such as paraplegia/hemiplegia (21.6% vs 1.3%), CHF (21.4% vs 13.6%), renal disease (23.3% vs 17.0%), diabetes (43.8% vs 39.1%), and dementia (2.4% vs 0.9%), and more frequent complications during their index admission, including stroke (16.0% vs 0.8%) and

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Table V. Perioperative outcomes of carotid endarterectomy (CEA) and carotid artery stenting (CAS) patients before and after coarsened exact matching (CEM) Before CEM, No. (%) CEA (n ¼ 82,817)

CAS (n ¼ 12,870)

After CEM, No. (%)

P value

CEA (n ¼ 8966)

CAS (n ¼ 8966)

P value

Readmission 30 days

5338 (6.5)

780 (6.1)

.1

560 (6.2)

438 (4.9)

<.001

90 days

8512 (10.3)

1286 (10.0)

.32

881 (9.8)

749 (8.3)

<.01

300 (0.4)

72 (0.6) <.001

111 (1.2)

161 (1.8)

<.01

In-hospital complications Stroke

1082 (1.3)

321 (2.5)

Cardiac MI

553 (0.7)

99 (0.8)

.19

49 (0.5)

42 (0.5)

.46

Heart failure

344 (0.4)

60 (0.5)

.41

24 (0.27)

22 (0.24)

.77

Arrhythmia

4202 (5.1)

907 (7.1)

<.001

439 (4.9)

598 (6.7)

<.001

Any cardiac

4794 (5.8)

999 (7.8)

<.001

489 (5.4)

637 (7.1)

<.001

6113 (7.4)

1149 (8.9)

<.001

666 (7.4)

772 (8.6)

79 (0.1)

87 (0.7)

<.001

500 (0.6)

112 (0.9)

<.001

Hemorrhage/shock/bleeding Vascular or stent complication

6 (0.07)

<.01

46 (0.5)

<.001

37 (0.4)

.20

Respiratory Pneumonia

49 (0.5)

Respiratory failure

1015 (1.2)

204 (1.6)

.001

113 (1.3)

88 (1.0)

.08

Any respiratory

1386 (1.7)

283 (2.2)

<.001

148 (1.7)

110 (1.2)

.02

1817 (2.2)

314 (2.4)

.08

164 (1.8)

130 (1.5)

.05

Renal or urologic Acute kidney injury

560 (0.7)

173 (1.3)

<.001

43 (0.5)

2264 (2.7)

464 (3.6)

<.001

203 (2.3)

Infectious

167 (0.2)

37 (0.3)

Ileus

112 (0.1) 58 (0.07)

Urinary tract infection Any renal

Venous thromboembolic event

.05

17 (0.2)

16 (0.1)

.75

10 (0.1)

22 (0.2)

<.001

Home under home health care

15 (0.2)

70,447 (85.1)

10,538 (81.9)

.58 .72

7 (90.08)

.47

5 (0.06)

.56

7746 (86.4)

7948 (88.7)

<.001

6655 (8.0)

824 (6.4)

677 (7.6)

433 (4.8)

402 (0.5)

112 (0.9)

38 (0.4)

51 (0.6)

Skilled nursing facility

3046 (3.7)

580 (4.5)

288 (3.2)

244 (2.7)

Others or unknown

1964 (2.4)

744 (5.8)

216 (2.4)

282 (3.2)

General hospital

.01

7 (0.08)

<.001

Discharge destination Home

73 (0.8) 192 (2.1)

MI, Myocardial infarction.

acute renal failure (10.7% vs 2.7%). This subpopulation of patients might benefit from more discharge planning and improved transitional care and, in certain cases, deferring carotid intervention, especially for asymptomatic high-risk patients. Similarly, patients who experience stroke and renal complications during their index admission have 40% and 14% increased odds of 30-day readmission (aOR, 1.4 [95% CI, 1.20-1.64] and 1.14 [95% CI, 1.01-1.30], respectively) and should be followed up closely. Because concomitant cardiac procedures were also associated with an increase in the odds of 30-day readmission (aOR, 1.18; 95% CI, 1.11-1.26; P < .001), staging of those procedures, especially in high-risk patients, could prove effective in reducing readmission (Table IV). Despite the granularity of our clinical data, the model was able to predict only around 9% of the variability in 30-day readmission (R2 ¼ 8.8; C statistic ¼ 69.5). Even

after including in-hospital complications, the predictability did not significantly improve (R2 ¼ 8.9; C statistic ¼ 69.6). This is not uncommon because the creation of models predicting preventable readmissions using inpatient hospital data and information present at discharge has been shown to be challenging in medical as well as in surgical patients, with C statistics similar to that reported in our study.19,31-34 Moreover, readmissions in patients undergoing vascular surgery are mainly driven by postoperative complications that are identified after discharge.34,35 Al-Damluji et al1 found that almost onethird of readmission diagnoses were potentially due to procedural complications. Similarly, Lawson et al35 also identified postoperative complications occurring after discharge as the single most predictive factor in surgical readmissions and a high-yield area for improvement of patient care.

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Table VI. In-hospital outcomes in readmitted patients Readmission after CEA (n ¼ 6205) Mortality, No. (%)

Readmission after CAS (n ¼ 948)

172 (2.8)

58 (6.2)

296 (4.8)

29 (3.1)

Adjusted OR P value (CAS vs CEA) <.001

2.03

.02

95% CI

P value

1.45-2.84

<.001

0.58

0.39-0.87

.01

0.82

0.18-3.62

.79 .22

Complications, No. (%) Hemorrhage/shock/bleeding Vascular or graft complication

15 (0.2)

2 (0.2)

1

Cardiac

418 (6.7)

58 (6.1)

.53

0.83

0.62-1.12

Respiratory

219 (3.5)

47 (5.0)

.03

1.31

0.94-1.82

.11

Renal or urologic

330 (5.3)

63 (6.7)

.1

1.19

0.89-1.58

.24

Neurologic

54 (0.9)

14 (1.5)

.1

1.55

0.85-2.84

.16

Infectious

62 (1.0)

15 (1.6)

.11

1.58

0.88-2.81

.12

Gastrointestinal

42 (0.7)

7 (0.7)

.83

1.1

0.449-2.48

.82

Venous thromboembolic

20 (0.3)

6 (0.6)

.15

1.96

0.77-4.95

.16 .01

Cost (U.S. $), median (IQR) Total cost

7629 (4428-14,457)

Fixed cost

3762 (2138-6852)

Variable cost

3651 (2010-6844)

8903 (4471-16,052)

.01

735

182-1288

4313 (2176-7645)

.02

368

95-640

.01

<.001

581

287-875

<.001

4390 (2211-7871)

CAS, Carotid artery stenting; CEA, carotid endarterectomy; CI, confidence interval; IQR, interquartile range; OR, odds ratio.

Readmission significantly constitutes a large burden to patients and health care systems.36-38 Prior studies have suggested several interventions that focus on minimizing risk factors and addressing known and preventable reasons for readmission, such as wound infections, to improve health care quality and resource use.26 Such interventions include improving outpatient management and transitional care,39,40 closer primary care follow-up after discharge,41 and avoidance of premature discharge in high-risk patients to limit early and short readmissions. The majority of readmissions in our study occurred within the first week of discharge (median, 6 [interquartile range, 1-16] days), with some patients having more than one readmission within 30 days. This was also reported in other published studies.1,42 However, the success of isolated interventions has been questioned, especially that most have been studied in a retrospective manner.43 Thus, prospective studies on overall cost-effectiveness of patient-centered bundled interventions are warranted.19 Until then, it is reasonable to reconsider penalizing hospitals with high risk-standardized rates of readmissions. Limitations. This retrospective analysis offers an overview of readmission after carotid revascularization using a large nationwide database, which can provide a platform for further investigations and targets for intervention. The multivariate analysis is further validated using CEM to ensure the validity and help reduce selection bias. However, risk adjustment and exact matching cannot control for all confounding variables or eliminate inherent selection bias of patients undergoing CAS vs those undergoing CEA. Furthermore, patients in both groups that could not be matched were discarded or

pruned from the matched cohort. Thus, the matched cohort is likely not representative of the whole population of patients but rather provides risk-adjusted estimates of treatment effects. Another important limitation is that readmissions to a different hospital, other than the index hospital, are not tracked in the database, which might underestimate readmission rates. We cannot provide exact estimates on the number of readmissions to hospitals other than the index hospital, but this should not compromise the validity of our findings because our readmissions are limited to 30 days after discharge, in which most patients are readmitted usually to the index hospital where their vascular surgeon is available, especially if the readmissions are procedure related. In addition, administrative claims data may not be suitable for identifying staged or planned revascularization procedures. Planned or staged readmissions are significant in discussing peripheral revascularization procedures rather than carotid revascularizations.

CONCLUSIONS In this study, overall 30-day readmission after carotid revascularization was 6.5%. After risk adjustment, CAS had lower readmission rates than CEA. However, the mortality and overall costs of readmissions were higher after CAS. Reducing readmissions requires identifying highrisk patients and managing their comorbidities and risk factors. Further prospective studies are needed to evaluate the cost-effectiveness of strategies aiming to reduce readmission rates after carotid revascularization. The authors thank Nasr Ghajar, MS, for his contribution in reviewing the literature.

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AUTHOR CONTRIBUTIONS Conception and design: HDA, BN, MM Analysis and interpretation: HDA, SA, BN, MM Data collection: HDA Writing the article: HDA, MM Critical revision of the article: HDA, SA, BN Final approval of the article: HDA, SA, BN, MM Statistical analysis: HDA, BN Obtained funding: Not applicable Overall responsibility: MM

REFERENCES 1. Al-Damluji MS, Dharmarajan K, Zhang W, Geary LL, Stilp E, Dardik A, et al. Readmissions after carotid artery revascularization in the Medicare population. J Am Coll Cardiol 2015;65:1398-408. 2. Mantese VA, Timaran CH, Chiu D, Begg RJ, Brott TG. The carotid revascularization endarterectomy versus stenting trial (CREST). Stroke 2010;41(Suppl 1):S34. 3. Mozes G, Sullivan TM, Torres-Russotto DR, Bower TC, Hoskin TL, Sampaio SM, et al. Carotid endarterectomy in SAPPHIRE-eligible high-risk patients: implications for selecting patients for carotid angioplasty and stenting. J Vasc Surg 2004;39:958-65. 4. Mahoney EM, Greenberg D, Lavelle TA, Natarajan A, Berezin R, Ishak KJ, et al. Costs and cost-effectiveness of carotid stenting versus endarterectomy for patients at increased surgical risk: results from the SAPPHIRE trial. Catheter Cardiovasc Intervent 2011;77:463-72. 5. Vilain KR, Magnuson EA, Li H, Clark WM, Begg RJ, Sam AD, et al. Costs and cost-effectiveness of carotid stenting versus endarterectomy for patients at standard surgical risk. Stroke 2012;43:2408-16. 6. Brott TG, Howard G, Roubin GS, Meschia JF, Mackey A, Brooks W, et al. Long-term results of stenting versus endarterectomy for carotid-artery stenosis. N Engl J Med 2016;374: 1021-31. 7. Featherstone RL, Dobson J, Ederle J, Doig D, Bonati LH, Morris S, et al. Carotid artery stenting compared with endarterectomy in patients with symptomatic carotid stenosis (International Carotid Stenting Study): a randomised controlled trial with cost-effectiveness analysis. Health Technol Assess 2016;20:1-94. 8. Yadav JS, Wholey MH, Kuntz RE, Fayad P, Katzen BT, Mishkel GJ, et al. Protected carotid-artery stenting versus endarterectomy in high-risk patients. N Engl J Med 2004;351: 1493-501. 9. Brooke BS, De Martino RR, Girotti M, Dimick JB, Goodney PP. Developing strategies for predicting and preventing readmissions in vascular surgery. J Vasc Surg 2012;56:556-62. 10. Centers for Medicare & Medicaid Services. Readmissions reduction program. Available at: https://www.cms.gov/ medicare/medicare-fee-for-service-payment/acuteinpatientpps/ readmissions-reduction-program.html. Accessed September 15, 2016. 11. Pizer SD. Should hospital readmissions be reduced through payment penalties? Med Care 2013;51:20-2. 12. Joynt KE, Jha AK. Characteristics of hospitals receiving penalties under the Hospital Readmissions Reduction Program. JAMA 2013;309:342-3. 13. Shaw FE, Asomugha CN, Conway PH, Rein AS. The Patient Protection and Affordable Care Act: opportunities for prevention and public health. Lancet 2014;384:75-82.

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14. Vaduganathan M, Bonow RO, Gheorghiade M. Thirty-day readmissions: the clock is ticking. JAMA 2013;309:345-6. 15. Ho KJ, Madenci AL, Semel ME, McPhee JT, Nguyen LL, Ozaki CK, et al. Predictors and consequences of unplanned hospital readmission within 30 days of carotid endarterectomy. J Vasc Surg 2014;60:77-84. 16. Lawson EH, Hall BL, Louie R, Zingmond DS, Ko CY. Readmission following surgical procedures: implications for quality improvement and cost savings. J Am Coll Surg 2011;213:S106. 17. Premier Healthcare database whitepaper. Available at: http://www.premierinc.com/transforming-healthcare/health care-performance-improvement/premier-research-services/. Accessed April 2017. 18. Iacus SM, King G, Porro G. Matching for casual inference without balance checking: coarsened exact matching. Available at: http://gking.harvard.edu/_les/abs/cem-abs.shtml. Accessed December 15, 2016. 19. Eun JC, Nehler MR, Black JH, Glebova NO. Measures to reduce unplanned readmissions after vascular surgery. Semin Vasc Surg 2015;28:103-11. 20. Rambachan A, Smith TR, Saha S, Eskandari MK, Bendok BR, Kim JY. Reasons for readmission after carotid endarterectomy. World Neurosurg 2014;82:e776. 21. Kennedy BS, Fortmann SP, Stafford RS. Elective and isolated carotid endarterectomy: health disparities in utilization and outcomes, but not readmission. J Natl Med Assoc 2007;99:480. 22. Nejim B, Obeid T, Arhuidese I, Hicks C, Wang S, Canner J, et al. Predictors of perioperative outcomes after carotid revascularization. J Surg Res 2016;204:267-73. 23. Gupta PK, Fernandes-Taylor S, Ramanan B, Engelbert TL, Kent KC. Unplanned readmissions after vascular surgery. J Vasc Surg 2014;59:473-82. 24. Greenleaf EK, Han DC, Hollenbeak CS. Carotid endarterectomy versus carotid artery stenting: no difference in 30-day postprocedure readmission rates. Ann Vasc Surg 2015;29: 1408-15. 25. Galinanes EL, Dombroviskiy VY, Hupp CS, Kruse RL, Vogel TR. Evaluation of readmission rates for carotid endarterectomy versus carotid artery stenting in the US Medicare population. Vasc Endovascular Surg 2014;48:217-23. 26. Katzen BT. Readmissions after carotid artery revascularization in the Medicare population. J Am Coll Cardiol 2015;65: 1409-10. 27. Brott TG, Hobson RW, Howard G, Roubin GS, Clark WM, Brooks W, et al. Stenting versus endarterectomy for treatment of carotid-artery stenosis. N Engl J Med 2010;363:11-23. 28. Fry DE, Pine M, Locke D, Reband A, Torres Z, Pine G. Medicare inpatient and 90-day post discharge adverse outcomes in carotid artery surgery. Surgery 2015;158:1056-64. 29. Jackson BM, Nathan DP, Doctor L, Wang GJ, Woo EY, Fairman RM. Low rehospitalization rate for vascular surgery patients. J Vasc Surg 2011;54:767-72. 30. Kind AJ, Bartels C, Mell MW, Mullahy J, Smith M. For-profit hospital status and rehospitalizations at different hospitals: an analysis of Medicare data. Ann Intern Med 2010;153:718-27. 31. Morris MS, Graham LA, Richman JS, Hollis RH, Jones CE, Wahl T, et al. Postoperative 30-day readmission: time to focus on what happens outside the hospital. Ann Surg 2016;264:621-31. 32. Donz J, Aujesky D, Williams D, Schnipper JL. Potentially avoidable 30-day hospital readmissions in medical patients: derivation and validation of a prediction model. JAMA Intern Med 2013;173:632-8. 33. Kansagara D, Englander H, Salanitro A, Kagen D, Theobald C, Freeman M, et al. Risk prediction models for hospital readmission: a systematic review. JAMA 2011;306:1688-98.

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34. Glebova NO, Bronsert M, Hammermeister KE, Nehler MR, Gibula DR, Malas MB, et al. Drivers of readmissions in vascular surgery patients. J Vasc Surg 2016;64:194.e3. 35. Lawson EH, Hall BL, Louie R, Ettner SL, Zingmond DS, Han L, et al. Association between occurrence of a postoperative complication and readmission: implications for quality improvement and cost savings. Ann Surg 2013;258: 10-8. 36. Hockenberry JM, Burgess JF Jr, Glasgow J, VaughanSarrazin M, Kaboli PJ. Cost of readmission: can the Veterans Health Administration (VHA) experience inform national payment policy? Med Care 2013;51:13-9. 37. Jencks SF, Williams MV, Coleman EA. Rehospitalizations among patients in the Medicare fee-for-service program. N Engl J Med 2009;360:1418-28. 38. Orszag PR, Emanuel EJ. Health care reform and cost control. N Engl J Med 2010;363:601-3. 39. Brooke BS, Kraiss LW, Stone DH, Nolan B, De Martino RR, Reiber GE, et al. Improving outcomes for diabetic patients undergoing revascularization for critical limb ischemia: does the quality of outpatient diabetic care matter? Ann Vasc Surg 2014;28:1719-28.

40. Rümenapf G, Geiger S, Schneider B, Amendt K, Wilhelm N, Morbach S, et al. Readmissions of patients with diabetes mellitus and foot ulcers after infra-popliteal bypass surgerydattacking the problem by an integrated case management model. Vasa 2013;42:56-67. 41. Brooke BS, Stone DH, Cronenwett JL, Nolan B, DeMartino RR, MacKenzie TA, et al. Early primary care provider follow-up and readmission after high-risk surgery. JAMA Surg 2014;149:821-8. 42. Dawes AJ, Sacks GD, Russell MM, Lin AY, MaggardGibbons M, Winograd D, et al. Preventable readmissions to surgical services: lessons learned and targets for improvement. J Am Coll Surg 2014;219:382-9. 43. Hansen LO, Young RS, Hinami K, Leung A, Williams MV. Interventions to reduce 30-day rehospitalization: a systematic review. Ann Intern Med 2011;155:520-8. Submitted Mar 6, 2017; accepted May 5, 2017.

Additional material for this article may be found online at www.jvascsurg.org.

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Supplementary Table I (online only). International Classification of Diseases, Ninth Revision diagnosis and procedure codes used to identify readmission diagnoses and certain major adverse events Diagnoses Hemorrhage, shock, or bleeding 285.1

Acute posthemorrhagic anemia

99.04

Transfusion of packed cells

458.29

Other iatrogenic hypotension

998

Other complications of procedures not elsewhere classified

998.1

Hemorrhage or hematoma complicating a procedure not elsewhere classified

99.06

Transfusion of coagulation factors

99.07

Transfusion of other serum

998.01

Postoperative shock, cardiogenic

998.11

Hemorrhage complicating a procedure

998.12

Hematoma complicating a procedure

39.41

Control of hemorrhage following vascular surgery

39.98

Control of hemorrhage, not otherwise specified

41.50

Total splenectomy

Vascular or graft related 996.1

Mechanical complication of other vascular device, implant, and graft

996.6

Infection and inflammatory reaction due to internal prosthetic device implant and graft

996.62

Infection and inflammatory reaction due to other vascular device, implant, and graft

996.74

Other complications due to other vascular device, implant, and graft

38.00

Incision of vessels, unspecified

38.06

Incision of vessels, abdominal arteries

38.08

Incision of vessels, lower limb arteries

38.80

Other surgical occlusion of vessels, unspecified

38.86

Other surgical occlusion of vessels, abdominal arteries

39.49

Other revision of vascular procedure

39.5

Other repair of vessels

39.56

Repair of blood vessel with tissue patch graft

39.57

Repair of blood vessel with synthetic patch graft

39.58

Repair of blood vessel with unspecified type of patch graft

39.59

Other repair of vessel

Respiratory Pneumonia 465.9

Acute upper respiratory infections of unspecified site

466

Acute bronchitis and bronchiolitis

481

Pneumococcal pneumonia (Streptococcus pneumoniae pneumonia)

482

Other bacterial pneumonia

482.1

Pneumonia due to Pseudomonas

482.2

Pneumonia due to Haemophilus influenzae (H. influenzae)

482.3

Pneumonia due to streptococcus

482.31

Pneumonia due to streptococcus, group A

482.32

Pneumonia due to streptococcus, group B

482.39

Pneumonia due to other streptococcus

482.4

Pneumonia due to staphylococcus

482.41

Methicillin-susceptible pneumonia due to Staphylococcus aureus

482.49

Other staphylococcus pneumonia

482.81

Pneumonia due to anaerobes

482.82

Pneumonia due to Escherichia coli (E. coli)

482.83

Pneumonia due to other gram-negative bacteria

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Supplementary Table I (online only). Continued. 482.84

Pneumonia due to Legionnaires’ disease

482.89

Pneumonia due to other specified bacteria

482.9

Bacterial pneumonia, unspecified

485

Bronchopneumonia, organism unspecified

486

Pneumonia, organism unspecified

Respiratory failure 518.81

Acute respiratory failure

518.84

Acute and chronic respiratory failure

799.1

Respiratory arrest

93.9

Insertion of airway and other continuous invasive mechanical ventilation

96.71

Continuous invasive mechanical ventilation for less than 96 consecutive hours

96.72

Continuous invasive mechanical ventilation for 96 consecutive hours or more

Other respiratory 491.21

Obstructive chronic bronchitis with (acute) exacerbation

507

Pneumonitis due to solids and liquids

511.8

Other specified forms of pleural effusion except tuberculous

511.9

Unspecified pleural effusion

512.1

Iatrogenic pneumothorax

518

Other diseases of lung

518.4

Acute edema of lung, unspecified

786.3

Hemoptysis

997.3

Respiratory complications not elsewhere classified

31.1

Temporary tracheostomy

31.21

Mediastinal tracheostomy

31.29

Other permanent tracheostomy

34.04

Insertion of intercostal catheter for drainage

96.04

Insertion of endotracheal tube

786.09

Other respiratory abnormalities

Cardiac Myocardial infarction 410

Acute myocardial infarction

411

Other acute and subacute forms of ischemic heart disease

411.1

Intermediate coronary syndrome

411.81

Acute coronary occlusion without myocardial infarction

411.89

Other acute and subacute forms of ischemic heart disease, other

412

Old myocardial infarction

Heart failure 428.21

Acute systolic heart failure

428.23

Acute on chronic systolic heart failure

428.31

Acute diastolic heart failure

428.33

Acute on chronic diastolic heart failure

428.41

Acute combined systolic and diastolic heart failure

428.43

Acute on chronic combined systolic and diastolic heart failure

785.51

Cardiogenic shock

Arrhythmia 00.51

Implantation of cardiac resynchronization defibrillator, total system

427

Cardiac dysrhythmias

Others 997.1

Cardiac complications, not elsewhere classified

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Supplementary Table I (online only). Continued. Renal or urologic Acute kidney injury 584.5

Acute kidney failure with lesion of tubular necrosis

584.6

Acute kidney failure with lesion of renal cortical necrosis

584.7

Acute kidney failure with lesion of renal medullary (papillary) necrosis

584.8

Acute kidney failure with other specified pathological lesion in kidney

584.9

Acute kidney failure, unspecified

Others 996.73

Other complications due to renal dialysis device, implant, and graft

59.8

Ureteral catheterization

585

Chronic kidney disease (CKD)

591

Hydronephrosis

592

Calculus of kidney and ureter

599

Other disorders of urethra and urinary tract

788.2

Retention of urine

788.29

Other specified retention of urine

997.5

Urinary complications, not elsewhere classified

593.81

Vascular disorders of kidney

Neurologic Paraplegia/monoplegia 344.1

Paraplegia

344.3

Monoplegia of lower limb

Spinal cord ischemia 336.1

Vascular myelopathies, applies to acute infarction of spinal cord

Stroke 434.11

Cerebral embolism with cerebral infarction

434.91

Cerebral artery occlusion, unspecified with cerebral infarction

437.1

Other generalized ischemic cerebrovascular disease

997.02

Iatrogenic cerebrovascular infarction or hemorrhage

Others 293.9

Unspecified transient mental disorder in conditions classified elsewhere

01.31

Incision of cerebral meninges

430

Subarachnoid hemorrhage

431

Intracerebral hemorrhage

436

Acute, but ill-defined, cerebrovascular disease

780.09

Other alteration of consciousness

780.39

Other convulsions

997

Complications affecting specified body system not elsewhere classified

997.01

Central nervous system complication

997.09

Other nervous system complications

351

Facial nerve disorders

351.0

Bell’s palsy

351.8

Other facial nerve disorders

351.9

Facial nerve disorders, unspecified

352.3

Disorders of pneumogastric (10th) nerve

352.5

Disorders of hypoglossal (12th) nerve

780.97

Altered mental status

Infections

Clostridium difficile 8.45

Intestinal infection due to Clostridium difficile

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Supplementary Table I (online only). Continued. Wound complications 998.13

Seroma complicating a procedure

998.3

Disruption of operation wound

998.30

Disruption of wound, unspecified

998.31

Disruption of internal operation (surgical) wound

998.32

Disruption of external operation (surgical) wound

998.5

Postoperative infection not elsewhere classified

998.51

Infected postoperative seroma

998.59

Other postoperative infection

998.83

Non-healing surgical wound

46.94

Revision of anastomosis of large intestine

54.0

Incision of abdominal wall

54.19

Other laparotomy

54.61

Reclosure of postoperative disruption of abdominal wall

54.91

Percutaneous abdominal drainage

86.22

Excisional débridement of wound, infection, or burn

86.27

Débridement of nail, nail bed, or nail fold

86.28

Nonexcisional débridement of wound, infection, or burn

Sepsis 038

Septicemia

995.91

Sepsis

995.92

Severe sepsis

Urinary tract infection 590.80 996.64

Infection and inflammatory reaction due to indwelling urinary catheter

996.65

Infection and inflammatory reaction due to other genitourinary device, implant, and graft

Others 682.8

Cellulitis and abscess of other specified sites

682.9

Cellulitis and abscess of unspecified sites

707.15

Ulcer of other part of foot

86.04

Other incision with drainage of skin and subcutaneous tissue

999.3

Other infection due to medical care not elsewhere classified

682.6

Cellulitis and abscess of leg, except foot

682.7

Cellulitis and abscess of foot, except toes

Gastrointestinal Bowel ischemia 557.0

Acute vascular insufficiency of intestine

Small bowel obstruction 560.81

Intestinal or peritoneal adhesions with obstruction (postoperative)

560.9

Unspecified intestinal obstruction

Ileus 537.2

Chronic duodenal ileus

560.1

Paralytic ileus

560.31

Gallstone ileus

Thromboembolic Pulmonary embolism 415.1

Pulmonary embolism and infarction (examples below)

415.11

Iatrogenic pulmonary embolism and infarction

415.12

Septic pulmonary embolism

415.19

Other pulmonary embolism and infarction

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Supplementary Table I (online only). Continued. Deep venous thrombosis 453.4

Acute venous embolism and thrombosis of deep vessels of lower extremity

Other venous 453.2

Other venous embolism and thrombosis of inferior vena cava

453.3

Other venous embolism and thrombosis of renal vein

453.8

Acute venous embolism and thrombosis of other specified veins

Reoperation Vascular 0.55

Insertion of drug-eluting peripheral vessel stent(s)

00.60

Insertion of drug-eluting stent(s) of superficial femoral artery

17.56

Atherectomy of other non-coronary vessel(s)

38.18

Endarterectomy, lower limb arteries

39.25

Aorta-iliac-femoral bypass

39.29

Other (peripheral) vascular shunt or bypass

39.49

Other revision of vascular procedure

39.50

Angioplasty of other non-coronary vessel

38.12

Carotid endarterectomy

0.61

Percutaneous angioplasty of extracranial vessel(s)

0.63

Carotid artery stenting

38.44

Resection of vessel with replacement, aorta

39.71

Endovascular implantation of graft in abdominal aorta

Other abdominal surgeries 568

Other disorders of peritoneum

44.61

Suture of laceration of stomach

45.71

Open and other multiple segmental resection of large intestine

45.72

Open and other cecectomy

45.73

Open and other right hemicolectomy

45.74

Open and other resection of transverse colon

45.75

Open and other left hemicolectomy

45.76

Open and other sigmoidectomy

45.79

Other and unspecified partial excision of large intestine

45.8

Total intra-abdominal colectomy

46.71

Suture of laceration of duodenum

46.73

Suture of laceration of small intestine, except duodenum

46.75

Suture of laceration of large intestine

46.79

Other repair of intestine

48.71

Suture of laceration of rectum

50.61

Closure of laceration of liver

51.91

Repair of laceration of gallbladder

53

Repair of hernia

53.1

Other bilateral repair of inguinal hernia

53.2

Unilateral repair of femoral hernia

53.3

Bilateral repair of femoral hernia

53.5

Repair of other hernia of anterior abdominal wall (without graft or prosthesis)

53.6

Repair of other hernia of anterior abdominal wall with graft or prosthesis

54.1

Laparotomy

54.11

Exploratory laparotomy

54.12

Reopening of recent laparotomy site

54.21

Laparoscopy

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Supplementary Table I (online only). Continued. 54.51

Laparoscopic lysis of peritoneal adhesions

54.59

Other lysis of peritoneal adhesions

54.92

Removal of foreign body from peritoneal cavity

55.81

Suture of laceration of kidney

56.75

Transureteroureterostomy

56.82

Suture of laceration of ureter

56.86

Removal of ligature from ureter

56.89

Other repair of ureter

57.81

Suture of laceration of bladder

57.83

Repair of fistula involving bladder and intestine

57.84

Repair of other fistula of bladder

58.41

Encounter for planned postoperative wound closure

69.41

Suture of laceration of uterus

Cancer 155

Malignant neoplasm of liver and intrahepatic bile ducts

V58.1

Encounter for antineoplastic chemotherapy

157

Malignant neoplasm of pancreas

162

Malignant neoplasm of trachea, bronchus, and lung

182

Malignant neoplasm of body of uterus

183

Malignant neoplasm of ovary and other uterine adnexa

185

Malignant neoplasm of prostate

197

Secondary malignant neoplasm of respiratory and digestive systems

173

Other and unspecified malignant neoplasm of skin

99.25

Injection or infusion of cancer chemotherapeutic substance

V58.0

Encounter for radiotherapy

Others nonspecific diagnoses Headache 784.0

Headache

Syncope/collapse 780.2

Syncope and collapse

Fever 780.6

Fever and other physiologic disturbances of temperature regulation

780.62

Postprocedural fever

Fatigue/weakness 780.79

Other malaise and fatigue

Gastrointestinal 787.0

Nausea and vomiting

787.2

Dysphagia

789.00

Abdominal pain, unspecified site

537.2

Chronic duodenal ileus

Physical therapy 93.39

Other physical therapy

V57.1

Care involving other physical therapy

93.89

Rehabilitation, not elsewhere classified

V57.89

Care involving other specified rehabilitation procedure

57.9

Care involving unspecified rehabilitation procedure

Palliative care V66.7

Encounter for palliative care

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Supplementary Table II (online only). Baseline characteristics of the study groups after coarsened exact matching (CEM)

No. of patients Age, years, mean (SD)

P value

CAS

8966

8966

72.4 (8.2)

72.4 (8.2) No. (%)

.63

No. (%)

Gender Female

3408 (37.9)

3408 (37.9)

Male

5588 (62.1)

5588 (62.1)

White

7814 (86.9)

7814 (86.9)

Black

230 (2.6)

230 (2.6)

Others

952 (10.6)

952 (10.6)

Medicare

7371 (82.2)

7371 (82.2)

Medicaid

157 (1.8)

157 (1.8)

Private insurance

1313 (14.7)

1313 (14.7)

Other

122 (1.4)

122 (1.4)

Elective

7154 (79.5)

7154 (79.5)

Emergency

868 (9.7)

868 (9.7)

Urgent

954 (10.6)

954 (10.6)

1.0

Race 1.0

Insurance type 1.0

Admission type

Others

20 (0.22)

1.0

20 (0.22)

Concomitant cardiac procedures

1894 (21.1)

1894 (21.1)

1.0

Teaching hospitals

5206 (57.9)

5206 (57.9)

1.0 1.0

Region Rural

528 (5.9)

528 (5.9)

Urban

8457 (94.1)

8457 (94.1)

Provider area Midwest

1721 (19.2)

1721 (19.2)

North-East

1365 (15.2)

1365 (15.2)

South

4846 (53.9)

4846 (53.9)

West

1053 (11.7)

1053 (11.7)

1.0

Comorbidities Symptomatic

993 (11.1)

993 (11.1)

2810 (31.2)

2710 (30.1)

.11

Old MI

844 (9.4)

844 (9.4)

1.0

CHF

654 (7.3)

654 (7.3)

1.0

Renal disease

751 (8.4)

751 (8.4)

1.0

1899 (21.1)

1940 (21.6)

47 (0.5)

47 (0.5)

Diabetes

COPD Connective tissue disease Peptic ulcer disease Paraplegia/hemiplegia Liver disease Peripheral vascular disease Cancer

43 (0.5) 150 (1.7)

Supplementary Table II (online only). Continued. No. (%)

No. (%)

I

3904 (43.4)

3904 (43.4)

II

2955 (32.9)

2955 (32.9)

III

1262 (14.0)

1262 (14.0)

IV

566 (6.3)

566 (6.3)

V

199 (2.2)

199 (2.2)

VI

110 (1.2)

110 (1.2)

Charlson Comorbidity Index

After CEM CEA

2017

41 (0.5) 150 (1.7)

60 (0.67)

48 (0.53)

2452 (27.3)

2452 (27.3)

96 (1.1)

123 (1.4)

1.0

.46 1.0 .83 1.0 .25 1.0 .07

(Continued)

1.0

CAS, Carotid artery stenting; CEA, carotid endarterectomy; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; MI, myocardial infarction; SD, standard deviation.