- Email: [email protected]
Carotid Endarterectomy versus Carotid Artery Stenting: No Difference in 30-Day Postprocedure Readmission Rates
Accepted Manuscript Carotid Endarterectomy versus Carotid Artery Stenting: No Difference in 30-Day PostProcedure Readmission Rates Erin K. Greenleaf, David C. Han, Christopher S. Hollenbeak PII:
S0890-5096(15)00564-6
DOI:
10.1016/j.avsg.2015.05.013
Reference:
AVSG 2453
To appear in:
Annals of Vascular Surgery
Received Date: 21 January 2015 Revised Date:
5 May 2015
Accepted Date: 19 May 2015
Please cite this article as: Greenleaf EK, Han DC, Hollenbeak CS, Carotid Endarterectomy versus Carotid Artery Stenting: No Difference in 30-Day Post-Procedure Readmission Rates, Annals of Vascular Surgery (2015), doi: 10.1016/j.avsg.2015.05.013. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1 Carotid Endarterectomy versus Carotid Artery Stenting: No Difference in 30-Day PostProcedure Readmission Rates
RI PT
Erin K. Greenleaf,a David C. Han,a and Christopher S. Hollenbeaka,b a
EP
TE D
Corresponding Author: Christopher S. Hollenbeak, PhD The Pennsylvania State University College of Medicine Department of Surgery 500 University Drive, H151 Hershey, PA 17033-0850 Tel #: +1 717 531 5890 Fax #: +1 717 531 4464 E-mail: [email protected]
M AN U
SC
Department of Surgery, The Pennsylvania State University, College of Medicine 500 University Drive, Hershey, PA 17033-0850, USA E-mail: [email protected]; [email protected] b Department of Public Health Sciences, The Pennsylvania State University, College of Medicine 500 University Drive, Hershey, PA 17033-0850, USA Email: [email protected]
Conflict of Interest: None
AC C
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Funding Source: None
ACCEPTED MANUSCRIPT 2 ABSTRACT
38
Objective: In the United States, ischemic stroke is a major cause of morbidity and mortality,
39
precipitated by carotid artery stenosis in one out of every five individuals who suffer a stroke.
40
Carotid endarterectomy (CEA) and carotid artery stenting (CAS) are two proven means of
41
intervening on this disease process, with similar patient outcomes. Little is known about the
42
burden of readmission following each of these procedures. We hypothesized that no difference in
43
readmission rates within 30 days would exist for these two procedures, in spite of baseline
44
differences that might exist between the two patient populations.
45
Methods: Using the Pennsylvania Health Care Cost Containment Council (PHC4) database, we
46
identified 4,319 people who underwent CEA (N=3,640) or CAS (N=679) in Pennsylvania in
47
2011. Univariate analyses were performed to compare patient characteristics and outcomes,
48
including reasons for readmission, between patients who underwent CEA and those who
49
underwent CAS. Logistic regression was used to estimate the effect of intervention on 30-day
50
readmission, after controlling for potential confounders. Time to readmission was analyzed using
51
the Kaplan-Meier method.
52
Results: Patients who underwent CEA and CAS differed in a few notable ways, including age,
53
race, admission type, and comorbid conditions such as CHF, hemiplegia and paraplegia, and
54
renal disease. The unadjusted rate of 30-day readmission was 9.37% for CEA and 10.75% for
55
CAS (P=0.26). After controlling for patient and procedure characteristics, differences between
56
30-day readmission rates were still not statistically significant (odds ratio=1.13; P=0.39). Finally,
57
time to readmission was similar for those who underwent CEA and those who underwent CAS
58
(P=0.19). Complications associated with surgery comprised less than 10% of primary
59
readmission diagnoses for both groups.
AC C
EP
TE D
M AN U
SC
RI PT
37
ACCEPTED MANUSCRIPT 3 Conclusions: Readmission rates following CEA and CAS for carotid artery stenosis are
61
approximately 10%. In spite of differences between patients with carotid stenosis who are
62
selected for endarterectomy and stenting, the choice of procedure does not appear to be
63
associated with different readmission rates or time to readmission, even after controlling for
64
patient characteristics.
RI PT
60
AC C
EP
TE D
M AN U
SC
65
ACCEPTED MANUSCRIPT 4 66
1. INTRODUCTION Cerebrovascular disease was among the top five causes of death in the United States in
67
2010.1 Among those who survive, stroke is linked to long-term physical and cognitive disability.2
69
The incidence of stroke in the US has been declining over the past three decades, a trend that
70
may be related to improved diagnostic methods and treatment options.3 Indeed, carotid
71
endarterectomy (CEA) and carotid artery stenting (CAS) are two interventions with proven
72
benefit in appropriately selected patients.4-7
SC
RI PT
68
In a milieu in which national annual expenditures on health care are measured on a scale
73
of trillions, accounting for nearly one fifth of the gross domestic product, the 2010 Patient
75
Protection and Affordable Care Act was passed.8 Section 3025 of the Act established the
76
Hospital Readmissions Reduction Program. The program required the Centers for Medicare and
77
Medicaid Services (CMS) to reduce payments to Medicare Inpatient Prospective Payment
78
System (IPPS) hospitals with excess readmissions.9 In fiscal year 2015, these readmission
79
penalties apply to five conditions—acute myocardial infarction, heart failure, pneumonia, total
80
hip arthroplasty and total knee arthroplasty.10 It is expected that within only a few years,
81
penalties will expand to readmissions following various procedures, including those of vascular
82
surgery, and potential penalties will total approximately $1 billion.11,12
EP
TE D
M AN U
74
In such an environment, it is important to understand variation in rates of readmission
AC C
83 84
and risk factors for readmission for vascular surgery procedures. Such data form the foundation
85
for initiatives to prevent their occurrence. The purpose of this study was to determine rates and
86
risk factors for readmission following two commonly performed vascular procedures, CEA and
87
CAS.
88
ACCEPTED MANUSCRIPT 5 89
2. METHODS
90
2.1 Data
91
This study was a retrospective cohort study using administrative data collected between 2011 and 2012 by the Pennsylvania Health Care Cost Containment Council (PHC4), an
93
independent state agency mandated by law to address state health care costs. PHC4 collects
94
detailed discharge data, including demographics, utilization, and source of admission
95
information, on all inpatient and outpatient ambulatory procedure records annually from
96
Pennsylvania hospitals and freestanding ambulatory surgery centers. Data on patients with
97
formal admissions, including those for observation only, were included. Within this database,
98
each patient is assigned a unique personal identifier, allowing readmissions to be tracked to a
99
corresponding individual across Pennsylvania hospitals, even when readmission occurred at a
SC
M AN U
101
facility different from that of the index admission.
We queried the PHC4 dataset to identify patients who underwent carotid endarterectomy
TE D
100
RI PT
92
and carotid artery stenting (N = 4,712) using International Classification of Disease, 9th Revision,
103
Clinical Modification (ICD-9-CM) procedure codes for carotid endarterectomy (38.12) and
104
carotid artery stenting (00.63). Patients who died during their index hospital admission were not
105
included in the sample. After excluding 387 patients for missing covariates or outcome data and
106
6 patients for undergoing both procedures, there were 3,640 index admissions for patients who
107
underwent carotid endarterectomy and 679 who underwent carotid artery stenting.
AC C
108
EP
102
Analyses controlled for several patient level variables, including demographics (age,
109
gender, and race), type of admission (elective, urgent, emergent), primary payer (Medicare,
110
commercial, self-pay, HMO), and comorbidities (history of acute myocardial infarction,
111
congestive heart failure, peripheral vascular disease, chronic obstructive pulmonary disease,
ACCEPTED MANUSCRIPT 6 112
diabetes, hemiplegia/paraplegia, renal disease, and cancer). Comorbidities were identified using
113
ICD-9-CM diagnosis codes and were restricted to those available within the PHC4 database,
114
coded according to the Charlson Comorbidity Index.13
RI PT
The primary outcome of interest in this study was 30-day readmission. PHC4 defines
115
“readmission” as repeat hospitalization occurring less than 30 days after a patient is discharged
117
alive.
118
2.2 Statistical Analysis
SC
116
Statistical analysis was used to determine predictors of 30-day readmission after carotid
120
endarterectomy and after carotid stenting, while controlling for the covariates described above.
121
Baseline patient characteristics and comorbidities were compared between patients who
122
underwent endarterectomy and patients who underwent stenting utilizing chi-square tests for
123
binary and categorical variables and t-tests for continuous variables. We reported means or
124
proportions with associated P-values.
TE D
125
M AN U
119
Logistic regression was used to model the effects of baseline characteristics and comorbidities on 30-day readmission. We report odds ratios with associated 95% confidence
127
intervals. Goodness of fit of the logistic regression model was measured as the area under the
128
receiver operating characteristic (ROC) curve. Odds ratios of readmission between patients
129
undergoing endarterectomy and stenting were compared. Logistic regression was then used to
130
generate coefficients for each covariate, for application in a decision-making model predicting
131
likelihood of readmission in any patient with a known set of risk factors.
AC C
132
EP
126
Percent not readmitted was defined as patients who were not readmitted to the hospital
133
within 30 days following discharge from their index hospitalization. After stratifying patients
134
according to intervention, time-to-event analyses were performed using Kaplan-Meier
ACCEPTED MANUSCRIPT 7 proportional hazards methods. Primary diagnoses for readmission were identified using ICD-9-
136
CM codes and categorized according to body system, if not clearly a complication related to a
137
recent procedure. A unique category for post-procedural complications was used for
138
classification of these diagnoses. This study was deemed to be exempt from IRB approval by the
139
Human Subjects Protection Office at Penn State College of Medicine. All analyses were
140
performed using STATA software (version 12, College Station, TX). Statistical significance for
141
all analyses was defined as a P-value <.05.
142
3. RESULTS
143
3.1 Patient characteristics
SC
M AN U
144
RI PT
135
Inpatient admissions to all non-VA Pennsylvania hospitals and free-standing surgical institutions during 2011 were included in the PHC4 database. The analysis sample included
146
4,319 admissions for patients who underwent a carotid intervention after excluding admissions
147
for which data regarding readmission status was missing (N = 387) as well as for patients who
148
underwent both endarterectomy and stenting on their index admission (N = 6). Of these patients,
149
3,640 underwent CEA and 679 underwent CAS. Demographic statistics are shown in Table I.
150
Compared to patients who underwent CEA, patients who underwent stenting were more likely to
151
be younger (P = .041), non-White (P < .0001), admitted non-electively (P < .0001), and have
152
shorter length of stay (P=.015). Patients who underwent stenting had greater numbers of
153
comorbidities, such as CHF (P < .0001), PVD (P = .004), hemiplegia and paraplegia (P = .011),
154
and renal disease (P = .014), relative to patients who underwent endarterectomy (Table II).
155
3.2 30-day readmission
156 157
AC C
EP
TE D
145
Table III presents the results of the logistic regression model of 30-day readmission, controlling for covariates. There was no statistically significant difference in likelihood of
ACCEPTED MANUSCRIPT 8 readmission based on intervention alone. However, there was a significantly lower likelihood of
159
readmission of patients of non-white and non-black race (odds ratio [OR] 0.49, 95% CI 0.24-
160
0.98). There was a significantly higher likelihood of readmission of patients admitted emergently
161
(OR 1.35, 95% CI 1.02-1.79) or discharged to a facility other than home (OR 1.71, 95% CI 1.33-
162
2.20). Having hemiplegia or paraplegia (OR 2.18, 95% CI 1.17-4.08), renal disease (OR 1.75,
163
95% CI 1.30-2.34), and cancer (OR 2.19, 95% CI 1.17-4.10) prior to discharge were
164
significantly associated with greater risk of readmission when all receiving CEA and CAS were
165
considered jointly. Fig. 1 presents the odds ratios of readmission, comparing covariates when
166
patients were segregated according to intervention. When modeled against each other, CAS
167
patients were more likely than similar CEA patients to be readmitted if they were older than 80
168
years old or female. They were less likely than similar CEA patients to be readmitted if they had
169
a history of hemiplegia or paraplegia. There were no covariates for which CEA patients were
170
more likely to be readmitted relative to comparable CAS patients.
173
SC
M AN U
TE D
172
Coefficients generated from logistic regression were used to create a predictive model for readmission using equation 1.
EP
171
RI PT
158
(1)
The probability of readmission following carotid intervention can be estimated for any patient
175
following either CEA or CAS, provided a complete profile of information on age, sex, race,
176
admission type, payer type, discharge destination, and pre-existing comorbidities. For example,
177
the probability of readmission for a 75-year-old Hispanic female with Medicare and a history of
178
diabetes and congestive heart failure admitted electively and discharged with home health care
179
following CAS would be:
AC C
174
ACCEPTED MANUSCRIPT 9
(2)
180
where the values in equation 2 are the coefficients found in Table III. Therefore, the probability
182
of readmission would be 0.0796 or 7.96% following discharge. Note that coefficients for
183
reference variables are not included in the computation of risk of readmission since they are
184
already captured in the intercept term.
Primary diagnoses for readmission are presented in Table IV. After categorization of
SC
185
RI PT
181
primary readmission diagnoses, both CEA and CAS patients were most often readmitted
187
secondary to cerebrovascular etiologies (CEA 23.41%, CAS 30.76%). Central cardiovascular-
188
related diagnoses (e.g. coronary atherosclerosis, atrial fibrillation) accounted for the next largest
189
proportion of readmission diagnoses for both intervention groups (CEA 20.78%, CAS 23.06%).
190
In spite of the known presence of vascular disease inherent to patients with carotid artery
191
stenosis, patients were less frequently readmitted for peripheral vascular-related diagnoses (CEA
192
4.45%, CAS 5.12%). Post-procedural complications accounted for 8.68% of readmissions
193
following CEA and 7.68% of readmissions following CAS.
194
3.3 Survival Analysis
TE D
EP
195
M AN U
186
Results of Kaplan-Meier analysis are presented in Fig. 2. Of those patients who were readmitted within 30 days, time to readmission was not significantly different between those who
197
underwent endarterectomy and those who underwent stenting (P = .19).
198
4. DISCUSSION
199
AC C
196
In our study of 30-day readmissions, we found no statistically significant difference in
200
30-day readmission rates between patients who underwent CEA and CAS. Moreover, odds of
201
readmission were similar between patients undergoing either intervention, as was time to
202
readmission within 30 days. When the intervention groups were modeled as a single sample, the
ACCEPTED MANUSCRIPT 10 odds of readmission were greater if patients were admitted emergently, discharged to a
204
destination other than home, or had a history of hemiplegia or paraplegia, renal disease, or
205
cancer. Other (non-white, non-black) race was protective for readmission. When risk was
206
modeled separately for CEA and CAS patients, we found that risk factors for readmission were
207
similar for both procedures, with few exceptions. CAS patients were more likely than CEA
208
patients to be readmitted if they were older than 80 years old or female but less likely than CEA
209
patients to be readmitted if they had histories of hemiplegia or paraplegia. When studying the
210
CEA sample separately, none of the observed covariates were associated with significantly
211
different risk of readmission relative to the CAS sample. Primary diagnoses for readmission were
212
predominantly cerebrovascular and cardiovascular for patients who underwent CEA and CAS,
213
with diagnoses unambiguously related to post-procedural complications ranking third and fourth,
214
respectively, in frequency of readmission diagnoses.
M AN U
SC
RI PT
203
Most previous studies of readmission rates following CEA report a rate between 6% and
216
11.2%, which is consistent with the estimate of readmission of 9.4% in our patient population.14-
217
19
218
previously published estimates. Galinanes et al. report a 30-day readmission rate of 11.11%, a
219
0.31 percentage point difference relative to the present study that may be of limited clinical
220
significance.14 Yet, our finding of no statistically significant difference in periprocedural
221
readmission between CEA and CAS is in contrast to the Galinanes study, which showed
222
significantly greater readmission rates after CAS relative to CEA at 30, 60, and 90 days
223
following interventions.14 Although both our study and Galinanes et al. demonstrated higher
224
absolute readmission rates for CAS relative to CEA, the difference between studies in
225
statistically significant findings may illustrate the variation in practice patterns, and therefore
TE D
215
AC C
EP
The readmission rate of 10.8% following CAS in our data was marginally lower than
ACCEPTED MANUSCRIPT 11 thresholds for readmission, across a national sample as in Galinanes et al. and a statewide sample
227
in the present study. Like the present study, although not in patients undergoing carotid
228
intervention specifically, other studies have failed to detect a consistent statistically significant
229
benefit of open vascular surgery relative to endovascular techniques with respect to readmission
230
rates.20,21
RI PT
226
Our study found that for all carotid interventions, the odds of readmission were lower in
232
patients who were in the “other” race category, which is consistent with previous studies.14,17,22
233
Also similar to previous studies, we found that patients admitted on an emergent basis or
234
discharged to a destination other than home were more likely to be readmitted within 30
235
days.13,15,23 With regard to patient comorbidities, many studies identify comorbidities
236
contributing to readmission in general, but fewer have investigated comorbidities that affect
237
readmission following carotid intervention.14-16,18,24 In an analysis of Medicare claims data,
238
Jencks et al. identified the majority of their studied comorbidities, including congestive heart
239
failure, chronic obstructive pulmonary disease, diabetes mellitus, coagulopathy, peripheral
240
vascular disease, pulmonary disease and renal disease, as contributors to greater odds of
241
readmission.25 We found, among a population of patients of all ages undergoing carotid
242
intervention, history of hemiplegia or paraplegia, renal disease and cancer were significantly
243
associated with greater odds of 30 day readmission. The present study is consistent with previous
244
studies looking at CEA, if not both CEA and CAS, exclusively.14-16,18
M AN U
TE D
EP
AC C
245
SC
231
A further analysis of risk factors for readmission, stratified according to intervention
246
type, interestingly demonstrated that age over 80 years old and female gender contributed to a
247
greater likelihood of readmission for patients undergoing CAS, but not for those undergoing
248
CEA. A history of hemiplegia or paraplegia was actually associated with lower odds of
ACCEPTED MANUSCRIPT 12 readmission following CAS. This finding may suggest a synergistic effect between a baseline
250
level of elevated risk, such as in CAS patients, and an incapacitating neurologic deficit, thereby
251
increasing the likelihood of a highly supportive home environment capable of managing post-
252
procedure sequelae, which might otherwise be cause for readmission. Yet although it is plausible
253
that those with a history of hemiplegia or paraplegia have a strong established support system, it
254
is also plausible that the protective role of hemiplegia or paraplegia is a spurious artifact born
255
from multivariable analysis on a large data set.26
SC
256
RI PT
249
When reasons for readmission were identified, cerebrovascular and central cardiovascular diagnoses accounted for approximately half of all diagnoses for 30-day readmission among
258
patients who underwent either CEA or CAS. Reasons for readmission that were unambiguously
259
procedure-related comprised only 8.68% and 7.68% of all readmission diagnoses for CEA and
260
CAS patients, respectively. While it may be expected that patients requiring carotid intervention
261
for carotid artery stenosis also have extensive cardiovascular pathology for which subsequent
262
hospital admissions would be warranted, readmission diagnoses related to peripheral vascular
263
diagnoses comprised only 4.45% of readmission diagnoses for CEA patients and 5.12% of
264
readmission diagnoses for CAS patients. Previous studies of patients undergoing carotid
265
intervention corroborate the finding of cardiac-related diagnoses as the most common cause of
266
unplanned readmission.14,16
TE D
EP
AC C
267
M AN U
257
Readmission diagnoses that are unequivocally associated with the index procedure are of
268
particular interest to providers as they represent an opportunity for preemptive intervention. In an
269
analysis of 30-day readmission diagnoses for all patients who underwent any inpatient surgery
270
within the Veterans Health Administration, patients who underwent peripheral vascular surgery
271
were most often readmitted for infection, commonly of an implanted prosthesis or otherwise
ACCEPTED MANUSCRIPT 13 localized to the surgical site.27 In the current study, however, post-procedural complications,
273
including infection, did not predominate among readmission diagnoses for patients undergoing
274
either CEA or CAS, whereas cardiovascular and cerebrovascular causes were more commonly
275
implicated in unplanned readmissions following both interventions. This may be related to the
276
typically clean nature of neck procedures and surgical wounds. Unfortunately, we were limited
277
in knowing whether patients with cerebrovascular-related diagnosis codes, which described the
278
most common readmission diagnoses, were actually readmitted for complications directly related
279
to their carotid interventions. The ambiguity in ICD-9-CM coding limits our confidence in the
280
reliability of readmission diagnoses.
SC
M AN U
281
RI PT
272
This is a retrospective analysis of administrative data, which carries some inherent limitations. First, there are variables that were not available in the data set that may be potential
283
confounders and could not be controlled. For example, presence and severity of neurologic
284
symptoms upon presentation at index admission is not captured in the PHC4 dataset, although it
285
may modulate relationships between predictive factors and readmission. Information on
286
preoperative functional status was also not part of the dataset. This additional information could
287
have potentially informed expectations for patient convalescence and likelihood of readmission.
288
Second, many of our variables, including the identification of CEA and CAS procedures, were
289
identified using diagnosis and procedure codes. There is always the potential for coding errors,
290
although it is unlikely that such errors would be systematic. Third, the PHC4 data set includes
291
only inpatient admission to acute care hospitals in Pennsylvania, which may not be
292
representative of all patients undergoing carotid interventions. Because patients are not tracked
293
beyond state borders, readmission to a non-Pennsylvania hospital would be outside of the scope
294
of this data set because of geographic limitations. Moreover, specific data regarding primary
AC C
EP
TE D
282
ACCEPTED MANUSCRIPT 14 295
diagnosis for readmission may not be reliably reported and coded, contributing to ambiguity
296
regarding the relationship between carotid intervention and readmission.
297
5. CONCLUSION We conclude based on this statewide analysis of discharge data that 30-day readmission
RI PT
298
rates are similar for patients undergoing CEA and CAS. Other factors, however, are related to
300
readmission for both procedures, such as urgency of admission and comorbidities. Thirty-day
301
readmissions have been under more intense scrutiny since the HRRP in 2010.9 Given the
302
forthcoming expansion of penalties for readmissions to include those within 30 days after
303
vascular surgery, it is crucial to determine targets for change for patients undergoing CEA and
304
CAS.8,11,12 Future efforts should be directed toward elucidating costs associated with
305
readmission, determining readmission and complication rates over a longer post-operative
306
interval, and ultimately, assessing the effectiveness of interventions to reduce readmissions in
307
this patient population.
M AN U
TE D EP AC C
308
SC
299
ACCEPTED MANUSCRIPT 15 309
REFERENCES
310
[1]
Yoon PW, Bastian B, Anderson RN, Collins JL, Jaffe HW. Potentially preventable deaths from the five leading causes of death--United States, 2008-2010. MMWR Morb Mortal
312
Wkly Rep 2014;63:369-74.
313
[2]
RI PT
311
Luengo-Fernandez R, Paul NL, Gray AM, Pendlebury ST, Bull LM, Welch SJ, et al. Population-based study of disability and institutionalization after transient ischemic
315
attack and stroke: 10-year results of the Oxford Vascular Study. Stroke 2013;44:2854-61.
316
[3]
SC
314
Koton S, Schneider AL, Rosamond WD, Shahar E, Sang Y, Gottesman RF, et al. Stroke incidence and mortality trends in US communities, 1987 to 2011. JAMA 2014;312:259-
318
68.
319
[4]
M AN U
317
North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis.
321
N Engl J Med 1991;325:445-53.
322
[5]
TE D
320
MRC European Carotid Surgery Trial: interim results for symptomatic patients with severe (70-99%) or with mild (0-29%) carotid stenosis. European Carotid Surgery
324
Trialists' Collaborative Group. Lancet 1991;337:1235-43. [6]
Asymptomatic Carotid Atherosclerosis Study. JAMA 1995;273:1421-8.
326 327
[7]
neurological symptoms: randomised controlled trial. Lancet 2004;363:1491-1502.
329
331
Halliday A, Mansfield A, Marro J, Peto C, Peto R, Potter J, et al. Prevention of disabling
and fatal strokes by successful carotid endarterectomy in patients without recent
328
330
Endarterectomy for asymptomatic carotid artery stenosis. Executive Committee for the
AC C
325
EP
323
[8]
Prabhakar AM, Harvey HB, Oklu R. Thirty-day hospital re-admissions: a metric that matters. J Vasc Interv Radiol 2013;24:1509-11.
ACCEPTED MANUSCRIPT 16 332
[9]
Centers for Medicare & Medicaid Services. Readmissions Reduction Program, http://www.cms.gov/Medicare/Medicare-Fee-for-Service-
334
Payment/AcuteInpatientPPS/Readmissions-Reduction-Program.html [accessed
335
08/21/2014].
336
[10]
RI PT
333
Centers for Medicare & Medicaid Services. CMS-1607-P, Proposed Rule, http://www.cms.gov/Medicare/Medicare-Fee-for-Service-
338
Payment/AcuteInpatientPPS/FY2015-IPPS-Proposed-Rule-Home-Page-Items/FY2015-
339
IPPS-Proposed-Rule-Regulations.html [accessed 04/15/2015].
SC
337
[11]
Kamerow D. Reassessing hospital readmission penalties. BMJ 2013;346:f1043.
341
[12]
Gonzalez AA, Girotti ME, Shih T, Wakefield TW, Dimick JB. Reliability of hospital readmission rates in vascular surgery. J Vasc Surg 2014;59:1638-43.
342
[13]
ICD-9-CM administrative databases. J Clin Epidemiol 1992;45:613-9.
344 345
Deyo RA, Cherkin DC, Ciol MA. Adapting a clinical comorbidity index for use with
[14]
TE D
343
M AN U
340
Galinanes EL, Dombroviskiy VY, Hupp CS, Kruse RL, Vogel TR. Evaluation of readmission rates for carotid endarterectomy versus carotid artery stenting in the US
347
Medicare population. Vasc Endovascular Surg 2014;48:217-23. [15]
readmissions after vascular surgery. J Vasc Surg 2014;59:473-82.
349 350 351 352
Gupta PK, Fernandes-Taylor S, Ramanan B, Engelbert TL, Kent KC. Unplanned
[16]
AC C
348
EP
346
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.
ACCEPTED MANUSCRIPT 17 353
[17]
Kennedy BS, Fortmann SP, Stafford RS. Elective and isolated carotid endarterectomy:
354
health disparities in utilization and outcomes, but not readmission. J Natl Med Assoc
355
2007;99:480-8.
Readmission After Carotid Endarterectomy. World Neurosurg 2013;82:e771-e776.
357
[19]
length of stay, and readmission rates in high-risk surgery. Ann Surg 2003;238:161-7.
359 360
[20]
Casey K, Hernandez-Boussard T, Mell MW, Lee JT. Differences in readmissions after open repair versus endovascular aneurysm repair. J Vasc Surg 2013;57:89-95.
361 362
Goodney PP, Stukel TA, Lucas FL, Finlayson EV, Birkmeyer JD. Hospital volume,
SC
358
Rambachan A, Smith TR, Saha S, Eskandari MK, Bendok BR, Kim JY. Reasons for
RI PT
[18]
[21]
M AN U
356
Holt PJ, Poloniecki JD, Hofman D, Hinchliffe RJ, Loftus IM, Thompson MM. Re-
363
interventions, readmissions and discharge destination: modern metrics for the assessment
364
of the quality of care. Eur J Vasc Endovasc Surg 2010;39:49-54.
Medicare beneficiaries by race and site of care. Ann Surg 2014;259:1086-90.
366
[23]
and surgical outcomes: it is not all black and white. Ann Surg 2008;248:647-55.
368 369
[24]
years of a statewide database. J Vasc Surg 2008;48:343-50; discussion 350.
371
373
Nazarian SM, Yenokyan G, Thompson RE, Griswold ME, Chang DC, Perler BA. Statistical modeling of the volume-outcome effect for carotid endarterectomy for 10
370
372
Esnaola NF, Hall BL, Hosokawa PW, Ayanian JZ, Henderson WG, Khuri SF, et al. Race
EP
367
Tsai TC, Orav EJ, Joynt KE. Disparities in surgical 30-day readmission rates for
TE D
[22]
AC C
365
[25]
Jencks SF, Williams MV, Coleman EA. Rehospitalizations among patients in the
Medicare fee-for-service program. N Engl J Med 2009;360:1418-28.
ACCEPTED MANUSCRIPT 18 374
[26]
Schonberger RB, Gilbertsen T, Dai F. The problem of controlling for imperfectly
375
measured confounders on dissimilar populations: a database simulation study. J
376
Cardiothorac Vasc Anesth 2014;28:247-54.
378
[27]
Han S, Smith TS, Gunnar W. Descriptive analysis of 30-day readmission after inpatient
RI PT
377
surgery discharge in the veterans health administration. JAMA Surg 2014;149:1162-68.
AC C
EP
TE D
M AN U
SC
379
ACCEPTED MANUSCRIPT 19 Table I. Comparison of baseline demographic and clinical data of all patients undergoing carotid intervention stratified by intervention type CEA CAS Variable (n = 3,640) (n = 679) P value Age 0.041 18-64 23.9% 25.2% 65-74 36.0% 39.2% 75-79 18.5% 16.2% 80+ 21.6% 19.4% Sex 0.443 Male 58.2% 59.8% Female 41.8% 40.2% Race <0.0001 White 94.6% 86.3% Black 2.8% 4.7% Other 2.6% 9.0% Admission type <0.0001 Elective 79.4% 72.0% Urgent 6.8% 13.4% Emergent 13.8% 14.6% Payer type 0.056 Medicare 74.4% 70.7% Commercial 20.6% 23.9% Selfpay 0.3% 0.1% HMO 33.6% 28.9% Discharge destination 0.213 Home 82.5% 85.0% SNF 4.2% 4.9% Home health Care 13.2% 10.2% Other 0.0% 0.0% LOS 2.71 2.36 0.015 HMO: Health maintenance organization; SNF: Skilled nursing facility; LOS: Length of stay
382 383
AC C
EP
TE D
M AN U
SC
RI PT
380 381
ACCEPTED MANUSCRIPT 20 Table II. Comparison of baseline comorbidities of all patients undergoing carotid intervention stratified by intervention type CEA CAS Variable (n = 3,640) (n = 679) P value AMI 12.0% 11.3% 0.652 CHF 5.5% 9.4% <0.0001 PVD 15.1% 19.6% 0.004 COPD 20.3% 21.4% 0.543 Diabetes 31.9% 33.4% 0.423 HP/PAPL 1.2% 2.5% 0.011 Renal Dz 9.5% 12.5% 0.014 Cancer 1.5% 1.9% 0.438 AMI: Acute myocardial infarction; CHF: Congestive heart failure; PVD: Peripheral vascular disease; COPD: Chronic obstructive pulmonary disease; HP/PAPL: Hemiplegia or Paraplegia
M AN U TE D EP AC C
386 387 388 389
SC
RI PT
384 385
ACCEPTED MANUSCRIPT
21
AC C
EP
TE D
M AN U
SC
RI PT
Table III. Results of a logistic regression model of intervention type on 30-day readmission, controlling for other covariates (area under ROC curve = 0.6262) 95% Confidence Variable Odds Ratio Coefficient Lower Upper P value Intervention CEA REFERENCE Stent 1.15 0.14 0.88 1.52 0.310 Age 18-64 REFERENCE 65-74 1.16 0.14 0.83 1.60 0.385 75-79 1.12 0.11 0.77 1.63 0.549 80+ 1.20 0.18 0.83 1.73 0.326 Sex Male REFERENCE Female 1.15 0.14 0.93 1.42 0.191 Race White REFERENCE Black 1.19 0.17 0.69 2.02 0.533 Other 0.49 -0.72 0.24 0.98 0.043 Admission Type Elective REFERENCE Urgent 1.21 0.19 0.84 1.73 0.314 Emergent 1.35 0.30 1.02 1.79 0.036 Payer type Medicare REFERENCE Commercial 1.06 0.06 0.77 1.47 0.716 Selfpay 0.84 -0.18 0.10 6.82 0.867 HMO 1.03 0.03 0.83 1.28 0.796
ACCEPTED MANUSCRIPT
22
AC C
EP
TE D
M AN U
SC
RI PT
Discharge destination Home REFERENCE Other 1.71 0.54 1.33 2.20 <0.0001 Comorbidities AMI 1.09 0.09 0.80 1.49 0.566 CHF 1.10 0.10 0.75 1.63 0.613 PVD 1.15 0.14 0.88 1.51 0.314 COPD 1.26 0.23 0.99 1.62 0.060 DM 1.10 0.10 0.89 1.37 0.376 HP/PAPL 2.18 0.78 1.17 4.08 0.015 Renal Disease 1.75 0.56 1.30 2.34 <0.0001 Cancer 2.19 0.78 1.17 4.10 0.014 HMO: Health maintenance organization; AMI: Acute myocardial infarction; CHF: Congestive heart failure; PVD: Peripheral vascular disease; COPD: Chronic obstructive pulmonary disease; DM: Diabetes mellitus; HP/PAPL: Hemiplegia or Paraplegia
ACCEPTED MANUSCRIPT 23
AC C
EP
TE D
M AN U
SC
RI PT
Table IV. Comparison of primary diagnoses for 30-day readmission stratified by intervention type CEA CAS Primary Diagnosis (n = 3,910) (n = 415) Cerebrovascular 23.41% 30.76% Cardiovascular, Central 20.78% 23.06% Procedure-related Complication 8.68% 7.68% Pulmonary 8.39% 6.41% Genitourinary 5.51% 8.97% Cardiovascular, Peripheral 4.45% 5.12% Gastrointestinal 6.01% 6.40% Neurologic 3.93% 5.12% Endocrine 2.62% 1.28% Hematologic 5.52% 1.28% Other 7.04% 3.84%
ACCEPTED MANUSCRIPT 24 FIGURE LEGENDS Fig. 1. Forest plot for relation between carotid intervention and odds of readmission. Relative to similar CEA patients, CAS patients were more likely to be readmitted if they were older than 80
RI PT
years old or female, but less likely to be readmitted if they had a history of hemiplegia or
paraplegia. There were no covariates for which CEA patients were more likely to be readmitted relative to comparable CAS patients.
SC
Fig. 2. Time to readmission for patients undergoing carotid intervention based on intervention type. Of those patients who were readmitted within 30 days, there was no statistically significant
M AN U
difference in time to readmission between those who underwent endarterectomy and those who
AC C
EP
TE D
underwent stenting.
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
S0890-5096(15)00564-6
DOI:
10.1016/j.avsg.2015.05.013
Reference:
AVSG 2453
To appear in:
Annals of Vascular Surgery
Received Date: 21 January 2015 Revised Date:
5 May 2015
Accepted Date: 19 May 2015
Please cite this article as: Greenleaf EK, Han DC, Hollenbeak CS, Carotid Endarterectomy versus Carotid Artery Stenting: No Difference in 30-Day Post-Procedure Readmission Rates, Annals of Vascular Surgery (2015), doi: 10.1016/j.avsg.2015.05.013. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1 Carotid Endarterectomy versus Carotid Artery Stenting: No Difference in 30-Day PostProcedure Readmission Rates
RI PT
Erin K. Greenleaf,a David C. Han,a and Christopher S. Hollenbeaka,b a
EP
TE D
Corresponding Author: Christopher S. Hollenbeak, PhD The Pennsylvania State University College of Medicine Department of Surgery 500 University Drive, H151 Hershey, PA 17033-0850 Tel #: +1 717 531 5890 Fax #: +1 717 531 4464 E-mail: [email protected]
M AN U
SC
Department of Surgery, The Pennsylvania State University, College of Medicine 500 University Drive, Hershey, PA 17033-0850, USA E-mail: [email protected]; [email protected] b Department of Public Health Sciences, The Pennsylvania State University, College of Medicine 500 University Drive, Hershey, PA 17033-0850, USA Email: [email protected]
Conflict of Interest: None
AC C
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Funding Source: None
ACCEPTED MANUSCRIPT 2 ABSTRACT
38
Objective: In the United States, ischemic stroke is a major cause of morbidity and mortality,
39
precipitated by carotid artery stenosis in one out of every five individuals who suffer a stroke.
40
Carotid endarterectomy (CEA) and carotid artery stenting (CAS) are two proven means of
41
intervening on this disease process, with similar patient outcomes. Little is known about the
42
burden of readmission following each of these procedures. We hypothesized that no difference in
43
readmission rates within 30 days would exist for these two procedures, in spite of baseline
44
differences that might exist between the two patient populations.
45
Methods: Using the Pennsylvania Health Care Cost Containment Council (PHC4) database, we
46
identified 4,319 people who underwent CEA (N=3,640) or CAS (N=679) in Pennsylvania in
47
2011. Univariate analyses were performed to compare patient characteristics and outcomes,
48
including reasons for readmission, between patients who underwent CEA and those who
49
underwent CAS. Logistic regression was used to estimate the effect of intervention on 30-day
50
readmission, after controlling for potential confounders. Time to readmission was analyzed using
51
the Kaplan-Meier method.
52
Results: Patients who underwent CEA and CAS differed in a few notable ways, including age,
53
race, admission type, and comorbid conditions such as CHF, hemiplegia and paraplegia, and
54
renal disease. The unadjusted rate of 30-day readmission was 9.37% for CEA and 10.75% for
55
CAS (P=0.26). After controlling for patient and procedure characteristics, differences between
56
30-day readmission rates were still not statistically significant (odds ratio=1.13; P=0.39). Finally,
57
time to readmission was similar for those who underwent CEA and those who underwent CAS
58
(P=0.19). Complications associated with surgery comprised less than 10% of primary
59
readmission diagnoses for both groups.
AC C
EP
TE D
M AN U
SC
RI PT
37
ACCEPTED MANUSCRIPT 3 Conclusions: Readmission rates following CEA and CAS for carotid artery stenosis are
61
approximately 10%. In spite of differences between patients with carotid stenosis who are
62
selected for endarterectomy and stenting, the choice of procedure does not appear to be
63
associated with different readmission rates or time to readmission, even after controlling for
64
patient characteristics.
RI PT
60
AC C
EP
TE D
M AN U
SC
65
ACCEPTED MANUSCRIPT 4 66
1. INTRODUCTION Cerebrovascular disease was among the top five causes of death in the United States in
67
2010.1 Among those who survive, stroke is linked to long-term physical and cognitive disability.2
69
The incidence of stroke in the US has been declining over the past three decades, a trend that
70
may be related to improved diagnostic methods and treatment options.3 Indeed, carotid
71
endarterectomy (CEA) and carotid artery stenting (CAS) are two interventions with proven
72
benefit in appropriately selected patients.4-7
SC
RI PT
68
In a milieu in which national annual expenditures on health care are measured on a scale
73
of trillions, accounting for nearly one fifth of the gross domestic product, the 2010 Patient
75
Protection and Affordable Care Act was passed.8 Section 3025 of the Act established the
76
Hospital Readmissions Reduction Program. The program required the Centers for Medicare and
77
Medicaid Services (CMS) to reduce payments to Medicare Inpatient Prospective Payment
78
System (IPPS) hospitals with excess readmissions.9 In fiscal year 2015, these readmission
79
penalties apply to five conditions—acute myocardial infarction, heart failure, pneumonia, total
80
hip arthroplasty and total knee arthroplasty.10 It is expected that within only a few years,
81
penalties will expand to readmissions following various procedures, including those of vascular
82
surgery, and potential penalties will total approximately $1 billion.11,12
EP
TE D
M AN U
74
In such an environment, it is important to understand variation in rates of readmission
AC C
83 84
and risk factors for readmission for vascular surgery procedures. Such data form the foundation
85
for initiatives to prevent their occurrence. The purpose of this study was to determine rates and
86
risk factors for readmission following two commonly performed vascular procedures, CEA and
87
CAS.
88
ACCEPTED MANUSCRIPT 5 89
2. METHODS
90
2.1 Data
91
This study was a retrospective cohort study using administrative data collected between 2011 and 2012 by the Pennsylvania Health Care Cost Containment Council (PHC4), an
93
independent state agency mandated by law to address state health care costs. PHC4 collects
94
detailed discharge data, including demographics, utilization, and source of admission
95
information, on all inpatient and outpatient ambulatory procedure records annually from
96
Pennsylvania hospitals and freestanding ambulatory surgery centers. Data on patients with
97
formal admissions, including those for observation only, were included. Within this database,
98
each patient is assigned a unique personal identifier, allowing readmissions to be tracked to a
99
corresponding individual across Pennsylvania hospitals, even when readmission occurred at a
SC
M AN U
101
facility different from that of the index admission.
We queried the PHC4 dataset to identify patients who underwent carotid endarterectomy
TE D
100
RI PT
92
and carotid artery stenting (N = 4,712) using International Classification of Disease, 9th Revision,
103
Clinical Modification (ICD-9-CM) procedure codes for carotid endarterectomy (38.12) and
104
carotid artery stenting (00.63). Patients who died during their index hospital admission were not
105
included in the sample. After excluding 387 patients for missing covariates or outcome data and
106
6 patients for undergoing both procedures, there were 3,640 index admissions for patients who
107
underwent carotid endarterectomy and 679 who underwent carotid artery stenting.
AC C
108
EP
102
Analyses controlled for several patient level variables, including demographics (age,
109
gender, and race), type of admission (elective, urgent, emergent), primary payer (Medicare,
110
commercial, self-pay, HMO), and comorbidities (history of acute myocardial infarction,
111
congestive heart failure, peripheral vascular disease, chronic obstructive pulmonary disease,
ACCEPTED MANUSCRIPT 6 112
diabetes, hemiplegia/paraplegia, renal disease, and cancer). Comorbidities were identified using
113
ICD-9-CM diagnosis codes and were restricted to those available within the PHC4 database,
114
coded according to the Charlson Comorbidity Index.13
RI PT
The primary outcome of interest in this study was 30-day readmission. PHC4 defines
115
“readmission” as repeat hospitalization occurring less than 30 days after a patient is discharged
117
alive.
118
2.2 Statistical Analysis
SC
116
Statistical analysis was used to determine predictors of 30-day readmission after carotid
120
endarterectomy and after carotid stenting, while controlling for the covariates described above.
121
Baseline patient characteristics and comorbidities were compared between patients who
122
underwent endarterectomy and patients who underwent stenting utilizing chi-square tests for
123
binary and categorical variables and t-tests for continuous variables. We reported means or
124
proportions with associated P-values.
TE D
125
M AN U
119
Logistic regression was used to model the effects of baseline characteristics and comorbidities on 30-day readmission. We report odds ratios with associated 95% confidence
127
intervals. Goodness of fit of the logistic regression model was measured as the area under the
128
receiver operating characteristic (ROC) curve. Odds ratios of readmission between patients
129
undergoing endarterectomy and stenting were compared. Logistic regression was then used to
130
generate coefficients for each covariate, for application in a decision-making model predicting
131
likelihood of readmission in any patient with a known set of risk factors.
AC C
132
EP
126
Percent not readmitted was defined as patients who were not readmitted to the hospital
133
within 30 days following discharge from their index hospitalization. After stratifying patients
134
according to intervention, time-to-event analyses were performed using Kaplan-Meier
ACCEPTED MANUSCRIPT 7 proportional hazards methods. Primary diagnoses for readmission were identified using ICD-9-
136
CM codes and categorized according to body system, if not clearly a complication related to a
137
recent procedure. A unique category for post-procedural complications was used for
138
classification of these diagnoses. This study was deemed to be exempt from IRB approval by the
139
Human Subjects Protection Office at Penn State College of Medicine. All analyses were
140
performed using STATA software (version 12, College Station, TX). Statistical significance for
141
all analyses was defined as a P-value <.05.
142
3. RESULTS
143
3.1 Patient characteristics
SC
M AN U
144
RI PT
135
Inpatient admissions to all non-VA Pennsylvania hospitals and free-standing surgical institutions during 2011 were included in the PHC4 database. The analysis sample included
146
4,319 admissions for patients who underwent a carotid intervention after excluding admissions
147
for which data regarding readmission status was missing (N = 387) as well as for patients who
148
underwent both endarterectomy and stenting on their index admission (N = 6). Of these patients,
149
3,640 underwent CEA and 679 underwent CAS. Demographic statistics are shown in Table I.
150
Compared to patients who underwent CEA, patients who underwent stenting were more likely to
151
be younger (P = .041), non-White (P < .0001), admitted non-electively (P < .0001), and have
152
shorter length of stay (P=.015). Patients who underwent stenting had greater numbers of
153
comorbidities, such as CHF (P < .0001), PVD (P = .004), hemiplegia and paraplegia (P = .011),
154
and renal disease (P = .014), relative to patients who underwent endarterectomy (Table II).
155
3.2 30-day readmission
156 157
AC C
EP
TE D
145
Table III presents the results of the logistic regression model of 30-day readmission, controlling for covariates. There was no statistically significant difference in likelihood of
ACCEPTED MANUSCRIPT 8 readmission based on intervention alone. However, there was a significantly lower likelihood of
159
readmission of patients of non-white and non-black race (odds ratio [OR] 0.49, 95% CI 0.24-
160
0.98). There was a significantly higher likelihood of readmission of patients admitted emergently
161
(OR 1.35, 95% CI 1.02-1.79) or discharged to a facility other than home (OR 1.71, 95% CI 1.33-
162
2.20). Having hemiplegia or paraplegia (OR 2.18, 95% CI 1.17-4.08), renal disease (OR 1.75,
163
95% CI 1.30-2.34), and cancer (OR 2.19, 95% CI 1.17-4.10) prior to discharge were
164
significantly associated with greater risk of readmission when all receiving CEA and CAS were
165
considered jointly. Fig. 1 presents the odds ratios of readmission, comparing covariates when
166
patients were segregated according to intervention. When modeled against each other, CAS
167
patients were more likely than similar CEA patients to be readmitted if they were older than 80
168
years old or female. They were less likely than similar CEA patients to be readmitted if they had
169
a history of hemiplegia or paraplegia. There were no covariates for which CEA patients were
170
more likely to be readmitted relative to comparable CAS patients.
173
SC
M AN U
TE D
172
Coefficients generated from logistic regression were used to create a predictive model for readmission using equation 1.
EP
171
RI PT
158
(1)
The probability of readmission following carotid intervention can be estimated for any patient
175
following either CEA or CAS, provided a complete profile of information on age, sex, race,
176
admission type, payer type, discharge destination, and pre-existing comorbidities. For example,
177
the probability of readmission for a 75-year-old Hispanic female with Medicare and a history of
178
diabetes and congestive heart failure admitted electively and discharged with home health care
179
following CAS would be:
AC C
174
ACCEPTED MANUSCRIPT 9
(2)
180
where the values in equation 2 are the coefficients found in Table III. Therefore, the probability
182
of readmission would be 0.0796 or 7.96% following discharge. Note that coefficients for
183
reference variables are not included in the computation of risk of readmission since they are
184
already captured in the intercept term.
Primary diagnoses for readmission are presented in Table IV. After categorization of
SC
185
RI PT
181
primary readmission diagnoses, both CEA and CAS patients were most often readmitted
187
secondary to cerebrovascular etiologies (CEA 23.41%, CAS 30.76%). Central cardiovascular-
188
related diagnoses (e.g. coronary atherosclerosis, atrial fibrillation) accounted for the next largest
189
proportion of readmission diagnoses for both intervention groups (CEA 20.78%, CAS 23.06%).
190
In spite of the known presence of vascular disease inherent to patients with carotid artery
191
stenosis, patients were less frequently readmitted for peripheral vascular-related diagnoses (CEA
192
4.45%, CAS 5.12%). Post-procedural complications accounted for 8.68% of readmissions
193
following CEA and 7.68% of readmissions following CAS.
194
3.3 Survival Analysis
TE D
EP
195
M AN U
186
Results of Kaplan-Meier analysis are presented in Fig. 2. Of those patients who were readmitted within 30 days, time to readmission was not significantly different between those who
197
underwent endarterectomy and those who underwent stenting (P = .19).
198
4. DISCUSSION
199
AC C
196
In our study of 30-day readmissions, we found no statistically significant difference in
200
30-day readmission rates between patients who underwent CEA and CAS. Moreover, odds of
201
readmission were similar between patients undergoing either intervention, as was time to
202
readmission within 30 days. When the intervention groups were modeled as a single sample, the
ACCEPTED MANUSCRIPT 10 odds of readmission were greater if patients were admitted emergently, discharged to a
204
destination other than home, or had a history of hemiplegia or paraplegia, renal disease, or
205
cancer. Other (non-white, non-black) race was protective for readmission. When risk was
206
modeled separately for CEA and CAS patients, we found that risk factors for readmission were
207
similar for both procedures, with few exceptions. CAS patients were more likely than CEA
208
patients to be readmitted if they were older than 80 years old or female but less likely than CEA
209
patients to be readmitted if they had histories of hemiplegia or paraplegia. When studying the
210
CEA sample separately, none of the observed covariates were associated with significantly
211
different risk of readmission relative to the CAS sample. Primary diagnoses for readmission were
212
predominantly cerebrovascular and cardiovascular for patients who underwent CEA and CAS,
213
with diagnoses unambiguously related to post-procedural complications ranking third and fourth,
214
respectively, in frequency of readmission diagnoses.
M AN U
SC
RI PT
203
Most previous studies of readmission rates following CEA report a rate between 6% and
216
11.2%, which is consistent with the estimate of readmission of 9.4% in our patient population.14-
217
19
218
previously published estimates. Galinanes et al. report a 30-day readmission rate of 11.11%, a
219
0.31 percentage point difference relative to the present study that may be of limited clinical
220
significance.14 Yet, our finding of no statistically significant difference in periprocedural
221
readmission between CEA and CAS is in contrast to the Galinanes study, which showed
222
significantly greater readmission rates after CAS relative to CEA at 30, 60, and 90 days
223
following interventions.14 Although both our study and Galinanes et al. demonstrated higher
224
absolute readmission rates for CAS relative to CEA, the difference between studies in
225
statistically significant findings may illustrate the variation in practice patterns, and therefore
TE D
215
AC C
EP
The readmission rate of 10.8% following CAS in our data was marginally lower than
ACCEPTED MANUSCRIPT 11 thresholds for readmission, across a national sample as in Galinanes et al. and a statewide sample
227
in the present study. Like the present study, although not in patients undergoing carotid
228
intervention specifically, other studies have failed to detect a consistent statistically significant
229
benefit of open vascular surgery relative to endovascular techniques with respect to readmission
230
rates.20,21
RI PT
226
Our study found that for all carotid interventions, the odds of readmission were lower in
232
patients who were in the “other” race category, which is consistent with previous studies.14,17,22
233
Also similar to previous studies, we found that patients admitted on an emergent basis or
234
discharged to a destination other than home were more likely to be readmitted within 30
235
days.13,15,23 With regard to patient comorbidities, many studies identify comorbidities
236
contributing to readmission in general, but fewer have investigated comorbidities that affect
237
readmission following carotid intervention.14-16,18,24 In an analysis of Medicare claims data,
238
Jencks et al. identified the majority of their studied comorbidities, including congestive heart
239
failure, chronic obstructive pulmonary disease, diabetes mellitus, coagulopathy, peripheral
240
vascular disease, pulmonary disease and renal disease, as contributors to greater odds of
241
readmission.25 We found, among a population of patients of all ages undergoing carotid
242
intervention, history of hemiplegia or paraplegia, renal disease and cancer were significantly
243
associated with greater odds of 30 day readmission. The present study is consistent with previous
244
studies looking at CEA, if not both CEA and CAS, exclusively.14-16,18
M AN U
TE D
EP
AC C
245
SC
231
A further analysis of risk factors for readmission, stratified according to intervention
246
type, interestingly demonstrated that age over 80 years old and female gender contributed to a
247
greater likelihood of readmission for patients undergoing CAS, but not for those undergoing
248
CEA. A history of hemiplegia or paraplegia was actually associated with lower odds of
ACCEPTED MANUSCRIPT 12 readmission following CAS. This finding may suggest a synergistic effect between a baseline
250
level of elevated risk, such as in CAS patients, and an incapacitating neurologic deficit, thereby
251
increasing the likelihood of a highly supportive home environment capable of managing post-
252
procedure sequelae, which might otherwise be cause for readmission. Yet although it is plausible
253
that those with a history of hemiplegia or paraplegia have a strong established support system, it
254
is also plausible that the protective role of hemiplegia or paraplegia is a spurious artifact born
255
from multivariable analysis on a large data set.26
SC
256
RI PT
249
When reasons for readmission were identified, cerebrovascular and central cardiovascular diagnoses accounted for approximately half of all diagnoses for 30-day readmission among
258
patients who underwent either CEA or CAS. Reasons for readmission that were unambiguously
259
procedure-related comprised only 8.68% and 7.68% of all readmission diagnoses for CEA and
260
CAS patients, respectively. While it may be expected that patients requiring carotid intervention
261
for carotid artery stenosis also have extensive cardiovascular pathology for which subsequent
262
hospital admissions would be warranted, readmission diagnoses related to peripheral vascular
263
diagnoses comprised only 4.45% of readmission diagnoses for CEA patients and 5.12% of
264
readmission diagnoses for CAS patients. Previous studies of patients undergoing carotid
265
intervention corroborate the finding of cardiac-related diagnoses as the most common cause of
266
unplanned readmission.14,16
TE D
EP
AC C
267
M AN U
257
Readmission diagnoses that are unequivocally associated with the index procedure are of
268
particular interest to providers as they represent an opportunity for preemptive intervention. In an
269
analysis of 30-day readmission diagnoses for all patients who underwent any inpatient surgery
270
within the Veterans Health Administration, patients who underwent peripheral vascular surgery
271
were most often readmitted for infection, commonly of an implanted prosthesis or otherwise
ACCEPTED MANUSCRIPT 13 localized to the surgical site.27 In the current study, however, post-procedural complications,
273
including infection, did not predominate among readmission diagnoses for patients undergoing
274
either CEA or CAS, whereas cardiovascular and cerebrovascular causes were more commonly
275
implicated in unplanned readmissions following both interventions. This may be related to the
276
typically clean nature of neck procedures and surgical wounds. Unfortunately, we were limited
277
in knowing whether patients with cerebrovascular-related diagnosis codes, which described the
278
most common readmission diagnoses, were actually readmitted for complications directly related
279
to their carotid interventions. The ambiguity in ICD-9-CM coding limits our confidence in the
280
reliability of readmission diagnoses.
SC
M AN U
281
RI PT
272
This is a retrospective analysis of administrative data, which carries some inherent limitations. First, there are variables that were not available in the data set that may be potential
283
confounders and could not be controlled. For example, presence and severity of neurologic
284
symptoms upon presentation at index admission is not captured in the PHC4 dataset, although it
285
may modulate relationships between predictive factors and readmission. Information on
286
preoperative functional status was also not part of the dataset. This additional information could
287
have potentially informed expectations for patient convalescence and likelihood of readmission.
288
Second, many of our variables, including the identification of CEA and CAS procedures, were
289
identified using diagnosis and procedure codes. There is always the potential for coding errors,
290
although it is unlikely that such errors would be systematic. Third, the PHC4 data set includes
291
only inpatient admission to acute care hospitals in Pennsylvania, which may not be
292
representative of all patients undergoing carotid interventions. Because patients are not tracked
293
beyond state borders, readmission to a non-Pennsylvania hospital would be outside of the scope
294
of this data set because of geographic limitations. Moreover, specific data regarding primary
AC C
EP
TE D
282
ACCEPTED MANUSCRIPT 14 295
diagnosis for readmission may not be reliably reported and coded, contributing to ambiguity
296
regarding the relationship between carotid intervention and readmission.
297
5. CONCLUSION We conclude based on this statewide analysis of discharge data that 30-day readmission
RI PT
298
rates are similar for patients undergoing CEA and CAS. Other factors, however, are related to
300
readmission for both procedures, such as urgency of admission and comorbidities. Thirty-day
301
readmissions have been under more intense scrutiny since the HRRP in 2010.9 Given the
302
forthcoming expansion of penalties for readmissions to include those within 30 days after
303
vascular surgery, it is crucial to determine targets for change for patients undergoing CEA and
304
CAS.8,11,12 Future efforts should be directed toward elucidating costs associated with
305
readmission, determining readmission and complication rates over a longer post-operative
306
interval, and ultimately, assessing the effectiveness of interventions to reduce readmissions in
307
this patient population.
M AN U
TE D EP AC C
308
SC
299
ACCEPTED MANUSCRIPT 15 309
REFERENCES
310
[1]
Yoon PW, Bastian B, Anderson RN, Collins JL, Jaffe HW. Potentially preventable deaths from the five leading causes of death--United States, 2008-2010. MMWR Morb Mortal
312
Wkly Rep 2014;63:369-74.
313
[2]
RI PT
311
Luengo-Fernandez R, Paul NL, Gray AM, Pendlebury ST, Bull LM, Welch SJ, et al. Population-based study of disability and institutionalization after transient ischemic
315
attack and stroke: 10-year results of the Oxford Vascular Study. Stroke 2013;44:2854-61.
316
[3]
SC
314
Koton S, Schneider AL, Rosamond WD, Shahar E, Sang Y, Gottesman RF, et al. Stroke incidence and mortality trends in US communities, 1987 to 2011. JAMA 2014;312:259-
318
68.
319
[4]
M AN U
317
North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis.
321
N Engl J Med 1991;325:445-53.
322
[5]
TE D
320
MRC European Carotid Surgery Trial: interim results for symptomatic patients with severe (70-99%) or with mild (0-29%) carotid stenosis. European Carotid Surgery
324
Trialists' Collaborative Group. Lancet 1991;337:1235-43. [6]
Asymptomatic Carotid Atherosclerosis Study. JAMA 1995;273:1421-8.
326 327
[7]
neurological symptoms: randomised controlled trial. Lancet 2004;363:1491-1502.
329
331
Halliday A, Mansfield A, Marro J, Peto C, Peto R, Potter J, et al. Prevention of disabling
and fatal strokes by successful carotid endarterectomy in patients without recent
328
330
Endarterectomy for asymptomatic carotid artery stenosis. Executive Committee for the
AC C
325
EP
323
[8]
Prabhakar AM, Harvey HB, Oklu R. Thirty-day hospital re-admissions: a metric that matters. J Vasc Interv Radiol 2013;24:1509-11.
ACCEPTED MANUSCRIPT 16 332
[9]
Centers for Medicare & Medicaid Services. Readmissions Reduction Program, http://www.cms.gov/Medicare/Medicare-Fee-for-Service-
334
Payment/AcuteInpatientPPS/Readmissions-Reduction-Program.html [accessed
335
08/21/2014].
336
[10]
RI PT
333
Centers for Medicare & Medicaid Services. CMS-1607-P, Proposed Rule, http://www.cms.gov/Medicare/Medicare-Fee-for-Service-
338
Payment/AcuteInpatientPPS/FY2015-IPPS-Proposed-Rule-Home-Page-Items/FY2015-
339
IPPS-Proposed-Rule-Regulations.html [accessed 04/15/2015].
SC
337
[11]
Kamerow D. Reassessing hospital readmission penalties. BMJ 2013;346:f1043.
341
[12]
Gonzalez AA, Girotti ME, Shih T, Wakefield TW, Dimick JB. Reliability of hospital readmission rates in vascular surgery. J Vasc Surg 2014;59:1638-43.
342
[13]
ICD-9-CM administrative databases. J Clin Epidemiol 1992;45:613-9.
344 345
Deyo RA, Cherkin DC, Ciol MA. Adapting a clinical comorbidity index for use with
[14]
TE D
343
M AN U
340
Galinanes EL, Dombroviskiy VY, Hupp CS, Kruse RL, Vogel TR. Evaluation of readmission rates for carotid endarterectomy versus carotid artery stenting in the US
347
Medicare population. Vasc Endovascular Surg 2014;48:217-23. [15]
readmissions after vascular surgery. J Vasc Surg 2014;59:473-82.
349 350 351 352
Gupta PK, Fernandes-Taylor S, Ramanan B, Engelbert TL, Kent KC. Unplanned
[16]
AC C
348
EP
346
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.
ACCEPTED MANUSCRIPT 17 353
[17]
Kennedy BS, Fortmann SP, Stafford RS. Elective and isolated carotid endarterectomy:
354
health disparities in utilization and outcomes, but not readmission. J Natl Med Assoc
355
2007;99:480-8.
Readmission After Carotid Endarterectomy. World Neurosurg 2013;82:e771-e776.
357
[19]
length of stay, and readmission rates in high-risk surgery. Ann Surg 2003;238:161-7.
359 360
[20]
Casey K, Hernandez-Boussard T, Mell MW, Lee JT. Differences in readmissions after open repair versus endovascular aneurysm repair. J Vasc Surg 2013;57:89-95.
361 362
Goodney PP, Stukel TA, Lucas FL, Finlayson EV, Birkmeyer JD. Hospital volume,
SC
358
Rambachan A, Smith TR, Saha S, Eskandari MK, Bendok BR, Kim JY. Reasons for
RI PT
[18]
[21]
M AN U
356
Holt PJ, Poloniecki JD, Hofman D, Hinchliffe RJ, Loftus IM, Thompson MM. Re-
363
interventions, readmissions and discharge destination: modern metrics for the assessment
364
of the quality of care. Eur J Vasc Endovasc Surg 2010;39:49-54.
Medicare beneficiaries by race and site of care. Ann Surg 2014;259:1086-90.
366
[23]
and surgical outcomes: it is not all black and white. Ann Surg 2008;248:647-55.
368 369
[24]
years of a statewide database. J Vasc Surg 2008;48:343-50; discussion 350.
371
373
Nazarian SM, Yenokyan G, Thompson RE, Griswold ME, Chang DC, Perler BA. Statistical modeling of the volume-outcome effect for carotid endarterectomy for 10
370
372
Esnaola NF, Hall BL, Hosokawa PW, Ayanian JZ, Henderson WG, Khuri SF, et al. Race
EP
367
Tsai TC, Orav EJ, Joynt KE. Disparities in surgical 30-day readmission rates for
TE D
[22]
AC C
365
[25]
Jencks SF, Williams MV, Coleman EA. Rehospitalizations among patients in the
Medicare fee-for-service program. N Engl J Med 2009;360:1418-28.
ACCEPTED MANUSCRIPT 18 374
[26]
Schonberger RB, Gilbertsen T, Dai F. The problem of controlling for imperfectly
375
measured confounders on dissimilar populations: a database simulation study. J
376
Cardiothorac Vasc Anesth 2014;28:247-54.
378
[27]
Han S, Smith TS, Gunnar W. Descriptive analysis of 30-day readmission after inpatient
RI PT
377
surgery discharge in the veterans health administration. JAMA Surg 2014;149:1162-68.
AC C
EP
TE D
M AN U
SC
379
ACCEPTED MANUSCRIPT 19 Table I. Comparison of baseline demographic and clinical data of all patients undergoing carotid intervention stratified by intervention type CEA CAS Variable (n = 3,640) (n = 679) P value Age 0.041 18-64 23.9% 25.2% 65-74 36.0% 39.2% 75-79 18.5% 16.2% 80+ 21.6% 19.4% Sex 0.443 Male 58.2% 59.8% Female 41.8% 40.2% Race <0.0001 White 94.6% 86.3% Black 2.8% 4.7% Other 2.6% 9.0% Admission type <0.0001 Elective 79.4% 72.0% Urgent 6.8% 13.4% Emergent 13.8% 14.6% Payer type 0.056 Medicare 74.4% 70.7% Commercial 20.6% 23.9% Selfpay 0.3% 0.1% HMO 33.6% 28.9% Discharge destination 0.213 Home 82.5% 85.0% SNF 4.2% 4.9% Home health Care 13.2% 10.2% Other 0.0% 0.0% LOS 2.71 2.36 0.015 HMO: Health maintenance organization; SNF: Skilled nursing facility; LOS: Length of stay
382 383
AC C
EP
TE D
M AN U
SC
RI PT
380 381
ACCEPTED MANUSCRIPT 20 Table II. Comparison of baseline comorbidities of all patients undergoing carotid intervention stratified by intervention type CEA CAS Variable (n = 3,640) (n = 679) P value AMI 12.0% 11.3% 0.652 CHF 5.5% 9.4% <0.0001 PVD 15.1% 19.6% 0.004 COPD 20.3% 21.4% 0.543 Diabetes 31.9% 33.4% 0.423 HP/PAPL 1.2% 2.5% 0.011 Renal Dz 9.5% 12.5% 0.014 Cancer 1.5% 1.9% 0.438 AMI: Acute myocardial infarction; CHF: Congestive heart failure; PVD: Peripheral vascular disease; COPD: Chronic obstructive pulmonary disease; HP/PAPL: Hemiplegia or Paraplegia
M AN U TE D EP AC C
386 387 388 389
SC
RI PT
384 385
ACCEPTED MANUSCRIPT
21
AC C
EP
TE D
M AN U
SC
RI PT
Table III. Results of a logistic regression model of intervention type on 30-day readmission, controlling for other covariates (area under ROC curve = 0.6262) 95% Confidence Variable Odds Ratio Coefficient Lower Upper P value Intervention CEA REFERENCE Stent 1.15 0.14 0.88 1.52 0.310 Age 18-64 REFERENCE 65-74 1.16 0.14 0.83 1.60 0.385 75-79 1.12 0.11 0.77 1.63 0.549 80+ 1.20 0.18 0.83 1.73 0.326 Sex Male REFERENCE Female 1.15 0.14 0.93 1.42 0.191 Race White REFERENCE Black 1.19 0.17 0.69 2.02 0.533 Other 0.49 -0.72 0.24 0.98 0.043 Admission Type Elective REFERENCE Urgent 1.21 0.19 0.84 1.73 0.314 Emergent 1.35 0.30 1.02 1.79 0.036 Payer type Medicare REFERENCE Commercial 1.06 0.06 0.77 1.47 0.716 Selfpay 0.84 -0.18 0.10 6.82 0.867 HMO 1.03 0.03 0.83 1.28 0.796
ACCEPTED MANUSCRIPT
22
AC C
EP
TE D
M AN U
SC
RI PT
Discharge destination Home REFERENCE Other 1.71 0.54 1.33 2.20 <0.0001 Comorbidities AMI 1.09 0.09 0.80 1.49 0.566 CHF 1.10 0.10 0.75 1.63 0.613 PVD 1.15 0.14 0.88 1.51 0.314 COPD 1.26 0.23 0.99 1.62 0.060 DM 1.10 0.10 0.89 1.37 0.376 HP/PAPL 2.18 0.78 1.17 4.08 0.015 Renal Disease 1.75 0.56 1.30 2.34 <0.0001 Cancer 2.19 0.78 1.17 4.10 0.014 HMO: Health maintenance organization; AMI: Acute myocardial infarction; CHF: Congestive heart failure; PVD: Peripheral vascular disease; COPD: Chronic obstructive pulmonary disease; DM: Diabetes mellitus; HP/PAPL: Hemiplegia or Paraplegia
ACCEPTED MANUSCRIPT 23
AC C
EP
TE D
M AN U
SC
RI PT
Table IV. Comparison of primary diagnoses for 30-day readmission stratified by intervention type CEA CAS Primary Diagnosis (n = 3,910) (n = 415) Cerebrovascular 23.41% 30.76% Cardiovascular, Central 20.78% 23.06% Procedure-related Complication 8.68% 7.68% Pulmonary 8.39% 6.41% Genitourinary 5.51% 8.97% Cardiovascular, Peripheral 4.45% 5.12% Gastrointestinal 6.01% 6.40% Neurologic 3.93% 5.12% Endocrine 2.62% 1.28% Hematologic 5.52% 1.28% Other 7.04% 3.84%
ACCEPTED MANUSCRIPT 24 FIGURE LEGENDS Fig. 1. Forest plot for relation between carotid intervention and odds of readmission. Relative to similar CEA patients, CAS patients were more likely to be readmitted if they were older than 80
RI PT
years old or female, but less likely to be readmitted if they had a history of hemiplegia or
paraplegia. There were no covariates for which CEA patients were more likely to be readmitted relative to comparable CAS patients.
SC
Fig. 2. Time to readmission for patients undergoing carotid intervention based on intervention type. Of those patients who were readmitted within 30 days, there was no statistically significant
M AN U
difference in time to readmission between those who underwent endarterectomy and those who
AC C
EP
TE D
underwent stenting.
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT