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Impact of Annual Hospital Volume on Outcomes after Left Ventricular Assist Device (LVAD) Implantation in the Contemporary Era
Accepted Manuscript Title: Impact of Annual Hospital Volume on Outcomes after Left Ventricular Assist Device (LVAD) Implantation in the Contemporary Era Author: Neeraj Shah, Ankit Chothani, Vratika Agarwal, Abhishek Deshmukh, Nileshkumar Patel, Jalaj Garg, Apurva Badheka, Matthew Martinez, Nauman Islam, Ronald Freudenberger PII: DOI: Reference:
S1071-9164(15)01169-0 http://dx.doi.org/doi:10.1016/j.cardfail.2015.10.016 YJCAF 3659
To appear in:
Journal of Cardiac Failure
Received date: Revised date: Accepted date:
9-6-2015 28-9-2015 6-10-2015
Please cite this article as: Neeraj Shah, Ankit Chothani, Vratika Agarwal, Abhishek Deshmukh, Nileshkumar Patel, Jalaj Garg, Apurva Badheka, Matthew Martinez, Nauman Islam, Ronald Freudenberger, Impact of Annual Hospital Volume on Outcomes after Left Ventricular Assist Device (LVAD) Implantation in the Contemporary Era, Journal of Cardiac Failure (2015), http://dx.doi.org/doi:10.1016/j.cardfail.2015.10.016. 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.
Impact of Annual Hospital Volume on Outcomes after Left Ventricular Assist Device (LVAD) Implantation in the Contemporary Era Neeraj Shah MD, MPH1, Ankit Chothani MD2, Vratika Agarwal MD3, Abhishek Deshmukh MD4, Nileshkumar Patel MD5, Jalaj Garg MD1, Apurva Badheka MD6, Matthew Martinez MD, FACC1, Nauman Islam MD, FACC1, Ronald Freudenberger MD, FACC1 Affiliations: 1
Department of Cardiology, Lehigh Valley Health Network, PA
2
Department of Cardiology, Mount Sinai St. Luke’s Roosevelt Hospital, NY
3
Department of Cardiology, Staten Island University Hospital
4
Department of Cardiology, Mayo Clinic, MN
5
Department of Cardiology, University of Miami, FL
6
Department of Cardiology, Everett Clinic, WA
Corresponding Author: Neeraj Shah, MD, MPH, Department of Cardiology, Lehigh Valley Health Network, 1250 S Cedar Crest Blvd, Allentown, PA 18103. E-mail: [email protected], Tel: 914-826-1033. Disclosures: None of the authors have any conflicts of interest. Keywords: Left Ventricular Assist Device (LVAD), Continuous Flow Devices, Annual hospital volume Word Count in Abstract: 214, Word Count in Manuscript: 1,569 Running title: Shah et al Annual hospital LVAD volume and outcomes
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Abbreviation List: LVAD: Left Ventricular Assist Device DT: Destination Therapy BTT: Bridge to Transplant NIS: Nationwide Inpatient Sample CHF: Congestive Heart Failure HCUP: Healthcare Cost and Utilization Project FDA: Food and Drug Administration CMS: Centers for Medicare and Medicaid VIF: Variance Inflation Factor OR: Odds ratio CI: Confidence Interval INTERMACS: Interagency Registry for Mechanical Assisted Circulatory Support NYHA: New York Heart Association MI: Myocardial Infarction CABG: Coronary Artery Bypass Grafting
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Highlights:
Increased annual hospital LVAD implantation volume predicts decreased in-hospital mortality and length of stay
An optimal volume threshold of 20 or more LVAD implantations per year is associated less than 10% in-hospital mortality
Improved outcomes at high volume centers may be due to early identification of patients, and improved surgical, postoperative care and long term follow up
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Abstract: Introduction: There is paucity of data in the literature regarding impact of annual hospital volume on outcomes such as mortality and length of stay (LOS) post LVAD implantation. Methods: We queried the nationwide inpatient sample from 2008-2011 using ICD-9 procedure code 37.66. We included patients >18 years without primary diagnosis of orthotopic heart transplant. Annual volume of LVAD implantation was computed for each hospital. Multivariable hierarchical mixed effect logistic regression models were used to determine predictors of inhospital mortality and LOS. Results: There were 1,749 LVAD implants from 2008 to 2011 with a mean age of 55.4 years and 23% females. In-hospital mortality decreased from 20.9% in first tertile (1-22 LVADs/year) to 13.7% in third tertile (> 35 LVADs/year) of hospital volume. Median LOS decreased from 34 days in first tertile to 28 days in third tertile of hospital volume. The adjusted ORs of the highest tertile of hospital volume in predicting in-hospital mortality and LOS were respectively 0.41 (0.26-0.64, p<0.001) & 0.41 (0.23-0.73, p = 0.003). Restricted cubic spline analysis showed that a volume threshold of >20 LVADs/year was associated with favorable mortality rates of <10%. Conclusions: High annual LVAD volume is associated with significantly decreased in-hospital mortality and LOS after LVAD implantation. Center experience is an important determinant of optimal patient outcomes.
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Introduction: The REMATCH trial (1998-2001) (1) showed that left ventricular assist devices (LVADs) as destination therapy (DT) improved survival compared to medical therapy alone in patients with advanced heart failure. Second generation continuous flow LVADs are smaller and non-pulsatile, compared to bulky first generation pulsatile flow devices. These devices used as DT or bridge to transplant (BTT) improve survival, hemodynamic support and quality of life (25). Thoratec HeartMate II and HeartWare HVAD are the FDA approved continuous flow devices for adults (6). Recent Interagency Registry for Mechanical Assisted Circulatory Support (INTERMACS) reports show survival rates of 80% and 70% at one and two years respectively with these devices (6). Since 2008, predominantly continuous flow devices are implanted in US (6, 7). There is paucity of data on the optimal number of LVADs to be performed by an institution. Latest facility criteria for LVAD recommend at least 10 LVAD implantations over a 36 month period (8, 9). Studies examining the relationship between hospital volume and mortality after LVAD implantation have shown varying volume cut offs (10-13). Our objective was to determine an optimal hospital volume threshold for LVAD implantation using Nationwide Inpatient Sample (NIS) database from 2008-2011. Methods NIS is the largest available all-payer database of hospital inpatient stays in US, containing an approximate 20% stratified sample of US hospitals. For detailed information regarding NIS, kindly refer to the Supplementary Appendix.
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Study design: We queried the NIS from 2008 to 2011 using International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) procedure code 37.66, Insertion of Implantable Heart Assist System. All patients > 18 years of age without a primary procedure code of orthotopic heart transplantation (37.5, 37.51 or 33.6) were included in the study. Individual comorbid conditions relevant to patients receiving LVADs in our study were identified using ICD-9 diagnoses or procedure codes. A prior study from NIS on short term mechanical circulatory support used Elixhauser comorbidity index derived from ICD-9 codes (14). Detailed descriptions and ICD-9 codes used to identify comorbidities have been listed in Supplementary Appendix. Preventable procedural complications were identified by Patient Safety Indicators (PSIs), v4.4, March 2012 (http://www.qualityindicators.ahrq.gov/modules/PSI_TechSpec.aspx) and specific ICD-9 diagnoses and/or procedure codes in the secondary diagnoses fields. Detailed descriptions regarding procedural complications are listed in Supplementary Appendix. Annual hospital volume was determined on a yearly basis. Unique hospital identification number was used to calculate the total number of procedures performed by a particular institution in a given year, which was considered as the annual LVAD volume of that institution for that year. Hospital volume was divided into tertiles for further analysis. The total duration of hospital stay in days was estimated for all patients, excluding those who died in the hospital, using the length of stay (LOS) information in the dataset.
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Statistical analysis: Stata SE 13.1 (StataCorp, College Station, TX) was utilized for all analyses, accounting for complex survey design and clustering. Hierarchical mixed effects logistic models were generated in order to identify multivariable predictors of in-hospital mortality & LOS (divided into two categories based on the median). Two level hierarchical models (with patient level factors nested within hospital level factors) were created with hospital identification number incorporated as random effects within the model, to account for clustering. Variables with >10% missing data (e.g. race) were not included in multivariable models. All interactions were thoroughly tested. Multicollinearity was assessed using variance inflation factor (VIF). No significant interactions were found and VIF was less than 5 for all covariates suggesting no significant correlation between the predictor variables. Restricted cubic splines were generated assuming a non-linear relationship between hospital volume and in-hospital mortality. The cubic splines were adjusted for the same covariates that were included in the multivariable models (Tables 2 & 3). Cubic knots were set at 5, 10, 25 and 45 annual LVAD implantations per year. Results: There were 1,749 LVAD implantations from 2008-2011. Table 1 shows the demographic characteristics and outcomes in the entire study population divided into hospital volume tertiles (tertile 1 is 1-22 LVADs/year, tertile 2 is 23-34 LVADs/year, and tertile 3 is > 35 LVADs/year). Demographics:
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Mean age of the population was 55.4 years, with 23% females and 66.2% Caucasians (Table 1). The mean length of stay was 37.1 days and median LOS was 30 days. Overall inhospital mortality was 15.9%. The median annual hospital volume was 28 LVADs per year (range: 1-70 procedures/year). The third tertile of annual hospital volume (> 35 LVADs/year) had a higher prevalence of hypertension, diabetes mellitus, chronic ischemic heart disease, history of CABG, ischemic etiology of cardiomyopathy, and pre-existing renal dysfunction (Table 1). The third tertile of hospital volume also had a higher incidence of major bleeding and acute renal failure, and a trend towards lower incidence of iatrogenic cardiac and other complications. Predictors of in-hospital mortality: Age > 65 years, acute myocardial infarction, acute renal failure, infection, major bleeding, iatrogenic cardiac complications and thromboembolism were significant predictors of increased in-hospital mortality, whereas teaching hospital status and increasing annual hospital volume were significant predictors of decreased in-hospital mortality (Table 2). Annual hospital volume & in-hospital mortality: The unadjusted in-hospital mortality rates in the three categories of hospital volume were respectively 20.9% for 1-22 LVADs/year, 12.6% for 23-34 LVADs/year and 13.7% for > 35 LVADs/year. The adjusted odds ratios (OR) of mortality (95% confidence interval, p) for the second and third tertiles of annual hospital volume were respectively 0.50 (0.34-0.73, p<0.001) and 0.41 (0.26-0.64, p<0.002) [Table 2].
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Figure 1 shows that there is a sharp decline in mortality with increasing annual hospital LVAD volume until an optimal volume threshold of 20 LVADs per year, after which there is no additional mortality benefit. Annual hospital volume & length of stay: Mean LOS decreased from 42.8 days in the first tertile to 33.2 days in the third tertile of hospital volume, and median LOS decreased from 34.0 days in the first tertile to 28.0 days in the third tertile of hospital volume (p<0.001). Age > 65 years, acute MI and periprocedural complications were significant predictors of LOS greater than median (Table 3). Third tertile of hospital volume was a predictor of decreased LOS with adjusted OR (95% CI, p) of 0.41 (0.230.73, p = 0.003). Discussion: A study from Thoratec HeartMate registry from 1998-2005 using pulsatile flow devices showed that centers with > 9 DT implants had improved 1 year survival (10). INTERMACS reports do not identify hospital volume as a mortality predictor; however, it is unclear if their risk models were adjusted for hospital volume (6). A study (11) using data from University Health Consortium Chicago from 2008-2012 showed decrease in in-hospital mortality with increasing annual hospital LVAD volume quartiles. Cowger et al showed that center volume of <15 procedures predicted higher 90 day mortality (12). Another study involving Medicare beneficiaries from 2006-2011 showed that centers implanting > 9 LVADs/year had improved outcomes (13). However, none of these studies employed cubic spline analysis to identify an optimal volume threshold.
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Our study reaffirms that increasing annual hospital LVAD volume is a predictor of decreased in-hospital mortality (11, 12). Moreover, the median mortality free length of stay was shorter by 6 days in patients in the third tertile of hospital volume (>= 35 procedures per year) compared to the first tertile, indirectly suggesting relatively faster patient recovery at high volume centers. The most important finding of our study is identification of an optimal volume threshold of 20 LVADs/year, associated with <10% in-hospital mortality (Figure 1). The lack of benefit beyond 20 LVADs/year maybe because very high volume centers are major tertiary care referral centers, caring for of critically ill advanced heart failure patients and any further mortality benefit is offset by the critical illness of these patients. This may also be the baseline mortality risk of end-stage heart failure patients undergoing LVAD implantation. An optimal annual hospital volume of >20 LVADs/year is considerably larger than the current criterion of > 10 LVADs over 3 years (9). Performing >20 LVADs/year would entail several logistic challenges. That being said, in our study overall 69% of LVADs (79.2% in 2011, compared to 47.8% in 2008) were performed in hospitals implanting >20 LVADs/year. With advancing technology and increasing experience, more centers would be able to attain this goal. It is difficult to establish a causal relationship between high LVAD volumes and outcomes. Lietz et al showed that patients in high volume centers had a lower overall preoperative risk score (10). Favorable outcomes seen in high volume centers may be due to better patient selection processes and appropriate referral systems leading to early identification of end-stage heart failure patients for advanced therapy. Better preoperative screening, surgical & postoperative care and long term follow up post LVAD implantation lead to improved outcomes at highly experienced centers (10).
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Limitations: Being an administrative database, NIS is susceptible to errors arising from coding inaccuracies. Inability to track patients after discharge and cross sectional nature of the database precludes assessment of long term outcomes. Due to a lack of ICD-9 codes, we could not identify the type of device implanted, DT vs. BTT, incidence of right ventricular failure or INTERMACS risk profiles. NIS does not have information on laboratory data, NYHA functional class, medications or echocardiography data. Conclusions: High annual LVAD volume is associated with significantly lower in-hospital mortality and length of stay post LVAD implantation, with an optimal volume threshold of >20 LVADs/year, suggesting that center volume is crucial for better care of these patients.
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References: 1.
Rose EA, Gelijns AC, Moskowitz AJ, Heitjan DF, Stevenson LW, Dembitsky W, et al.
Long-term use of a left ventricular assist device for end-stage heart failure. The New England journal of medicine. 2001;345(20):1435-43. Epub 2002/01/17. 2.
Slaughter MS, Rogers JG, Milano CA, Russell SD, Conte JV, Feldman D, et al.
Advanced heart failure treated with continuous-flow left ventricular assist device. The New England journal of medicine. 2009;361(23):2241-51. Epub 2009/11/19. 3.
Pagani FD, Miller LW, Russell SD, Aaronson KD, John R, Boyle AJ, et al. Extended
mechanical circulatory support with a continuous-flow rotary left ventricular assist device. Journal of the American College of Cardiology. 2009;54(4):312-21. Epub 2009/07/18. 4.
Holman WL, Naftel DC, Eckert CE, Kormos RL, Goldstein DJ, Kirklin JK. Durability of
left ventricular assist devices: Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) 2006 to 2011. The Journal of thoracic and cardiovascular surgery. 2013;146(2):437-41 e1. Epub 2013/03/16. 5.
Rogers JG, Aaronson KD, Boyle AJ, Russell SD, Milano CA, Pagani FD, et al.
Continuous flow left ventricular assist device improves functional capacity and quality of life of advanced heart failure patients. Journal of the American College of Cardiology. 2010;55(17):1826-34. Epub 2010/04/24. 12 Page 12 of 20
6.
Kirklin JK, Naftel DC, Pagani FD, Kormos RL, Stevenson LW, Blume ED, et al. Sixth
INTERMACS annual report: a 10,000-patient database. The Journal of heart and lung transplantation : the official publication of the International Society for Heart Transplantation. 2014;33(6):555-64. Epub 2014/05/27. 7.
Kirklin JK, Naftel DC, Kormos RL, Stevenson LW, Pagani FD, Miller MA, et al. The
Fourth INTERMACS Annual Report: 4,000 implants and counting. The Journal of heart and lung transplantation : the official publication of the International Society for Heart Transplantation. 2012;31(2):117-26. Epub 2012/02/07. 8.
Requirements for Ventricular Assist Device Destination Therapy Advanced Certification.
2014 [updated 1/17/20142/1/2015]; Prepublication Standards - Revisions to Ventricular Assist Device
Destination
Therapy
Requirements].
Available
from:
http://www.jointcommission.org/prepublication_standards_revisions_ventricular_assist_device_ destination_therapy_req/. 9.
Decision Memo for Ventricular Assist Devices for Bridge-to-Transplant and Destination
Therapy (CAG-00432R). Centers for Medicare & Medicaid Services; 2013 [updated 10/20132/1/2015];
Available
from:
http://www.cms.gov/medicare-coverage-
database/details/nca-decision-memo.aspx?NCAId=268. 10.
Lietz K, Long JW, Kfoury AG, Slaughter MS, Silver MA, Milano CA, et al. Impact of
center volume on outcomes of left ventricular assist device implantation as destination therapy: analysis of the Thoratec HeartMate Registry, 1998 to 2005. Circulation Heart failure. 2009;2(1):3-10. Epub 2009/10/08.
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11.
Feldman K, Doukky, R., Johnson T., Levine, D., Hohmann, S. Hospital Volume of
LVAD Procedures Determines Patient Outcome. Circ Cardiovasc Qual Outcomes. 2013;6(3 Supplement):A289. 12.
Cowger J, Sundareswaran K, Rogers JG, Park SJ, Pagani FD, Bhat G, et al. Predicting
survival in patients receiving continuous flow left ventricular assist devices: the HeartMate II risk score. Journal of the American College of Cardiology. 2013;61(3):313-21. Epub 2012/12/26. 13.
Khazanie P, Hammill BG, Patel CB, Eapen ZJ, Peterson ED, Rogers JG, et al. Trends in
the use and outcomes of ventricular assist devices among medicare beneficiaries, 2006 through 2011. Journal of the American College of Cardiology. 2014;63(14):1395-404. Epub 2014/02/04. 14.
Stretch R, Sauer CM, Yuh DD, Bonde P. National trends in the utilization of short-term
mechanical circulatory support: incidence, outcomes, and cost analysis. Journal of the American College of Cardiology. 2014;64(14):1407-15. Epub 2014/10/04.
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Figure Legends:
Figure 1: Adjusted restricted cubic spline showing the relationship between annual hospital LVAD volume and in-hospital mortality after LVAD implantation from 2008-2011. (The curve was adjusted for: age, gender, hypertension, diabetes mellitus, peripheral vascular disease, chronic ischemic heart disease, acute MI, history of CABG, history of other cardiac surgery, pre-existing renal dysfunction, major bleeding, infectious complications, iatrogenic cardiac complications, thromboembolic complications, acute renal failure, other complications, primary payer, hospital region, teaching hospital and hospital bed size)
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Overall Population (N = 1,749)
Hospital Volume Tertile 1 (1-22/yr) (N = 607)
Hospital Volume Tertile 2 (23-34/yr) (N = 618)
Hospital Volume Tertile 3 (> 35/yr) (N = 524)
p-value
Age in years (Mean + SD)
55.4 + 13.5
54.8 + 13.7
55.5 + 13.5
56.1 + 13.2
0.162
Female gender
397 (22.7%)
146 (24.1%)
147 (23.8%)
104 (19.9%)
0.176
Variable Demographics
Race
*
0.634 White
988 (66.2%)
333 (65.2%)
382 (67.0%)
273 (66.3%)
Black
300 (20.1%)
106 (20.7%)
118 (20.7%)
76 (18.4%)
Other
205 (13.7%)
72 (14.1%)
70 (12.3%)
63 (15.3%)
Hypertension
739 (42.3%)
237 (39.0%)
249 (40.3%)
258 (48.3%)
0.003
Diabetes Mellitus
440 (25.2%)
130 (21.4%)
164 (26.5%)
146 (27.9%)
0.028
Pre-existing renal dysfunction†
541 (30.9%)
139 (22.9%)
200 (32.4%)
202 (38.6%)
<0.001
Acute Myocardial Infarction
238 (13.6%)
93 (15.3%)
69 (11.2%)
76 (14.5%)
0.082
835 (47.7%)
256 (42.2%)
296 (47.9%)
283 (54.0%)
<0.001
139 (8.0%)
32 (5.3%)
60 (9.7%)
47 (9.0%)
0.01
917 (52.4%)
287 (47.3%)
322 (52.1%)
308 (58.8%)
0.001
27 (1.5%)
5 (0.8%)
16 (2.6%)
6 (1.2%)
0.029
70 (4.0%)
25 (4.1%)
21 (3.4%)
24 (4.6%)
0.587
Chronic ischemic heart disease
†
History of CABG §
Ischemic Cardiomyopathy History of other cardiac € surgery Peripheral vascular disease Primary Payer
0.014
Medicare/Medicaid
970 (55.7%)
319 (52.8%)
329 (53.6%)
322 (61.4%)
Private
689 (39.5%)
250 (41.4%)
253 (41.2%)
186 (35.5%)
Other
83 (4.8%)
35 (5.8%)
32 (5.2%)
16 (3.1%)
Major bleeding
310 (17.7%)
94 (15.5%)
80 (12.9%)
136 (26.0%)
<0.001
Infection
417 (23.8%)
148 (24.4%)
136 (22.0%)
133 (25.4%)
0.381
Cardiac complications
239 (13.7%)
98 (16.1%)
75 (12.1%)
66 (12.6%)
0.09
Thromboembolic complications
325 (18.6%)
100 (16.5%)
114 (18.5%)
111 (21.2%)
0.127
Acute renal failure Acute renal failure requiring dialysis
929 (53.1%)
297 (48.9%)
294 (47.6%)
338 (64.5%)
<0.001
132 (7.6%)
46 (7.6%)
50 (8.1%)
36 (6.7%)
0.738
Complications
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Other complications
335 (19.2%)
133 (21.9%)
111 (18.0%)
91 (17.4%)
0.099 <0.001
Disposition Home
1,098 (62.8%)
391 (64.4%)
432 (69.9%)
275 (52.6%)
Nursing home or other facility
372 (21.3%)
88 (14.5%)
108 (17.5%)
176 (33.6%)
In-hospital mortality
278 (15.9%)
128 (21.1%)
78 (12.6%)
72 (13.8%)
30
34
29
28
----
37.1 + 26.6
43.0 + 34.6
34.9 + 21.3
33.3 + 20.8
<0.001
Teaching hospital
1,679 (96.1%)
571 (94.2%)
584 (94.5%)
524 (100%)
<0.001
Large Hospital bed size
1,644 (94.1%)
535 (88.9%)
585 (94.7%)
524 (100%)
<0.001
Length of stay (Median)
‡
Length of stay (Mean + SD)
‡
Hospital characteristics
<0.001
Hospital region NE
380 (21.7%)
135 (22.2%)
129 (20.9%)
116 (22.1%)
MW
554 (31.7%)
125 (20.6%)
196 (31.7%)
233 (44.5%)
South
502 (28.7%)
171 (28.2%)
198 (32.0%)
133 (25.4%)
West
313 (17.9%)
176 (29.0%)
95 (15.4%)
42 (8.0%)
Table 1: Demographic characteristics, length of stay, complications & disposition in patients undergoing LVAD implantation from 2008-2011, divided into tertiles of annual hospital volume MI stands for myocardial infarction, CABG stands for coronary artery bypass grafting. Race includes 1,493 observations, †Chronic ischemic heart disease included subacute MI, old MI, Angina Pectoris, Other forms of coronary artery disease (CAD), and history of percutaneous coronary intervention (PCI), §Ischemic cardiomyopathy was defined as a composite of acute MI, chronic ischemic heart disease and history of CABG, €History of other cardiac surgery included history of congenital heart disease surgery or valvular heart surgery including valve repair or valve replacement, †Renal dysfunction defined as history of chronic kidney disease stage III or greater and/or end-stage renal disease on dialysis, ‡ LOS excludes those who died in the hospital & includes 1,471 observations. *
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Variable
Odds ratio
95% CI
p-value
1.53 1.18 1.09 1.04 1.79 0.93 0.93 2.86 0.82 0.80 1.35 3.07 1.85 1.73 3.65 1.17
1.07-2.18 0.83-1.67 0.78-1.52 0.72-1.49 0.90-3.56 0.65-1.31 0.67-1.29 1.96-4.17 0.43-1.56 0.18-3.69 0.94-1.94 2.24-4.20 1.27-2.70 1.23-2.44 2.59-5.14 0.83-1.66
0.021 0.363 0.697 0.845 0.099 0.662 0.655 <0.001 0.55 0.779 0.102 <0.001 0.001 0.002 <0.001 0.376
1.03 1.51
0.74-1.42 0.79-2.88
0.869 0.217
Teaching hospital Large hospital bed size
0.92 0.87 0.47 0.34 1.01
0.57-1.48 0.54-1.42 0.27-0.84 0.17-0.70 0.51-2.00
0.725 0.59 0.011 0.003 0.974
Hospital Volume (1st tertile as referent) 2nd tertile 3rd tertile
0.50 0.41
0.34-0.73 0.26-0.64
<0.001 <0.001
Age > 65 years Female gender Hypertension Diabetes Mellitus Peripheral vascular disease Pre-existing renal dysfunction† Chronic Ischemic Heart Disease‡ Acute Myocardial Infarction History of CABG History of other cardiac surgery€ Bleeding complications Infectious complications Cardiac complications Thromboembolic complications Acute renal failure Other Complications Primary Payer (Medicare/Medicaid as referent) Private insurance Other Hospital Region (Northeast as referent) Midwest South West
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Table 2: Multivariable predictors of in-hospital mortality after LVAD implantation from 2008-2011 95% CI stands for 95% confidence interval, CABG stands for coronary artery bypass grafting, †Renal dysfunction defined as history of chronic kidney disease stage III or greater and/or end-stage renal disease on dialysis, ‡Chronic ischemic heart disease includes subacute MI, old MI, Angina Pectoris, Other forms of coronary artery disease (CAD), and history of percutaneous coronary intervention (PCI), € History of other cardiac surgery includes history of congenital heart disease surgery or valvular heart surgery including valve repair or valve replacement.
Variable Age > 65 years Female gender Hypertension Diabetes Mellitus Peripheral vascular disease Pre-existing renal dysfunction† Chronic Ischemic Heart Disease‡ Acute Myocardial Infarction History of CABG History of other cardiac surgery€ Bleeding complications Infectious complications Cardiac complications Thromboembolic complications Acute renal failure Other Complications
Odds ratio
95% CI
p-value
1.37 1.24 0.81 0.95 0.75 1.02 0.81 1.56 0.99 0.72 1.28 3.97 1.54 1.90 2.75 1.64
1.03-1.81 0.91-1.69 0.62-1.08 0.70-1.28 0.38-1.47 0.76-1.38 0.61-1.08 1.03-2.37 0.60-1.61 0.27-1.88 0.91-1.81 2.84-5.55 1.05-2.27 1.35-2.66 2.11-3.59 1.19-2.28
0.03 0.165 0.151 0.731 0.407 0.872 0.157 0.038 0.96 0.498 0.155 <0.001 0.028 <0.001
0.94 0.77
0.72-1.23 0.40-1.46
0.664 0.417
0.61 0.65 1.06 1.35 2.12
0.29-1.28 0.32-1.34 0.47-2.39 0.47-3.87 0.80-5.62
0.19 0.245 0.885 0.575 0.131
0.72 0.41
0.47-1.09 0.23-0.73
0.115 0.003
0.003
Primary Payer (Medicare/Medicaid as referent) Private insurance Other Hospital Region (Northeast as referent) Midwest South West Teaching hospital Large hospital bed size Hospital Volume (1st tertile as referent) 2nd tertile 3rd tertile
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Table 3: Multivariable predictors of length of stay greater than median after LVAD implantation from 2008-2011 (n=1,465) 95% CI stands for 95% confidence interval, CABG stands for coronary artery bypass grafting,
†Renal dysfunction defined as history of chronic kidney disease stage III or greater and/or end-stage renal disease on dialysis, ‡Chronic ischemic heart disease includes subacute MI, old MI, Angina Pectoris, Other forms of coronary artery disease (CAD), and history of percutaneous coronary intervention (PCI), € History of other cardiac surgery includes history of congenital heart disease surgery or valvular heart surgery including valve repair or valve replacement.
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S1071-9164(15)01169-0 http://dx.doi.org/doi:10.1016/j.cardfail.2015.10.016 YJCAF 3659
To appear in:
Journal of Cardiac Failure
Received date: Revised date: Accepted date:
9-6-2015 28-9-2015 6-10-2015
Please cite this article as: Neeraj Shah, Ankit Chothani, Vratika Agarwal, Abhishek Deshmukh, Nileshkumar Patel, Jalaj Garg, Apurva Badheka, Matthew Martinez, Nauman Islam, Ronald Freudenberger, Impact of Annual Hospital Volume on Outcomes after Left Ventricular Assist Device (LVAD) Implantation in the Contemporary Era, Journal of Cardiac Failure (2015), http://dx.doi.org/doi:10.1016/j.cardfail.2015.10.016. 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.
Impact of Annual Hospital Volume on Outcomes after Left Ventricular Assist Device (LVAD) Implantation in the Contemporary Era Neeraj Shah MD, MPH1, Ankit Chothani MD2, Vratika Agarwal MD3, Abhishek Deshmukh MD4, Nileshkumar Patel MD5, Jalaj Garg MD1, Apurva Badheka MD6, Matthew Martinez MD, FACC1, Nauman Islam MD, FACC1, Ronald Freudenberger MD, FACC1 Affiliations: 1
Department of Cardiology, Lehigh Valley Health Network, PA
2
Department of Cardiology, Mount Sinai St. Luke’s Roosevelt Hospital, NY
3
Department of Cardiology, Staten Island University Hospital
4
Department of Cardiology, Mayo Clinic, MN
5
Department of Cardiology, University of Miami, FL
6
Department of Cardiology, Everett Clinic, WA
Corresponding Author: Neeraj Shah, MD, MPH, Department of Cardiology, Lehigh Valley Health Network, 1250 S Cedar Crest Blvd, Allentown, PA 18103. E-mail: [email protected], Tel: 914-826-1033. Disclosures: None of the authors have any conflicts of interest. Keywords: Left Ventricular Assist Device (LVAD), Continuous Flow Devices, Annual hospital volume Word Count in Abstract: 214, Word Count in Manuscript: 1,569 Running title: Shah et al Annual hospital LVAD volume and outcomes
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Abbreviation List: LVAD: Left Ventricular Assist Device DT: Destination Therapy BTT: Bridge to Transplant NIS: Nationwide Inpatient Sample CHF: Congestive Heart Failure HCUP: Healthcare Cost and Utilization Project FDA: Food and Drug Administration CMS: Centers for Medicare and Medicaid VIF: Variance Inflation Factor OR: Odds ratio CI: Confidence Interval INTERMACS: Interagency Registry for Mechanical Assisted Circulatory Support NYHA: New York Heart Association MI: Myocardial Infarction CABG: Coronary Artery Bypass Grafting
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Highlights:
Increased annual hospital LVAD implantation volume predicts decreased in-hospital mortality and length of stay
An optimal volume threshold of 20 or more LVAD implantations per year is associated less than 10% in-hospital mortality
Improved outcomes at high volume centers may be due to early identification of patients, and improved surgical, postoperative care and long term follow up
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Abstract: Introduction: There is paucity of data in the literature regarding impact of annual hospital volume on outcomes such as mortality and length of stay (LOS) post LVAD implantation. Methods: We queried the nationwide inpatient sample from 2008-2011 using ICD-9 procedure code 37.66. We included patients >18 years without primary diagnosis of orthotopic heart transplant. Annual volume of LVAD implantation was computed for each hospital. Multivariable hierarchical mixed effect logistic regression models were used to determine predictors of inhospital mortality and LOS. Results: There were 1,749 LVAD implants from 2008 to 2011 with a mean age of 55.4 years and 23% females. In-hospital mortality decreased from 20.9% in first tertile (1-22 LVADs/year) to 13.7% in third tertile (> 35 LVADs/year) of hospital volume. Median LOS decreased from 34 days in first tertile to 28 days in third tertile of hospital volume. The adjusted ORs of the highest tertile of hospital volume in predicting in-hospital mortality and LOS were respectively 0.41 (0.26-0.64, p<0.001) & 0.41 (0.23-0.73, p = 0.003). Restricted cubic spline analysis showed that a volume threshold of >20 LVADs/year was associated with favorable mortality rates of <10%. Conclusions: High annual LVAD volume is associated with significantly decreased in-hospital mortality and LOS after LVAD implantation. Center experience is an important determinant of optimal patient outcomes.
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Introduction: The REMATCH trial (1998-2001) (1) showed that left ventricular assist devices (LVADs) as destination therapy (DT) improved survival compared to medical therapy alone in patients with advanced heart failure. Second generation continuous flow LVADs are smaller and non-pulsatile, compared to bulky first generation pulsatile flow devices. These devices used as DT or bridge to transplant (BTT) improve survival, hemodynamic support and quality of life (25). Thoratec HeartMate II and HeartWare HVAD are the FDA approved continuous flow devices for adults (6). Recent Interagency Registry for Mechanical Assisted Circulatory Support (INTERMACS) reports show survival rates of 80% and 70% at one and two years respectively with these devices (6). Since 2008, predominantly continuous flow devices are implanted in US (6, 7). There is paucity of data on the optimal number of LVADs to be performed by an institution. Latest facility criteria for LVAD recommend at least 10 LVAD implantations over a 36 month period (8, 9). Studies examining the relationship between hospital volume and mortality after LVAD implantation have shown varying volume cut offs (10-13). Our objective was to determine an optimal hospital volume threshold for LVAD implantation using Nationwide Inpatient Sample (NIS) database from 2008-2011. Methods NIS is the largest available all-payer database of hospital inpatient stays in US, containing an approximate 20% stratified sample of US hospitals. For detailed information regarding NIS, kindly refer to the Supplementary Appendix.
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Study design: We queried the NIS from 2008 to 2011 using International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) procedure code 37.66, Insertion of Implantable Heart Assist System. All patients > 18 years of age without a primary procedure code of orthotopic heart transplantation (37.5, 37.51 or 33.6) were included in the study. Individual comorbid conditions relevant to patients receiving LVADs in our study were identified using ICD-9 diagnoses or procedure codes. A prior study from NIS on short term mechanical circulatory support used Elixhauser comorbidity index derived from ICD-9 codes (14). Detailed descriptions and ICD-9 codes used to identify comorbidities have been listed in Supplementary Appendix. Preventable procedural complications were identified by Patient Safety Indicators (PSIs), v4.4, March 2012 (http://www.qualityindicators.ahrq.gov/modules/PSI_TechSpec.aspx) and specific ICD-9 diagnoses and/or procedure codes in the secondary diagnoses fields. Detailed descriptions regarding procedural complications are listed in Supplementary Appendix. Annual hospital volume was determined on a yearly basis. Unique hospital identification number was used to calculate the total number of procedures performed by a particular institution in a given year, which was considered as the annual LVAD volume of that institution for that year. Hospital volume was divided into tertiles for further analysis. The total duration of hospital stay in days was estimated for all patients, excluding those who died in the hospital, using the length of stay (LOS) information in the dataset.
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Statistical analysis: Stata SE 13.1 (StataCorp, College Station, TX) was utilized for all analyses, accounting for complex survey design and clustering. Hierarchical mixed effects logistic models were generated in order to identify multivariable predictors of in-hospital mortality & LOS (divided into two categories based on the median). Two level hierarchical models (with patient level factors nested within hospital level factors) were created with hospital identification number incorporated as random effects within the model, to account for clustering. Variables with >10% missing data (e.g. race) were not included in multivariable models. All interactions were thoroughly tested. Multicollinearity was assessed using variance inflation factor (VIF). No significant interactions were found and VIF was less than 5 for all covariates suggesting no significant correlation between the predictor variables. Restricted cubic splines were generated assuming a non-linear relationship between hospital volume and in-hospital mortality. The cubic splines were adjusted for the same covariates that were included in the multivariable models (Tables 2 & 3). Cubic knots were set at 5, 10, 25 and 45 annual LVAD implantations per year. Results: There were 1,749 LVAD implantations from 2008-2011. Table 1 shows the demographic characteristics and outcomes in the entire study population divided into hospital volume tertiles (tertile 1 is 1-22 LVADs/year, tertile 2 is 23-34 LVADs/year, and tertile 3 is > 35 LVADs/year). Demographics:
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Mean age of the population was 55.4 years, with 23% females and 66.2% Caucasians (Table 1). The mean length of stay was 37.1 days and median LOS was 30 days. Overall inhospital mortality was 15.9%. The median annual hospital volume was 28 LVADs per year (range: 1-70 procedures/year). The third tertile of annual hospital volume (> 35 LVADs/year) had a higher prevalence of hypertension, diabetes mellitus, chronic ischemic heart disease, history of CABG, ischemic etiology of cardiomyopathy, and pre-existing renal dysfunction (Table 1). The third tertile of hospital volume also had a higher incidence of major bleeding and acute renal failure, and a trend towards lower incidence of iatrogenic cardiac and other complications. Predictors of in-hospital mortality: Age > 65 years, acute myocardial infarction, acute renal failure, infection, major bleeding, iatrogenic cardiac complications and thromboembolism were significant predictors of increased in-hospital mortality, whereas teaching hospital status and increasing annual hospital volume were significant predictors of decreased in-hospital mortality (Table 2). Annual hospital volume & in-hospital mortality: The unadjusted in-hospital mortality rates in the three categories of hospital volume were respectively 20.9% for 1-22 LVADs/year, 12.6% for 23-34 LVADs/year and 13.7% for > 35 LVADs/year. The adjusted odds ratios (OR) of mortality (95% confidence interval, p) for the second and third tertiles of annual hospital volume were respectively 0.50 (0.34-0.73, p<0.001) and 0.41 (0.26-0.64, p<0.002) [Table 2].
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Figure 1 shows that there is a sharp decline in mortality with increasing annual hospital LVAD volume until an optimal volume threshold of 20 LVADs per year, after which there is no additional mortality benefit. Annual hospital volume & length of stay: Mean LOS decreased from 42.8 days in the first tertile to 33.2 days in the third tertile of hospital volume, and median LOS decreased from 34.0 days in the first tertile to 28.0 days in the third tertile of hospital volume (p<0.001). Age > 65 years, acute MI and periprocedural complications were significant predictors of LOS greater than median (Table 3). Third tertile of hospital volume was a predictor of decreased LOS with adjusted OR (95% CI, p) of 0.41 (0.230.73, p = 0.003). Discussion: A study from Thoratec HeartMate registry from 1998-2005 using pulsatile flow devices showed that centers with > 9 DT implants had improved 1 year survival (10). INTERMACS reports do not identify hospital volume as a mortality predictor; however, it is unclear if their risk models were adjusted for hospital volume (6). A study (11) using data from University Health Consortium Chicago from 2008-2012 showed decrease in in-hospital mortality with increasing annual hospital LVAD volume quartiles. Cowger et al showed that center volume of <15 procedures predicted higher 90 day mortality (12). Another study involving Medicare beneficiaries from 2006-2011 showed that centers implanting > 9 LVADs/year had improved outcomes (13). However, none of these studies employed cubic spline analysis to identify an optimal volume threshold.
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Our study reaffirms that increasing annual hospital LVAD volume is a predictor of decreased in-hospital mortality (11, 12). Moreover, the median mortality free length of stay was shorter by 6 days in patients in the third tertile of hospital volume (>= 35 procedures per year) compared to the first tertile, indirectly suggesting relatively faster patient recovery at high volume centers. The most important finding of our study is identification of an optimal volume threshold of 20 LVADs/year, associated with <10% in-hospital mortality (Figure 1). The lack of benefit beyond 20 LVADs/year maybe because very high volume centers are major tertiary care referral centers, caring for of critically ill advanced heart failure patients and any further mortality benefit is offset by the critical illness of these patients. This may also be the baseline mortality risk of end-stage heart failure patients undergoing LVAD implantation. An optimal annual hospital volume of >20 LVADs/year is considerably larger than the current criterion of > 10 LVADs over 3 years (9). Performing >20 LVADs/year would entail several logistic challenges. That being said, in our study overall 69% of LVADs (79.2% in 2011, compared to 47.8% in 2008) were performed in hospitals implanting >20 LVADs/year. With advancing technology and increasing experience, more centers would be able to attain this goal. It is difficult to establish a causal relationship between high LVAD volumes and outcomes. Lietz et al showed that patients in high volume centers had a lower overall preoperative risk score (10). Favorable outcomes seen in high volume centers may be due to better patient selection processes and appropriate referral systems leading to early identification of end-stage heart failure patients for advanced therapy. Better preoperative screening, surgical & postoperative care and long term follow up post LVAD implantation lead to improved outcomes at highly experienced centers (10).
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Limitations: Being an administrative database, NIS is susceptible to errors arising from coding inaccuracies. Inability to track patients after discharge and cross sectional nature of the database precludes assessment of long term outcomes. Due to a lack of ICD-9 codes, we could not identify the type of device implanted, DT vs. BTT, incidence of right ventricular failure or INTERMACS risk profiles. NIS does not have information on laboratory data, NYHA functional class, medications or echocardiography data. Conclusions: High annual LVAD volume is associated with significantly lower in-hospital mortality and length of stay post LVAD implantation, with an optimal volume threshold of >20 LVADs/year, suggesting that center volume is crucial for better care of these patients.
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References: 1.
Rose EA, Gelijns AC, Moskowitz AJ, Heitjan DF, Stevenson LW, Dembitsky W, et al.
Long-term use of a left ventricular assist device for end-stage heart failure. The New England journal of medicine. 2001;345(20):1435-43. Epub 2002/01/17. 2.
Slaughter MS, Rogers JG, Milano CA, Russell SD, Conte JV, Feldman D, et al.
Advanced heart failure treated with continuous-flow left ventricular assist device. The New England journal of medicine. 2009;361(23):2241-51. Epub 2009/11/19. 3.
Pagani FD, Miller LW, Russell SD, Aaronson KD, John R, Boyle AJ, et al. Extended
mechanical circulatory support with a continuous-flow rotary left ventricular assist device. Journal of the American College of Cardiology. 2009;54(4):312-21. Epub 2009/07/18. 4.
Holman WL, Naftel DC, Eckert CE, Kormos RL, Goldstein DJ, Kirklin JK. Durability of
left ventricular assist devices: Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) 2006 to 2011. The Journal of thoracic and cardiovascular surgery. 2013;146(2):437-41 e1. Epub 2013/03/16. 5.
Rogers JG, Aaronson KD, Boyle AJ, Russell SD, Milano CA, Pagani FD, et al.
Continuous flow left ventricular assist device improves functional capacity and quality of life of advanced heart failure patients. Journal of the American College of Cardiology. 2010;55(17):1826-34. Epub 2010/04/24. 12 Page 12 of 20
6.
Kirklin JK, Naftel DC, Pagani FD, Kormos RL, Stevenson LW, Blume ED, et al. Sixth
INTERMACS annual report: a 10,000-patient database. The Journal of heart and lung transplantation : the official publication of the International Society for Heart Transplantation. 2014;33(6):555-64. Epub 2014/05/27. 7.
Kirklin JK, Naftel DC, Kormos RL, Stevenson LW, Pagani FD, Miller MA, et al. The
Fourth INTERMACS Annual Report: 4,000 implants and counting. The Journal of heart and lung transplantation : the official publication of the International Society for Heart Transplantation. 2012;31(2):117-26. Epub 2012/02/07. 8.
Requirements for Ventricular Assist Device Destination Therapy Advanced Certification.
2014 [updated 1/17/20142/1/2015]; Prepublication Standards - Revisions to Ventricular Assist Device
Destination
Therapy
Requirements].
Available
from:
http://www.jointcommission.org/prepublication_standards_revisions_ventricular_assist_device_ destination_therapy_req/. 9.
Decision Memo for Ventricular Assist Devices for Bridge-to-Transplant and Destination
Therapy (CAG-00432R). Centers for Medicare & Medicaid Services; 2013 [updated 10/20132/1/2015];
Available
from:
http://www.cms.gov/medicare-coverage-
database/details/nca-decision-memo.aspx?NCAId=268. 10.
Lietz K, Long JW, Kfoury AG, Slaughter MS, Silver MA, Milano CA, et al. Impact of
center volume on outcomes of left ventricular assist device implantation as destination therapy: analysis of the Thoratec HeartMate Registry, 1998 to 2005. Circulation Heart failure. 2009;2(1):3-10. Epub 2009/10/08.
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11.
Feldman K, Doukky, R., Johnson T., Levine, D., Hohmann, S. Hospital Volume of
LVAD Procedures Determines Patient Outcome. Circ Cardiovasc Qual Outcomes. 2013;6(3 Supplement):A289. 12.
Cowger J, Sundareswaran K, Rogers JG, Park SJ, Pagani FD, Bhat G, et al. Predicting
survival in patients receiving continuous flow left ventricular assist devices: the HeartMate II risk score. Journal of the American College of Cardiology. 2013;61(3):313-21. Epub 2012/12/26. 13.
Khazanie P, Hammill BG, Patel CB, Eapen ZJ, Peterson ED, Rogers JG, et al. Trends in
the use and outcomes of ventricular assist devices among medicare beneficiaries, 2006 through 2011. Journal of the American College of Cardiology. 2014;63(14):1395-404. Epub 2014/02/04. 14.
Stretch R, Sauer CM, Yuh DD, Bonde P. National trends in the utilization of short-term
mechanical circulatory support: incidence, outcomes, and cost analysis. Journal of the American College of Cardiology. 2014;64(14):1407-15. Epub 2014/10/04.
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Figure Legends:
Figure 1: Adjusted restricted cubic spline showing the relationship between annual hospital LVAD volume and in-hospital mortality after LVAD implantation from 2008-2011. (The curve was adjusted for: age, gender, hypertension, diabetes mellitus, peripheral vascular disease, chronic ischemic heart disease, acute MI, history of CABG, history of other cardiac surgery, pre-existing renal dysfunction, major bleeding, infectious complications, iatrogenic cardiac complications, thromboembolic complications, acute renal failure, other complications, primary payer, hospital region, teaching hospital and hospital bed size)
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Overall Population (N = 1,749)
Hospital Volume Tertile 1 (1-22/yr) (N = 607)
Hospital Volume Tertile 2 (23-34/yr) (N = 618)
Hospital Volume Tertile 3 (> 35/yr) (N = 524)
p-value
Age in years (Mean + SD)
55.4 + 13.5
54.8 + 13.7
55.5 + 13.5
56.1 + 13.2
0.162
Female gender
397 (22.7%)
146 (24.1%)
147 (23.8%)
104 (19.9%)
0.176
Variable Demographics
Race
*
0.634 White
988 (66.2%)
333 (65.2%)
382 (67.0%)
273 (66.3%)
Black
300 (20.1%)
106 (20.7%)
118 (20.7%)
76 (18.4%)
Other
205 (13.7%)
72 (14.1%)
70 (12.3%)
63 (15.3%)
Hypertension
739 (42.3%)
237 (39.0%)
249 (40.3%)
258 (48.3%)
0.003
Diabetes Mellitus
440 (25.2%)
130 (21.4%)
164 (26.5%)
146 (27.9%)
0.028
Pre-existing renal dysfunction†
541 (30.9%)
139 (22.9%)
200 (32.4%)
202 (38.6%)
<0.001
Acute Myocardial Infarction
238 (13.6%)
93 (15.3%)
69 (11.2%)
76 (14.5%)
0.082
835 (47.7%)
256 (42.2%)
296 (47.9%)
283 (54.0%)
<0.001
139 (8.0%)
32 (5.3%)
60 (9.7%)
47 (9.0%)
0.01
917 (52.4%)
287 (47.3%)
322 (52.1%)
308 (58.8%)
0.001
27 (1.5%)
5 (0.8%)
16 (2.6%)
6 (1.2%)
0.029
70 (4.0%)
25 (4.1%)
21 (3.4%)
24 (4.6%)
0.587
Chronic ischemic heart disease
†
History of CABG §
Ischemic Cardiomyopathy History of other cardiac € surgery Peripheral vascular disease Primary Payer
0.014
Medicare/Medicaid
970 (55.7%)
319 (52.8%)
329 (53.6%)
322 (61.4%)
Private
689 (39.5%)
250 (41.4%)
253 (41.2%)
186 (35.5%)
Other
83 (4.8%)
35 (5.8%)
32 (5.2%)
16 (3.1%)
Major bleeding
310 (17.7%)
94 (15.5%)
80 (12.9%)
136 (26.0%)
<0.001
Infection
417 (23.8%)
148 (24.4%)
136 (22.0%)
133 (25.4%)
0.381
Cardiac complications
239 (13.7%)
98 (16.1%)
75 (12.1%)
66 (12.6%)
0.09
Thromboembolic complications
325 (18.6%)
100 (16.5%)
114 (18.5%)
111 (21.2%)
0.127
Acute renal failure Acute renal failure requiring dialysis
929 (53.1%)
297 (48.9%)
294 (47.6%)
338 (64.5%)
<0.001
132 (7.6%)
46 (7.6%)
50 (8.1%)
36 (6.7%)
0.738
Complications
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Other complications
335 (19.2%)
133 (21.9%)
111 (18.0%)
91 (17.4%)
0.099 <0.001
Disposition Home
1,098 (62.8%)
391 (64.4%)
432 (69.9%)
275 (52.6%)
Nursing home or other facility
372 (21.3%)
88 (14.5%)
108 (17.5%)
176 (33.6%)
In-hospital mortality
278 (15.9%)
128 (21.1%)
78 (12.6%)
72 (13.8%)
30
34
29
28
----
37.1 + 26.6
43.0 + 34.6
34.9 + 21.3
33.3 + 20.8
<0.001
Teaching hospital
1,679 (96.1%)
571 (94.2%)
584 (94.5%)
524 (100%)
<0.001
Large Hospital bed size
1,644 (94.1%)
535 (88.9%)
585 (94.7%)
524 (100%)
<0.001
Length of stay (Median)
‡
Length of stay (Mean + SD)
‡
Hospital characteristics
<0.001
Hospital region NE
380 (21.7%)
135 (22.2%)
129 (20.9%)
116 (22.1%)
MW
554 (31.7%)
125 (20.6%)
196 (31.7%)
233 (44.5%)
South
502 (28.7%)
171 (28.2%)
198 (32.0%)
133 (25.4%)
West
313 (17.9%)
176 (29.0%)
95 (15.4%)
42 (8.0%)
Table 1: Demographic characteristics, length of stay, complications & disposition in patients undergoing LVAD implantation from 2008-2011, divided into tertiles of annual hospital volume MI stands for myocardial infarction, CABG stands for coronary artery bypass grafting. Race includes 1,493 observations, †Chronic ischemic heart disease included subacute MI, old MI, Angina Pectoris, Other forms of coronary artery disease (CAD), and history of percutaneous coronary intervention (PCI), §Ischemic cardiomyopathy was defined as a composite of acute MI, chronic ischemic heart disease and history of CABG, €History of other cardiac surgery included history of congenital heart disease surgery or valvular heart surgery including valve repair or valve replacement, †Renal dysfunction defined as history of chronic kidney disease stage III or greater and/or end-stage renal disease on dialysis, ‡ LOS excludes those who died in the hospital & includes 1,471 observations. *
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Variable
Odds ratio
95% CI
p-value
1.53 1.18 1.09 1.04 1.79 0.93 0.93 2.86 0.82 0.80 1.35 3.07 1.85 1.73 3.65 1.17
1.07-2.18 0.83-1.67 0.78-1.52 0.72-1.49 0.90-3.56 0.65-1.31 0.67-1.29 1.96-4.17 0.43-1.56 0.18-3.69 0.94-1.94 2.24-4.20 1.27-2.70 1.23-2.44 2.59-5.14 0.83-1.66
0.021 0.363 0.697 0.845 0.099 0.662 0.655 <0.001 0.55 0.779 0.102 <0.001 0.001 0.002 <0.001 0.376
1.03 1.51
0.74-1.42 0.79-2.88
0.869 0.217
Teaching hospital Large hospital bed size
0.92 0.87 0.47 0.34 1.01
0.57-1.48 0.54-1.42 0.27-0.84 0.17-0.70 0.51-2.00
0.725 0.59 0.011 0.003 0.974
Hospital Volume (1st tertile as referent) 2nd tertile 3rd tertile
0.50 0.41
0.34-0.73 0.26-0.64
<0.001 <0.001
Age > 65 years Female gender Hypertension Diabetes Mellitus Peripheral vascular disease Pre-existing renal dysfunction† Chronic Ischemic Heart Disease‡ Acute Myocardial Infarction History of CABG History of other cardiac surgery€ Bleeding complications Infectious complications Cardiac complications Thromboembolic complications Acute renal failure Other Complications Primary Payer (Medicare/Medicaid as referent) Private insurance Other Hospital Region (Northeast as referent) Midwest South West
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Table 2: Multivariable predictors of in-hospital mortality after LVAD implantation from 2008-2011 95% CI stands for 95% confidence interval, CABG stands for coronary artery bypass grafting, †Renal dysfunction defined as history of chronic kidney disease stage III or greater and/or end-stage renal disease on dialysis, ‡Chronic ischemic heart disease includes subacute MI, old MI, Angina Pectoris, Other forms of coronary artery disease (CAD), and history of percutaneous coronary intervention (PCI), € History of other cardiac surgery includes history of congenital heart disease surgery or valvular heart surgery including valve repair or valve replacement.
Variable Age > 65 years Female gender Hypertension Diabetes Mellitus Peripheral vascular disease Pre-existing renal dysfunction† Chronic Ischemic Heart Disease‡ Acute Myocardial Infarction History of CABG History of other cardiac surgery€ Bleeding complications Infectious complications Cardiac complications Thromboembolic complications Acute renal failure Other Complications
Odds ratio
95% CI
p-value
1.37 1.24 0.81 0.95 0.75 1.02 0.81 1.56 0.99 0.72 1.28 3.97 1.54 1.90 2.75 1.64
1.03-1.81 0.91-1.69 0.62-1.08 0.70-1.28 0.38-1.47 0.76-1.38 0.61-1.08 1.03-2.37 0.60-1.61 0.27-1.88 0.91-1.81 2.84-5.55 1.05-2.27 1.35-2.66 2.11-3.59 1.19-2.28
0.03 0.165 0.151 0.731 0.407 0.872 0.157 0.038 0.96 0.498 0.155 <0.001 0.028 <0.001
0.94 0.77
0.72-1.23 0.40-1.46
0.664 0.417
0.61 0.65 1.06 1.35 2.12
0.29-1.28 0.32-1.34 0.47-2.39 0.47-3.87 0.80-5.62
0.19 0.245 0.885 0.575 0.131
0.72 0.41
0.47-1.09 0.23-0.73
0.115 0.003
0.003
Primary Payer (Medicare/Medicaid as referent) Private insurance Other Hospital Region (Northeast as referent) Midwest South West Teaching hospital Large hospital bed size Hospital Volume (1st tertile as referent) 2nd tertile 3rd tertile
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Table 3: Multivariable predictors of length of stay greater than median after LVAD implantation from 2008-2011 (n=1,465) 95% CI stands for 95% confidence interval, CABG stands for coronary artery bypass grafting,
†Renal dysfunction defined as history of chronic kidney disease stage III or greater and/or end-stage renal disease on dialysis, ‡Chronic ischemic heart disease includes subacute MI, old MI, Angina Pectoris, Other forms of coronary artery disease (CAD), and history of percutaneous coronary intervention (PCI), € History of other cardiac surgery includes history of congenital heart disease surgery or valvular heart surgery including valve repair or valve replacement.
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