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\begin{document}

\title{Comparison of Household Income In In-Hospital Outcomes After
Implantation of Left Ventricular Assist Device}



\author[1]{Bertrand Ebner}%
\author[1]{Morgan Karetnick}%
\author[2]{Jelani Grant}%
\author[3]{Louis Vincent }%
\author[4]{Jennifer Maning}%
\author[1]{Neal Olarte}%
\author[1]{Odunayo Olorunfemi}%
\author[4]{Rosario Colombo}%
\author[5]{Sandra Chaparro}%
\affil[1]{University of Miami Miller School of Medicine}%
\affil[2]{Affiliation not available}%
\affil[3]{University of Miami}%
\affil[4]{Jackson Memorial Hospital}%
\affil[5]{Baptist Health South Florida}%


\vspace{-1em}



  
  \date{May 05, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
Introduction: Due to the inability to keep up with the demand for heart
transplantation, there is an increased utilization of left ventricular
assist devices (LVAD). However, paucity of data exists regarding the
association of household income with in-hospital outcomes after LVAD
implantation. Methods: Retrospective cohort study using the NIS to
identify all patients [?]18 years who underwent LVAD implantation from
2011-2017. Statistical analysis was performed comparing low household
income ([?]50th percentile) and high income (\textgreater{}50th
percentile). Results: A total of 25,503 patients underwent LVAD
implantation. The low-income group represented 53\% and the high-income
group corresponded to 47\% of the entire cohort. The low-income group
was found to be younger (mean age 55 \selectlanguage{ngerman}±14 vs. 58 ±14 years), higher
proportion of females (24\% vs. 22\%), and higher proportion of blacks
(32\% vs. 16\%, p\textless{}0.001 for all). The low-income group was
found to have higher prevalence of hypertension, chronic pulmonary
disease, smoking, dyslipidemia, obesity and pulmonary hypertension
(p\textless{}0.001 for all). However, the high-income cohort had higher
rate of atrial tachyarrhythmias and end-stage renal disease
(p\textless{}0.001). During hospitalization, patients in the high-income
group had increased rates of ischemic stroke, acute kidney injury, acute
coronary syndrome, bleeding and need of extracorporeal membrane
oxygenation (p\textless{}0.001 for all). We found that the unadjusted
mortality had an OR 1.30 (CI {[}1.21-1.41{]}, p\textless{}0.001) and
adjusted mortality of OR 1.14 (CI {[}1.05-1.23{]}, p=0.002). Conclusion:
In patients undergoing LVAD implantation nationwide, low-income was
associated with increased comorbidity burden, younger age, and fewer
in-hospital complications and all-cause mortality.%
\end{abstract}\selectlanguage{ngerman}%



\sloppy


\textbf{Introduction}

Heart failure has become increasingly prevalent with more than 6.5
million Americans currently impacted (1). Individuals of lower
socioeconomic classes are significantly more likely to develop heart
failure compared with their wealthier counterparts (2). Differences in
the allocation of medical resources, access to quality medical care,
ability for self-care, level of education, and generalized support are
among the multifactorial reasons that contribute to this disparity (2,
3). Heart transplantation remains the gold standard for patients
experiencing end stage heart disease. However, due to the paucity of
donor hearts and the multiple contraindications based on strict
transplantation recipient criteria, this option is limited to a small
select group of individuals (4). When controlling for risk factors for
post-transplant mortality, individuals of lower socioeconomic class have
also been shown to have worse outcomes and decreased post-transplant
survival (3-6). Socioeconomic deprivation may modify several
cardiovascular risk factors, making these individuals even less likely
to be considered for transplantation. The utilization of alternative
therapies is currently thriving. LVADs double the one-year survival rate
of patients with end-stage heart failure as compared with drug treatment
alone and provide an effective alternative to individuals who are unable
to receive a transplant (7, 8). LVADs have also advanced to not only
serve as a heart transplantation bridge but also as a destination
therapy. These serial improvements have led to the growing use of LVADs
in a large percentage of the heart failure population. For individuals
of lower socioeconomic classes, numerous studies have shown that these
patients more often had an upfront strategy with LVAD implantation
compared with remaining on pharmacologic therapy and perpetual waiting
on the transplant list (3). The Registry Evaluation of Vital Information
for VADs in Ambulatory Life (REVIVAL) study expanded on this by
demonstrating that there was a greater preference for individuals with
an annual income \textless{}\$40,000 to receive an LVAD compared with
higher income individuals who were significantly more reluctant to
accept an LVAD (9). As the technology driving LVADs continues to improve
and as more studies demonstrate the benefits of these devices as
destination therapy, together with an increased willingness of a
population subset to receive these devices, it is important to look at
the rate of utilization of these devices across different socioeconomic
classes. Our study aims to analyze the current trends and variances in
LVAD utilization and to further delve into the reasons for, and
implications of, these socioeconomic disparities.

\textbf{Material and Methods}

\emph{Data Source}

Institutional review board approval was not needed, as all patient
information is de-identified within the NIS, and informed consent was
waived. The National Inpatient Sample (NIS) offers the largest database
of hospitalizations, representing a 20\% random, stratified, sample of
hospital discharges in the United States. To identify the study
population, International Classification of Diseases, ninth (ICD-9) and
tenth (ICD-10) revisions, Clinical Modification (CM) and Procedure
Coding System (PCS) codes were used.

\emph{Data Disclosure}

All the data under NIS are publicly available. Detailed methods used for
statistical analyses are presented under the~Data Supplement, which can
be used for replication of our results.

\emph{Study Population}

From 2011 to 2017, a total of 43,077,206 discharge records comprised the
NIS for the US adult population (age 18 years or above), corresponding
to a national estimate of 214,107,782 hospitalizations across the
country. We identified all patients aged 18 years or older undergoing
LVAD implantation using ICD-9-PCS code 37.66 and~ICD-10-PCS code 02HA0QZ
in any procedure field. Our final study cohort comprised 5,131 patients
undergoing LVAD implantation, corresponding to a weighted estimate of
25,503 overall LVAD implantations during this time period. This estimate
was calculated by using discharge weights provided with the NIS files.
The study population was reflective of the one device era---the
continuous flow (CF) device based on the US Food and Drug Administration
approval of CF devices in 2008.~ICD-9-CM/PCS and ICD-10-CM/PCS~coding
for comorbidities, post-LVAD complications and other procedures is
listed in Table I in the~Data Supplement.

\emph{Outcome Measures}

Our primary outcome was post-LVAD implantation all-cause inpatient
mortality. Secondary outcomes of interest were intraoperative cardiac
arrest, post-procedure ischemic stroke, post-procedure thromboembolism,
infections, major gastrointestinal (GI) bleeding, cardiac complications
(such as pericardial complications, complete heart block and insertion
of permanent pacemaker), short-term percutaneous mechanical circulatory
support (PCMS), implant-related complications and acute kidney injury
(AKI) for index hospitalization during which patients received LVADs.
Detailed methods, including covariate ascertainment, are included under
the~Data Supplement.

\emph{Statistical Analysis}

As recommended by the Agency for Healthcare Research and Quality,
weighted data were used for all statistical analyses. Temporal trends in
LVAD utilization as well as post-LVAD mortality were assessed using the
average annual growth rate formula. Baseline characteristics and
post-LVAD outcomes were compared using the Pearson Chi-Squared (\selectlanguage{greek}χ\selectlanguage{english}2)
tests for categorical variables, independent samples T-test for
parametric continuous variables, and Mann-Whitney U test for
non-parametric continuous variables. We considered statistical
significance when p value was below 0.001. Categorical variables of
interest included hypertension (HTN), diabetes mellitus (DM),
malnutrition, coronary artery disease (CAD), atrial tachyarrhythmias
(Atach) which include atrial fibrillation and atrial flutter, peripheral
arterial disease (PAD), chronic kidney disease (CKD), history tobacco
use, history of stroke, dyslipidemia, and chronic liver disease (CLD).
Continuous variables of interest included mean age, total cost of
hospitalization, and hospital length of stay. NIS provides median
household income for patient's ZIP code divided by percentile.
High-income patients were considered between the
51\textsuperscript{st}to 100\textsuperscript{th} percentile and
low-income individuals were considered between 0 to
50\textsuperscript{th} percentile. The association between income and
post-LVAD mortality was analyzed using multivariable logistic
regression. All multivariable regression models were created using
generalized estimating equations. Missing data for race were handled
using multiple imputation as recommended by Healthcare Cost and
Utilization Project. Missing primary payer status in patients 65 years
old or older was imputed to Medicare, whereas missing data for all other
variables were imputed to the dominant category (See supplemental
material). All statistical analyses were performed using SPSS (IBM SPSS
Statistics for Mac, Version 23.0. Armonk, NY: IBM Corp.).

\textbf{Results}

A total weighted estimate of 25,503 hospitalizations for LVAD
implantation were identified during 2011 to 2017. Average age of the
entire cohort was 57 \selectlanguage{ngerman}±13 years, with a median of 59 years, ranging from
18 to 90 years. Female gender accounted for 23\% (n=5,820) of the total
population. The high-income group comprised 47\% (n=11,907) of the
cohort and the low-income group represented 53\% (n=13,595) (See Table
1). All comparisons henceforth are reported as low-income versus (vs.)
high-income for consistency. We found an average increased rate of LVAD
implantation from 2011 to 2017 of 11\% for the low-income group and 8\%
for higher income individuals (See Figure A).

Low-income group mean age was significantly lower (55±14 vs. 58±13,
p\textless{}0.001), with an increased proportion of females (24\% vs.
22\%, p\textless{}0.001) when compared to the high-income group.
Patients with higher income are more likely to be from suburbs of metro
areas of \selectlanguage{english}[?] 1 million population (13\% vs. 42\%, p\textless{}0.001) and
self-identified as White (57\% vs. 70\%, p\textless{}0.001). In term of
comorbidities, the low-income group was found to have significantly
higher proportions of hypertension (41\% vs. 37\%, p\textless{}0.001),
smoking (28\% vs. 24\%, p\textless{}0.001), anemia (7\% vs. 6\%,
p\textless{}0.001), dyslipidemia (39\% vs. 35\%, p\textless{}0.001),
obesity (18\% vs. 15\%, p\textless{}0.001) and pulmonary hypertension
(41\% vs. 36\%, p\textless{}0.001). However, the high-income group had
increased rates of atrial tachyarrhythmias including atrial fibrillation
and atrial flutter (48\% vs. 50\%, p\textless{}0.001) and history of
coronary artery bypass graft (9\% vs. 11\%, p\textless{}0.001). There
were no significant differences found in diabetes, alcohol and substance
abuse, malnutrition, prior strokes, coronary artery disease, peripheral
artery disease, chronic kidney disease, chronic liver disease, history
of percutaneous coronary intervention or obstructive sleep apnea between
both groups.

However, in the high-income group, we found significantly longer
hospital stay (median 29 {[}20-42{]} vs. 29 {[}20-44{]} days,
p\textless{}0.001) (See Figure B), higher hospital charges (median
\$770,852 {[}544,193-1,135,933{]} vs. \$727,922 {[}539,402-1,034,619{]},
p\textless{}0.001), increased proportion of post procedure strokes
(5.6\% vs. 8.3\%, p\textless{}0.001) with ischemic strokes comparison of
4\% vs. 7\% (p\textless{}0.001), acute kidney injury (59\% vs. 63\%,
p\textless{}0.001), bleeding (29\% vs. 33\%, p\textless{}0.001) and need
of extracorporeal membrane oxygenation (6\% vs. 8\%, p\textless{}0.001)
(see Table 2).

No significant differences were found in the incidences of ventricular
arrhythmias, blood product transfusions, pericardial complications,
postoperative deep venous thrombosis and pulmonary embolism, LVAD
thrombosis or embolism between groups. There was a decreased rate of
in-hospital mortality in patients undergoing LVAD from 2011 to 2017 in
both groups (See Figure C).

Combining data from all years (2011--2017), high-income was associated
with higher post-LVAD all-cause inpatient mortality (odds ratio (OR)
1.303; 95\%, confidence interval (CI) 1.207--1.407;~p\textless{}0.001)
that remained significant beyond adjustment for demographic factors and
comorbidities (OR 1.178; 95\% CI 1.085--1.280;~p\textless{}0.001).

\textbf{Discussion}

In the current study, we demonstrated that inpatient mortality post-LVAD
implantation was lower in individuals with a lower income
(50\textsuperscript{th} percentile or below) when combining data from
2011 to 2017. Other salient findings of our analysis can be summarized
as: i) the low-income group represented a younger population of
individuals receiving LVADs despite increased rates of comorbidities,
ii) the high-income group present at later stages of chronic diseases,
iii) there is an increased cost of hospital admission among higher
income individuals, and iv) the high-income group had higher rates of
severe post-LVAD outcomes.

Previous published studies agreed with our results indicating that the
primary population of LVAD recipients are middle-aged men of lower
socioeconomic class (10). Our study further demonstrates that low-income
recipients had a younger average age at 55 years. Increased burden of
medical comorbidities in lower income communities has been long
recognized and provides added risk factors for individuals to experience
more severe illness at a young age (3, 11, 12). Several studies have
shown that the higher prevalence of cardiovascular risk factors
underlies the earlier age of heart failure onset in African Americans,
who coincidentally also make up a larger population of the lower
socioeconomic class (9, 13-15). It is estimated that African Americans
are 30\% more likely to die from heart disease and are significantly
more prone to comorbidities including diabetes, hypertension, and
obesity, among many others, which leads to the use of advanced therapies
at an earlier age in this population (14-16). The REVIVAL Registry
further delves into how socioeconomic factors impact patient preference
for LVAD devices. Consistent with our study demonstrating higher LVAD
use and acceptance among socioeconomically disadvantaged patients, the
REVIVAL study has shown that there is a greater preference for LVAD
devices among patients with high school education or less and those with
an annual income less than \$40,000 (9). The reasoning behind this
decision making is complex and may reflect limited health literacy, lack
of knowledge of alternative therapies, and ineligibility for heart
transplantation (9, 17).

The National Survey of Families and Households, the Survey of Income and
Program Participation, and the National Health Interview Survey
represent the keystone of information necessary to study the link
between income and health. Researchers have long noted a positive
correlation between wealth and longevity, with higher income individuals
having greater life expectancy compared to low-income counterparts (18).
It has been previously shown that the incidence of obesity and smoking
has declined as wealth increases in the general United States
population, whereas those in the poorest wealth category have a 2.5- and
5-times higher incidence of obesity and tobacco smoking, respectively
(19). However, it would be incorrect to say that higher wealth
individuals do not experience health adversity as well. Diseases of
affluence primarily reflect chronic non-communicable ailments including,
but not limited to: cancer, degenerative autoimmune diseases, chronic
lung diseases, type 2 diabetes mellitus, and hypertension (20). These
comorbidities and their chronic progression are risk factors for
cardiovascular disease, providing a rudimentary explanation for heart
failure and the need for advanced cardiac intervention at a later point
in the lives of wealthy individuals (3, 21).

When differentiating between patients eligible for transplantation
versus alternative therapies, many patients with significant
comorbidities are deemed ineligible for transplantation, leaving LVADs
as one of the few advanced therapy options available (17). Previous
studies indicate that individuals are more willing to receive an LVAD as
the severity of their disease worsens and as their health-related
quality of life diminishes. Furthermore, many wealthy individuals have
at least one contraindication to heart transplantation often stemming
from chronic diseases and ailments such as pulmonary hypertension and
advanced age (22). Despite limited options, higher socioeconomic status
patients are significantly more reluctant to undergo LVAD implantation
as opposed to a heart transplant for a multitude of reasons (9).
Potential reasons for this decision-making include perception of
quality-of-life restrictions with the device, death as simply another
alternative to refusing therapy rather than a definitive event, and lack
of knowledge about both the LVAD device and associated procedure.
Patients may instead elect to seek out other options and underestimate
the severity of their illness (9). Delayed decision-making may lead to
progression of disease, which might reduce LVAD utility (23).

For those who elect to undergo LVAD implantation, the mean cost for the
procedure alone is \$175,420 (24). Patients then remain in the hospital
for at least two to three weeks as care is adjusted to meet individual
patient needs with the median length of stay at 20 days (24, 25). Our
study found a significantly longer hospital stay for both groups at 35
days and 37 days for low- and high-income groups, respectively. A number
of pre- and peri-implant factors contribute to hospital length of stay.
Increased age, as with the high-income population, is one of the largest
risk factors for increased hospital length of stay (25). Prolonged
admission time inevitably increases the all-encompassing cost of this
procedure. Thus, longer hospital stays in the high-income population are
also reflected in correlational higher hospital charge. Other factors
that have been shown to increase length of hospital stay include prior
cardiac procedures, such as coronary artery bypass and valve surgery, as
well as significant comorbid factors that are taken into consideration
when determining LVAD recipient eligibility (20).

In 2013, the Centers for Medicare and Medicaid Services published strict
criteria for destination therapy LVAD eligibility. Several risk
assessment tools have been developed to predict postoperative
complications and mortality and to determine which patients are
qualified to receive these therapeutic devices (15). Most studies have
focused on patient populations of men \textgreater{}60 years with
ischemic cardiomyopathy (22). The tremendous impact of patient selection
on the outcomes of LVAD implantation has long been recognized. Patients
are classified as ``high risk'' for this intervention if they have any
form of liver or renal dysfunction, hematological and coagulation
abnormalities, or lower serum albumin levels (22). As demonstrated in
the aforementioned study, many of these high-risk patients crossover
with those in the high-income group. Our study shows that compared with
lower socioeconomic status individuals, high-income patients are more
likely to experience ischemic strokes, acute kidney injury, bleeding
abnormalities, and to undergo extracorporeal membrane oxygenation. We
also found that higher-income patients have a higher post-LVAD all-cause
inpatient mortality (unadjusted and adjusted for comorbidities). Prior
studies show that important determinants of in-hospital mortality
include poor nutrition, hematological abnormalities, markers of
end-organ or right ventricular dysfunction, and lack of inotropic
support (22). Although difficult to assess the primary cause of
mortality in our study due to the nature of the NIS database, we did
find a higher proportion of post-operative complications as detailed in
Table 2. Taking into consideration all of the above-mentioned factors
and in line with the REMATCH trial, there are significant benefits
associated with the long-term use of LVAD devices for end-stage heart
failure (26). As we continue to elucidate the benefits of these devices
and incorporate them into routine practice, it is imperative to find the
balance between survival benefit and risk of surgery when discussing the
appropriate timing for LVAD implantation.

\emph{Strengths and Limitations}

Utilization of the NIS provides us with an opportunity to analyze a
large number of LVAD patients, from hundreds of nationwide centers,
across a 7-year timeframe (weighted estimate of 25,503 LVAD implants).
However, as NIS represents hospitalizations and not individual patients,
there is a possibility that patients undergoing pump exchanges may
feature more than once in the data set. Our analyses are also limited by
a lack of longitudinal follow-up and are valid for a short-term period
(\textasciitilde{}10--70 days as suggested by mean +- standard deviation
LOS). The inability of NIS to define the proportion of individuals
eligible for LVAD implantation despite income, as opposed to the
proportion who ultimately undergo LVAD implantation, is important.
Lastly, with the NIS, we are unable to assess echocardiographic findings
that might affect the eligibility or feasibility of LVAD, laboratories
data which is critical for patients undergoing LVAD and the severity of
advanced heart failure assessed by INTERMACS score of patients
undergoing LVAD implantation. Prospective studies of income differences
in patients with advanced heart failure are needed to confirm whether
such differences may exist.

\textbf{Conclusion}

Health inequities based on socioeconomic status have long contributed to
disparities in cardiac care and treatment strategies. Although patients
with low-income were found to have higher comorbidities, they were found
to have lower complications and inpatient mortality post-LVAD
implantation. Improving our understanding of the impact of socioeconomic
factors on patient eligibility, health literacy and pursuit of
treatment, and outcomes of LVAD intervention is incredibly important as
health care providers continue to integrate and evolve this therapeutic
technique into routine practice.

\textbf{Author contributions}

1) Authors make substantial contributions to conception and design,
and/or acquisition of data, and/or analysis and interpretation of data:

Bertrand Ebner, Morgan Karetnick, Jelani Grant, Louis Vincent, Jennifer
Maning.

2) Authors participate in drafting the article or revising it critically
for important intellectual content:

Bertrand Ebner, Morgan Karetnick, Neal Olarte, Odunayo Olorunfemi.

3) Authors give final approval of the version to be submitted and any
revised version.

Colombo Rosario, Sandra Chaparro.

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Table 1: Values are reported as mean +- standard deviation for continuous
variables. Categorical variables are represented as n (\%).
Between-group comparisons were performed for continuous data using
T-test for parametric and Mann-Whitney~U~test for nonparametric
variables, respectively. Categorical variables were compared using Chi
squared~test.~p\textless{}0.001 considered for statistical significance
per Holm-Bonferroni correction for multiple comparisons. p value
considered significant \textless{}0.001 (bold). NS=Non-Significant.

Table 2: Values are reported as mean +- standard deviation and median
{[}IQR 25-75{]} for parametric and non-parametric continuous variables,
respectively. Categorical variables are represented as n (\%).
Between-group comparisons were performed for continuous data using
T-test for parametric and Mann-Whitney~U~test for nonparametric
variables, respectively. Categorical variables were compared using Chi
squared~test.~p\textless{}0.001 considered for statistical significance
per Holm-Bonferroni correction for multiple comparisons. p value
considered significant \textless{}0.001 (bold). NS=Non-Significant.

Figure A: Number of left ventricular assist devices implanted per every
calendar year by income. Average increase per year of the low-income
group was 11\% and for the high-income group was 8\%.

Figure B: Median length of stay (LOS) in days in patients undergoing
left ventricular assist device (LVAD) implantation by income per every
calendar year. Variables were compared using Mann-Whitney U test with
p\textless{}0.001 considered for statistical significance (Black X).
Dots=Non-significant difference.

Figure C: Trend and comparison of inpatient all-cause mortality of
patients undergoing left ventricular assist device (LVAD) by income per
every calendar year. Variables were compared using Chi squared~test with
p\textless{}0.001 considered for statistical significance (Black X).
Dots=Non-significant difference.

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