Discharge Against Medical Advice after Hospitalization for Acute Myocardial

Infarction

Running title: Discharge against medical advice after acute myocardial infarction

Chun Shing Kwok MBBS MSc BSc1,2, Mary Norine Walsh MD3, Annabelle Volgman MD4,

Mirvat Alasnag MD5, Glen P. Martin PhD6, Diane Barker MD2, Ashish Patwala MD2,

Rodrigo Bagur MD PhD1, David L Fischman MD7, Mamas A Mamas BM BCh DPhil1,2

1. Keele University, Stoke-on-Trent, UK.

2. Royal Stoke University Hospital, Stoke-on-Trent, UK.

3. St Vincent Heart Center, Indianapolis, Indiana, USA.

4. Rush University Medical Center, Chicago, Illinois, USA.

5. Cardiac Center, King Fahd Armed Forces Hospital, Jeddah, Saudi Arabia.

6. Faculty of Biology, Medicine and Health, University of Manchester, Manchester

Academic Health Science Centre, Manchester, UK.

7. Thomas Jefferson University Hospital, Philadelphia, USA.

Corresponding author:

Dr Chun Shing Kwok

Keele Cardiovascular Research Group,

Centre for Prognosis Research

Keele University,

Stoke-on-Trent, UK

E-mail: shingkwok@doctors.org.uk

Tel: +44 1782 732911 Fax: +44 1782 734719

Keywords: acute myocardial infarction; quality and outcomes of care

Word count: 3,000

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its Licensees to permit this article (if accepted) to be published in Heart and any other

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Abstract

Background: Discharge against medical advice (AMA) occurs infrequently but is associated

with poor outcomes. There are limited descriptions of discharges AMA in national cohorts of

patients with acute myocardial infarction (AMI). This study aims to evaluate discharge AMA

in AMI and how it affects readmissions.

Methods: We conducted a cohort study of patients with AMI in the United States in the

Nationwide Readmission Database who were admitted between the years 2010-2014.

Descriptive statistics were presented for variables according to discharge home or against

medical advice. The primary endpoint was all-cause 30-day unplanned readmissions and their

causes.

Results: 2,663,019 patients were admitted with AMI of which 10.3% (n=162,070) of

1,569,325 patients had an unplanned readmission within 30-days. The crude rate of discharge

AMA remained stable between 2010 and 2014 at 1.5%. Discharge AMA was an independent

predictor of unplanned all-cause readmissions (OR 2.27 95%CI 2.14-2.40); patients who

discharged AMA had >2-fold increased crude rate of readmission for acute myocardial

infarction (30.4% vs 13.4%) and higher crude rate of admissions for neuropsychiatric reasons

(3.2% vs 1.3%). After adjustment, discharge AMA was associated with increased odds of

readmissions for AMI (OR 3.65 95%CI 3.31-4.03, p<0.001). We estimate that there are 1,420

excess cases of AMI among patients who discharged AMA.

Conclusions: Discharge AMA occurs in 1.5% of the population with AMI and these patients

are at higher risk of early readmissions for re-infarction. Interventions should be developed to

reduce discharge AMA in high-risk groups and initiate interventions to avoid adverse

outcomes and readmission.

3

Key Questions:

What is already known about the subject?

Discharge against medical advice (AMA) with patients leaving hospital before the

treating physician’s recommendation, occurs in 1-2% of all medical admissions and it

poses a challenge for physicians.

There are limited descriptions of discharges AMA in national cohorts of patients with

acute myocardial infarction (AMI).

What does the study add?

Discharge AMA in patients admitted with an AMI occurs in less than 2% of patients.

These patients represent a high-risk cohort with a 2-fold increase in odds of 30-day

unplanned readmission and a four-fold increase in re-infarction within 30 days.

How might this impact on clinical practice?

Interventions should be developed to reduce discharge AMA in high-risk groups and

avoid adverse outcomes and readmission when it occurs.

4

Introduction

Discharge against medical advice (AMA) with patients leaving hospital before the

treating physician’s recommendation, occurs in 1-2% of all medical admissions[1] and it

poses a challenge for physicians.

Discharge AMA may be associated with lack of trust and poor/patient/provider

communications, which may be markers for poor outpatient treatment adherence, and

decreased utilization of necessary healthcare services. [2] A variety of factors have been

associated with discharge AMA including financial constraints, family pressures,

dissatisfaction with the hospital routine and treatment for substance seeking behaviour.[3]

Discharge AMA is important because it is associated with greater risk of 30-day mortality.[4]

Management of acute myocardial infarction (AMI) includes pharmacotherapy and

interventional treatments shown to improve prognosis. Among discharge AMA patients there

are concerns of inadequate treatment for their index AMI. Continuation of medications such

as beta-blockers, angiotensin converting enzyme inhibitors, statins and dual antiplatelet

therapy post discharge is important to lower the risk of further cardiovascular events and

death.[5,6] Prolonged dual antiplatelet therapy is necessary to avoid stent thrombosis in

patients who undergo percutaneous coronary intervention. To our knowledge, only one study

has previously evaluated hospital discharges AMA after acute myocardial infarction (AMI) in

a single state in the United States in an era when PCI was less widespread.[7] This study

reported a 1.1% rate of discharged AMA with no difference in the crude rate of 30-day all-

cause readmission between the discharge AMA and comparison group (9.3% vs 8.4%) [7]

In this study, we examined the crude rates, trends and predictors of discharge AMA,

and the association between discharge AMA and unplanned 30-day readmission in a

contemporary national cohort of patients following an index admission with AMI.

5

Methods

Study design and participants

The Nationwide Readmission Database (NRD) is a publicly available database of all-

payer hospital inpatients stays, developed by the Agency for Healthcare Research and Quality

(AHRQ) as a part of the U.S. Healthcare Cost and Utilization Project (HCUP).[8] The data

are drawn from 21 states that account for approximately half of the total U.S. resident

population and hospitalizations.[9,10]

In the current study, we included men and women aged 18 years or older who were

hospitalized with a primary diagnosis of AMI between 2010 and 2014 and were either

discharged AMA or discharged home. A primary diagnosis of AMI was defined by the

following International Classification of Disease – 9th Clinical Modification (ICD-9) codes:

4100*, 4101*, 4102*, 4103*, 4104*, 4105*, 4106*, 4107*, 4108* and 4109* which is a

combination of ST-elevation myocardial infarction (STEMI) and non-ST-elevation

myocardial infarction (NSTEMI). Discharge AMA was defined from the variable

"DISPUNIFORM", which represents the disposition of patient at discharge. We excluded

patients who were discharged in December (because they may not have had 30-day of follow

up), those who died during their index admission for AMI, those who had an elective

readmission and those who were not discharged home/self-care or AMA. We only considered

the first AMI admission within a calendar year for a patient.

Variables and outcomes

We used ICD-9 and Clinical classification software (CCS) of diseases codes to

determine comorbidities, in-hospital procedures and outcomes. Alcohol misuse was defined

by the AHRQ comorbidity measure for ICD-9 codes alcohol abuse. The 30-day unplanned

readmissions were defined as first rehospitalization after discharge within 30 days from

admission for AMI that was not elective. The causes of readmissions were determined from

6

the principle diagnosis based on CCS codes (Supplementary Table 1). The primary endpoint

was all-cause 30-day readmissions and readmission cause.

Statistical analysis

Statistical analysis was performed using Stata 14.0 (College Station, Texas, USA). A

flow diagram was used to show the proportion of patients at each stage of the analysis and

those who were readmitted. Descriptive statistics were used to compare patients who were

discharge AMA compared to those discharged home, with further stratification depending on

whether or not they were readmitted. Statistical differences between groups for continuous

variables were tested using the t-test and for categorical variables the chi-squared test. For all

analyses, the survey estimation commands were used (e.g. svy: logistic for multiple logistic

regression), following the recommendations from AHRQ for analysis of survey data to

account for the complex survey design of the NRD. Using the survey estimation commands,

national sample sizes were determined by applying the discharge weights to the crude sample

and the weight was propagated to determine the patients excluded and the estimated final

sample size analysed. Multiple logistic regression was used to determine independent

variables associated with discharge AMA and the influence of discharge AMA on 30-day

unplanned readmission. All variables were adjusted for in the models. A multivariable model

was used to determine if discharge AMA was associated with readmissions for AMI. The

excess admissions associated with AMI and excess deaths from readmission among discharge

AMA patients was estimated by considering the crude rate of deaths and readmissions in the

non-discharge AMA group compared to the observed crude rate of deaths and readmissions

in the discharge AMA group. We further performed subgroup analysis for odds of AMI

readmission depending on the subgroup of patients without a coronary angiogram and among

those who had PCI. We also determined the crude rate of discharge AMA by length of stay.

7

Results

There were 2,663,019 patients with acute myocardial infarction between 2010 and

2014 captured in the Nationwide Readmission Database. After exclusion of patients admitted

in December (n=234,702), patients who died in-hospital (n=136,047), patients with elective

readmissions (n=88,166) and patients who were discharged to short term hospital, care home

or law enforcement (n=634,779) there were 1,569,325 patients included in the analysis of

which 10.3% had a 30-day unplanned readmission. The crude rate of discharge AMA was

1.45% in 2010, which increased to 1.49% in 2014.

Patients who were discharged AMA were younger (59.9 vs 63.5 years, p<0.001),

more likely to be male (75.8% vs 66.4%, p<0.001) and more likely to be uninsured (14.6% vs

7.9%) (Table 1). Patients who discharged AMA were less likely to have private insurance

(13.4% vs 31.5%, p<0.001) and more had Medicaid (19.8% vs 9.1%, p<0.001). Smokers

(58.0% vs 45.0%, p<0.001), alcohol misusers (9.6% vs 3.5%, p<0.001), patients with chronic

lung disease (25.0% vs 17.5%, p<0.001) and renal failure (18.1% vs 14.4%, p<0.001) had

higher crude rates of discharge AMA. In addition, discharge AMA patients were less likely to

receive coronary angiography (46.4% vs 86.6%, p<0.001), be treated with PCI (27.8% vs

63.3%, p<0.001) or receive a drug eluting stent (15.4% vs 46.2%, p<0.001). The crude 30-

day unplanned readmission rate was 24.9% among patients who discharged AMA and 10.1%

among patients discharged home. The mean time to 30-day readmission was shorter in the

discharge AMA group (10.6 vs 14.1 days, p<0.001) and the discharge AMA group had

longer length of stay at readmission (5.1 vs 4.5 days, p<0.001) and higher crude rate of

mortality at readmission (4.2% vs 3.5%, p=0.047).

Independent predictors of discharge AMA included smoking (OR 1.66 95%CI 1.57-

1.75, p<0.001), alcohol misuse (OR 1.49 95%CI 1.35-1.63, p<0.001), male sex (OR 1.92

8

95%CI 1.81-2.03, p<0.001), and younger age (OR 0.97 95%CI 0.96-0.97, p<0.001) (Table

2). STEMI patients were more likely to discharge AMA (OR 1.16 95%CI 1.09-1.23,

p<0.001). Variables associated with a reduced odds of discharge AMA included private

insurance (OR 0.40 95%CI 0.36-0.43, p<0.001), receipt of CABG (OR 0.11 95%CI 0.08-

0.13, p<0.001) and need for ICD/pacemaker insertion (OR 0.27 95%CI 0.18-0.40, p<0.001).

Comorbidities that was associated with reduced the odds of discharged AMA included heart

failure (OR 0.72 95%CI 0.52-1.00, p=0.049), atrial fibrillation (OR 0.83 95%CI 0.77-0.89,

p<0.001), renal failure (OR 0.79 95%CI 0.73-0.85, p<0.001), cancer (OR 0.67 95%CI 0.57-

0.78, p<0.001), depression (OR 0.87 95%CI 0.79-0.96, p=0.004) and dementia (OR 0.69

95%CI 0.58-0.81, p<0.001). In terms of non-patient data, medium hospital bed size and urban

location were associated with discharge AMA whilst patients admitted to teaching hospitals

were less likely to discharge AMA.

Discharge AMA was an independent predictor of unplanned readmissions (OR 2.27

95%CI 2.14-2.40). Causes of 30-day unplanned readmissions according to discharge AMA

status are depicted in Figure 1 and Supplementary Table 2. Patients with discharge AMA had

more than a 2-fold increased crude rate of readmission for AMI (30.4% (95%CI 30.4%-

30.5%) vs 13.4% (95%CI 13.4%-13.5%)) and a higher crude rate of admissions for

neuropsychiatric reasons (3.2% (95%CI 3.2%-3.2%) vs 1.3% (95%CI 1.3%-1.3%)).

Multivariable analysis reveals that discharge AMA was associated with increased odds of

readmissions for AMI (OR 3.65 95%CI 3.31-4.03, p<0.001). We estimate that there are 1,420

excess cases of AMI among patients who discharged AMA and 58 excess deaths during

readmissions among discharged AMA patients.

Among patients who discharge AMA and did not receive an angiogram the odds of

readmission for AMI was OR 3.59 95%CI 3.18-4.04, p<0.001. For patients who received

PCI, the odds of readmission for AMI was OR 3.65 95%CI 2.94-4.53, p<0.001.

9

The crude rate of discharge AMA peaked at 1-day length of stay whilst the

corresponding peak for patients who were not discharged against medical advice was 2 days

(Supplementary Table 3).

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Discussion

Our analysis reveals that discharge AMA in patients admitted with an AMI occurs in

less than 2% of patients. Nevertheless, these patients represent a high-risk cohort with a 2-

fold increase in odds of 30-day unplanned readmission and a one in three chance of

readmission with re-infarction within 30 days. Once differences in baseline characteristics are

adjusted for, patients who discharged AMA have a four-fold increased odd of admission with

re-infarction within 30 days. Our study adds to the current understanding of discharge AMA

in AMI based on the study of Fiscella et al conducted nearly 20 years ago [7] and show that

the crude rates of discharge AMA have remained similar (1.5% versus 1.1% in previous

study).

We identify several variables associated with discharge AMA including smoking,

alcohol misuse and younger males, although prevalent comorbidities such as obesity, heart

failure, atrial fibrillation, renal failure, cancer and depression reduced the odds of discharge

AMA. Patients who discharge AMA differ from those who are discharged home in that they

are more likely to receive Medicaid or be uninsured, live in lower income areas, smoke,

misuse alcohol and tend to be younger males. The study in California by Fiscella et al

reported similar findings that discharge AMA was more common in younger, male low

income, black, insured through Medicaid or uninsured and had less physical comorbidity and

greater mental health comorbidity.[7] In addition, we observe important health service system

level elements associated with AMA discharge such as bed size, urban location and teaching

hospital.[11-13] Our results suggest that medium hospital bed size and those from an urban

location are more likely to discharge AMA. Interestingly, we observed that patients from

teaching hospitals were less likely to discharge AMA. The effect of teaching hospital was

considered in a previous Statewide study in California by Fiscella et al which found a no

significant differences in discharge AMA among teaching hospitals compared to non-

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teaching hospitals (11.1% vs 9.8%).[7] Another qualitative study of 9 patients, 10 physicians

and 23 nurses/social workers, despite being limited because the study was not generalizable

to community or smaller hospitals, suggests that discharge AMA was more common in

teaching hospital settings because patients felt confused and frustrated.[14] However, in the

current study of patients all across the United States showed that patients from teaching

hospitals were less likely to discharge AMA (53.4% vs 57.8%), although the absolute

difference was relatively small, hence the clinical relevance of this observation is unclear.

Future work would need to both confirm this finding, and understand the mechanisms that

underlie potential differences in discharge AMA amongst different institutional structures.

We found that a few comorbidities were associated with discharge AMA but there

may be differences in why they show the association. Smoking and alcohol misuse may make

it challenging for patients to seek the substance they desire so they discharge AMA. We also

observed increased discharge AMA among patients with hypertension, diabetes and chronic

lung disease. One possible reason may be that these chronic conditions may have been

managed by community physicians or care teams and patients may feel more comfortable and

supported by these teams so are more willing to leave hospital and return to their usual care

providers once the acute problem is treated. In addition, previous myocardial infarction and

PCI were associated with increased discharge AMA. We speculate that this may be related to

a patient’s previous experience and felt that a period of observation once problem was treated

was not necessary so they choose to discharge AMA once acute problem is treated. The

literature suggests that discharge AMA stigmatizes patients, reduces their access to care and

can reduce the quality of informed consent discussions in discharge planning.[15]

The complexity of discharge AMA in AMI may be related to the extent of care and

resulting outcomes will obviously depend on the point at which the patient is discharged. A

patient who undergoes PCI or CABG and chooses to leave hospital will at least receive

12

partial treatment compared to a patient who leaves prior to coronary revascularization. It may

be important for clinicians to be aware that despite differences in the extent to which patients

are treated prior to discharge AMA, a physician still has a responsibility to advocate for a

patient’s well-being so AMA discharges should be accompanied by reasonable efforts to

coordinate a patient’s ongoing care.[16]

An interesting observation in the current study is that some comorbidities including

heart failure, atrial fibrillation, cancer, dementia and renal failure reduce the odds of

discharge AMA. Possible explanations include that patients recognize that their condition

will require long-term care and discharge AMA may damage the relationship with care

professionals. Dementia may remove the patient’s autonomy to make decisions to leave

against advice. Reasons for discharge AMA in cardiovascular diseases have been previously

explored in a qualitative study.[14] Communications were identified as an area that required

improvement and healthcare providers should be trained in cultural diversity, interpersonal

skills, customer service and also be accurate and open about wait times.

In the setting of an AMI patients require treatment with potent anti-thrombotic agents

and may undergo percutaneous revascularisation procedures that require prolonged dual

antiplatelet (DAPT) including lifelong single antiplatelet therapy. Our study demonstrates

that the performance of a coronary angiogram or PCI occur less frequently in cases that

discharge AMA. This may relate to the fact that patients leave prior to the possibility of

performing cardiac catheterization or that the clinician don’t offer these procedures due to a

concern of non-compliance with post PCI DAPT. Patients with NSTEMI may be more likely

to leave prior to PCI but this is less likely in STEMI because PCI is an emergency procedure.

The risks of associated with discharge AMA among NSTEMI patients includes the risks

related to not getting PCI as well as PCI related complications like stent thrombosis whilst

those with STEMI are more likely to only have readmissions due to complications from PCI.

13

We observed lower crude rates of readmissions for bleeding and renal failure among patients

that discharge AMA. This may be related to patients not taking their medications if they

discharged AMA, but also due to the fact that these patients were younger and their baseline

risk of bleeding is likely to be less. Among cases that did undergo PCI, discharge AMA

patients were more likely to receive bare metal stents that require shorter DAPT regimes

despite the evidence of poorer outcomes compared to drug eluting stents.[17,18]

A key finding of the current study is the 4-fold increase in odds of readmissions for

AMI among patients who discharge AMA. There are a few possible reasons for this finding.

Patients can discharge AMA at any point in their care so there will be heterogeneity in the

treatments received by patients. We found that evidence based diagnostics procedures and

treatments including coronary angiograms, PCI and CABG were lower in patients who

discharge AMA. The potential unstable coronary lesion poses a significant risk when left

untreated compounded by the lack of secondary prevention with statins and antithrombotic

therapies. Secondly, if a patient receives treatment but discharges AMA they may not receive

secondary prevention medications such as antithrombotic medications and statins that would

place them at increased risk of re-infarction. In addition, patients who undergo PCI may be

discharged without appropriate antiplatelet therapy increasing the risk of stent thrombosis.

Finally, the discharge AMA group may be discharged without the necessary tools for

smoking cessation.

In the current study, we report an unplanned readmissions crude rate of 10.3% which

is lower that the 19.3% described by Fiscella.[7] This is likely because of better quality of

care, more widespread adoption of PCI, anti-thrombotics and better provision of evidence

based therapies in contemporary practice. In the study of Fiscella, the authors did not study

specific causes of readmission (apart from ACS or non-ACS), or differentiate between the

non-ACS causes of readmission.[7] In contrast, our analysis provides more granular insight

14

into both cardiovascular and non-cardiovascular causes for readmissions and shows that there

are a broad range of causes of unplanned readmissions with important differences between

the discharge AMA and non-discharge AMA groups.

Despite this lower overall lower crude rate of readmission our analysis reveals a

nearly 4-fold increase in odds of unplanned readmission for AMI compared to the 2-fold

increase reported by Fiscella[7] This suggests that re-infarction for discharge AMA patients

have worsened over time, perhaps relating to the more widespread use of PCI as a treatment

strategy, and hence a greater potential for stent thrombosis with the premature

discontinuation of DAPT.

Among patients that choose to discharge AMA, measures should be developed to

obviate potential risks such as prescription of dual antiplatelet therapy and other secondary

prevention medications prior to discharge or a means to deliver these in the community.

Interventions should be developed across healthcare providers spanning secondary and

primary care interface including pharmacy outreach programs to enable prescription

and/continuation of therapies in the community. We observed higher crude rates of

neuropsychiatric reasons for readmission in patients with discharge AMA and care may be

improved by early involvement of psychiatric services particularly patients with a history of

mental health conditions or substance abuse.

We speculate that one of the factors that may influence patient’s decision to discharge

AMA is how ill or symptomatic they are which is influenced by the severity of the acute

myocardial infarction. We found that patients who discharge AMA had less circulatory

support (1.8% vs 2.9%), vasopressor use (0.3% vs 0.5%) and intra-aortic balloon pump use

(1.7% vs 2.8%). In addition, these patients had fewer complications such as complete heart

block (0.6% vs 0.9%), ventricular fibrillation (1.2% vs 2.3%), ventricular tachycardia (4.3%

vs 5.4%), cardiogenic shock (2.1% vs 2.5%) and cardiac arrest (1.2% vs 1.5%). These

15

findings may suggest that patients who have less severe AMI are more likely to discharge

AMA.

There are several limitations to this study. The overall data is derived from five

unique datasets corresponding to each year between 2010 and 2014 so there is no possible

linkage between years and the same patient can appear more than once in different years. The

dataset does not capture pharmacotherapy data and the compliance/prescription of

medications is unknown. The population at risk of readmission may be overestimated

because of survivorship. We do not have data on out-of-hospital mortality which would

reduce the population at risk of unplanned readmissions. Causes of readmissions were

identified using the primary discharge diagnosis codes which may be subject to reporting

biases. In the interest of reducing potential confounding, we determined adjusted odds ratios

to estimate the association between collected variables and discharge AMA. However, odds

ratios, which can approximate for rate ratio, have limitations because odds ratios may

overestimate associations especially the case for events which are not rare like 30-day

readmissions. Another limitation of the study is that we are unable to comment definitively

about reasons for our findings due to the observation nature of this study. Furthermore, even

though we are able to adjust for a variety of variables such as comorbidities, hospital and

system related factors and socioeconomic factors, these adjustments may not fully account

for the extent of their effect on the models of the current study because of unmeasured

confounders.

In conclusion, discharge AMA occurs in 1.5% of the population treated for an AMI

and is associated with greater risk of 30-day unplanned readmissions. These patients are at

particularly high-risk for readmission due to AMI, with a nearly 4-fold independent increase

in odds for these readmissions. Our multivariable analysis suggests that patients who are

16

more likely to discharge AMA appear to be younger, male, uninsured, from low-income areas

who were also smokers and misused alcohol. We estimate that there are 1,420 excess cases of

AMI among patients that discharge AMA. Interventions should be developed to reduce

discharge AMA in high-risk groups to avoid adverse outcomes and readmission.

Contributorship

CSK and MAM were responsible for the study design and concept. CSK performed

the data cleaning and analysis. CSK wrote the first draft of the manuscript and all authors

contributed to the writing of the paper.

Transparency declaration

CSK affirms that the manuscript is an honest, accurate, and transparent account of the

study being reported; that no important aspects of the study have been omitted; and that any

discrepancies from the study as planned have been explained.

Ethical committee approval

This is anonymised data and there is no patient identifiable information. This study

was determined to be exempt from review by the Medical Research Council’s “Does our

study need NHS REC approval form” and was conducted in accordance to the HCUP Data

Use Agreement.

Acknowledgements

We are grateful to the Healthcare Cost and Utilization Project (HCUP) and the HCUP

Data Partners for providing the data used in the analysis.

Funding

17

The study was supported by a grant from the Research and Development Department

at the Royal Stoke Hospital. This work is conducted as a part of PhD for CSK which is

supported by Biosensors International.

Competing Interests and Disclosures

None.

List of Tables and Figures

Table 1: Characteristics of patients with primary diagnosis of acute myocardial infarction according to discharge against medical advice status

Table 2: Independent predictors of discharge against medical advice

Figure 1: Causes of 30-day unplanned readmissions

Supplementary Table 1: Classification of Clinical Classifications Software (CCS) Codes for Readmissions Causes

Supplementary Table 2: Causes of unplanned 30-day readmissions

Supplementary Table 3: Influence of length of stay on the rate of patients discharged against medical advice

18

Table 1: Characteristics of patients with primary diagnosis of acute myocardial infarction according to discharge against medical advice statusVariable No discharge

against medical advice (n=1,546,406)

Discharge against medical advice (n=22,919)

P-value

Age (year) 63.5±13.2 59.9±13.5 <0.001Female 33.6% 24.2% <0.001Weekend admission 27.1% 27.1% 0.90Year20102011201220132014

18.9%19.0%19.2%21.1%21.8%

18.7%18.8%19.1%21.1%22.3%

0.85

Diagnosis of STEMI 34.8% 26.5% <0.001Primary expected payerMedicareMedicaidPrivateUninsuredNo chargeOther

47.4%8.1%31.5%7.9%1.0%4.2%

46.1%19.8%13.4%14.6%1.4%4.8%

<0.001

Median household income centile0-25th

26-50th

51-75th

76-100th

29.6%25.6%24.1%20.7%

37.7%25.3%21.7%15.3%

<0.001

Smoking 45.0% 58.0% <0.001Alcohol misuse 3.5% 9.6% <0.001Dyslipidemia 67.2% 49.7% <0.001Hypertension 71.7% 70.9% 0.063Diabetes mellitus 34.0% 36.6% <0.001Obesity 16.1% 14.2% <0.001Heart failure 0.5% 0.7% 0.003Coronary artery disease 84.6% 65.6% <0.001Previous myocardial infarction 11.7% 16.1% <0.001Previous PCI 15.6% 18.0% <0.001Previous CABG 7.6% 10.0% <0.001Valvular heart disease 0.1% 0.2% 0.078Atrial fibrillation 12.2% 11.1% 0.002Previous stroke/TIA 6.7% 7.8% <0.001Peripheral vascular disease 9.9% 10.2% 0.32Pulmonary circulatory disorder 0.07% 0.10% 0.18Peptic ulcer disease 0.03% 0.01% 0.28Chronic lung disease 17.5% 25.0% <0.001Renal failure 14.4% 18.1% <0.001Liver disease 1.4% 2.6% <0.001Hypothyroidism 9.2% 5.3% <0.001Fluid and electrolyte disorders 15.0% 19.1% <0.001

19

Anemia 12.0% 13.5% <0.001Cancer 2.1% 2.3% 0.19Depression 6.6% 6.5% 0.63Dementia 2.4% 2.2% 0.12Charlson score 1.2±1.5 1.5±1.6 <0.001BedsizeSmallMediumLarge

6.6%22.7%70.8%

7.7%25.6%66.7%

<0.001

Urban location 5.4% 5.9% 0.026Teaching hospital 57.8% 53.4% <0.001Circulatory support 2.9% 1.8% <0.001Vasopressor use 0.5% 0.3% 0.020Intra-aortic balloon pump use 2.8% 1.7% <0.001Ventilation 2.2% 3.0% <0.001Drug eluting stent 46.2% 15.4% <0.001In-hospital eventsComplete heart block 0.9% 0.6% <0.001Ventricular fibrillation 2.3% 1.2% <0.001Ventricular tachycardia 5.4% 4.3% <0.001Stroke/TIA 2.4% 2.4% 0.86Cardiogenic shock 2.5% 2.1% 0.008Cardiac arrest 1.5% 1.2% 0.014Acute kidney injury 0.7% 1.3% <0.001Major bleeding 0.9% 1.4% <0.001Blood transfusion 0.19% 0.02% <0.001Vascular complication 0.5% 0.2% <0.001Receipt of coronary angiogram 86.6% 46.4% <0.001Receipt of PCI 63.3% 27.8% <0.001Receipt of thrombolysis 1.6% 1.3% 0.025Receipt of CABG 5.8% 1.0% <0.001Receipt of ICD/pacemaker 0.9% 0.3% <0.001Receipt of LV assist device 0.15% 0.07% 0.040Length of stay (days) 3.8±3.7 2.6±3.9 <0.001Cost of index admission (USD) $19,035±14,357 $11,451±12,501 <0.001Cost of readmission (USD) $12,607±17,715 $15,417±20,895 <0.001Cost of index admission and readmission USD)

$31,536±25,443 $26,676±25,112 <0.001

Readmission rate at 30 days 10.1% 24.9% <0.001Mean time to readmission in days (SD)

14.1±7.7 10.6±8.0 <0.001

Mean length of stay for readmission in days (SD)

4.5±5.7 5.1±6.8 <0.001

Readmission death 3.5% 4.2% 0.047P-value from T-test for continuous variables and Chi2-test for categorical variables.

20

Table 2: Independent predictors of discharge against medical adviceVariable Odds ratio (95% CI) p-valueAge 0.97 (0.96-0.97) <0.001Male 1.92 (1.81-2.03) <0.001Diagnosis of STEMI 1.16 (1.09-1.23) <0.001Primary expected payer vs MedicareMedicaidPrivateUninsuredOther

1.30 (1.20-1.41)0.40 (0.36-0.43)1.13 (1.03-1.24)0.86 (0.76-0.98)

<0.001<0.0010.0080.021

Median household income vs 0-25th

26-50th

51-75th

76-100th

0.89 (0.84-0.95)0.88 (0.82-0.95)0.84 (0.77-0.91)

0.0010.001<0.001

Smoking 1.66 (1.57-1.75) <0.001Alcohol misuse 1.49 (1.35-1.63) <0.001Dyslipidemia 0.65 (0.61-0.68) <0.001Hypertension 1.10 (1.04-1.17) <0.001Diabetes mellitus 1.13 (1.08-1.20) <0.001Obesity 0.88 (0.82-0.95) 0.001Heart failure 0.72 (0.52-1.00) 0.049Coronary artery disease 0.79 (0.74-0.84) <0.001Previous myocardial infarction 1.27 (1.18-1.36) <0.001Previous PCI 1.25 (1.18-1.36) <0.001Previous CABG 0.92 (0.85-1.00) 0.049Atrial fibrillation 0.83 (0.77-0.89) 0.24Chronic lung disease 1.14 (1.08-1.21) <0.001Renal failure 0.79 (0.73-0.85) <0.001Liver disease 0.86 (0.74-0.85) 0.046Anemia 0.86 (0.80-0.92) <0.001Cancer 0.67 (0.57-0.78) <0.001Depression 0.87 (0.79-0.96) 0.004Dementia 0.69 (0.58-0.81) <0.001Bed size vs SmallMedium 1.20 (1.06-1.35) 0.004Urban location 1.15 (1.02-1.30) 0.022Teaching hospital 0.81 (0.76-0.87) <0.001Receipt of ventilation 1.48 (1.25-1.75) <0.001Drug eluting stent 0.57 (0.52-0.63) <0.001Ventricular fibrillation 0.59 (0.47-0.74) <0.001Receipt of angiogram 0.18 (0.17-0.19) <0.001Receipt of PCI 0.57 (0.52-0.63) <0.001Receipt of CABG 0.11 (0.08-0.13) <0.001Receipt of ICD/pacemaker 0.27 (0.18-0.40) <0.001Receipt of thrombolysis 1.22 (1.01-1.47) 0.043*Acute kidney injury, major bleeding and blood transfusions were not included in analysis because there were too few events.

21

Figure 1

22

Supplementary Table 1: Classification of Clinical Classifications Software (CCS) Codes for Readmissions Causes

Causes of Readmission CCS code

Diagnosis

Respiratory 127 Chronic obstructive pulmonary disease and bronchiectasis128 Asthma130 Pleurisy, pneumothorax, pulmonary collapse131 Respiratory failure, insufficiency and arrest132 Lung disease due to external agents133 Other lower respiratory disease134 Other upper respiratory disease221 Respiratory distress syndrome

Infection 1 Tuberculosis2 Septicemia3 Bacterial infection4 Mycoses5 Human Immunodeficiency Virus (HIV) infection6 Hepatitis7 Viral infection8 Other infection9 Sexually transmitted infection76 Meningitis77 Encephalitis78 Other central nervous system infection and poliomyelitis90 Inflammation or infection of eye122 Pneumonia123 Influenza124 Acute and chronic tonsillitis125 Acute bronchitis126 Other upper respiratory infections129 Aspiration pneumonitis135 Intestinal infection197 Skin and subcutaneous tissue infections201 Infective arthritis and osteomyelitis (except that caused by tuberculosis or

sexually transmitted disease)Bleeding 60 Acute posthemorrhagic anemia

153 Gastrointestinal hemorrhage182 Hemorrhage during pregnancy; placental abruption; placenta previa

Peripheral vascular disease 114 Peripheral and visceral atherosclerosis115 Aortic, peripheral and visceral artery aneurysms116 Aortic and peripheral arterial embolism or thrombosis117 Other circulatory disease118 Phlebitis, thrombophlebitis and thromboembolism119 Varicose veins of lower extremities

Genitourinary 159 Urinary tract infection160 Calculus of the urinary tract

23

161 Other diseases of kidney and ureters162 Other diseases of bladder and urethra163 Genitourinary symptoms and ill-defined conditions164 Hyperplasia of prostate165 Inflammatory conditions of the male genital organs166 Other male genital disorders170 Prolapse of female genital organs175 Other female genital disorders215 Genitourinary congenital anomalies

Renal disease 156 Nephritis; nephrosis; renal sclerosis157 Acute and unspecified renal failure158 Chronic kidney disease

Gastrointestinal 138 Esophageal disorders139 Gastroduodenal ulcer (except hemorrhage)140 Gastritis and duodenitis141 Other disorders of stomach and duodenum142 Appendicitis and other appendiceal conditions143 Abdominal hernia144 Regional enteritis and ulcerative colitis145 Intestinal obstruction without hernia146 Diverticulosis and diverticulitis147 Anal and rectal conditions148 Peritonitis and intestinal abscess149 Biliary tract disease150 Liver disease; alcohol-related151 Other liver diseases152 Pancreatic disorders (not diabetes)154 Noninfectious gastroenteritis155 Other gastrointestinal disorders214 Digestive congenital anomalies222 Hemolytic jaundice and perinatal jaundice250 Nausea and vomiting251 Abdominal pain

Transient ischemic attack/stroke

109 Acute cerebrovascular disease110 Occlusion of stenosis of precerebral arteries111 Other and ill-defined cerebrovascular disease112 Transient cerebral ischemia113 Late effects of cerebrovascular disease

Trauma 207 Pathological fracture225 Joint disorders and dislocations; trauma-related226 Fracture of neck of femur (hip)227 Spinal cord injury228 Skull and face fractures229 Fracture of upper limb230 Fracture of lower limb231 Other fractures232 Sprains and strains

24

233 Intracranial injury234 Crushing injury or internal injury235 Open wounds of head; neck; and trunk236 Open wounds of extremities239 Superficial injury; contusion244 Other injuries and conditions due to external causes260 All (external causes of injury and poisoning)

Endocrine/metabolic 48 Thyroid disorders49 Diabetes mellitus without complication50 Diabetes mellitus with complication51 Other endocrine disorders53 Disorders of lipid metabolism58 Other nutritional and endocrine/metabolic disorders186 Diabetes or abnormal glucose tolerance complicating pregnancy; childbirth; or

the puerperiumNeuropsychiatric 79 Parkinson's disease

80 Multiple sclerosis81 Other hereditary and degenerative nervous system conditions82 Paralysis83 Epilepsy, convulsions84 Headache including migraine85 Coma, stupor and brain damage95 Other nervous system disorders216 Nervous system congenital anomalies650 Adjustment disorders651 Anxiety disorders652 Attention-deficit, conduct, and disruptive behavior disorders653 Delirium, dementia, and amnestic and other cognitive disorders654 Developmental disorders655 Disorders usually diagnosed in infancy and childhood or adolescence656 Impulse control disorders, NEC657 Mood disorders658 Personality disorders659 Schizophrenia and other psychotic disorders660 Alcohol-related disorders661 Substance-related disorders662 Suicide and intentional self-inflicted injury663 Screening and history of mental health and substance abuse codes670 Miscellaneous mental health disorders

Hematological/neoplastic 11 Cancer of head and neck12 Cancer of esophagus13 Cancer of stomach14 Cancer of colon15 Cancer of rectum and anus16 Cancer of liver and intrahepatic bile ducts17 Cancer of pancreas

25

18 Cancer of other GI organs, peritoneum19 Cancer of bronchus, lung20 Cancer of other respiratory and intrathoracic21 Cancer of bone and connective tissue22 Melanoma of skin23 Other non-epithelial cancer of skin24 Cancer of breast25 Cancer of uterus26 Cancer of cervix27 Cancer of ovary28 Cancer of other female genital organs29 Cancer of prostate30 Cancer of testis31 Cancer of other male genital organs32 Cancer of bladder33 Cancer of kidney and renal pelvis34 Cancer of other urinary organs35 Cancer of brain and nervous system36 Cancer of thyroid37 Hodgkin's disease38 Non-Hodgkin's lymphoma39 Leukemia40 Multiple myeloma41 Cancer, other and unspecified primary42 Secondary malignancies43 Malignant neoplasm without specification of site44 Neoplasm of unspecified nature or uncertain behavior46 Benign neoplasm of uterus47 Other and unspecified benign neoplasm59 Deficiency and other anemias61 Sickle cell anemia62 Coagulation and hemorrhagic disorders63 Disease of white blood cells64 Other hematologic conditions

Rheumatology problem 54 Gout and other crystal arthropathiesOphthalmology problem 86 Cataract

87 Retinal detachment defects, vascular occlusion and retinopathy88 Glaucoma89 Blindness and vision defects91 Other eye disorders

ENT problem 92 Otitis media and related conditions93 Conditions associate with dizziness or vertigo94 Other ear and sense organ disorder

Non-specific chest pain 102 Non-specific chest painOral health problem 136 Disorders of teeth and jaw

137 Diseases of mouth; excluding dental

26

Obstetric admission including pregnancy

174 Female infertility176 Contraceptive and procreative management177 Spontaneous abortion178 Induced abortion179 Postabortion complication180 Ectopic pregnancy181 Other complications of pregnancy184 Early or threatened labor185 Prolonged pregnancy187 Malposition; malpresentation188 Fetopelvic disproportion; obstruction189 Previous C-section190 Fetal distress and abnormal forces of labor191 Polyhydramnios and other problems of amniotic cavity192 Umbilical cord complication193 OB-related trauma to perineum and vulva194 Forceps delivery195 Other complications of birth; puerperium affecting management of mother196 Other pregnancy and deliver including normal218 Liveborn

219 Short gestation; low birth weight; and fetal growth retardation220 Intrauterine hypoxia and birth asphyxia223 Birth trauma224 Other perinatal conditions

Dermatology problem 198 Other inflammatory condition of skin199 Chronic ulcer of skin200 Other skin disorders

Poisoning 241 Poisoning by psychotrophic agents242 Poisoning by other medication and drugs243 Poisoning by nonmedical substances

Syncope 245 SyncopeOther non-cardiac 10 Immunization and screening for infectious disease

45 Maintenance chemotherapy, radiotherapy52 Nutritional deficiencies55 Fluid and electrolyte disorders56 Cystic fibrosis57 Immunity disorder120 Hemorrhoids121 Other diseases of veins and lymphatics167 Nonmalignant breast conditions168 Inflammatory disease of female pelvic organs169 Endometriosis172 Ovarian cyst173 Menopausal disorders202 Rheumatoid arthritis and related disease203 Osteoarthritis

27

204 Other non-traumatic joint disorders205 Spondylosis; intervertebral disc disorders; other back problems206 Osteoporosis208 Acquired foot deformities209 Other acquired deformities210 Systemic lupus erythematosus and connective tissue disorders211 Other connective tissue disease212 Other bone disease and musculoskeletal deformities217 Other congenital anomalies237 Complication of device; implant or graft238 Complications of surgical procedure or medical care240 Burns246 Fever of unknown origin247 Lymphadenitis248 Gangrene252 Malaise and fatigue253 Allergic reactions254 Rehabilitation care; fitting of prostheses; and adjustment of devices255 Administrative/social admission256 Medical examination/evaluation257 Other aftercare258 Other screening for suspected conditions (not mental disorders or infectious

disease)259 Residual codes; unclassified

Heart failure 108 Congestive heart failure non-hypertensiveArrhythmia 106 Cardiac dysrhythmias

107 Cardiac arrest and ventricular fibrillationConduction disorder 105 Conduction disordersValve disorders 96 Heart valve disorderHyper/hypotension 98 Essential hypertension

99 Hypertension with complications and secondary hypertension183 Hypertension complicating pregnancy; childbirth and the puerperium249 Shock

Pericarditis 97 Peri-, endo- and myocarditis, cardiomyopathyCoronary artery disease including angina

101 Coronary atherosclerosis and other heart disease

Acute myocardial infarction 100 Acute myocardial infarctionOthers (cardiac) 103 Pulmonary heart disease

104 Other and ill-defined heart disease213 Cardiac and circulatory congenital anomalies

28

Supplementary Table 2: Causes of unplanned 30-day readmissions

Causes of 30-day unplanned readmission

No DAMA (%) DAMA (%)

Acute myocardial infarction 13.4 30.4Coronary artery disease including angina

13.8 15.4

Heart failure 12.6 11.3Arrhythmias 7.0 5.8Infections 6.2 4.9Other non-cardiac 7.9 4.9Non-specific chest pain 7.0 4.9Respiratory 4.5 4.2Neuropsychiatric 1.3 3.2Gastrointestinal 5.2 2.4TIA/stroke 2.8 1.9Renal failure 2.2 1.4Endocrine/metabolic 1.5 1.4Hematological/neoplasm 1.6 0.9Peripheral vascular disease 2.2 0.9Bleeding 2.4 0.8Trauma 1.2 0.8Other cardiac 1.3 0.7Valve disorders 0.5 0.6Pericarditis 0.7 0.6Poisoning 0.3 0.6Rheumatological 0.8 0.5Genitourinary 1.4 0.5ENT problem 0.7 0.5Syncope 0.9 0.4Conduction disorders 0.3 0.1Hyper/hypotension 0.0 0.0Opthalmological 0.0 0.0Oral health problem 0.1 0.0Obstetric or pregnancy problem 0.0 0.0Dermatological 0.0 0.0

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Supplementary Table 3: Influence of length of stay on the rate of patients discharged against medical advice

Length of stay (days) Rate of discharge among patients discharged AMA (%)

Rate of discharge among patients not discharged AMA (%)

0 11.7% 0.6%1 34.6% 10.8%2 22.4% 31.3%3 10.9% 23.1%4 6.4% 11.6%5 3.8% 6.4%6 2.4% 4.2%7 1.6% 3.0%

30

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