ORIGINAL ARTICLES Determinants of Resource Utilization for Patients Admitted for Evaluation of Acute Chest Pain L E,TEVENUDVARHELYI, MD, ME,c, LEE GOLDMAN, MD, MPH, ANTHONY L. KOMAROFF, MD, THOMAS H. LEE, MD, ME,c Objective: To identify d e t e r m i n a n t s o f resource utilization a m o n g p a t i e n t s with suspected acute m y o c a r d i a l i n -

farctiom Design: Prospective c o h o r t study, with p r o s p e c t i v e collection o f detailed clinical data a n d retrospective collection o f n o n c l i n i c a l d a t a a n d resource utilization d a t ~ Setting: Urban, tertiary-care, t e a c h i n g h o s p i t a l P a t i e n t p o p u l a t i o n : 992 consecutive p a t i e n t s o v e r the age o f 3O years, a d m i t t e d f r o m the emergency d e p a r t m e n t f o r evaluation o f acute chest p a i n u n e x p l a i n e d by obvious t r a u m a o r chest r o e n t g e n o g r u p h i c abnormality, were eligible f o r the study. After excluding p a t i e n t s w h o h a d left a g a i n s t medical advice, w h o h a d been t r a n s f e r r e d to ano t h e r hospita~ o r w h o h a d incomplete utilization data, 903 p a t i e n t s were included i n the analyses. M e a s u r e m e n t s a n d o u t c o m e s : The a u t h o r s evaluated the effects o f 22 clinical a n d n o n c l i n i c a l f a c t o r s o n resource use. Resource u s e w a s p r i m a r i l y et,~!;~_~ed by length o f stay; charges were evaluated in s e c o n d a r y analyses. Results: I n the entire stady population, i n c r e a s e d length o f stay w a s associated with a d i a g n o s i s o f acute m y o c a r d i a l i n f a r c t i o n o r angina, setmrity o f complications, use o f invasive a n d n o n i n v a s i v e t e s t i n ~ a n d initial triage to the c o r o n a r y care unit. I n the 424 (4 7%)patients w h o h a d h a d completely uncomplicated courses after admi&vion, high coefftcients o f variability were f o u n d f o r length o f stay (0. 88) a n d f o r total charges (0. 78). I n these uncomplicated patients, i n c r e a s e d length o f stay was associated with the u s e o f n o n i n v a s i v e c a r d i a c testing (66% l o n g e r f o r p a tients u n d e r g o i n g e c h o c a r d i o g r a p h y o r r a d i o n u c l i d e ventriculography, a n d 46% l o n g e r f o r p a t i e n t s u n d e r g o i n g exercise tests o r ambulatory a r r h y t h m i a monitoring), initial triage to the c o r o n a r y care u n i t (23% longer), admiss i o n a t the e n d o f the week (21% longer), a n d i n s u r a n c e coverage o t h e r t h a n Blue C r o s s / B l u e Shield o r a commercial c a r r i , ~ ( 2 1 % f o r self-pay, 2 5 % f o r Medicaid, a n d 48% f o r Medicare).

Received from the Divisions of Clinical Epidemiology and General Medicine and the Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School; and the Department of Health Care Policy, Harvard Medical School, Boston, Massachusetts. Presented in part at the annual meeting of the American Federation for Clinical Research, April 2 8 - M a y 2, 1989, Washington, DC. Supported in part by grants from the National Center for Health Services Research (HS 05927), the Robert Wood Johnson Foundation, Princeton, NJ (678105), the John A. Hartford Foundation, New York, NY (83102-2H), and the Agency for Health Care Policy and Research (1-PO1-HS06431-02 and HS 06452-02). Dr. Lee is the recipient of an Established Investigator Award (900119) from the American Heart Association. Dr. Udvarhelyi is the recipient of a Medical Foundation Fellowship award. Address correspondence and reprint requests to Dr. Lee: Division of Clinical Epidemiology, Department of Medicine, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115.

Conclusions: These f i t u l i n g s indicate that a f t e r a d j u s t m e n t f o r i m p o r t a n t clinical f a c t o r s , n o n c l i n i c a l f a c t o r s h a d a significant i m p a c t o n length o f stay a m o n g a large g r o u p o f uncomplica~ed patients. I n t e r v e n t i o n s a i m e d at r e d u c i n g

logistic di~zwlaes in the performance o f noninvasive testing a n d decreasing the n u m b e r o f low-risk p a t i e n t s w h o a r e triaged to c o r o n a r y care u n i t beds m a y decrease res o u r c e utilization. Key w o r d s : costs; cost analysis; length o f stay; acute myocardial infarction; chestpain,, severity o f illness; c o r o n a r y care units; exercise t e s t i n ~ echocardiogruphy; ambulatory m o n / t o r i n ~ ut//ization~ J GEN INTERN MED 1992; 7:1-10.

BECAUSE of the potentially catastrophic c o n s e q u e n c e s of an inappropriate discharge of a patient with acute myocardial infarction,l physicians have a l o w threshold for admitting patients with acute chest pain. As a result, only a b o u t 3% of patients with acute myocardial infarction are sent h o m e from the e m e r g e n c y department,1 but this excellent sensitivity has b e e n achieved by the admission of large n u m b e r s of patients w i t h l o w risks of acute myocardial infarction or its complications to the coronary care unit or o t h e r m o n i t o r e d facilities. 2-11 In response to pressures for increased efficiency, several investigators have studied strategies for estimating the risk of acute myocardial infarction and complications,3-5, 8, 12 so that patients with lower risks may avoid admission to the hospital or be triaged to lower levels of care such as intermediate care units. 6 However, the e c o n o m i c implications of such m a n a g e m e n t strategies are uncertain, since little is k n o w n a b o u t the determinants of resource utilization in this population, and previous reports have not included sufficient clinical data to allow c o m p a r i s o n s of amounts of resource utilization a m o n g subgroups of patients. 6, 13-15 To h e l p define the determinants of resource utilization for patients w h o present with acute chest pain, we d e v e l o p e d a database w i t h detailed clinical and resource utilization data for 903 patients w h o had b e e n admitted for evaluation of their acute chest pain. This database permits the identification of factors associated with resource utilization, after adjustment for clinical differences b e t w e e n subgroups of patients. Our findings suggest that several factors that lend themselves to specific interventions may be determinants of increased length of stay.

2

Udvarhelyieta/., RESOURCEUTIUZATION IN CHEST PAIN

METHODS All 992 patients aged 30 years or older who had been admitted to Brigham and Women's Hospital, Boston, MA, between January 1984 and September 1986 after presenting to the emergency department with a chief complaint of acute anterior, precordial, or leftsided chest pain unexplained by obvious local trauma or abnormalities on chest roentgenograms were eligible for the study. Patients were excluded if they had left the hospital against medical advice (5 patients), if they had been transferred to another acute care hospital (19 patients), or if complete resource utilization data were unavailable (65 patients). Thus, the final study population included 903 patients. Data Collection Clinical characteristics a n d procedures. Detailed clinical data were collected prospectively for each patient about his or her clinical characteristics at presentation to the emergency department, hospital course, and final clinical diagnosis. In the emergency department, data from the history, the physical examination, and the initial electrocardiogram were recorded by a resident or by a research nurse on a standard data collection form according to a protocol that has been described in detail previously), s. 11, 12 The person who completed the form had no knowledge of, and thus could not be influenced by, the patient's course after treatment in the emergency department. After admission, data were collected about each patient's clinical course, including the timing and levels of cardiac enzymes and isoenzyme measurements, the nursing unit to which the patient had been admitted and lengths of stay in different units, and the occurrences of 32 specific complications and 15 different invasive procedures. Data regarding the use of noninvasive cardiac tests, such as exercise treadmill tests, echocardiography, ambulatory arrhythmia monitoring, and cardiovascular nuclear medicine studies, were obtained from the hospital's fiscal/utilization database. Clinical characteristics at presentation. Those characteristics recorded at the time of presentation included: age; gender; cardiac history (angina, previous acute myocardial infarction, coronary artery bypass surgery, prior cardiac catheterization results); associated symptoms (nausea, vomiting, diaphoresis, dyspnea); pain, including its location, quality, and pattern of radiation; comparison of the pain to that associated with prior diagnoses; blood pressure; reproducibility of chest pain by deep inspiration, change in position, or palpation; findings from the physical examination; and the interpretation of the initial electrocardiogram. Complications. On the basis of his or her most severe postadmission complication, each patient was

classified into one of four hierarchical complication categories: 1) life-threatening, 2) major, 3) minor, and 4) none. Life-threatening complications included ventricular fibrillation, complete atrioventricular block, shock, cardiac arrest, Mobitz II atrioventricular block, atrioventricular dissociation, pulmonary edema, and infarct extension. Major complications included ventricular tachycardia, pulmonary embolus, congestive heart failure, and recurrent ischemia. Minor complications included pericarditis and any other arrhythmia or conduction disturbance other than occasional premature ventricular contractions. Procedures a n d tests. Invasive tests and procedures were recorded individually, including emergent and elective cardioversion, pulmonary artery catheterization, left heart catheterization, four types of cardiac surgery, the use of an intra-aortic balloon pump, temporary and permanent electrical pacing, endotracheal intubation, the use of intravenous or intracoronary thrombolytic therapy, and the use of intravenous nitroglycerin. Noninvasive tests were grouped into three separate categories: 1) provocative tests for ischemia (exercise electrocardiography and exercise thallium scintigraphy), 2) tests of left ventricular function (radionuclide ventriculography and echocardiography), and 3) tests for arrhythmias (ambulatory or Holter monitoring). Diagnoses. Patients were divided into four categories on the basis of their final diagnoses: 1) acute myocardial infarction, 2) angina, 3) other cardiac diagnosis, 4) noncardiac diagnosis. A final diagnosis of myocardial infarction was made if any one of the following criteria were met: 1) characteristic evolution of serum enzyme levels, including creatine kinase (CK)MB isoenzyme levels detected in more than trace amounts by the qualitative electrophoretic assay or at least 5% of an elevated total CK level, with a typical rise and fall by the quantitative assay; or a lactate dehydrogenase (LDH) isoenzyme- 1 level higher than the isoenzyme-2 level in the absence of hemolysis or renal infarction; or, if CK and LDH isoenzymes were not assayed, serial total CK levels demonstrating a typical rise and fall with a peak value exceeding twice the usual upper limit of normal; 2) electrocardiogram showing development of pathologic Q waves (at least 0.04 sec in duration) and at least a 25% decrease in the amplitude of the following R wave compared with that of the emergency department electrocardiogram; 3) scintiscan showing focal uptake of technetium-99m stannous pyrophosphate in the cardiac area if the serum enzyme peak might have occurred before hospitalization and if the patient had no prior history of myocardial infarction or valvular calcification; or (4) sudden unexplained death within 72 hours of presentation. Angina was diagnosed if: 1) the patient's emergency department chest pain syndrome was consistent with

JOURNALOFGENERALINTERNALMEDICINE,Volume 7

his or her chronic anginal syndrome; or 2) the diagnosis of angina was made by the senior clinician involved with the case. Other cardiac diagnoses, such as congestive heart failure or arrhythmias, and noncardiac diagnoses w e r e those made by the senior clinician involved with the case. N o n c l i n i c a l variables. Information regarding race, primary insurer, and the day of the w e e k on w h i c h admission had o c c u r r e d (e.g., Monday, Tuesday), were obtained from the hospital's fiscal/utilization database. Resource u t i l i z a t i o n variables. The primary resource utilization o u t c o m e was length of stay (LOS). This endpoint was chosen because lengths of stay may be c o m p a r e d between settings and are not subject to the biases found in hospital charges. ~6 To provide some estimate of resource use in dollar amounts, total hospital charges, normalized to 1986 dollars, were used as a secondary endpoint in selected analyses.

Data Analysis Coefficients of variation for length of stay and charges were calculated by dividing the standard deviations by the means of each parameter. The correlation between these two measures of resource use was tested by calculating a Pearson correlation coefficient. 17 Univariate analyses w e r e done using a Wilcoxon rank sum test m or a Kruskal-Wallis test as appropriate. ~9 Multiple linear regression analyses were used to determine the i n d e p e n d e n t effects of clinical and nonclinical characteristics on length of stay. 17, 2o Because length of stay had an approximately log-normal distribution, the natural logarithm of length of stay was used as the d e p e n d e n t variable. The relationship between each characteristic and length of stay was expressed as the adjusted percentage change in length of stay associated with the presence of that characteristic, 2~, 22 and the partial correlation coefficient for that characteristic.~7 The adjusted percentage change in length of stay was derived from the ratio of the length of stay for patients with a characteristic to the length o f stay for patients without that characteristic, after adjusting for other variables in the model. The partial correlation coefficient reflects the percentage variation in length of stay explained by a characteristic after controlling for the other variables in the model, and was used as an indicator for the i n d e p e n d e n t importance o f each characteristic in determining length of stay. We constructed multivariate models to control for 22 clinical and nonclinical variables simultaneously. To minimize collinearity b e t w e e n i n d e p e n d e n t variables in the models, we did not include in the models certain characteristics at presentation that were highly correlated with final diagnosis and complications, w h i c h were both included in the models. The final models included the following variables: age, gender,

(Januao//Februag/),

1992

history of coronary artery disease, history of cardiac catheterization, history of coronary artery bypass surgery, time b e t w e e n onset of pain and presentation to the e m e r g e n c y ward, rales on initial physical examination, ischemic changes on initial electrocardiogram, admission triage location (coronary care unit or intermediate care unit), discharge diagnosis, worst complication, mortality, use of selected cardiac procedures (pulmonary artery catheterization, cardiac catheterization, and coronary bypass surgery), use of other invasive procedures (electrical cardioversion, intra-aortic balloon p u m p , endotracheal intubation, and electrical pacing), use of noninvasive tests to assess left ventricular function, use of provocative tests for ischemia, use of ambulatory monitoring to detect arrhythmias, admission at the end of the w e e k (Thursday-Saturday), insurer, and race. Age, discharge diagnosis, worst complication, insurer, and race were represented by d u m m y variables. Age was categorized as 30 - 49 years, 50 - 64 years, 65 - 74 years, and 75 and over. Discharge diagnosis was categorized as noncardiac, acute myocardial infarction, angina, and other cardiac diagnosis. There were four levels for the variable worst complication; five categories for insurer (Blue Cross or commercial, Medicaid, Medicare, other, and none); and three categories for race (white, minority, and u n k n o w n ) . For each variable, we calculated p values and a partial R2 that corresponded to the partial F-test for all levels of the variable combined. However, we calculated adjusted percentage change for each level of a variable, comparing each level with a reference level. Two sets of multivariate analyses were performed, one on the total patient population and one on an uncomplicated subset of patients. Separate analyses were performed for u n c o m p l i c a t e d patients because these patients were unlikely to have the clinical characteristics that had the greatest influence on resource use, and therefore resource utilization was less likely to be determined by clinical events. Patients were classified as " u n c o m p l i c a t e d " if they had no acute myocardial infarction or cardiac complication other than occasional premature ventricular contractions, and had no invasire procedure, including the use of intravenous nitroglycerin or thrombolytic agents.

RESULTS Total Patient Population The 903 patients admitted for evaluation of acute chest pain included 214 (24%) w h o were ultimately diagnosed as having acute myocardial infarction, 321 (36%) w h o were diagnosed as having angina, and 368 (40%) w h o received other diagnoses (Table 1). The overall in-hospital mortality was 5%, and 72% of the patients had no or only minor complications during their hospitalizations.

4

Udvarhelyietal.. RESOURCEUTIUZATION IN CHEST PAIN

TABLE 1 Clinical Characteristicsof the 903 Patients Admitted with Acute Chest Pain Age--mean _+SD

63 + 13 years

Gender--male

455 (50%)

History of angina History of acute myocardial infarction History of coronary bypass surgery

493 (55%) 368 (41%) 105 (12%)

Presentationwithin 4 hours of onset of pain Raleson admissionexamination New ST elevation or depressionon initial electrocardiogram

444 (49%) 273 (30%) 452 (50%)

Diagnosis Acute myocardial infarction Angina Other cardiac Noncardiac

214 (24%) 321 (36%) 102 (I 1%) 266 (29%)

Complications None Minor Major Life-threatening

494 (55%) 153 (17%) 153 (17%) 103 (11%)

In-hospital mortality

47 ( 5 % )

For all patients, the median length of stay was five days and the mean (+SD) was 7.7 + 10.4 days. For hospital charges the median was $4,676 and the mean was $9,437 + 15,370. The Pearson correlation coefficient was 0.88 for length of stay and charges, and 0.92 for the natural logarithms of length of stay and charges.

Multivariate analysis of correlates of length of stay in allpatients. The 22 clinical and nonclinical variables included in the multivariate analysis accounted for 61% of the variation in log length of stay (model R2 of 0.61). Twelve of the 22 characteristics were independently correlated with length of stay (Table 2), and ten did not have an independent association with length of stay (Table 3). Prior coronary artery bypass surgery was the only historical factor with an independent association with length of stay. Patients who presented to the hospital more than four hours after the onset of symptoms had lengths of stay that were 9% longer than patients who presented sooner. Patients with final diagnoses of acute myocardial infarction or angina had lengths of stay that were 76% and 39% longer, respectively, than those of patients with noncardiac diagnoses. Patients with other cardiac diagnoses such as congestive heart failure or arrhythmias had lengths of stay that were 16% longer than those of patients with noncardiac diagnoses. Compared with patients with no complication, patients with major or life-threatening complications had lengths of stay that were 76% longer, and patients with minor complications had lengths of stay that were 54% longer. In univariate analyses, death was associated with shorter lengths of stay for patients with acute myocardial infarction, and longer lengths of stay for patients with

other diagnoses. The association of death with shorter lengths of stay in the multivariate models was primarily due to deaths among patients with acute myocardial infarction occurring relatively early in the course of hospitalization (Table 4). The use of diagnostic and therapeutic procedures and tests was strongly associated with longer lengths of stay, independently of complications and diagnosis. Patients who underwent pulmonary artery catheterization, cardiac catheterization, and coronary bypass surgery had lengths of stay that were 27%, 66%, and 104% longer than those of patients who did not undergo these procedures, after controlling for other variables. The use of noninvasive tests to assess left ventricular function (echocardiography and radionuclide ventriculography) was associated with lengths of stay that were 66% longer than those of patients who did not receive these tests, and the use of provocative tests for ischemia (exercise electrocardiography and exercise thallium scintigraphy) and ambulatory arrhythmia monitoring was associated with lengths of stay that were 22% and 25% longer, respectively. Initial triage of a patient to the coronary care unit versus the intermediate care unit was the only other nonclinical factor to have an independent effect on length of stay among all 903 patients. Patients admitted to the coronary care unit stayed 22% longer than did patients admitted to the intermediate care unit, after adjusting for all other clinical and nonclinical factors. To describe resource utilization in monetary terms for clinically meaningful subgroups of patients, the population was stratified by diagnosis, complications, and survival status (Table 4). Patients with diagnoses other than acute myocardial infarction or angina had the lowest resource use. Among patients who survived until discharge in all three diagnostic categories, resource use increased progressively with the severity of complications. Uncomplicated Patients

Of the 903 patients initially admitted for evaluation of acute chest pain, 424 patients (47%) did not have acute myocardial infarction, had no complication during their hospital stay other than occasional premature ventricular contractions, and did not undergo invasive procedures, including intravenous nitroglycerin and intravenous thrombolytic therapy. In particular, none of these patients experienced ischemic chest pain or had clinical evidence of congestive heart failure after admission to the hospital. In this very uncomplicated subset of patients, the median length of stay was two days and the mean length of staywas 3.1 + 2.8 days; for hospital charges the median was $2,375 and the mean was $3,073 + 2,405. The coefficients of variation for length of stay and total charges (0.88 and 0.78, respectively) demonstrated a

JOURNALOFGENERALINTERNALMEDICINE,Volume 7 (January/Februa~), 1992

high degree of variability in resource utilization among these patients, despite hospital courses that were consistently uncomplicated.

S

sive cardiac testing had the greatest impact on length of stay. Patients undergoing tests of left ventricular function (echocardiography or radionuclide ventriculography) stayed 66% longer than did patients not getting these tests. Patients who underwent provocative tests for ischemia (exercise electrocardiography and exercise thallium scintigraphy) or ambulatory arrhythmia monitoring had lengths of stay that were 46% longer than those of patients who did not receive these tests.

Multivariate analyses of uncomplicated patients. Among the 21 variables entered into the multivariate linear regression models for uncomplicated patients, eight had independent correlations with length of hospitalization (Table 5). The use of noninva-

TABLE 2

Factors with an IndependentCorrelation with Length of Stay (LOS) among the Entire Study Population LOS n History of coronary bypass surgery No Yes

798 105

Median 5.0 days 5.0 days

Mean +_ SD

Adjusted % Increase in LOS*

7.7 _+ 10.5 days 7.9 + 10.0 days

t 16%

Time since onset of pain until presentation to emergency department Less than 4 hours More than 4 hours

444 459

4.5 days 5.0 days

7.9 + 12.7 days 7.5 + 7.7 days

t

Admission triage location Intermediate care Coronary care unit

187 716

2.0 clays 6.0 days

4.3 + 5.7 days 8.6 + 11.2 days

t 22%

Diagnosis Noncardiac Acute myocardial infarction Angina Other cardiac

266 214 321 102

2.0 days 3.5 + 5.9 11,0 days 14.4 _ 14.6 5.0 days 6.9 + 6.7 4.0 days 7.2 + 12.3

Complications None Minor Major Life-threatening

494 153 153 103

2.0 7.0 11.0 12.0

In-hospital mortality Survived Died

856 47

Pulmonary artery catheterization No Yes

Partial Rz

0.05

0.0018

0.03

0.0021

0.0008

0.0051

0.0001

0,024

0.0001

0.037

0.0012

0.0048

0,027

0.0022

0.0001

0.025

0.0001

0.022

0.0001

0.043

0.0004

0.0058

0,0005

0.0055

9%

days days days days

t 76% 39% 16%

days 4.0 + 4.2 days days 8.7 + 8.2 days days 14.1 + 15.4 days days 14.6 + 15.7 days

t 54% 76% 76%

5.0 days 5.0 days

p Value

7.6 +__ 9,9 days 10.3 +_ 17.3 days

t --37%

851 52

4.0days 7.1 +_ 9.8days 14,5 days 18.2 _ 14.9 days

t 27%

Cardiac catheterization No Yes

728 175

4.0 days 13.0 days

5.4 _+ 5.6 days 17.2_+ 18.0 days

t 66%

Coronary bypass surgery No Yes

844 59

4,0 days 6.7 _ 8,4 days 18.0 days 22.5 _ 21.0 days

t 104%

Noninvasive tests of left ventricular function No Yes

599 304

3.0 days 5 . 4 _ 5.5 days 8.5 days 12.3 + 15.2 days

t 66%

Provocative tests for ischemia No Yes

638 265

4.0 days 8.0 days

7.2 + 9.9 days 9.0 _+ 11.7 days

t 22%

Ambulatory arrhythmia monitoring No Yes

684 216

3.0 days 10,0 days

6.2 _+ 9,6 days 12.4 _ 11.5 days

t 25%

*,,The percentage increase in length of stay for a patient with that characteristic compared with that of a patient without that characteristic (reference group, which is marked with t). controlling for the other 21 characteristics.

Udvarhelyi etaL.

6

RESOURCEUTIUZATION IN CHEST PAIN

O t h e r factors that w e r e i n d e p e n d e n t l y associated w i t h longer lengths of stay a m o n g u n c o m p l i c a t e d patients i n c l u d e d a duration of m o r e than four hours b e t w e e n the onset of chest pain and e m e r g e n c y ward presentation, a diagnosis of angina or other cardiac disease, admission triage to the coronary care unit instead of the intermediate care unit, admission at the end of the w e e k (Thursday, Friday, and Saturday), and insurance coverage other than Blue Cross/Blue Shield or a commercial carrier. (Table 6 displays the variables w i t h o u t i n d e p e n d e n t correlations w i t h length of stay a m o n g u n c o m p l i c a t e d patients.)

DISCUSSION The n e e d to contain health care costs w i t h o u t c o m p r o m i s i n g the quality o f patient care is p e r h a p s the dominant challenge facing m e d i c i n e today, but efforts to d e v e l o p optimal m a n a g e m e n t strategies have b e e n hindered by uncertainty over their clinical and econ o m i c consequences. Prior studies have evaluated determinants of resource use a m o n g clinically diverse groups of patients in intensive care settings, 13.15 making it difficult to understand h o w changes in m a n a g e m e n t of a given disease might affect costs. However, the database d e v e l o p e d for this report includes detailed, pro-

TABLE 3

Factors without an Independent Correlation with Length of Stay (LOS) among the Entire Study Population LOS

AdJusted °h

n

Median

Mean -J- SD

Age 30-49years 5 0 - 6 4 years 6 5 - 7 4 years Over 74 years

168 314 229 192

3.0days 5.0 days 6.0 days 5.0 days

5 . 8 + 8.1 7.0 _ 6.8 9.6 +__15.5 8.3 _+ 9.3

Gender Female

448

5.0 days

7.8 + 10.1 days

t

Male

455

4.0 days

7.6 + 10.7 days

-4%

History of coronary artery disease No Yes

340 563

5.0 days 5.0 days

7.6 + 10.9 days 7.8 +_ 10.1 days

t 0%

History of cardiac catheterization No Yes, positive Yes, negative

755 133 15

5.0 days 4.0 days 4.0 days

7.5 + 8.5 days 8.1 _ 15.6 days 13.2 + 28.2 days

t 3% 29%

Rales on initial examination No Yes

630 273

4.0 days 7.0 days

6.6-- 7.6 days 10.3 -- 14.8 days

t 7%

Ischemic changeson initial electrocardiogram No Yes

451 452

3.0 days 7.5 days

5 . 3 + 6.0 days 10.2 + 13.0 days

t 6%

Other invasivetests* No Yes

874 29

5.0 days 4.0 days

7.7 + 10.5 days 7.4 + 8.4 days

t -- ~8%

Admission at the end of the week No (Sun-Wed) Yes (Thurs-Sat)

582 321

5.0 days 5.0 days

7.4 + 9.3 days 8.4 _ 12.2 days

t 6%

Insurer Blue Cross/Blue Shield or commercial Medicaid Medicare Other None

272 85 434 33 79

4.0 3.0 5.0 5.0 3.0

days days days days days

7.5 + 11.5 days 7.1 _ 10.1 days 8.6 +-- 10.7 days 6.2 + 5.5 days 5.0 +-- 5.6 days

t 14% 15% -- 1% 4%

Race White Minority Unknown

472 234 197

5.0 clays 4.0 days 5.0 days

8.0 +_ 11.0 days 6.8 _+ 10.7 days 8 . 2 _ 8.5 days

t 6% 0%

days days days days

Increase in LOS*

p Value

Partial Rz

0.67

0.0007

0.40

0.0003

0.97

0.0000

0.33

0.0010

0.20

0.0007

0.28

0.0005

O. 17

0.0008

O. 19

0.0008

0.35

0.0020

0.33

0.0004

t 5% 7% 12%

*,tThe percentage increase in length of stay for a patient with that characteristic compared with that of a patient without that characteristic (reference group, which is marked with t), controlling for the other 21 characteristics.

SElectrical cardioversion,intra-aortic balloon pump, endotracheal intubation, and electiveor emergent pacing.

JOURNALOFGENERALINTERNALMEDICINE,Volume 7 (January/February), 1992 TABLE 4

Charges and Lengthsof Stay Stratified by Diagnosisand Complications

Length of Stay Diagnosis

Complications

n

Median

Acute myocardialinfarction

None Minor Major Life-threatening Survived Died

33 42 67

9.0 days 10.0 days 13.0 days

41 31

Angina

Other

None Minor Major Life-threatening Survived Died

None Minor Major Life-threatening Survived Died

Total Charges Median

Mean -+ SD

11.1-+ 7.7days 12.0-+ 6.0days 18.3 -+ 21.3 d a y s

$ 7,441 $ 9,684 $17,387

$11,048-+ 8,914 $12,403-+ 8,371 $21,746-+ 17,796

15.0 days 3.0 days

19.7 -+ 11.9 d a y s 5.3-+ 5.1 clays

$21,320 $ 7,036

$27,526 -+ 20,337 $11,949-+ 12,461

214

11.0 days

14.4-+ 14.6 d a y s

$12,701

$17,951 -+ 16,949

187 43 73

3.0 days 7.0 days 10.0 days

4.6-+ 3.8 days 6.9 -+ 4.2 days 11.2-+ 7.1 days

$ 3,232 $ 5,666 $ 8,938

$ 4,679 + 4,850 $ 7,804 -+ 7,707 $14,324-+ 12,991

7 11

7.0 days 11.0 days

17.0 -+ 20.7 d a y s 13.4-+ 9.8days

$13,458 $25,923

$29,290 -+ 35,376 $29,549-+ 22,005

321

5.0 days

6.9-+ 6.7 days

$ 4,782

$ 8,665-+ 11,793

274 68 13

2.0days 5.0days 9.0 days

2.7+ 2.6days 7.7+lO.5days 9.0-+ 4.7 days

$ 2,159 $ 4,325 $ 8,943

$ 2,862-+ 2,292 $ 7,313-+ 10,428 $ 9,906-+ 6,761

8

5

6.0days 20.0 days

11.4-+ 12.gdays 35.2 -+ 44.8 d a y s

$ 5,994 $27,622

$17,869-+ 25,054 $68,824 -+ 108,954

368

2.0days

$ 2,623

$ 5,156--+ 15,197

spectively r e c o r d e d clinical and resource utilization data for a patient population with a single, well-defined, c o m m o n clinical syndrome, with sufficient disease-specific clinical information to allow the analysis of relationships among clinical and nonclinical patient characteristics, and resource utilization. Our analyses indicate that variability in the length of hospitalization for patients w h o are admitted for evaluation of acute chest pain is primarily determined by the acute ischemic heart disease syndrome (e.g., final diagnosis of acute myocardial infarction versus other noninfarction diagnoses), the severity of underlying cardiac disease (e.g., a history of cardiac bypass surgery), the severity of cardiac complications, and the subsequent use of both invasive and noninvasive cardiac procedures. However, our data also show that almost half of patients admitted with a suspected cardiac cause of acute chest pain did n o t have acute myocardial infarction, significant complications, or evidence of active ischemia or congestive heart failure following admission, and required no invasive procedure. In this u n c o m p l i c a t e d group of patients, variability in length of stay was primarily related to the use of predischarge testing with exercise tests, echocardiography, radionuclide ventriculography, and ambulatory monitoring. The initial triage decision of w h e t h e r to admit the patient to a coronary care unit or intermediate care unit was also an important determinant of length of stay in this population. The effects of other nonclinical factors, including admission day and insur-

Mean -+ SD

4.5+

8.3days

ance coverage, upon length of stay were apparent only in the u n c o m p l i c a t e d group o f patients. Overall, the results of our study of correlates of resource utilization for patients admitted for evaluation of acute chest pain suggest several strategies for lowering the cost of care for patients with suspected acute myocardial infarction. First, identification of low-risk patients in the e m e r g e n c y ward, and subsequent triage to intermediate care units instead of coronary care units, c o u l d be e x p e c t e d to achieve cost savings by decreasing lengths of stay for these patients by up to 20%. Our analyses suggested that the association b e t w e e n triage decision and length of stay was independent of disease severity. It is possible, however, that a decision to triage a patient to the coronary care unit was a marker for disease severity that w e failed to capture in our data collection efforts. We have previously shown, however, that admitting patients to intermediate care units rather than coronary care units could decrease nursing time and labor costs per day. 23 Our finding that noninvasive diagnostic testing was c o m m o n l y p e r f o r m e d u p o n patients w h o have uncomplicated hospital courses may have several explanations. First, it is possible that the use of noninvasive testing was a marker for unmeasured disease severity, even in this very u n c o m p l i c a t e d population. It is also possible that clinicians believed the prognostic information obtained from the noninvasive testing was essential in planning discharges and follow-up care. Alternatively, m u c h of the testing could have b e e n a

8

Udvarhe/yiet aL, R~SOUF~EUTIUZATION IN CHEST PAIN

" s p i l l o v e r " p h e n o m e n o n from the increasingly prevalent practice of performing multiple predischarge tests on patients w h o do have acute myocardial infarctions. 24"28 If clinicians believe these tests are essential to the predischarge management of some patients, then logistic difficulties in having these tests performed in a timely manner should be identified to prevent hospitalizations from being prolonged. However, clinicians should also consider w h e t h e r the prognostic information from these tests w o u l d be of the same value if it had b e e n obtained with the patients as outpatients in the immediate post-discharge period. The finding that patients w h o are admitted at the end of the w e e k have longer hospitalizations is consistent with results from previous studies 29,3° and further suggests that logistic problems in scheduling tests and services may increase costs by prolonging hospitalizations. Especially for patients w h o are covered by insurance plans that pay on a prospective per-case basis, hospital administrators and clinicians should evaluate h o w many patients wait for tests or other services during the w e e k e n d and other times w h e n the hospital

operates with r e d u c e d personnel. It is possible that the increased costs of providing personnel at these times might be offset by the reductions in length o f stay. The association of Blue Cross/Blue Shield and commercial insurance coverage with shorter lengths o f stay is also consistent with prior studies. 3~ It is likely that the association b e t w e e n insurance status and length of stay was related to patient factors other than severity of illness. For example, patients with commercial insurance or Blue Cross/Blue Shield coverage are usually e m p l o y e d and may be able to leave the hospital earlier because of support services at h o m e that are better than those available to elderly patients insured by Medicare, patients w h o receive Medicaid, or patients w h o are uninsured. This explanation w o u l d also be consistent with the relationship of lower socioeconomic status and longer lengths of stay shown in previous investigations. 32 The association o f length o f stay with the time between onset of pain and presentation to the e m e r g e n c y ward does not have a clear explanation. While patients w h o had presented earlier after the start of their symp-

TABLE 5

Factors with an Independent Correlation with Length of Stay (LOS) among Uncomplicated Patients LOS n

Median

Mean _ SD

Adjusted % Increase in LOS*

Time since onset of pain until presentation to emergency ward Less than 4 hours More than 4 hours

203 221

2.0 days 2.0 days

2.8 +_ 2.3 days 3.4 +_ 3.1 days

t 17%

Admission triage location Intermediate care Coronary care unit

129 295

2.0 days 2.0 days

2.5 +-- 2.2 days 3.4 + 2.9 days

t 23%

Discharge diagnosis Noncardiac diagnosis Angina Other cardiac diagnosis

219 158 47

2.0 days 3.0 days 3.0 days

2.4 _ 2.2 days 3.9 _ 3.0 days 3.8 +- 3.0 days

t 34% 18%

Noninvasive tests of left ventricular function No Yes

326 98

2.0 days 4.0 days

2.6 _ 2.4 days 4.9 +-- 3.1 days

t 66%

Provocative tests for ischemia No Yes

315 109

2.0 days 3.0 days

2.9 + 2.7 days 3.9 + 2.8 days

t 46%

Ambulatory monitoring for arrhythmias No Yes

380 44

2.0 days 5.5 days

2.8 _ 2.6 days 5.5 _ 2.8 days

t 46%

Admission at the end of the week No (Sun-Wed) Yes (Thurs-Sat)

281 143

2.0 days 3.0 days

2.9 _+ 2.8 days 3.5 _+ 2.6 days

t 21%

Insurer Blue Cross/Blue Shield or commercial insurer Medicaid Medicare Other Self-pay

140 50 167 17 50

2.0 days 2.0 days 3.0 days 2.0 days 2.0 days

2.6 +__2.4 days 3.3 + 3.1 days 3.4 + 2.6 days 3.6 +__3.8 days 3.1 _ 3.2 days

p Value

Partial Rz

0.0020

0.016

0.0036

0.014

0.0005

0.026

0.0001

0.068

0.0001

0.044

0,0006

0.020

0.0033

0.014

0.012

0.022

t 25% 48% 23% 21%

*.t The percentagein length of stay for a patient with that characteristic comparedwith that of a patient without that characteri~c (referencegroup, which is marked with t), controlling for other characteristics in the model.

JOURNALOFGENERALINTERNALMEDICINE,Volume 7 (January/February), 1992 TABLE 6

Factors without an IndependentCorrelation with Length of Stay (LOS) among UncomplicatedPatients

LOS n

Median

Age 3 0 - 4 9 years 5 0 - 6 4 years 6 5 - 7 4 years Over 74 years

103 162 86 73

2.0 2.0 3.0 2.0

Gender Female Male

226 198

days days days days

Mean _+ SD 2.6 3.2 3.3 3.4

_+ 2.9 + 2.7 _+ 2.6 + 2.8

Adjusted % Increase in LOS*

days days days days

t 5% -17% --12%

2.0 days 2.0 days

3.0 _+ 2.6 days 3.3 _+ 2.8 days

t 0%

History of cardiac catheterization No Yes, positive Yes, negative History of cardiac catheterization No Yes, positive Yes, negative

357 59 8

2.0 days 2.0 days 3.0 days

3.2 + 2.8 days 2.8 + 2.4 days 2.8 + 1.7 days

t --5% 5%

357 59 8

2.0 days 2.0 days 3.0 days

3.2 + 2.8 days 2.8 + 2.4 days 2.8 _+ 1.7 days

t --5% 5%

History of coronary bypass surgery No Yes

377 47

2.0 days 3.0 days

3.1 _+ 2.7 days 3.5 + 3.0 days

t 15%

Rales on initial examination No Yes

332 92

2.0 days 3.0 days

2.9 + 2.7 days 3.9 + 3.0 days

t 6%

Ischemic changes on initial electrocardiogram No Yes

278 146

2.0 days 2.5 days

2.9 _+ 2.5 days 3.6 + 3.1 days

t 3%

Race White Minority Unknown

202 131 91

2.0 days 2.0 days 2.0 days

3.1 + 2.8 days 3.0 + 2.5 days 3.2 + 3.1 days

t --4% 0%

p Value

Partial Rz

0.32

0.0056

0.97

0.0000

0.86

0.0005

0.86

0.0005

O. 19

0.0027

0.47

0.0008

0.67

0.0003

0.55

0.0006

*,tThe percentagein length of stay for a patient with that characteristic comparedwith that of a patient without that characteristic (referencegroup, which is marked with t), controlling for other characteristics in the model.

toms may have had the severity of their ischemic episode modified b y acute interventions such as intravenous nitrates and t h r o m b o l y t i c agents, w e controlled for disease severity in our analyses and the effect was also n o t e d a m o n g u n c o m p l i c a t e d patients. It is possible that these patients differed on dimensions of severity that w e r e not c a p t u r e d b y the data collected, b u t an alternative explanation is that earlier presentation is a marker for patient characteristics that are associated w i t h earlier discharge. For e x a m p l e , patients w h o present earlier after the onset of pain m a y have a better understanding of their disease, or they may have coronary artery disease of k n o w n severity. Either of these characteristics may require patients to s p e n d less time in the hospital prior to safe discharge. Although o u r study was p e r f o r m e d using an unusually detailed clinical and nonclinical database, several limitations should be noted. First, m u c h of the variability in length of stay c o u l d not be e x p l a i n e d by the factors w e included in o u r analyses. This suggests that unidentified factors, such as noncardiac c o m o r b i d dis-

ease, also influenced the duration of hospitalization. While we do not believe that noncardiac m o r b i d i t y w o u l d alter the associations of cardiac p r o c e d u r e s and noninvasive testing w i t h length of stay, o u r findings related to the association of nonclinical factors with length of stay should be interpreted in light of this limitation. A second c o n c e r n is the generalizability of findings f r o m an urban teaching hospital, w h i c h may not be valid in other types of hospitals. Despite these limitations, these data indicate that clinicians and health care managers should carefully examine their current triage practices and their patterns and guidelines for ordering predischarge testing on u n c o m p l i c a t e d patients. They also suggest that previously d o c u m e n t e d associations b e t w e e n nonclinical factors and resource use are not r e m o v e d after adjustm e n t for m o s t clinical characteristics. Future research should e x a m i n e w h e t h e r the relationships b e t w e e n clinical and nonclinical factors and length of stay are generalizable to other settings and diseases, and should e x p l o r e alternative measures of resource use.

10

UdvarhelyietaL,

RESOURCEUI"IUZATION IN CHEST PAIN

The authors thank E. Francis Cook, ScD, for advice and help with data management and statistical analysis.

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