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Differences in management and outcomes of acute myocardial infarction among four general hospitals in Japan
International Journal of Cardiology 78 (2001) 277–284 www.elsevier.com / locate / ijcard
Differences in management and outcomes of acute myocardial infarction among four general hospitals in Japan a
a,
a
b
b
Kunihiko Matsui , Tsuguya Fukui *, Kenji Hira , Atsushi Sobashima , Syuichi Okamatsu , Masakiyo Nobuyoshi c , Noriaki Hayashida d , Shigemichi Tanaka e a
Department of General Medicine and Clinical Epidemiology, Kyoto University Hospital, Kyoto University Graduate School of Medicine, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606 -8507, Japan b Aso Iizuka Hospital, Iizuka, Japan c Kokura Memorial Hospital, Kitakyusyu, Japan d St. Luke’ s International Hospital, Tokyo, Japan e Teine Keijinkai Hospital, Sapporo, Japan Received 27 July 2000; received in revised form 31 August 2000; accepted 11 January 2001
Abstract Objective: To ascertain the differences among hospitals in Japan in the management patterns and outcomes of patients with acute myocardial infarction (AMI). Design: Retrospective cohort study by means of patient chart review. Setting: Four tertiary-care teaching hospitals in Japan observed over a 1-year period. Study participants: Consecutive patients (N5482) admitted for AMI. Main outcome measures: Clinical characteristics, rates of diagnostic and therapeutic procedures performed, cardiac complications, and length of stay. Results: Patients’ clinical characteristics differed significantly among the four hospitals in terms of age, gender, and prior cardiac history, but not in terms of comorbidity or infarct location. The frequency and type of diagnostic and therapeutic procedures were different, and in-hospital mortality varied (4–14%, P50.022). Average length of hospital stay ranged from 15.8612.6 days to 41.0619.4 days (P50.0001). After adjustment for the clinical characteristics, these differences remained significant among hospitals. Conclusion: Considerable differences in the management and outcomes of patients with AMI exist in Japan. 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Acute myocardial infarction; Management; Outcomes; Japanese
1. Introduction Cardiovascular disease is currently the second most common cause of death in Japan [1]. As is the case with other developed countries, acute myocardial infarction (AMI) is by far the most common cardiovascular disease. Myocardial infarction has been the target of therapeutic efforts using such recent *Corresponding author. Tel.: 181-75-751-4210; fax: 181-75-7514211. E-mail address: [email protected] (T. Fukui).
medical technologies as thrombolytic therapy, angioplasty, and coronary bypass graft surgery [2]. Faced with a wide array of treatment modalities, physicians are not likely to make consistent clinical judgments. In fact, inconsistencies in management patterns of AMI have been reported not only between but also within countries [3,4]. Many studies have clearly demonstrated variations in management patterns, but no major differences were found in patient outcomes among different institutions, regions, and countries [5–15]. Most of these studies, however, were conducted in the United States, Canada and
0167-5273 / 01 / $ – see front matter 2001 Elsevier Science Ireland Ltd. All rights reserved. PII: S0167-5273( 01 )00387-4
278
K. Matsui et al. / International Journal of Cardiology 78 (2001) 277 – 284
other Western countries, and it is not yet clear whether the same holds true in Japan. The health care system in Japan is different from that in most other developed countries in that all people are covered by one of the national, government-run or private, corporate-run insurance systems in the context of fee-for-service reimbursement [16]. However, as the population in Japan is graying at an ever faster rate, medical expenditure is increasing almost exponentially [16,17]. As a result, assessment of the efficacy and effectiveness of any clinical interventions is crucial for the maintenance of adequate medical care with limited financial resources. Against this background, we tried to determine to what extent the management patterns and patient outcomes varied for AMI patients admitted to four teaching hospitals in Japan.
2. Methods
2.1. Study sites and population The study subjects were consecutive patients who were admitted with a diagnosis of AMI to four Japanese hospitals (Aso Iizuka Hospital, Iizuka; Kokura Memorial Hospital, Kitakyusyu; St. Luke’s International Hospital, Tokyo; and Teine Keijinkai Hospital, Sapporo) over 1 year between July 1995 and June 1996. All of these hospitals are tertiary-care teaching hospitals with cardiac catheterization and cardiac surgery capabilities. They play an important role in the management of AMI patients in their respective areas. The patients were identified through the medical records kept at the hospitals. Myocardial infarction was defined according to generally accepted criteria, including: (1) the documentation of elevated creatine kinase (total or creatine kinase-MB), in addition to (2) a history of typical chest pain and other symptoms and / or (3) electrocardiographic (ECG) abnormalities defined as $0.1 mV ST segment elevation in contiguous leads, or $0.1 mV ST segment depression and / or definite T wave inversion. The four hospitals will be denoted simply as A, B, C, and D, in order to prevent identification. We have data on the total number of beds at each hospital
(hospital A51157, hospital B5658, hospital C5520, and hospital D5524) and the number of staff physicians working for cardiology patients (hospital A5 13, hospital B519, hospital C54, and hospital D5 13). However, the number of the beds for cardiology patients was not available at hospital C, because cardiology ward was not completely independent from other subspecialty departments of medicine (hospital A561, hospital B593, and hospital D541).
2.2. Data collection The physician reviewers conducted a detailed chart review. For comparative analyses of the four hospitals in terms of management patterns, the following items were included: (1) gender, (2) age, (3) vital signs (blood pressure and heart rate on admission), (4) referral status, (5) smoking status, (6) previous histories [congestive heart failure (CHF), myocardial infarction, angina, coronary revascularization (percutaneous transluminal coronary angioplasty, stent placement, and other procedures using cardiac catheterization), and coronary artery bypass graft surgery (CABG)], (7) comorbidities (hypertension, diabetes, gastrointestinal disease, liver disease, renal disease, pulmonary disease, and hyperlipidemia), (8) ECG changes (ST elevation, ST depression), (9) infarct location (antero-septal, inferior), (10) cardiac complications during hospitalization [no complications, recurrent chest pain indicative of ischemia, reinfarction, CHF, pulmonary edema, cardiogenic shock, Mobitz type II block, complete AV block, ventricular tachycardia / ventricular fibrillation (VT / VF), respiratory failure requiring intubation, cardiac arrest], (11) major procedures [thrombolytic therapy, pulmonary artery catheter, coronary angiography, revascularization, CABG, exercise tolerance test (ETT), holter ECG, echo cardiography, temporary pacemaker, intra-aortic balloon pumping (IABP), nuclear studies], (12) length of stay [intensive care unit (ICU), total], and (13) final disposition (survival or death at hospital discharge). We regarded these cardiac complications, length of stay, and final disposition as short term outcomes.
2.3. Statistical analysis For statistical comparisons the Wilcoxon rank sum
K. Matsui et al. / International Journal of Cardiology 78 (2001) 277 – 284
test or the Kruskal–Wallis test was used as appropriate for continuous variables, and the chi-square test or Fisher’s exact test with appropriate degrees of freedom for categorical variables. A logistic regression model was used to identify correlation with in-hospital mortality after adjustment for clinical characteristics which univariate analyses had shown to be significantly correlated. In this model, the following variables were included: hospitals (B, C, and D), age by year, male gender, previous histories (myocardial infarction, CHF), antero-septal wall as an infarct location, and complications (none, infarct extension, CHF, pulmonary edema, cardiogenic shock, VT / VF, respiratory failure requiring intubation, and cardiac arrest). We did not include procedures in the variables since our main concern was whether the hospital correlated with the outcomes after adjustment for clinical data. We thus developed ‘optimal clinical models’ based on clinical variables and complications, but not procedures. Furthermore, to identify independent correlates of length of stay, stepwise multiple linear regression analyses were performed, using the log transformation of length of stay as the dependent variable. Since the data for length of stay are highly skewed, the natural logarithm of length of stay was used as the dependent variable. In the multiple linear regression model, adjusted percent change in length of stay was derived from the ratio of the length of stay for patients with a given characteristic to the length of stay for patients without the given characteristic, after adjustment for other variables in the model. The resultant partial correlation coefficient reflects the percentage variation in length of stay in terms of a given characteristic after controlling the other variables in the model [18]. The final model included the following variables: hospitals (B, C, D), age by year, male gender, referral status, previous histories (myocardial infarction, CHF, angina, CABG, and coronary revascularization), ECG changes (ST elevation, ST depression), infarct location (antero-septal, inferior), disposition (ICU), complications (none, recurrent chest pain, infarct extension, CHF, pulmonary edema, cardiogenic shock, new Mobitz II block, complete AV block, VT / VF, cardiac arrest, respiratory failure requiring intubation, and death). All statistical analyses were done with the SAS statistical program (SAS Institute, Cary, NC, 1996).
279
3. Results
3.1. Study population and clinical characteristics at admission A total of 482 consecutively patients admitted with AMI were included, consisting of 131 patients from hospital A, 224 from hospital B, 90 from hospital C and 37 from hospital D (Table 1). The characteristics of patients by hospital significantly differed in terms of age (P50.019), gender (P50.031), and referral status (P,0.001). However, their cardiac histories were similar except for previous angina, which was more common in hospital C and previous revascularization therapy, which was more common in hospital B. The prevalence of comorbid conditions, ST elevation on the initial electrocardiogram (ECG) and antero-septal and inferior infarct location were similar. The average heart rate showed a borderline difference (P50.054) and systolic blood pressure a significant difference (P,0.0001). Data on the use of medications at the time of admission were not available.
3.2. Management There were significant differences in management patterns among the four institutions (Table 2). Hospital B was least likely to triage patients into the intensive care unit. Although the frequency of thrombolytic therapy and temporary pacemakers was not different among these four hospitals, the rates for other procedures, including pulmonary artery catheter, coronary angiography, coronary revascularization, CABG, ETT, Holter EKG, echocardiography, IABP, and nuclear studies, were significantly different. Patients at hospital B were more likely to have cardiac catheterization and coronary revascularization performed while those at hospital D were more likely to undergo a CABG.
3.3. Short-term outcomes during hospitalization The percentages of patients who had an uneventful course were similar for all hospitals (Table 3), but cardiac arrest and death occurred more frequently among patients in hospital C. However, no significant differences were found in the prevalence of other
K. Matsui et al. / International Journal of Cardiology 78 (2001) 277 – 284
280 Table 1 Clinical characteristics at admission a
A (N5131) N
B (N5224)
C (N590) N
D (N537)
%
N
%
%
64.2611.3 170 169 100
76 75 45
63.6612.5 67 40 51
74 44 57
History Age b Male Referred patient Current smoker
67.8611.7 81 73 64
62 56 49
Past histories CHF AMI Angina CABG Revascularization
5 16 15 0 6
4 12 11 0 5
4 44 60 4 34
2 20 27 2 15
2 17 33 1 4
2 19 37 1 4
Comorbid conditions Hypertension Diabetes Gastrointestinal disease Liver disease Renal disease Pulmonary disease Hyperlipidemia
70 40 16 7 13 8 20
53 31 12 5 10 6 23
101 56 33 9 13 13 32
45 25 15 4 6 6 14
41 26 18 2 5 9 21
46 29 20 2 6 10 23
Initial examination Heart rate b Systolic BP b
79.76 21.6 136.6634.1
75.7619.0 132.7630.7
72.56 21.9 119.8628.9
N
P-value %
63.4612.5 28 18 20
76 49 54
0.019 0.031 0.001 0.242
1 6 6 0 2
3 16 16 0 5
0.696 0.330 0.001 0.394 0.001
12 10 4 2 3 2 4
32 27 11 5 8 5 11
0.128 0.076 0.376 0.690 0.466 0.563 0.065
80.96 21.4 117.1619.6
0.054 0.0001
Initial ECG ST elevation ST depression
90 35
69 27
178 82
79 37
74 11
82 12
29 2
78 5
0.063 0.001
Infarct location Inferior Antero-septal
44 52
34 40
75 92
33 41
40 32
44 36
12 19
32 51
0.272 0.426
a b
CHF5Congestive heart failure; AMI5acute myocardial infarction; CABG5coronary bypass graft surgery; BP5blood pressure. Mean6S.D.
cardiac complications. Multivariate logistic regression analysis identified the independent correlates of in-hospital mortality as age by year [odds ratio (OR)51.10; 95% CI, 1.04–1.16], hospital C (OR5 9.61; 95% CI, 2.59–35.61), cardiogenic shock (OR5 7.90; 95% CI 2.62–23.80), VF / VT (OR517.19; 95% CI, 5.13–57.62), respiratory failure requiring intubation (OR519.78; 95% CI, 5.48–71.46), and cardiac arrest (OR540.30; 95% CI, 7.73–210.08).
3.4. Length of stay There were significant differences in the average
length of stay for both intensive care unit and total hospitalization (Table 3). Among the dead cases, the average length of stay (15.2 days) for each hospital was not significantly different (P50.1595). Multivariate models adjusted for variations in clinical data at hospital admission and subsequent complications showed significantly shorter length of stay for hospital B (partial R 2 50.0692) and hospital C (0.1790) cohorts than for those in hospital A and hospital D (model R 2 50.5411) (Table 4). Other independent correlates of length of stay were age by year (0.0092), ST elevation on ECG (0.0122), anteroseptal wall infarction (0.0072), CHF (0.0865), pul-
K. Matsui et al. / International Journal of Cardiology 78 (2001) 277 – 284
281
Table 2 Management a A (N5131)
B (N5224)
N Disposition ICU Procedures Thrombolytic therapy Pulmonary artery catheter Coronary angiography Revascularization CABG ETT Holter ECG Echo cardiography Temporary pacemaker IABP Nuclear studies a
%
N
C (N590)
D (N537)
P-value
%
N
%
N
%
80
61
63
28
85
94
14
35
0.001
41 115 116 85 6 90 58 126 7 10 114
31 88 89 65 5 69 44 96 5 8 87
68 176 215 196 7 64 18 206 8 46 96
30 79 96 85 3 29 8 92 4 21 43
25 11 79 52 6 0 24 74 8 12 61
28 12 88 58 7 0 27 82 9 13 68
10 2 33 17 6 12 20 35 3 3 35
27 5 89 46 16 32 54 95 8 8 95
0.922 0.001 0.024 0.001 0.009 0.001 0.001 0.003 0.246 0.005 0.001
ICU5Intensive care unit; CABG5coronary artery bypass graft surgery; ETT5exercise tolerance test; IABP5intra-aortic balloon pumping.
Table 3 Short-term outcomes during hospitalization a A (N5131) N Complications during hospitalization No complications Recurrent chest pain, presumed ischemia Infarct extension CHF Pulmonary edema Cardiogenic shock New Mobitz II block Complete heart block Sustained VT / VF Cardiac arrest Respiratory failure Death
71 19 7 21 2 11 1 11 12 6 14 11
Length of Stay ICU stay (days)b Median Total length of stay (days)b Median
2.062.4 2.0 41.0619.4 40.0
Disposition at discharge Home a b
112
B (N5224)
C (N590)
D (N537)
P-value
%
N
%
N
%
N
%
54 15 5 16 2 8 1 8 9 5 11 8
128 19 10 43 9 35 1 19 17 5 22 10
57 8 4 19 4 16 0.5 8 8 2 10 4
53 8 5 14 6 9 1 4 10 8 4 13
59 9 6 16 7 10 1 4 11 9 4 14
18 2 2 12 2 3 0 3 8 0 1 2
49 5 5 32 5 8 0 8 22 0 3 5
2.368.9 0 21.4626.4 15.0
86
200
7.265.1 6.0 15.8612.6 13.0
89
70
1.462.1 0 37.0622.6 30.0
78
VT / VF5Ventricular tachycardia / ventricular fibrillation; CHF5congestive heart failure; ICU5intensive care unit. Mean6S.D.
27
0.704 0.209 0.971 0.120 0.262 0.154 0.865 0.651 0.061 0.027 0.186 0.022
0.0001
0.0001
73
0.012
K. Matsui et al. / International Journal of Cardiology 78 (2001) 277 – 284
282
Table 4 Independent correlates of log length of stay in total study population a Predictor variable
Hospitals B C Clinical characteristics Age (years) ST elevation on ECG Antero-septal infarction Complications CHF Pulmonary edema Cardiogenic shock Respiratory failure Death a
Adjusted increase in LOS (%)
95% CI adjusted increase in LOS (%)
P-value
Partial R 2
256.7 261.9
(261.4, 251.3) (267.2, 255.7)
0.0001 0.0001
0.0692 0.1790
(0.3, 1.2) (8.2, 38.1) (4.0, 28.5)
0.0026 0.0006 0.0076
0.0092 0.0122 0.0072
0.0001 0.0001 0.0003 0.0001 0.0001
0.0865 0.0189 0.0143 0.0380 0.1067
0.7 22.2 15.6
45.4 64.4 38.0 67.4 281.9
(25.8, (23.1, (16.3, (33.0, (285.7,
68.2) 119.5) 63.8) 110.6) 277.2)
LOS5Length of stay; CHF5congestive heart failure. F-test for the model: P,0.0001, Model R 2 50.5411.
monary edema (0.0189), cardiogenic shock (0.0143), respiratory failure requiring intubation (0.0380), and death (0.1067).
4. Discussion Our study found there were considerable differences in the management patterns and outcomes for AMI patients in tertiary-care hospitals in Japan. The most striking finding was that the length of hospital stay varied significantly among the four hospitals even after adjustment for the differences in important clinical characteristics. This is consistent with the results of previous reports from the United States, Canada, and European countries. For example, Lee and colleagues showed variations in hospital length of stay for patients with uncomplicated AMI at three hospitals in the Boston area and Chen et al. produced similar findings for Canadian patients [5,6]. With respect to AMI management, Pilote et al. demonstrated in the GUSTO trial that American physicians were more likely to recommend coronary angiography than Canadian physicians [7]. Although rates of performance of coronary angiography and CABG have generally been shown to differ within and between countries, the important point is that there appears to be no
evidence of a major impact of these differences on health outcomes of patients [5–15]. The health care system in Japan is different from that in most other developed countries and the average length of stay in Japanese hospitals is extremely long [14,16,19]. There are some obvious disadvantages for long length of hospital stay. Long hospital stay raises medical cost and patients may suffer functional decline and deconditioning and high chances of nosocomial infection, especially among elderly patients. On the other hand, there are some potential advantages. It may prevent early hospital readmission and lessen the burden of care on family members after discharge. However, it is not certain whether these potential advantages outweigh the disadvantages. Our final multivariate model identified a 54% variation in length of hospital stay and as much as half of this variation could be explained by hospital factors. This means the length of hospital stay in Japan is for the most part influenced by institutional characteristics. Moreover, in spite of a similar prevalence of ST elevation on initial ECG and infarct location among the patients in these four hospitals, the choice of therapy, including revascularization and CABG, was significantly different. In view of the similarity of patient characteristics, these observed differences in management patterns were less likely to be due to clinical necessity than to variations in
K. Matsui et al. / International Journal of Cardiology 78 (2001) 277 – 284
physician-initiated practice style or hospital management patterns, as has already been shown in other studies [5]. With regard to clinical outcome, hospital C was unique in that it had the highest in-hospital mortality and shortest length of stay even after adjustment for clinical characteristics, while the other three hospitals had similar in-hospital mortality. However, some important patients’ factors such as LV function and infarct size were not taken into account in the multivariate models. High mortality rate at the hospital C may simply reflect greater severity of myocardial infarction in patients at the index admission. Moreover, some hospital factors could have influenced the outcome. For example, the number of cardiologists and the number of available hospital beds were not included into our analyses because we studied for only four hospitals, although these factors could represent the capacity and ability of each hospital to care of patients of myocardial infarction. Regarding the patients’ characteristics, our results showed high prevalence of ST elevation on the initial ECG. There was a study from the US showing that only 29% of patients presenting to the emergency room because of myocardial infarction had ST elevation [20]. Another study from the US and Russia showed that 27.4 and 47.6%, respectively, of the patients with transmural or Q wave infarction had ST elevation [15]. The high proportion of ST elevation (69–82%) in our study may indicate higher prevalence of transmural infarction among Japanese patients than among those in the US and Russia. However, our sample size was too small to evaluate this possibility in a statistically meaning way. In addition, the current results should be interpreted with caution because of the limitations of the study design. First, the four institutions from which the data were obtained are tertiary-care, urban teaching hospitals. The results may not be generalizable to secondary-care or community hospitals in less populated areas. Second, we investigated only in-hospital short-term outcomes, so that long-term outcomes including mortality after discharge of index admission remain unexamined. In spite of these possible limitations, our results suggest that there is room for eliminating unnecessary medical practice while maintaining the same level of quality of care and health care costs in Japan.
283
In conclusion, the current study showed that there were significant differences in the management patterns and short-term clinical outcomes among AMI patients admitted to different tertiary-care hospitals in Japan. Further detailed analysis of the use of cardiac procedures and of long-term outcomes should lead to more effective resource utilization for the care of AMI patients in Japan.
Acknowledgements Dr. Matsui was supported by grants from St. Luke’s Life Science Institute and Aso Cement Co., Japan.
References [1] Health and Welfare Statistics Association. Japanese Population Health Trends [Kokumin-eisei no Doko] Tokyo 1999;:41–72, In Japanese. [2] Gersh BJ. Current issues in reperfusion therapy. Am J Cardiol 1998;82(8B):3–11. [3] Califf RM, Harrington RA. Improved outlook for patients with acute myocardial infarction: an interim progress report. Eur Heart J 1998;19:1416–8. [4] Every NR, Spertus J, Fihn SD et al. Length of hospital stay after acute myocardial infarction in the myocardial infarction triage and intervention (MITI) project registry. J Am Coll Cardiol 1996;28:287–93. [5] Lee TH, Gottlieb LK, Weitzman LJ et al. Length of stay of patients with uncomplicated acute myocardial infarction at three Boston hospitals. J Gen Intern Med 1988;3:239–44. [6] Chen E, Naylor CD. Variation in hospital length of stay for acute myocardial infarction in Ontario. Can Med Care 1994;32:420–35. [7] Pilote L, Granger C, Armstrong PW et al. Differences in the treatment of myocardial infarction between the United States and Canada: a survey of physicians in the GUSTO trial. Med Care 1995;33:598–610. [8] Rouleau JL, Moye LA, Pfeffer MA et al. A comparison of management patterns after acute myocardial infarction in Canada and the United States. N Engl J Med 1993;328:779–84. [9] Pilote L, Racine N, Hlatky MA. Differences in the treatment of myocardial infarction in the United States and Canada: a comparison of two university hospitals. Arch Intern Med 1994;154:1090–6. [10] Mark DB, Naylor CD, Hlatky MA et al. Use of medical resources and quality of life after acute myocardial infarction in Canada and the United States. N Engl J Med 1994;331:1130–5. [11] Pilote L, Califf RM, Sapp S et al. Regional variation across the United States in the management of acute myocardial infarction. N Engl J Med 1995;333:565–72. [12] Guadagnoli E, Hauptman PJ, Ayanian JZ et al. Variation in the use of cardiac procedures after acute myocardial infarction. N Engl J Med 1995;333:573–8.
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[13] Van de Werf F, Topol EJ et al. Variations in patient management and outcomes for acute myocardial infarction in the United States and other countries: results from the GUSTO trial. J Am Med Assoc 1995;273:1586–91. [14] Matsui K, Polanczyk CA, Gaspoz JM et al. Management of patients with acute myocardial infarction at five academic medical centers: clinical characteristics, resource utilization, and outcome. J Invest Med 1999;47:134–40. [15] Reiss JA, Every N, Weaver WD. A comparison of the treatment of acute myocardial infarction between St. Petersburg, Russia and Seattle, Washington. Int J Cardiol 1995;53:29–36. [16] Ikegami N, Campbell JC. Medical care in Japan. N Engl J Med 1995;333:1295–9.
[17] Oliver AJ, Ikegami N, Ikeda S. Japan’s aging population. Implications for healthcare. Pharmacoeconomics 1997;11:306–18. [18] Matsui K, Goldman L, Johnson PA et al. Comorbidity as a correlate of length of stay for hospitalized patients with acute chest pain. J Gen Intern Med 1996;11:262–8. [19] Muramatsu N, Liang J. Hospital length of stay in the United States and Japan: a case study of myocardial infarction patients. Int J Health Serv 1999;29:189–209. [20] Otto J, Aufderheide TP. Evaluation of ST segment elevation criteria for the prehospital electrocardiographic diagnosis of acute myocardial infarction. Ann Emerg Med 1994;23:17–24.
Differences in management and outcomes of acute myocardial infarction among four general hospitals in Japan a
a,
a
b
b
Kunihiko Matsui , Tsuguya Fukui *, Kenji Hira , Atsushi Sobashima , Syuichi Okamatsu , Masakiyo Nobuyoshi c , Noriaki Hayashida d , Shigemichi Tanaka e a
Department of General Medicine and Clinical Epidemiology, Kyoto University Hospital, Kyoto University Graduate School of Medicine, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606 -8507, Japan b Aso Iizuka Hospital, Iizuka, Japan c Kokura Memorial Hospital, Kitakyusyu, Japan d St. Luke’ s International Hospital, Tokyo, Japan e Teine Keijinkai Hospital, Sapporo, Japan Received 27 July 2000; received in revised form 31 August 2000; accepted 11 January 2001
Abstract Objective: To ascertain the differences among hospitals in Japan in the management patterns and outcomes of patients with acute myocardial infarction (AMI). Design: Retrospective cohort study by means of patient chart review. Setting: Four tertiary-care teaching hospitals in Japan observed over a 1-year period. Study participants: Consecutive patients (N5482) admitted for AMI. Main outcome measures: Clinical characteristics, rates of diagnostic and therapeutic procedures performed, cardiac complications, and length of stay. Results: Patients’ clinical characteristics differed significantly among the four hospitals in terms of age, gender, and prior cardiac history, but not in terms of comorbidity or infarct location. The frequency and type of diagnostic and therapeutic procedures were different, and in-hospital mortality varied (4–14%, P50.022). Average length of hospital stay ranged from 15.8612.6 days to 41.0619.4 days (P50.0001). After adjustment for the clinical characteristics, these differences remained significant among hospitals. Conclusion: Considerable differences in the management and outcomes of patients with AMI exist in Japan. 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Acute myocardial infarction; Management; Outcomes; Japanese
1. Introduction Cardiovascular disease is currently the second most common cause of death in Japan [1]. As is the case with other developed countries, acute myocardial infarction (AMI) is by far the most common cardiovascular disease. Myocardial infarction has been the target of therapeutic efforts using such recent *Corresponding author. Tel.: 181-75-751-4210; fax: 181-75-7514211. E-mail address: [email protected] (T. Fukui).
medical technologies as thrombolytic therapy, angioplasty, and coronary bypass graft surgery [2]. Faced with a wide array of treatment modalities, physicians are not likely to make consistent clinical judgments. In fact, inconsistencies in management patterns of AMI have been reported not only between but also within countries [3,4]. Many studies have clearly demonstrated variations in management patterns, but no major differences were found in patient outcomes among different institutions, regions, and countries [5–15]. Most of these studies, however, were conducted in the United States, Canada and
0167-5273 / 01 / $ – see front matter 2001 Elsevier Science Ireland Ltd. All rights reserved. PII: S0167-5273( 01 )00387-4
278
K. Matsui et al. / International Journal of Cardiology 78 (2001) 277 – 284
other Western countries, and it is not yet clear whether the same holds true in Japan. The health care system in Japan is different from that in most other developed countries in that all people are covered by one of the national, government-run or private, corporate-run insurance systems in the context of fee-for-service reimbursement [16]. However, as the population in Japan is graying at an ever faster rate, medical expenditure is increasing almost exponentially [16,17]. As a result, assessment of the efficacy and effectiveness of any clinical interventions is crucial for the maintenance of adequate medical care with limited financial resources. Against this background, we tried to determine to what extent the management patterns and patient outcomes varied for AMI patients admitted to four teaching hospitals in Japan.
2. Methods
2.1. Study sites and population The study subjects were consecutive patients who were admitted with a diagnosis of AMI to four Japanese hospitals (Aso Iizuka Hospital, Iizuka; Kokura Memorial Hospital, Kitakyusyu; St. Luke’s International Hospital, Tokyo; and Teine Keijinkai Hospital, Sapporo) over 1 year between July 1995 and June 1996. All of these hospitals are tertiary-care teaching hospitals with cardiac catheterization and cardiac surgery capabilities. They play an important role in the management of AMI patients in their respective areas. The patients were identified through the medical records kept at the hospitals. Myocardial infarction was defined according to generally accepted criteria, including: (1) the documentation of elevated creatine kinase (total or creatine kinase-MB), in addition to (2) a history of typical chest pain and other symptoms and / or (3) electrocardiographic (ECG) abnormalities defined as $0.1 mV ST segment elevation in contiguous leads, or $0.1 mV ST segment depression and / or definite T wave inversion. The four hospitals will be denoted simply as A, B, C, and D, in order to prevent identification. We have data on the total number of beds at each hospital
(hospital A51157, hospital B5658, hospital C5520, and hospital D5524) and the number of staff physicians working for cardiology patients (hospital A5 13, hospital B519, hospital C54, and hospital D5 13). However, the number of the beds for cardiology patients was not available at hospital C, because cardiology ward was not completely independent from other subspecialty departments of medicine (hospital A561, hospital B593, and hospital D541).
2.2. Data collection The physician reviewers conducted a detailed chart review. For comparative analyses of the four hospitals in terms of management patterns, the following items were included: (1) gender, (2) age, (3) vital signs (blood pressure and heart rate on admission), (4) referral status, (5) smoking status, (6) previous histories [congestive heart failure (CHF), myocardial infarction, angina, coronary revascularization (percutaneous transluminal coronary angioplasty, stent placement, and other procedures using cardiac catheterization), and coronary artery bypass graft surgery (CABG)], (7) comorbidities (hypertension, diabetes, gastrointestinal disease, liver disease, renal disease, pulmonary disease, and hyperlipidemia), (8) ECG changes (ST elevation, ST depression), (9) infarct location (antero-septal, inferior), (10) cardiac complications during hospitalization [no complications, recurrent chest pain indicative of ischemia, reinfarction, CHF, pulmonary edema, cardiogenic shock, Mobitz type II block, complete AV block, ventricular tachycardia / ventricular fibrillation (VT / VF), respiratory failure requiring intubation, cardiac arrest], (11) major procedures [thrombolytic therapy, pulmonary artery catheter, coronary angiography, revascularization, CABG, exercise tolerance test (ETT), holter ECG, echo cardiography, temporary pacemaker, intra-aortic balloon pumping (IABP), nuclear studies], (12) length of stay [intensive care unit (ICU), total], and (13) final disposition (survival or death at hospital discharge). We regarded these cardiac complications, length of stay, and final disposition as short term outcomes.
2.3. Statistical analysis For statistical comparisons the Wilcoxon rank sum
K. Matsui et al. / International Journal of Cardiology 78 (2001) 277 – 284
test or the Kruskal–Wallis test was used as appropriate for continuous variables, and the chi-square test or Fisher’s exact test with appropriate degrees of freedom for categorical variables. A logistic regression model was used to identify correlation with in-hospital mortality after adjustment for clinical characteristics which univariate analyses had shown to be significantly correlated. In this model, the following variables were included: hospitals (B, C, and D), age by year, male gender, previous histories (myocardial infarction, CHF), antero-septal wall as an infarct location, and complications (none, infarct extension, CHF, pulmonary edema, cardiogenic shock, VT / VF, respiratory failure requiring intubation, and cardiac arrest). We did not include procedures in the variables since our main concern was whether the hospital correlated with the outcomes after adjustment for clinical data. We thus developed ‘optimal clinical models’ based on clinical variables and complications, but not procedures. Furthermore, to identify independent correlates of length of stay, stepwise multiple linear regression analyses were performed, using the log transformation of length of stay as the dependent variable. Since the data for length of stay are highly skewed, the natural logarithm of length of stay was used as the dependent variable. In the multiple linear regression model, adjusted percent change in length of stay was derived from the ratio of the length of stay for patients with a given characteristic to the length of stay for patients without the given characteristic, after adjustment for other variables in the model. The resultant partial correlation coefficient reflects the percentage variation in length of stay in terms of a given characteristic after controlling the other variables in the model [18]. The final model included the following variables: hospitals (B, C, D), age by year, male gender, referral status, previous histories (myocardial infarction, CHF, angina, CABG, and coronary revascularization), ECG changes (ST elevation, ST depression), infarct location (antero-septal, inferior), disposition (ICU), complications (none, recurrent chest pain, infarct extension, CHF, pulmonary edema, cardiogenic shock, new Mobitz II block, complete AV block, VT / VF, cardiac arrest, respiratory failure requiring intubation, and death). All statistical analyses were done with the SAS statistical program (SAS Institute, Cary, NC, 1996).
279
3. Results
3.1. Study population and clinical characteristics at admission A total of 482 consecutively patients admitted with AMI were included, consisting of 131 patients from hospital A, 224 from hospital B, 90 from hospital C and 37 from hospital D (Table 1). The characteristics of patients by hospital significantly differed in terms of age (P50.019), gender (P50.031), and referral status (P,0.001). However, their cardiac histories were similar except for previous angina, which was more common in hospital C and previous revascularization therapy, which was more common in hospital B. The prevalence of comorbid conditions, ST elevation on the initial electrocardiogram (ECG) and antero-septal and inferior infarct location were similar. The average heart rate showed a borderline difference (P50.054) and systolic blood pressure a significant difference (P,0.0001). Data on the use of medications at the time of admission were not available.
3.2. Management There were significant differences in management patterns among the four institutions (Table 2). Hospital B was least likely to triage patients into the intensive care unit. Although the frequency of thrombolytic therapy and temporary pacemakers was not different among these four hospitals, the rates for other procedures, including pulmonary artery catheter, coronary angiography, coronary revascularization, CABG, ETT, Holter EKG, echocardiography, IABP, and nuclear studies, were significantly different. Patients at hospital B were more likely to have cardiac catheterization and coronary revascularization performed while those at hospital D were more likely to undergo a CABG.
3.3. Short-term outcomes during hospitalization The percentages of patients who had an uneventful course were similar for all hospitals (Table 3), but cardiac arrest and death occurred more frequently among patients in hospital C. However, no significant differences were found in the prevalence of other
K. Matsui et al. / International Journal of Cardiology 78 (2001) 277 – 284
280 Table 1 Clinical characteristics at admission a
A (N5131) N
B (N5224)
C (N590) N
D (N537)
%
N
%
%
64.2611.3 170 169 100
76 75 45
63.6612.5 67 40 51
74 44 57
History Age b Male Referred patient Current smoker
67.8611.7 81 73 64
62 56 49
Past histories CHF AMI Angina CABG Revascularization
5 16 15 0 6
4 12 11 0 5
4 44 60 4 34
2 20 27 2 15
2 17 33 1 4
2 19 37 1 4
Comorbid conditions Hypertension Diabetes Gastrointestinal disease Liver disease Renal disease Pulmonary disease Hyperlipidemia
70 40 16 7 13 8 20
53 31 12 5 10 6 23
101 56 33 9 13 13 32
45 25 15 4 6 6 14
41 26 18 2 5 9 21
46 29 20 2 6 10 23
Initial examination Heart rate b Systolic BP b
79.76 21.6 136.6634.1
75.7619.0 132.7630.7
72.56 21.9 119.8628.9
N
P-value %
63.4612.5 28 18 20
76 49 54
0.019 0.031 0.001 0.242
1 6 6 0 2
3 16 16 0 5
0.696 0.330 0.001 0.394 0.001
12 10 4 2 3 2 4
32 27 11 5 8 5 11
0.128 0.076 0.376 0.690 0.466 0.563 0.065
80.96 21.4 117.1619.6
0.054 0.0001
Initial ECG ST elevation ST depression
90 35
69 27
178 82
79 37
74 11
82 12
29 2
78 5
0.063 0.001
Infarct location Inferior Antero-septal
44 52
34 40
75 92
33 41
40 32
44 36
12 19
32 51
0.272 0.426
a b
CHF5Congestive heart failure; AMI5acute myocardial infarction; CABG5coronary bypass graft surgery; BP5blood pressure. Mean6S.D.
cardiac complications. Multivariate logistic regression analysis identified the independent correlates of in-hospital mortality as age by year [odds ratio (OR)51.10; 95% CI, 1.04–1.16], hospital C (OR5 9.61; 95% CI, 2.59–35.61), cardiogenic shock (OR5 7.90; 95% CI 2.62–23.80), VF / VT (OR517.19; 95% CI, 5.13–57.62), respiratory failure requiring intubation (OR519.78; 95% CI, 5.48–71.46), and cardiac arrest (OR540.30; 95% CI, 7.73–210.08).
3.4. Length of stay There were significant differences in the average
length of stay for both intensive care unit and total hospitalization (Table 3). Among the dead cases, the average length of stay (15.2 days) for each hospital was not significantly different (P50.1595). Multivariate models adjusted for variations in clinical data at hospital admission and subsequent complications showed significantly shorter length of stay for hospital B (partial R 2 50.0692) and hospital C (0.1790) cohorts than for those in hospital A and hospital D (model R 2 50.5411) (Table 4). Other independent correlates of length of stay were age by year (0.0092), ST elevation on ECG (0.0122), anteroseptal wall infarction (0.0072), CHF (0.0865), pul-
K. Matsui et al. / International Journal of Cardiology 78 (2001) 277 – 284
281
Table 2 Management a A (N5131)
B (N5224)
N Disposition ICU Procedures Thrombolytic therapy Pulmonary artery catheter Coronary angiography Revascularization CABG ETT Holter ECG Echo cardiography Temporary pacemaker IABP Nuclear studies a
%
N
C (N590)
D (N537)
P-value
%
N
%
N
%
80
61
63
28
85
94
14
35
0.001
41 115 116 85 6 90 58 126 7 10 114
31 88 89 65 5 69 44 96 5 8 87
68 176 215 196 7 64 18 206 8 46 96
30 79 96 85 3 29 8 92 4 21 43
25 11 79 52 6 0 24 74 8 12 61
28 12 88 58 7 0 27 82 9 13 68
10 2 33 17 6 12 20 35 3 3 35
27 5 89 46 16 32 54 95 8 8 95
0.922 0.001 0.024 0.001 0.009 0.001 0.001 0.003 0.246 0.005 0.001
ICU5Intensive care unit; CABG5coronary artery bypass graft surgery; ETT5exercise tolerance test; IABP5intra-aortic balloon pumping.
Table 3 Short-term outcomes during hospitalization a A (N5131) N Complications during hospitalization No complications Recurrent chest pain, presumed ischemia Infarct extension CHF Pulmonary edema Cardiogenic shock New Mobitz II block Complete heart block Sustained VT / VF Cardiac arrest Respiratory failure Death
71 19 7 21 2 11 1 11 12 6 14 11
Length of Stay ICU stay (days)b Median Total length of stay (days)b Median
2.062.4 2.0 41.0619.4 40.0
Disposition at discharge Home a b
112
B (N5224)
C (N590)
D (N537)
P-value
%
N
%
N
%
N
%
54 15 5 16 2 8 1 8 9 5 11 8
128 19 10 43 9 35 1 19 17 5 22 10
57 8 4 19 4 16 0.5 8 8 2 10 4
53 8 5 14 6 9 1 4 10 8 4 13
59 9 6 16 7 10 1 4 11 9 4 14
18 2 2 12 2 3 0 3 8 0 1 2
49 5 5 32 5 8 0 8 22 0 3 5
2.368.9 0 21.4626.4 15.0
86
200
7.265.1 6.0 15.8612.6 13.0
89
70
1.462.1 0 37.0622.6 30.0
78
VT / VF5Ventricular tachycardia / ventricular fibrillation; CHF5congestive heart failure; ICU5intensive care unit. Mean6S.D.
27
0.704 0.209 0.971 0.120 0.262 0.154 0.865 0.651 0.061 0.027 0.186 0.022
0.0001
0.0001
73
0.012
K. Matsui et al. / International Journal of Cardiology 78 (2001) 277 – 284
282
Table 4 Independent correlates of log length of stay in total study population a Predictor variable
Hospitals B C Clinical characteristics Age (years) ST elevation on ECG Antero-septal infarction Complications CHF Pulmonary edema Cardiogenic shock Respiratory failure Death a
Adjusted increase in LOS (%)
95% CI adjusted increase in LOS (%)
P-value
Partial R 2
256.7 261.9
(261.4, 251.3) (267.2, 255.7)
0.0001 0.0001
0.0692 0.1790
(0.3, 1.2) (8.2, 38.1) (4.0, 28.5)
0.0026 0.0006 0.0076
0.0092 0.0122 0.0072
0.0001 0.0001 0.0003 0.0001 0.0001
0.0865 0.0189 0.0143 0.0380 0.1067
0.7 22.2 15.6
45.4 64.4 38.0 67.4 281.9
(25.8, (23.1, (16.3, (33.0, (285.7,
68.2) 119.5) 63.8) 110.6) 277.2)
LOS5Length of stay; CHF5congestive heart failure. F-test for the model: P,0.0001, Model R 2 50.5411.
monary edema (0.0189), cardiogenic shock (0.0143), respiratory failure requiring intubation (0.0380), and death (0.1067).
4. Discussion Our study found there were considerable differences in the management patterns and outcomes for AMI patients in tertiary-care hospitals in Japan. The most striking finding was that the length of hospital stay varied significantly among the four hospitals even after adjustment for the differences in important clinical characteristics. This is consistent with the results of previous reports from the United States, Canada, and European countries. For example, Lee and colleagues showed variations in hospital length of stay for patients with uncomplicated AMI at three hospitals in the Boston area and Chen et al. produced similar findings for Canadian patients [5,6]. With respect to AMI management, Pilote et al. demonstrated in the GUSTO trial that American physicians were more likely to recommend coronary angiography than Canadian physicians [7]. Although rates of performance of coronary angiography and CABG have generally been shown to differ within and between countries, the important point is that there appears to be no
evidence of a major impact of these differences on health outcomes of patients [5–15]. The health care system in Japan is different from that in most other developed countries and the average length of stay in Japanese hospitals is extremely long [14,16,19]. There are some obvious disadvantages for long length of hospital stay. Long hospital stay raises medical cost and patients may suffer functional decline and deconditioning and high chances of nosocomial infection, especially among elderly patients. On the other hand, there are some potential advantages. It may prevent early hospital readmission and lessen the burden of care on family members after discharge. However, it is not certain whether these potential advantages outweigh the disadvantages. Our final multivariate model identified a 54% variation in length of hospital stay and as much as half of this variation could be explained by hospital factors. This means the length of hospital stay in Japan is for the most part influenced by institutional characteristics. Moreover, in spite of a similar prevalence of ST elevation on initial ECG and infarct location among the patients in these four hospitals, the choice of therapy, including revascularization and CABG, was significantly different. In view of the similarity of patient characteristics, these observed differences in management patterns were less likely to be due to clinical necessity than to variations in
K. Matsui et al. / International Journal of Cardiology 78 (2001) 277 – 284
physician-initiated practice style or hospital management patterns, as has already been shown in other studies [5]. With regard to clinical outcome, hospital C was unique in that it had the highest in-hospital mortality and shortest length of stay even after adjustment for clinical characteristics, while the other three hospitals had similar in-hospital mortality. However, some important patients’ factors such as LV function and infarct size were not taken into account in the multivariate models. High mortality rate at the hospital C may simply reflect greater severity of myocardial infarction in patients at the index admission. Moreover, some hospital factors could have influenced the outcome. For example, the number of cardiologists and the number of available hospital beds were not included into our analyses because we studied for only four hospitals, although these factors could represent the capacity and ability of each hospital to care of patients of myocardial infarction. Regarding the patients’ characteristics, our results showed high prevalence of ST elevation on the initial ECG. There was a study from the US showing that only 29% of patients presenting to the emergency room because of myocardial infarction had ST elevation [20]. Another study from the US and Russia showed that 27.4 and 47.6%, respectively, of the patients with transmural or Q wave infarction had ST elevation [15]. The high proportion of ST elevation (69–82%) in our study may indicate higher prevalence of transmural infarction among Japanese patients than among those in the US and Russia. However, our sample size was too small to evaluate this possibility in a statistically meaning way. In addition, the current results should be interpreted with caution because of the limitations of the study design. First, the four institutions from which the data were obtained are tertiary-care, urban teaching hospitals. The results may not be generalizable to secondary-care or community hospitals in less populated areas. Second, we investigated only in-hospital short-term outcomes, so that long-term outcomes including mortality after discharge of index admission remain unexamined. In spite of these possible limitations, our results suggest that there is room for eliminating unnecessary medical practice while maintaining the same level of quality of care and health care costs in Japan.
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In conclusion, the current study showed that there were significant differences in the management patterns and short-term clinical outcomes among AMI patients admitted to different tertiary-care hospitals in Japan. Further detailed analysis of the use of cardiac procedures and of long-term outcomes should lead to more effective resource utilization for the care of AMI patients in Japan.
Acknowledgements Dr. Matsui was supported by grants from St. Luke’s Life Science Institute and Aso Cement Co., Japan.
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