Temporal Trends and Associated Factors of Inpatient Cardiac Rehabilitation in Patients With Acute Myocardial Infarction: A Community-wide Perspective

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1 Temporal Trends and Associated Factors of Inpatient Cardiac Rehabilitation in Patients With Acute Myocardial Infarction: A Community-wide Perspective Frederick A. Spencer, MD; Bobak Salami, MD; Jorge Yarzebski, MD; Darleen Lessard, MS; Joel M. Gore, MD; Robert J. Goldberg, PhD PURPOSE: Cardiac rehabilitation (CR) has been shown to be an important therapeutic intervention after the development of acute myocardial infarction (AMI), but historically has been underused. Inpatient CR often represents cardiac patients first exposure to risk factor modification education and acts as a gateway to outpatient programs. METHODS: The authors performed a longitudinal study of the use of inpatient CR in 5204 Worcester residents hospitalized with validated AMI in seven 1-year periods between 1986 and RESULTS: The overall rate of referral to inpatient CR was 68%, with a slight decline in use to less than 60% in the authors most recent study year of Referred patients were significantly more likely to be younger, male, or enrolled in a health maintenance organization; they were less likely to have a history of heart failure or stroke. They were significantly more likely to receive medications shown to be of benefit in the management of AMI and to undergo cardiac interventional procedures. In 1997, patients participating in inpatient CR were more likely to have documented inpatient counseling about nutrition, exercise, smoking, and stress reduction. DISCUSSION: The results of this multihospital community-wide study suggest relatively stable, but recently decreasing, use of inpatient CR over the past decade. Women and the elderly are underrepresented in these programs. Patients not referred to inpatient rehabilitation were less likely to be prescribed effective cardiac medications and undergo risk factor modification counseling prior to discharge. Further studies are needed to better understand the reasons for patient exclusion from the benefits of inpatient CR. K E Y W O R D S cardiac rehabilitation acute myocardial infarction inpatient risk factor modification From the Department of Medicine, Division of Cardiovascular Medicine, University of Massachusetts Medical School, Worcester, Mass. Support by a grant from the National Heart, Lung, and Blood Institute (R01 HL35434). Address correspondence to: Frederick A. Spencer, MD, Department of Medicine, Division of Cardiovascular Medicine, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA ( spencerf@ummhc.org). Formal cardiac rehabilitation has been shown to be an important therapeutic intervention after the development of acute myocardial infarction (AMI). Historically, rehabilitation after AMI has been divided into several phases. Phase I generally consists of early inpatient ambulation, identification of risk factors, and educational interventions. Phases II, III, and IV occur after hospital discharge and are characterized by gradual increases in activity levels, continuation of risk factor modifications, and development of maintenance programs. To date, most studies of cardiac rehabilitation (CR) have focused on the delivery and efficacy of outpatient interventions. Indeed, meta-analyses of randomized controlled trials suggest significant beneficial effects on long-term mortality for patients participating in outpatient CR programs. 1,2 Despite these suggestive findings, use of CR in patients with AMI historically has been poor. Inpatient CR in Patients With AMI / 377

2 Participation in these risk factor modification programs has been estimated at approximately 20% for eligible patients with recent AMI, with less than 15% going on to an exercise or risk factor maintenance program. 3 Few studies have adequately explored factors associated with the use of CR. In one study, strength of the primary care physician s referral to CR was the most powerful predictor of subsequent participation. 4 Other studies suggest younger age, male sex, higher socioeconomic status, and receipt of coronary revascularization to be associated with increased use of CR. 3-7 The varying usage of CR by different subgroups is particularly problematic given the benefits associated with CR and exercise training in women and the elderly. 4,8,9 Unlike former studies, we examined referral rates and factors associated with use of inpatient CR from a population-based perspective. This approach was chosen for a number of reasons. First, initial referral to outpatient CR generally occurs at the time of hospitalization for AMI when patients are first introduced to the rehabilitation staff. Second, referral to inpatient rehabilitation would be expected to be primarily influenced by physicians attitudes toward the usefulness of these secondary prevention services and their beliefs about which types of patients might benefit. Finally, although few data are available regarding the efficacy or value of inpatient CR, this intervention is widely available in most hospitals. To our knowledge, this study is the first to evaluate rates and patterns of use of this intervention. Given the changing cardiovascular healthcare landscape of increasing surgical and percutaneous interventions and shortened length of stay, we felt it was particularly important and timely to examine trends over the past decade ( ) in these referral patterns. In addition, because there is a paucity of data about the impact of inpatient CR on the delivery of individual risk factor counseling, we assessed whether referral to inpatient CR enhanced the delivery of risk factor interventions in a community-wide sample of patients hospitalized with AMI. Our study examined overall rates, and temporal trends therein, of inpatient CR use in 5738 residents of the Worcester, Massachusetts metropolitan area hospitalized with AMI in all greater-worcester hospitals during seven annual periods between 1986 and METHODS The population under study consisted of residents of the Worcester metropolitan area hospitalized with a primary or secondary discharge diagnosis of AMI (International Classification of Diseases, 9th revision, code 410) in all acute general hospitals in the Worcester standard metropolitan statistical area (1990 census estimate 437,000) during calendar years 1986, 1988, 1990, 1991, 1993, 1995, and All 16 teaching and community hospitals were included in this study through the late 1980s, but fewer hospitals were included thereafter due to hospital closures or conversion to chronic care facilities A random sample of related diagnostic rubrics in which the diagnosis of AMI might have occurred also was carried out to identify possible cases of AMI in metropolitan Worcester residents that might have been misclassified. The medical records of Worcester residents with a discharge diagnosis of AMI from these hospitals were reviewed individually and validated as described previously In brief, these criteria consisted of a supportive clinical history, cardiac enzyme elevations, and serial electrocardiogram changes. Patients with perioperative-associated AMI were not included. The complications of AMI, including heart failure and cardiogenic shock, were assessed on the basis of information available from clinical charts. 13,14 This report is based on information from 5738 residents of the Worcester standard metropolitan statistical area who met the diagnostic criteria for AMI in the periods examined. Of these, 765 patients were hospitalized in 1986, 659 in 1988, 718 in 1990, 796 in 1991, 885 in 1993, 908 in 1995, and 1007 in Data Collection The hospital records of patients with validated AMI were abstracted for demographic and clinical data including age, gender, medical history of angina, diabetes, hypertension, heart failure or stroke, occurrence of heart failure and shock during hospitalization, and use of selected diagnostic procedures and therapeutic approaches. All medication usage was coded as present if it was either started before or during the time of the index hospitalization. Information was collected about whether the patient underwent CR during the index hospitalization. If the patient participated in at least one CR session, they were considered to have undergone CR. Information was not collected about the number of inpatient rehabilitation sessions attended or about the content of each CR program. Records of previous hospitalizations for coronary heart disease were reviewed (where available) when the review of the hospital chart indicated that the present hospitalization was not the first for coronary heart disease to identify initial cases of AMI. Data Analysis Differences in the distribution of selected characteristics between patients referred and those not referred to inpatient CR were examined by use of chi-square tests of statistical significance for discrete variables, whereas t tests were used for the analysis of between-group differences for continuous variables. We also carried out a multivariable regression analysis to examine factors associated with receipt of CR. The variables examined 378 / Journal of Cardiopulmonary Rehabilitation 2001;21:

3 in relation to enrollment in CR were age, gender, marital and medical insurance status, history of hypertension, angina, diabetes, heart failure or stroke, infarct location (anterior versus inferior-posterior), infarct type (Q wave or non-q wave), AMI order (initial versus prior), and development of heart failure or cardiogenic shock during hospitalization. We also controlled for length of hospital stay and whether the patient survived his or her index hospitalization in this analysis. RESULTS Trends Over Time in Participation in Inpatient CR Increases between 1986 and 1991, followed by consistent decreases thereafter, were observed in the use of inpatient CR (Figure 1). Overall, approximately 68% of patients underwent inpatient CR over the period under study. In 1997, however, the percentage of patients referred to CR dropped below 60% for the first time in more than a decade. Characteristics of Patients Participating in CR In comparing the characteristics of patients undergoing compared with those not undergoing rehabilitation, patients participating in inpatient CR were significantly younger, more likely to be male, and married (Table 1). Patients enrolled in health maintenance organizations and those with indemnity insurance were more likely to undergo inpatient rehabilitation; patients with Medicare coverage were much less likely to be referred for this intervention. Patients undergoing inpatient rehabilitation were more likely to include persons with a history of hypertension or an initial Q wave MI, but less likely to include those with prior stroke or heart failure. Patients experiencing heart failure or cardiogenic shock during hospitalization were much less likely to be referred to inpatient rehabilitation. The average length of stay was significantly longer for patients receiving compared with those not receiving inpatient rehabilitation (10.4 versus 7.6 days; P.001). Comparison of these characteristics in only hospital survivors revealed similar trends; the sole exception was that there were no differences in the rates of heart failure or cardiogenic shock in patients offered, compared with those not offered, inpatient rehabilitation. Patients undergoing inpatient rehabilitation were more likely to be treated with medications shown to be of benefit in the management of AMI, including aspirin, beta blockers, angiotensin-converting enzyme inhibitors, lipid-lowering agents, and thrombolytics (Table 1). They also were significantly more likely to have undergone cardiac catheterization, coronary artery bypass surgery, and coronary angioplasty than patients who did not undergo inpatient rehabilitation (Table 1). Figure 1. Proportion of patients with acute myocardial infarction undergoing inpatient cardiac rehabilitation by time: Worcester Heart Attack Study. Inpatient CR in Patients With AMI / 379

4 Table 1 CHARACTERISTICS OF PATIENTS WITH ACUTE MYOCARDIAL INFARCTION ACCORDING TO IN- PATIENT CARDIAC REHABILITATION: WORCESTER HEART ATTACK STUDY Referred to Inpatient Cardiac Rehabilitation Yes No Characteristic (n = 3914) (n = 1822) P Age (mean, yrs) Age (yrs) (%) Male (%) Marital status (%) Single Married Widowed Divorced/separated Medical Insurance Status (%) Blue Cross/Blue Shield Medicaid Medicare HMO Private payment/insurance Other Medical history (%) Angina Hypertension Stroke Diabetes Heart failure AMI characteristics (%) Initial Q wave Anterior Hospital complications (%) Heart failure Cardiogenic shock Medications (%) ACE inhibitors Aspirin Beta blockers Ca 2+ blockers Digoxin Diuretics Lipid lowering agents Thrombolytics Procedures (%) Cardiac catheterization CABG PTCA HMO, health maintenance organization; AMI, acute myocardial infarction; ACE, angiotensin-converting enzyme; CABG, coronary artery bypass graft; PTCA, percutaneous transluminal coronary angioplasty. Because there were increases, followed by decreases, in the rates of CR over time, we examined possible changes in the characteristics of patients undergoing inpatient rehabilitation in our two earliest study periods (1986 and 1988) compared with the most recent study periods (1995 and 1997) (Table 2). Over the decade-long period under study, elderly patients ( 65 years of age) and females made up an increasing proportion of patients undergoing inpatient CR. While patients without various comorbidities remained more likely to undergo rehabilitation, an increasing proportion of rehabilitation participants had a history of hypertension, stroke, diabetes, or heart failure in the two most recently hospitalized cohorts. We examined the association between demographic, medical history, and AMI-associated characteristics to receipt of CR (Table 3). In this multivariable regression analysis, we also controlled for hospital survival status and length of stay. Participation in inpatient rehabilitation was significantly associated with younger age, being married, enrollment in a health maintenance Table 2 CHARACTERISTICS OF PATIENTS UNDERGOING INPATIENT CARDIAC REHABILITATION OVER TIME: WORCESTER HEART ATTACK STUDY 1986/ /97 n = 930 n = 1242 Age (y) % % P Sex Male Female Medical insurance Private payment/insurance Blue cross Medicaid Medicare HMO Medical history Angina Hypertension Stroke Diabetes Heart failure AMI characteristic Initial Q wave Anterior Hospital complications Heart failure Shock HMO, health maintenance organization; AMI, acute myocardial infarction. 380 / Journal of Cardiopulmonary Rehabilitation 2001;21:

5 Table 3 FACTORS ASSOCIATED WITH RECEIPT OF CARDIAC REHABILITATION IN PATIENTS WITH ACUTE MYOCARDIAL INFARCTION: WORCESTER HEART ATTACK STUDY Multivariable Adjusted Odds Ratio* 95% CI Age (y) , , , 0.90 Male , 1.26 Married , 1.35 Insurance status Blue Cross/Blue Shield , 1.35 HMO , 1.60 Medicare , 1.20 Medical History Angina , 1.56 Hypertension , 1.51 Heart failure , 0.99 Stroke , 0.99 AMI characteristics Q wave , 1.76 Cardiac complications Heart failure , 1.40 Cardiogenic shock , 0.87 CI, confidence interval; HMO, health maintenance organization; AMI, acute myocardial infarction. *Referent categories = age 55 years, women, not married, other insurance (private, other), absence of each comorbidity, prior MI, non-q wave MI, inferior/posterior MI, absence of heart failure or shock during hospitalization. Table 4 INPATIENT CARDIAC REHABILITATION AND HOSPITAL-BASED RISK FACTOR INTERVENTIONS: WORCESTER HEART ATTACK STUDY Referred to Inpatient Cardiac Rehabilitation Yes No Intervention (%) (n = 593) (n = 414) P Risk factor modification plan Discussed exercise Nutritional counseling Low cholesterol diet prescribed Smoking cessation Stress reduction organization, and a history of angina or hypertension. Patients with a Q wave MI and these whose hospital course was complicated by heart failure also were more likely to participate in rehabilitation. Conversely, patients with a history of stroke or heart failure, and those who developed cardiogenic shock, were significantly less likely to undergo rehabilitation than respective comparison groups. We also examined whether participation in inpatient CR was associated with greater use and documentation of patient specific coronary risk factor interventions (Table 4). Due to our methods of data collection, these data were only available for Worcester residents hospitalized with confirmed AMI in As expected, patients undergoing inpatient rehabilitation were significantly more likely to have documentation of nutritional, smoking, and other risk factor counseling during their acute hospitalization than were patients who did not undergo rehabilitation. Finally, we used available hospital administrative databases to examine the use of outpatient CR in patients hospitalized in our most recent study year of We further restricted our patient sample to persons from the city of Worcester to minimize the proportion of patients enrolling in outpatient rehabilitation operated by out-of-area hospitals at which we do not collect data. In this subset, 3.3% of patients underwent outpatient CR based on billing and other administrative data sources. DISCUSSION The results of this multihospital community-wide study of residents from a geographically defined and sociodemographically representative Northeast metropolitan area provide insights to the use of inpatient CR in patients with AMI overall and by time. The present results also provide information about the demographic and clinical factors associated with referral to these coronary risk factor intervention programs. A number of prior studies have assessed the rates of participation in outpatient CR by patients with recent MI. Historically, these rates have been abysmally low, with a recent study estimating that less than 20% of eligible patients undergo CR. 3 Studies assessing factors influencing rates of participation (or nonparticipation) in these risk factor modification programs have consistently identified younger age, male gender, and high socioeconomic status as being associated with increased participation. 3-7,15 It is unclear, however, whether these factors are linked with patients willingness or ability to participate in these programs or reflect physicians referral patterns. The strength of the primary care physician s recommendation for participation has been shown to be a powerful predictor of CR in older coronary patients. 4 Strength of physician recommendation referral also accounted for higher participation rates for men than women in a separate study by the same team of investigators. 8 While these studies confirmed the importance of physicians attitudes toward rehabilitation in relation to subsequent patient participation, they did not adequately explain how patient Inpatient CR in Patients With AMI / 381

6 characteristics affected physicians decisions to refer for these services. To our knowledge this is the first study, particularly from a more generalizable community-wide perspective, evaluating the use of inpatient CR services after AMI. Commonly available in most hospitals, this intervention often represents cardiac patients first exposure to risk factor modification education. These programs also provide an opportunity to review the use of new drugs for the prevention of recurrent coronary events, and help patients to overcome fears about resumption of usual activities during recovery from AMI. Referral to inpatient rehabilitation would be expected to be primarily influenced by physicians attitudes toward the usefulness of these services and their beliefs about which types of patients might benefit. These rates should be less influenced by patients beliefs, financial or employment constraints, or geographic inaccessibility, factors that have been found to play a larger role in the use of outpatient rehabilitation services. In addition, subsequent referrals to outpatient programs frequently arise from this initial hospital contact. Indeed, in our study patients exposed to inpatient CR were approximately twice as likely to participate in outpatient rehabilitation programs than those not offered these services during hospitalization, though the absolute rates of outpatient CR remained low in our community-based sample of patients. The results of our observational study suggest that only two thirds of patients with AMI were referred to inpatient CR, with only slight declines in the use of CR over time. The relative steadiness in the use of CR over our study period was of interest given the changing healthcare environment, clinician s practice patterns, and changes in patient demographic and clinical characteristics over the decade-long period under study. In our multivariable regression analyses, increasing age was the factor most strongly associated with nonreferral for these services. Women also were underrepresented in our CR programs comprising less than 40% of patients referred to rehabilitation services throughout our decade-long study. Women and the elderly are the patients shown to be at highest risk for recurrent coronary events and cardiac mortality in a number of longitudinal studies, including previous findings from the Worcester Heart Attack Study. 16,17 Therefore, one might presume that these high-risk subgroups have the most to gain from early entry into CR. However, increasing age and female sex have been identified in numerous other studies as being independently associated with failure to be referred to, or participate in, such programs. 3,4,8 It is unclear why physicians do not refer more of these high-risk patients for systematic risk factor modification. In the previously mentioned study by Ades et al, 8 only 15% of eligible women 62 years and older participated in an outpatient CR program compared to 25% of older men. Although less fit at entry, women achieved improvements in aerobic capacity similar to men at 12 weeks after program enrollment. Similarly, several studies have documented improvements in exercise tolerance in elderly patients participating in CR comparable to that achieved by younger patients despite poorer fitness levels at baseline. In one study of 92 patients participating in CR after a major cardiac event, patients 65 years and older achieved similar improvements in exercise capacity, measures of obesity, and serum lipid levels as younger patients. 9 Although much attention has been called to age and gender disparities in the receipt of outpatient rehabilitation over the last decade, our study suggests only small improvements in referral patterns for inpatient CR in women and elderly patients over our decade-long experience. Although our data suggest that healthier patients were more likely to be referred to inpatient rehabilitation, these patients had a significantly increased length of stay. We suspect the reasons for this are multifactorial. They may reflect other differences in the characteristics of this population (eg, higher proportion of patients undergoing coronary artery bypass surgery) as well as the limited availability of this intervention because inpatient rehabilitation is generally not available on weekends. Patients offered inpatient rehabilitation in our study were more likely to be treated with thrombolytics and coronary revascularization approaches. Receipt of thrombolytics has previously been shown to be significantly associated with participation in CR in MI patients enrolled in the Nottingham Heart Attack Register in 1992 and The investigators suggest that this is because patients in this group are the ones most easily identified and the diagnosis of MI most clear. In addition, administration of thrombolytic therapy also may identify a healthier subset of patients with AMI, as studies have shown this therapy is often withheld in the elderly, those who experience prolonged delay in seeking medical care, and in those with comorbidities. 18,19. The higher rates of participation in CR of patients undergoing coronary artery bypass surgery also has been previously demonstrated. A survey of CR programs in the United States demonstrated that twice as many patients participated in CR after coronary artery bypass surgery than did after the development of AMI or use of percutaneous revascularization procedures. 3 The rationale for the increased use of rehabilitation in patients undergoing coronary artery bypass surgery relative to other patient subgroups is not completely clear. We suspect that the increased use of this risk factor modification program may have roots in the long held perception of CR as a reconditioning tool. Another finding of interest in our study was that patients not referred to CR also were less likely to receive medications shown to be of benefit in the secondary prevention of patients with AMI. This may suggest that 382 / Journal of Cardiopulmonary Rehabilitation 2001;21:

7 patients with possible contraindications to these proven modalities were considered unlikely to benefit from inpatient CR. However, as previous studies have documented a troubling underuse of effective cardiac therapies in the elderly or those with a greater prevalence of comorbidities, we suspect that many patients who might benefit from these inpatient services are being excluded. Hospital-based Risk Factor Interventions The period immediately after hospitalization for AMI represents an important opportunity to educate the patient with respect to risk-factor modification strategies. Data from smoking cessation studies suggest that this is a particularly fertile period for initiating important lifestyle changes (likely due to enhanced patient motivation and smoking deprivation during hospitalization). In one study, patients undergoing a brief inpatient smoking cessation counseling followed by telephone follow-up had a 67% quit rate compared with a rate of 43% in those receiving usual care. 22 Accordingly, we were interested in the impact of formal CR on the delivery of hospital-based risk factor interventions during the patient s index hospitalization. In our most recently hospitalized cohort (1997), patients referred to inpatient CR were significantly more likely to be instructed on exercise, to be recommended low-salt or low-fat diets, and were more likely to undergo smoking cessation counseling than patients not referred to CR. While these markedly discrepant risk factor intervention rates may reflect better documentation of such interventions and not full implementation, they still suggest that the use of inpatient CR provides for delivery of a great deal of information and positive feedback to hospitalized patients. In this era of increasing patient volume and decreasing length of stay, it is not feasible to expect that physicians and staff nurses will be able to provide these important services. Study Strengths and Limitations The strengths of this study include the inclusion of all patients from a defined metropolitan area whose sociodemographic characteristics have been shown to be similar to those of the continental United States, thereby enhancing the generalizability of the present study findings. Additional positive aspects of this study include an examination of decade-long trends in the use of this risk reduction modality. The limitations of this study include our inability to examine other patient and provider factors associated with use of CR as well as our inability to document actual implementation rates of individual risk factor modification interventions. In addition, the observed rates of out-patient CR in our subsample of patients from the city of Worcester may have underestimated the actual rates of participation. This is because some patients may have enrolled in CR or other risk-factor modification programs outside the greater Worcester area. Finally, it must be acknowledged that personnel and content of the inpatient rehabilitation intervention varied between hospitals and, over time, within hospitals. CONCLUSIONS The results of this multihospital community-based study suggest decreasing use of inpatient CR in patients with AMI during the most recent study years ( ). Advanced age was significantly associated with nonreferral for these services. Women also were underrepresented in participation in CR. Patients not referred to CR, although comprising a high-risk subset, are less likely to be prescribed secondary prevention medications of proven benefit and much less likely to receive counseling and education about risk-factor modification to enhance their long-term outcomes and quality of life. Further studies are needed to better understand the reasons for patient exclusion from CR and to more systematically use this modality in patients with AMI. References 1. O Connor GT, Buring JE, Yusuf S, et al. An overview of randomized trials of rehabilitation with exercise after myocardial infarction. Circulation. 1989;80: Oldridge NB, Guyatt GH, Fischer ME, et al. Cardiac rehabilitation after myocardial infarction: combined experience of randomized clinical trials. JAMA. 1988;260: Thomas RJ, Miller NH, Lamendola C, et al. National survey on gender differences in cardiac rehabilitation programs: patient characteristics and enrollment patterns. 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