Quality of Life After Acute Myocardial Infarction Among Patients Treated at Sites With and Without On-site Availability of Angiography FREE

THE USE OF CARDIAC procedures has been shown in many studies to be related to availability of procedures at the sites where patients are admitted for acute myocardial infarction (AMI).¹ Patients treated at sites without cardiac procedures are likely to undergo fewer invasive cardiac procedures, and their clinical outcomes are possibly inferior to those of patients treated at sites with availability of cardiac procedures. In studies that have compared the treatment and outcome of patients with AMI admitted at sites with and without angiography, mortality did not differ between the 2 groups.^2- 8 However, these studies were limited by the lack of information on outcomes other than mortality such as quality of life and functional status. Similarly, several randomized clinical trials that have compared different approaches to post-AMI care did not present data on outcomes related to quality of life.^9- 21 Thus, we conducted a prospective cohort study to measure quality of life after AMI among patients admitted at sites with and without angiography within the province of Québec.

The study population consisted of patients who were treated in an acute care facility (coronary care unit) for AMI diagnosed according to the World Health Organization criteria.²² The same criteria were used at both types of hospitals. Patients had to be admitted through the emergency department. We excluded patients transferred from another hospital for treatment of their index AMI or from another floor in the hospital. Any patient able to read and understand French or English was eligible for the study if he or she had sustained a Q- ornon–Q-wave AMI and had survived up to 24 hours after hospital admission. A patient was excluded if he or she was physically incapable of responding to a questionnaire (eg, if intubated) or if unable to give informed consent. A total of 10 sites enrolled patients in the study. The 5 sites without angiography were located at least 1 hour by car away from a site with angiography. The choice of sites at this minimum distance from sites with angiography was to avoid the possibility that sites without angiography would have practice patterns similar to sites with angiography because of geographic proximity.

For the present study, we wanted to estimate a difference between the 2 groups with high precision using a 95% confidence interval (CI).²³ To make our original sample size requirement calculations, we obtained estimates of the proportions from one of our studies in which we measured quality of life after AMI in a randomly selected subgroup of American and Canadian patients enrolled in the GUSTO-I study.²⁴ Based on these calculations, it was our goal to enroll a total of 1000 patients. An interim analysis, however, showed that our sample of 253 patients from sites with and 334 patients from sites without angiography was sufficient to obtain the precision required (total CI width of 10%) to estimate clinically meaningful differences in patient scores of quality of life.

The primary end points were ascertained through chart review and patient questionnaires at baseline, 30 days, 6 months, and 1 year after AMI. For baseline measurements, patients were asked to remember their health state during the month preceding their admission to the hospital for AMI. After completing the baseline questionnaire during hospitalization, patients completed follow-up mail surveys. Patients who did not respond to the mail survey were contacted by telephone for an interview. Among patients lost to follow-up, vital status at 1 year after AMI was obtained on all patients from a central death registry. At each follow-up contact, details about all hospitalizations that occurred since the last contact were obtained from the patient. For patients with an emergency department visit, rehospitalization, or a cardiac procedure, a chart review was performed by the study nurse.

Primary end points included quality of life, functional status, return to work, and cardiac symptoms. The Short Form 36 (SF-36) questionnaire measures health-related quality of life.²⁵ This instrument characterizes the respondent's health state, yielding a profile of scores (0, poor to 100, optimal), one score for each health dimension. Differences of 5 points are considered clinically relevant.^26- 27 The SF-36 questionnaire has been validated and shown to be reliable in French and English.²⁸ The visual analog scale adopted from the Torrance Feeling Thermometer²⁹ and the EuroQol³⁰ measure were used to elicit patient ratings of their overall quality of life. Depression symptoms were measured using the Beck Depression Inventory questionnaire.³¹

Functional status was assessed with the Duke Activity Status Index³² and the Katz activities of daily living scale,³³ a single 4-level question about the effects of the patient's health on overall functioning. Questions on bed days and reduced activity days were taken from the National Center for Health Statistics.³⁴ Disease-specific symptoms (angina and dyspnea) were assessed with the Rose questionnaire.³⁵ To measure return to work, employment status was evaluated using the instrument of the Study of Economics and Quality of Life, a substudy of the Bypass Angioplasty Revascularization Investigation.³⁶ These measures include employment history over the preceding 6 months, annual income, days lost from work due to illness, and need for domestic help. Finally, secondary end points included readmission for a cardiac cause and all-cause mortality.

First, patient characteristics and the different outcome measures were compared between patients admitted at sites with and without angiography in univariate analyses. Rates of noninvasive and invasive cardiac procedures during hospitalization for the index AMI and over the year following discharge and time to receipt of these cardiac procedures were also compared. Second, multivariate analyses were performed to obtain adjusted comparisons of SF-36 quality of life measures between patients admitted at sites with and without angiography. Specifically, the models included the following variables: age, sex, education, depression score, history of angina and diabetes, peak creatine kinase, type of AMI (Q wave or not, first or second episode, location), and hospital course for index AMI (complicated by congestive heart failure, recurrent infarct, and/or ischemia).

For these analyses, the dependent variable of the primary regression model was health status represented by the various components of the SF-36 questionnaire. Model selection used Bayes factors as approximated by the Bayesian information criterion.³⁷ These models have demonstrated better prediction properties on average than other model selection algorithms such as backward or forward stepwise procedures.

Between January 1997 and November 1998, 952 patients were approached for study enrollment during their hospitalization for their index AMI. Of these patients, 587 were enrolled in our study and observed for 1 year; 253 patients were treated at 5 sites with angiography (Montreal General Hospital, Jewish General Hospital, Royal Victoria Hospital, Notre-Dame Hospital, and Complèxe Hospitalier de La Sagamie) and 334 at 5 sites without angiography (Centre Hospitalier de la Région de l'Amiante, Centre Hospitalier de Val-D'Or, Hôpital Sainte-Croix de Drummondville, Centre Hospitalier regional du Grand Portage, and Centre Hospitalier Beauce Etchemin). All sites were in Montreal, Québec. Timing of enrollment was between 2 and 5 days after AMI and was the same at both types of site. Reasons for nonenrollment included patient refusal (57%), feeling too sick (21%), death (11%), physician refusal (2%), participation in another study (2%), and other reasons combined (7%). Patients who refused to participate were older than study participants (mean age, 69 vs 61 years), more likely to be female (37% vs 21%), and less likely to have sustained a Q-wave infarct (43% vs 49%). Otherwise, they were similar.

Patients at sites with and without angiography were similar but for the following characteristics: patients at sites with angiography were more likely to be male (83% vs 75%) and their level of education was higher (13 vs 9 years) (Table 1). Additionally, prior AMI (23% vs 19%) and angina (30% vs 22%) were more common and creatinine kinase level higher at sites with angiography.

The proportion of patients who completed 1 year of follow-up was 84% at sites with angiography and 91% at sites without angiography. Patients lost to follow-up were more likely to have diabetes (25% vs 15%) and smoke (52% vs 40%) and were less likely to have sustained recurrent ischemia (17% vs 22%) than those who completed the 1-year questionnaire. Otherwise they were similar.

Whereas the use of cardiac medications after AMI was similar at the 2 types of sites, the use of invasive and noninvasive cardiac procedures differed (Table 2). Overall, patients at sites with angiography were more likely to undergo invasive procedures early in the post-AMI period. The median time to angiography was 4 days at sites with angiography and 17 days at sites without angiography. Although in-hospital rates of angiography, angioplasty, and coronary artery bypass surgery were greater at sites with angiography than at those without, the difference in invasive procedure rates narrowed over time. In contrast, noninvasive procedures were used less often at sites with angiography. By 1 year, more patients at sites without angiography had undergone exercise treadmill testing (80% vs 65%) and twice as many had undergone thallium testing (47% vs 25%). Thus, even though by 1 year the difference in use of noninvasive testing remained, the difference in use of invasive testing and procedures decreased.

Patients admitted at sites with angiography were more likely to be treated by a cardiologist. The yearly AMI volume in the hospitals with angiography was higher (212 vs 160 patients), and so was the number of hospital beds (555 vs 208). These hospitals were representative of other hospitals in the province.

At baseline, patients at sites with and without angiography seemed to have a similar perception of their health status (Table 3). However, at 30 days after AMI, general health perception on a scale of 0 (death) to 100 (perfect health) of patients at sites with angiography tended to be superior to that of patients at sites without angiography. Furthermore, 30% of patients at sites with angiography ranked their general health perception as very good to excellent compared with 17% of patients at sites without angiography. Also, at 30 days, patients at sites with angiography ranked their physical ability higher. Except for the rating of general health, which remained higher at sites with angiography, by 6 months and 1 year, general health perception and expectations returned to a similar level between the 2 groups. Thus, health perceptions and expectations were superior among patients treated at sites with angiography only in the early post-AMI period.

Physical activity did not differ between the 2 groups at baseline as indicated by the Duke Activity Status Index (Table 3). Furthermore, measures at 6 months and 1 year did not differ from measures at baseline, but measures at 30 days were equally lower in both groups (data not shown).

At baseline, 43% of patients at both sites worked full-time (roughly 44 hours per week) or part-time, and a similar proportion of patients planned to return to work (73% vs 76%). Over 75% of patients were the major income earners. At 30 days, twice as many patients at sites with angiography had gone back to work than patients at sites without angiography. However, by 6 months and 1 year, the proportion of patients back to work was similar at both sites. Similarly, at 30 days both groups reduced their activities, but patients at sites with angiography reported a lower number of days of reduced activities. However, by 6 months and 1 year, the level of reduced activity was back to baseline in both groups. Days in bed followed a similar trend.

For the outcome of health status at baseline, emotional role limitations were ranked higher by patients at sites without angiography; otherwise, the unadjusted and adjusted measures of SF-36 did not differ significantly between patients in the 2 groups (Table 4). But by 6 months, patients at sites with angiography scored higher on the subscale of "role limitations–emotional" and also on "role limitations–physical." However by 1 year, most subscales were back to baseline except for role limitations–emotional, which was still scored higher by patients at sites with angiography. Thus, although patients at sites without angiography started with higher scores for role limitations–emotional, by 6 months and 1 year, patients treated at sites with angiography exhibited higher scores for the subscales of role limitations–emotional and role limitations–physical.

Furthermore, compared with baseline, the subscales of role limitations–emotional and role limitations–physical indicated a deterioration at 1 year among patients at sites without angiography but no notable differences among patients at sites with angiography. For example, between baseline and 1 year after AMI, the score for the subscale of role limitations–emotional declined by 12.2 points, compared with an increase in 1 point for patients at sites with angiography (difference, 13.2 points; 95% CI, 8.9-17.5). Similarly, the score for the subscale of role limitations–physical declined by 10.1 points at sites without angiography compared with 3.8 points at sites with angiography (difference, 6.4; 95% CI, 2.1-10.7). Of note, most SF-36 subscales remained similar between the 2 groups throughout the study period, indicating a minimal impact of AMI on quality of life as measured by SF-36.

A higher proportion of patients at sites without angiography were readmitted to the hospital after AMI than occurred at sites with angiography (52% vs 33%) (Table 5). Several of these patients were readmitted to undergo the cardiac procedure they were waiting for. Nevertheless, readmission for a cardiac complication occurred more frequently among patients at sites without angiography (23% vs 19%), and the difference was attributed to a higher readmission rate for angina (18% vs 12%). However, the proportions of patients who reported post-AMI angina and dyspnea were similar. For example, at baseline, the prevalence of angina was 10% at sites with angiography and 9% at sites without angiography, and for dyspnea, 49% and 52%, respectively. At 1 year, the prevalence of angina was 7% and 7%, respectively, and that of dyspnea, 37% and 33%, respectively (Table 3). Thus, even though the prevalence of angina reported by patients did not differ between the 2 groups, more patients at sites without angiography were readmitted for angina after index AMI. Finally, even if the sample size is too small to make any strong conclusions about mortality, the mortality was higher at sites with angiography, probably reflecting baseline differences in severity and possibly procedure-related complications.

In this study, we observed modest differences in quality of life that were more marked when differences in cardiac procedure use were greatest. At sites without angiography, the treatment approach tended to be that of risk stratification, with a higher use of noninvasive diagnostic testing and a lower use early in the post-AMI period of invasive procedures. In contrast, the approach at sites with angiography consisted of early use of angiography and revascularization. As a result, the 2 different approaches seemed to affect the speed of recovery. Patients at sites without angiography tended to have a slower recovery as manifested by their inferior scores on some of the SF-36 scales at 6 months, greater number of days with limited activity, and slower return to work. Furthermore, answers to questions about health perception revealed that patients admitted at sites without angiography perceived their health to be inferior to that of patients at sites with angiography. Finally, even though symptoms of angina did not differ between the 2 groups, patients admitted at sites without angiography had more readmissions for angina after AMI. But overall, the magnitude of the differences was small, and by 1 year after AMI, patients admitted at sites with and without angiography had similar quality of life and functional status.

The higher readmission rates for angina at sites without angiography could be explained by the fact that coronary anatomy was known in fewer patients at these sites. As a result, physicians may have been more likely to diagnose a patient presenting with chest pain as having angina. Furthermore, return-to-work differences could be attributed to physician attitudes rather than an effect of revascularization procedures.

Several randomized clinical trials have compared different approaches to post-MI care.^9- 18 In most of those studies, the principal outcome of interest was mortality, and the different approaches did not result in any difference in mortality rate. Studies have also compared the treatment of AMI in Canadian and American patients.^24,38- 43 Similarly, in these studies, the different approaches failed to result in any differences in mortality.

Only few studies have looked at other outcomes such as functional status, cardiac symptoms, and quality of life. In the SAVE study, Rouleau et al⁴⁰ showed that Canadian patients had a higher rate of activity-limiting angina than American patients (relative risk, 1.27; 95% CI, 1.06-1.51). In the GUSTO study, Mark et al²⁴ surveyed a random sample of Canadian and American patients and found that Canadians rated quality of life lower than did Americans. However, similar to our study, the differences were small. Additionally, findings of studies on quality of life comparisons between American and Canadian patients after AMI are limited because the results might be explained by cultural differences rather than differences in care. The natural experiment in the present study has allowed us to compare quality of life outcome in patients treated with different rates of cardiac procedure within the same health care system.

In our study, the intensity of procedure use in this cohort of Canadian patients was greater than expected. In fact, the proportion of patients who underwent angiography during hospitalization at sites with angiography approached that found in the US GUSTO-I study.⁴⁴ In the GUSTO study, depending on the region of the United States, between 52% and 81% of patients underwent this procedure, compared with 68% in the present cohort. The use of revascularization procedures in the present cohort also approached that of the GUSTO US participants. Furthermore, within 1 year, patients at sites without angiography in our study had rates of revascularization similar to that of patients admitted at sites with angiography. Thus, even if previous studies have shown marked discrepancies in the treatment of Canadian and American patients, there are groups of patients in Canada who receive post-AMI care akin to that in the United States.

Finally, although a careful economic analysis was not performed, there might be economic implications of this delay in resuming baseline level of quality of life among patients treated more conservatively. First, patients returned to work later after AMI, thus incurring loss of productivity. Second, several patients had to wait in the hospital before transfer to another hospital for an angiographic cardiac procedure. For patients who underwent angiography, the length of stay was longer at sites without angiography (median stay, 19 days; 25th-75th percentiles, 12-30 days vs 8 days; 5-13 days). Third, many patients were transferred and then readmitted, contributing to a prolonged overall hospital stay after AMI. Finally, a high proportion of patients at sites without angiography underwent noninvasive testing. Thus, the cost to society of the risk stratification approach is not negligible, even though it may appear reasonable since (1) fewer patients undergo potentially unnecessary cardiac procedures, and (2) by 1 year, quality of life is similar with the 2 different approaches.

Several limitations to our study must be considered. First, recall bias for baseline measurements is a potential problem, although recall is not likely to differ between patients admitted at sites with and without angiography. This study is one of the few to provide baseline measurements for quality of life. Baseline measures are the most powerful predictors of long-term quality of life, and this study provides multivariate analyses with adjustments for baseline quality of life. Second, even though this cohort consisted of a consecutive series of patients with AMI, patients who died early were excluded, and several eligible patients refused enrollment. But because the excluded patients and patients who refused enrollment had similar characteristics at sites with and without angiography, our findings are probably generalizable to all patients with AMI who survive the first 2 days after hospitalization. Finally, although statistical adjustments were made for measured differences in demographic and clinical characteristics, differences may have persisted. For example, patients treated at sites without angiography were less likely to be treated by a cardiologist, were treated at hospitals with smaller AMI volume, and were more likely to live in rural areas.

In conclusion, in areas where access to angiography is limited, risk stratification and selection of patients for invasive cardiac procedures results in patient quality of life by 1 year after AMI similar to prompt performance of invasive cardiac procedures. Differences in quality of life were greatest when differences in treatment were greatest, lending support to a positive albeit small association between an early invasive approach to post-AMI care and improved quality of life.

Accepted for publication July 17, 2001.

This study was supported by grant 961305-104 from the Fonds de la recherche en santé du Québec, Montreal. Drs Pilote and Eisenberg are Research Scholars of the Heart and Stroke Foundation of Canada, Ottawa, Ontario.

We wish to thank our participating patients; our project coordinators, Karen Brown, MPH, and Maria Masi, MSc; our research nurses, Francine Ouimet, RN, Brigitte Roberge, RN, Alyne Landry, RN, Carolyn Boudreault, RN, Andrée Morisette, RN, Marcel Rodrigue, RN, Manon Lévesque, RN, Diane Therrien, RN, Louise Patrie, RN, Marjolaine Roussel, RN, Cécile Dufour, RN, Eileen Shalit, RN, Dominique Brassard, RN, and Marcel Rehel, RN; our technical staff, Christine Beck, MSc, and Ewurabena Simpson, BSc; and our secretary, Barbara Cont.

Corresponding author: Louise Pilote, MD, MPH, PhD, Division of Clinical Epidemiology, Montreal General Hospital, 1650 Cedar Ave, Montreal, Québec, Canada H3G 1A4 (e-mail: louise.pilote@musica.mcgill.ca).