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J Gen Intern Med. Jun 2003; 18(6): 423–431.
PMCID: PMC1494881
Narrowing Gender Differences in Procedure Use for Acute Myocardial Infarction
Insights from the Worcester Heart Attack Study
Leslie R Harrold, MD, MPH,1 Julian Esteban, MD, MS,1 Darleen Lessard, MS,1 Jorge Yarzebski, MD, MPH,1 Jerry H Gurwitz, MD,1 Joel M Gore, MD,1 and Robert J Goldberg, PhD1
1Received from the Department of Medicine, Division of Cardiovascular Medicine, University of Massachusetts Medical School, Worcester, Mass
Address correspondence and requests for reprints to Dr. Harrold: Department of Medicine, University of Massachusetts Medical School 55 Lake Ave. North, Worcester, MA 01655 (e-mail: HarroldL/at/ummhc.org).
OBJECTIVE
To examine age-specific gender differences and trends over time in the management of patients with acute myocardial infarction (AMI).
DESIGN
Cross-sectional study of patients admitted with AMI from a community-wide perspective over a 10-year period (1990–1999).
SETTING
All hospitals in the Worcester (Mass) metropolitan area (1990 census = 437,000).
PATIENTS/PARTICIPANTS
We identified 2,037 women and 2,645 men who were hospitalized in the Worcester metropolitan area with confirmed AMI during six 1-year periods between 1990 and 1999. Four age groups (<55, 55 to 64, 65 to 74 and ≥75 years) of men and women were studied.
MEASUREMENTS AND MAIN RESULTS
Use of echocardiography, exercise treadmill testing (ETT), cardiac catheterization, percutaneous coronary interventions (PCI), and coronary artery bypass grafting (CABG) during the index hospitalization was examined in relation to age and gender. Overall, women were less likely to undergo ETT, cardiac catheterization, and CABG than were men, and these trends remained after controlling for potentially confounding factors. Between 1990 and 1999, there was a dramatic decrease in ETT, whereas the use of echocardiography remained unchanged. There were marked increases over time in the use of cardiac catheterization and PCI in women and men. Use of cardiac catheterization and PCI increased to a greater extent in women as compared to men. In patients who underwent cardiac catheterization, rates of coronary revascularization were similar between men and women.
CONCLUSIONS
Our data suggest that women and men with AMI are treated differently with respect to use of diagnostic and revascularization procedures. However, gender differences in the use of these diagnostic and interventional approaches have narrowed over time.
Keywords: myocardial infarction, gender differences, procedures
Coronary heart disease continues to be the leading cause of morbidity and mortality among persons in industrialized countries. Each year more than 1 million American women and men are diagnosed with acute myocardial infarction (AMI) with more women dying from AMI than men.1,2 Previous reports suggest that women developing an AMI may have worse in-hospital and long-term outcomes than men.35 There are also data to suggest that gender differences may exist in the management of patients with AMI, with men treated more aggressively than women.6,7 Several other studies have reported that women are less likely to undergo both diagnostic and revascularization procedures than men among persons with coronary disease.810 However, the inclusion of patients from single hospitals or specialty referral centers, the comparatively small number of women studied, and failure to control for potentially confounding factors that may affect test-ordering practices raise concerns about the interpretation and generalizability of these findings. Moreover, recent investigations suggest that gender differences in the management and/or outcomes associated with AMI may have narrowed or may be less apparent when differences in age, symptom presentation, and other clinical and prognostic factors are taken into account.11,12
Important insights into clinical practice patterns may be obtained by the examination of age-specific gender differences in the utilization of diagnostic and interventional procedures. This is particularly relevant because women are typically 8 to 10 years older than men when they experience AMI and these differences in age may obscure diagnostic evaluation and interventional practices. Information on practice pattern trends over the past decade also may help identify patient groups that may be targeted for better care.
The purpose of this multihospital observational study is to describe age-specific gender differences, and changes over time therein, in the utilization of diagnostic and revascularization procedures in the work-up and management of a large community-based sample of women and men hospitalized with confirmed AMI. By including all patients hospitalized with validated AMI from a defined metropolitan area, our findings may be more generalizable to patients with acute coronary disease treated in a community setting.
This study is part of an ongoing population-based investigation that is examining changes over time in the incidence, in-hospital, and long-term case-fatality rates of residents of the Worcester metropolitan area hospitalized with a primary or secondary discharge diagnosis of AMI from all greater Worcester Standard Metropolitan Statistical Area (SMSA) hospitals.1317 The medical records of residents of the Worcester SMSA (1990 census estimate = 437,000) hospitalized for possible AMI were individually reviewed and validated according to predefined diagnostic criteria that have been previously described.1315,17 In brief, the criteria consisted of a positive clinical history, serum cardiac enzyme level elevations, and serial electrocardiographic findings consistent with AMI. At least 2 of these 3 criteria needed to be satisfied for study inclusion. All autopsy-proven cases of AMI were included. Patients transferred from another health care facility, irrespective of geography, and perioperative-associated cases of AMI were excluded. We restricted the study sample to patients hospitalized with AMI in six 1-year periods between 1990 and 1999 for the purposes of examining recent and decade-long trends in our principal study endpoints.
To examine possible age differences in the receipt of diagnostic and revascularization procedures, 4 age-specific strata in women and men were created. These included patients <55 years (139 women, 544 men), 55 to 64 years (218 women, 564 men), 65 to 74 years (521 women, 707 men), and those 75 years and older (1,159 women, 830 men). The mean ages of these comparison groups were 46, 60, 71, and 83 years, respectively, in women, and 47, 60, 70, and 81 years, respectively, in men.
Data Collection
The medical records of women and men of all ages from the Worcester SMSA who were hospitalized with validated AMI during the periods under study were reviewed by trained physician and nurse study coordinators. Data collected from the review of medical charts included the following: history of angina, diabetes, hypertension, stroke, and congestive heart failure; AMI-associated characteristics including order (initial versus prior), type (Q wave vs non–Q wave) and location (anterior vs inferior/posterior); and occurrence of in-hospital complications such as heart failure and cardiogenic shock.18,19 Information was collected about the diagnostic procedures and coronary revascularization approaches used during the index hospitalization. Both nurses' and physicians' test-ordering notes were reviewed to ascertain this information. The diagnostic procedures examined in this study included echocardiography, exercise treadmill testing (ETT), and cardiac catheterization. The revascularization procedures examined included percutaneous coronary interventions (PCI) and coronary artery bypass grafting (CABG).
Data Analysis
The distribution of selected characteristics between women and men within selected age strata (<55, 55–64, 65–74, ≥75 years) were compared using χ2 tests of statistical significance for discrete variables and analysis of variance for continuous variables. The Mantel-Haenszel χ2 test was used to examine trends across the different age groups in terms of clinical characteristics and the use of each of the procedures over the 10-year study period. A multivariable logistic regression analysis was used to examine the independence of the association between age and gender and the receipt of diagnostic and interventional procedures during the index hospitalization while controlling for potentially confounding variables. Age was controlled for as a continuous variable in the regression analyses, including comparisons between women and men in the same age group. Race was not included as a controlling variable because the vast majority of study patients were white. The variables controlled for in these analyses included medical history (presence of 1 or more of the following conditions: angina, diabetes mellitus, hypertension, stroke, or heart failure), AMI order (initial vs prior), AMI type (Q wave vs non–Q wave) and AMI location (anterior vs inferior/posterior), clinical complications (occurrence of heart failure or cardiogenic shock), length of stay, and hospital survival status. These variables were included because of their potentially confounding effects and because of differences in their distribution between respective comparison groups. All tests of statistical significance were 2- tailed.
Demographic and Clinical Characteristics According to Age and Gender
In examining differences in demographic and clinical characteristics in the 2,037 women and 2,645 men with AMI at all Worcester area hospitals between 1990 and 1999, women were significantly older than men and were more likely to have a history of diabetes mellitus, hypertension, or heart failure (Table 1). Women were also more likely to have a non–Q wave or anterior MI and have a complicated course, as reflected by the development of heart failure and cardiogenic shock during hospitalization. In examining age-specific differences in both women and men with regard to these characteristics, advancing age was associated with a greater likelihood of having a comorbid condition present and a history of a prior non–Q wave MI (Table 1). Increasing age in both men and women also was associated with an increased risk of developing clinical complications during the index hospitalization. There were no significant differences between women and men with regard to in-hospital death rates at 24 and 48 hours.
Table 1
Table 1
Characteristics of Patients Hospitalized with Acute Myocardial Infarction (AMI) Between 1990 and 1999 According to Gender and Age: Worcester Heart Attack Study
Age- and Gender-specific Utilization of Diagnostic and Revascularization Procedures
Examining possible differences between men and women in the utilization of diagnostic procedures revealed that women were overall less likely to undergo ETT and cardiac catheterization (Table 2). Although gender differences in ETT use were present in all age groups, discrepancies in cardiac catheterization rates were only present when comparing patients 55 to 64 years old and those 75 years and older. Increasing age in both women and men was also associated with a decreased likelihood of ETT and cardiac catheterization. There were no significant differences in the use of echocardiography between women and men in all age groups. Advanced age in men was associated with a greater likelihood of having an echocardiogram performed during their acute hospitalization (Table 2).
Table 2
Table 2
Use of Noninvasive and Invasive Procedures in Patients Hospitalized with Acute Myocardial Infarction Between 1990 and 1999 According to Gender and Age: Worcester Heart Attack Study
Overall, women were less likely to undergo PCI and CABG (Table 2). Use of PCI was higher in men except among those 65 to 74 years old. Similarly, CABG rates were higher in men with the exception of patients 55 to 64 years old. Increasing age in both women and men was associated with a decreased likelihood of coronary revascularization.
Use of Noninvasive and Invasive Procedures According to Age and Gender: Multivariable Adjusted Results
A series of age-specific regression analyses was carried out separately in women and men to examine the association between age and the receipt of each procedure of interest while simultaneously controlling for previously described covariates. After controlling for these factors, increasing age in both women and men was associated with a decreased likelihood of receipt of ETT, cardiac catheterization, and PCI as compared to the reference population of patients less than 55 years of age (Table 3). Men 75 years and older were significantly less likely to undergo CABG surgery as compared to those less than 55 years old. These results were unchanged when hospital facilities and capabilities were included in the regression model. Among men only, increasing age was associated with an increased likelihood of receiving an echocardiogram.
Table 3
Table 3
Adjusted Odds Ratios for Receiving Noninvasive and Invasive Procedures in Women and Men During Hospitalization for Acute Myocardial Infarction (AMI) Between 1990 and 1999 According to Age: Worcester Heart Attack Study*
Use of Noninvasive and Invasive Procedures According to Gender: Multivariable Adjusted Results
A multivariable regression analysis was carried out to more systematically examine the association between gender and the receipt of each procedure of interest while simultaneously controlling for differences in age and medical history (presence of 1 of the following: angina, diabetes mellitus, hypertension, stroke, or heart failure); AMI order, type, and location; hospital complications; duration of hospitalization; and hospital survival. After controlling for these potentially confounding factors, women were overall significantly less likely to receive ETT, cardiac catheterization, and CABG surgery (Table 4). These results were unchanged when hospital capabilities to perform invasive procedures were included in our regression models. Further multivariable regression analyses were performed comparing the use of each diagnostic and interventional procedure in women and men in each age group (Table 5)Women 75 years and older were less likely than were men in the same age group to undergo echocardiography, ETT, cardiac catheterization, PCI, and CABG surgery. In terms of ETT, women 65 to 74 years of age were also less likely than their male counterparts to receive this procedure. Similarly, women 55 to 64 years of age were less likely to receive cardiac catheterization than were men in the same age strata.
Table 4
Table 4
Adjusted Odds Ratios Comparing Women Relative to Men in the Receipt of Noninvasive and Invasive Procedures During Hospitalization for Acute Myocardial Infarction Between 1990 and 1999: Worcester Heart Attack Study
Table 5
Table 5
Adjusted Odds Ratios for Receiving Noninvasive and Invasive Procedures in Women as Compared to Men During Hospitalization for Acute Myocardial Infarction (AMI) Between 1990 and 1999 According To Age: Worcester Heart Attack Study*
Trends Over Time in the Use of Diagnostic Procedures
We examined changes over time (1990–1999) in the use of diagnostic procedures in women and men (Figs. 15). During this period, the use of echocardiography remained stable in both women and men (P > .05 for all age groups in both genders). On the other hand, ETT dramatically decreased between 1990 and 1999 in both women and men of all ages (P < .001 in all age groups in both genders). There was no clear trend observed in the magnitude of the decline in ETT utilization among the different age groups or between women and men. On the contrary, marked increases were seen in the use of cardiac catheterization in both women and men of all ages (P < .005 in all age groups in both genders). Although more men underwent cardiac catheterization compared to women throughout the study period, the magnitude of the increase in procedure utilization was greater among women. In each age group, the differences between women and men in terms of use of cardiac catheterization decreased substantially over time.
FIGURE 1
FIGURE 1
Trends in the use of echocardiography during hospitalization for acute myocardial infarction according to gender and age from 1990 to 1999: Worcester Heart Attack Study.
FIGURE 5
FIGURE 5
Trends in the use of CABG during hospitalization for acute myocardial infarction according to gender and age from 1990 to 1999: Worcester Heart Attack Study.
Trends Over Time in the Use of Revascularization Procedures
The use of PCI dramatically increased over time (P < .001 in all patient groups with the exception of women less than 55 years of age). In men, increased utilization was greatest in those 65 years and older. Among women, there were no age-specific trends in the increased utilization of PCI. The gap between women and men in the use of PCI over time narrowed appreciably between 1990 and 1999. There was an increase in the proportion of patients undergoing CABG surgery over time, although these trends were only significant in men aged 55 to 74 years (P < .05). Although this trend was observed in all patient groups, the magnitude of increased utilization was greater in men as compared to women. However, these trends need to be interpreted with caution, given the relatively low prevalence rates of CABG surgery. Among men, the greatest increase in CABG utilization occurred in those aged 55 to 74 years, whereas no age-specific trends were apparent in women. To minimize the potential effects of selection bias associated with the greater use of cardiac catheterization in men, we examined differences in the proportion of women and men who underwent coronary revascularization after cardiac catheterization. Over the decade under study, the use of coronary revascularization procedures increased in both women and men in all age groups. By the end of the decade, revascularization rates were similar between women and men, with approximately 60 to 75% of women and men who underwent cardiac catheterization subsequently receiving a revascularization procedure.
DISCUSSION
The results of this community-based observational study of patients hospitalized with confirmed AMI between 1990 and 1999 demonstrate that, overall, women are less likely to undergo ETT, cardiac catheterization, and CABG surgery even after controlling for potentially confounding factors. Over the period under study, use of ETT dramatically decreased, use of echocardiography remained stable, and the use of therapeutic revascularization procedures (PCI and CABG surgery) markedly increased. While the decline in use of ETT was noted in both sexes, women in all age groups remained less likely to undergo ETT. It has been suggested that ETT is less likely to predict ischemic events in women as compared to men, which may partially explain our findings.20 In addition, use of ETT after myocardial infarction is used to establish prognosis, guide therapy, and assess the need for revascularization procedures.21 Given the widespread availability of cardiac catheterization, which systematically assesses coronary anatomy, this procedure may have replaced ETT as the diagnostic procedure of choice for many patients.
As has been previously demonstrated, there were marked increases over time in the use of cardiac catheterization and PCI.22 Interestingly, the magnitude of increase was greater in women as compared to men. Among patients who underwent cardiac catheterization by the end of the decade, the coronary revascularization rates were similar in men and women. Overall, while the rates of procedure use in men remained relatively stable, the rates increased for women over the decade.
Gender Differences in the Use of Procedures During Hospitalization for AMI
Since the late 1980s, there have been several published reports suggesting that men with AMI are more likely to undergo more aggressive diagnostic evaluation and treatment than women.8,9 Ayanian and Epstein examined the use of coronary angiography and revascularization in women and men hospitalized for coronary heart disease in 1987, using data abstracted on 49,623 hospital discharges in Massachusetts and 33,159 discharges in Maryland.8 After controlling for a variety of different factors, the adjusted odds of undergoing angiography were 28% and 15% higher for men than for women in Massachusetts and Maryland, respectively. The respective adjusted odds of undergoing revascularization were 45% and 27% higher for men than for women. These results are similar to those noted in our community-wide study. The overall adjusted odds of undergoing catheterization and revascularization were 40% and 62% higher, respectively, for men as compared with women. Other studies based on larger national samples of patients with AMI also have demonstrated similar differences in the use of these diagnostic and interventional approaches between men and women.5,18
Given that women develop evidence of AMI almost a decade later than men, further complexity is added to the evaluation of possible gender-related treatment differences. Gan et al. examined whether women and men who were ideal candidates for treatment after AMI were managed differently.23 These investigators evaluated the charts of 138,956 Medicare beneficiaries (49% of whom were women) who had an AMI in the mid-1990s. Among ideal candidates for therapy, women in all age groups were less likely to undergo diagnostic catheterization than men. However, these gender differences were more pronounced in older patients. For example, women aged 65 to 69 years were 6% less likely to undergo cardiac catheterization than men, whereas women 85 years and older were 25% less likely to undergo catheterization than men. The differential use of ETT in women and men during hospitalization for AMI in our study has not been noted by other investigators. In our study, as in others, among persons who undergo cardiac catheterization, women and men are equally likely to receive revascularization procedures, suggesting that this decision is not influenced by the patient's gender.23
Gender-related differences in the use of procedures for AMI may have been partially explained by differing patient characteristics. In our study, women were older, more likely to have a history of diabetes and hypertension, and were more likely to have a complicated hospital course than were men. However, residual gender differences in the use of some of these procedures may be the result of differences in physician practice patterns. Few studies have examined the role of physician decision making as the cause for gender bias in the treatment of patients with coronary artery disease. Schulman et al. assessed physicians' recommendations for managing chest pain using actors portraying patients with particular characteristics in scripted interviews.24 A total of 720 physicians at 2 national meetings of primary care physicians participated in the survey. Each physician was asked to make recommendations about that patient's care after viewing a recorded interview and reviewing other clinical data. Women were referred for cardiac catheterization less often than men. Similarly, an earlier study found that academic cardiologists referred women less often for catheterization than men.11 However, differences in this latter study were accounted for by differences in the pretest probability of coronary disease, rather than by any preconceived biases based on gender.
Trends in the Use of Diagnostic Procedures
A unique aspect of our study was the ability to examine decade-long trends in selected diagnostic procedures. In the extremely limited published data in this area, the use of angioplasty and urgent coronary bypass surgery in patients with AMI was examined by Heidenreich and McClellan using Medicare claims files.25 During the first 30 days after myocardial infarction, the use of coronary angioplasty increased from 4% in 1985 to 21% approximately 10 years later. Data from the Minnesota Heart Survey and Medicare claims files suggest that use of CABG surgery during hospitalization for AMI has modestly increased over the last decade (8% in 1985 vs 14% in 1995).26,27 To the best of our knowledge, the present study is the first to assess recent age-specific trends in both women and men in the use of diagnostic and revascularization procedures in patients hospitalized with AMI, providing insights into changing practice patterns over time.
Study Strengths and Limitations
Residents of the Worcester metropolitan area have been shown to reflect the composition of the overall U.S. population in terms of age, gender, and socioeconomic status but not race.1316 By including all patients hospitalized with AMI from a defined geographic area, this study minimized the likelihood of selection biases that might be operative in studies of patients hospitalized in single or referral hospitals or of more narrowly selected patients who might be enrolled in clinical trials. Although this study controlled for many covariates of importance in examining possible gender and age differences in the use of diagnostic and revascularization procedures for AMI, information was not collected on other factors that may have affected the use of these tests, such as functional status or clinical contraindications. Specifically, data concerning the appropriateness of use with regard to the procedures under study were not available.
Conclusions
In summary, the results of our study suggest that there were gender and age differences in the demographic and clinical characteristics of patients hospitalized with AMI in the Worcester area. These differences, however, did not account for differences in the hospital utilization of diagnostic and revascularization procedures in the management of men and women with acute coronary disease. During the 1990s, gender differences in the use of cardiac catheterization and PCI clearly narrowed. In addition, no gender differences were observed in the hospital use of echocardiography or in revascularization rates among patients who underwent cardiac catheterization. Further investigation is needed to examine overall and/or sex-specific factors affecting these trends, and why possible gaps in the use of different management approaches for patients with AMI are narrowing.
FIGURE 2
FIGURE 2
Trends in the use of exercise treadmill testing during hospitalization for acute myocardial infarction according to gender and age from 1990 to 1999: Worcester Heart Attack Study.
FIGURE 3
FIGURE 3
Trends in the use of cardiac catheterization during hospitalization for acute myocardial infarction according to gender and age from 1990 to 1999: Worcester Heart Attack Study.
FIGURE 4
FIGURE 4
Trends in the use of PCI during hospitalization for acute myocardial infarction according to gender and age from 1990 to 1999: Worcester Heart Attack Study.
Acknowledgments
This study was made possible through the cooperation of the administration, medical records, and cardiology departments of participating Worcester metropolitan area hospitals. Dr. Harrold was supported by a Beginning Grant-in-Aid award from the American Heart Association. Grant support for this project was provided by the National Heart, Lung, and Blood Institute (RO1 HL35434).
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