CLINICAL STUDIES
Utilization of coronary angiography and revascularization after acute myocardial infarction in men and women risk stratified by the American College of Cardiology/American Heart Association guidelines
Prasad K. Kilaru, MD*,
Russell F. Kelly, MD, FACC*  ,
James E. Calvin, MD, FACC* and
Joseph E. Parrillo, MD, FACC
* Division of Cardiology, Cook County Hospital, Chicago, Illinois, USA
Section of Cardiology, Rush–Presbyterian–St. Luke’s Medical Center, Chicago, Illinois, USA
Manuscript received April 30, 1999;
revised manuscript received October 25, 1999,
accepted December 2, 1999.
Reprint requests and correspondence: Dr. Russell F. Kelly, 1725 W. Harrison Street, Suite 1159, Chicago, Illinois 60612
rkelly{at}rush.edu
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Abstract
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OBJECTIVES
We sought to determine whether men and women are equally likely to receive coronary angiography and revascularization after acute myocardial infarction (AMI) when they are risk stratified according to American College of Cardiology/American Heart Association (ACC/AHA) practice guidelines for post-MI care.
BACKGROUND
Several previous studies have suggested that women may undergo angiography and revascularization procedures less frequently than men.
METHODS
In 439 consecutive patients admitted to a public hospital with AMI, rates of coronary angiography and revascularization were compared in men and women categorized, according to ACC/AHA practice guidelines, as having strong (class I or IIa) or weaker (class IIb) indications for angiography.
RESULTS
Women were older and more likely to be diabetic or hypertensive, but men and women were equally likely to meet class I/IIa criteria for post-MI angiography (both 51%). Angiography rates were nearly identical in men and women overall (63% vs. 64%), as well as in patients in class I/IIa (80% vs. 82%) and class IIb (46% vs. 46%) (all p > 0.80, with >80% power to detect important differences); the only multivariate predictors of post-MI angiography were age and ACC/AHA class. Significant coronary artery disease was equally prevalent in men and women undergoing angiography, and men and women were equally likely to undergo revascularization, whether they were in class I/IIa (both 55%, p = 0.90) or class IIb (59% vs. 58%, p = 0.88). No significant differences in mortality were noted between men and women.
CONCLUSIONS
Despite being older and having more risk factors than men, women were equally likely to undergo coronary angiography and revascularization procedures after AMI, and they had in-hospital clinical outcomes that were at least as favorable.
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Abbreviations and Acronyms
| | ACC/AHA | = American College of Cardiology/American Heart Association | | AMI | = acute myocardial infarction | | CAD | = coronary artery disease |
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Several studies have found that women may be less likely than men to undergo coronary angiography and revascularization procedures after acute myocardial infarction (AMI) (1–5) and in other settings (6–8), although other studies have found no gender differences in procedural rates (9,10). Determining whether observed differences in angiography and revascularization rates reflect inappropriate care in women has been confounded by a number of factors. Until late in life, coronary artery disease (CAD) is less prevalent in women than in men (11). More women have atypical symptoms (12), and false-positive stress tests are more common in women (12). Women are older and have more comorbid conditions when they present with CAD, which may limit procedure utilization (13).
One method of determining the appropriateness of care is to compare recommended standards of practice with actual rates of procedure utilization. The American College of Cardiology (ACC) and American Heart Association (AHA) have published guidelines for the care of patients with AMI (14,15). These guidelines categorize indications for performing coronary angiography as class I (usually indicated, always acceptable), class IIa (controversial, but favored owing to the weight of evidence and/or opinion), class IIb (not well established by evidence, but probably not harmful) or class III (not indicated). In the present study, we compared the utilization of coronary angiography in men and women with AMI who had strong (ACC/AHA class I or IIa) or weak (class IIb) criteria for performing post-MI angiography.
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Methods
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Data from all patients (n = 462) diagnosed with AMI at Cook County Hospital between 1994 and 1997 were prospectively collected and entered into a data base. The criteria used for the diagnosis of AMI were elevation of creatine kinase MB fraction in conjunction with a clinical presentation and/or electrocardiographic evidence consistent with a diagnosis of AMI. Twenty-three patients undergoing primary angioplasty (6 women and 17 men) were excluded from the present study, leaving a final study group of 439 patients. Data were initially abstracted from patient charts by trained nursing personnel and were audited for accuracy by two cardiologists who reviewed the medical records and coronary angiograms, when necessary.
Clinical data collected included age, gender, traditional coronary risk factors (e.g., hypertension, diabetes mellitus, hyperlipidemia, smoking, family history of early CAD), Q wave versus non–Q wave MI and complications. Patients were risk stratified according to the ACC/AHA guidelines published in 1990 (14). (Although new guidelines were issued in 1996 [15], the 1990 criteria were in force during most of this study period.) Patients were considered to have a stronger (class I or IIa) indication for coronary angiography if any of the following clinical features were present: hemodynamic instability or shock, recurrent ischemia, evidence of ischemia by noninvasive testing, mechanical complication (acute mitral regurgitation due to papillary muscle dysfunction or rupture, ventricular septal defect, pseudoaneurysm), congestive heart failure, left ventricular ejection fraction <40% or malignant arrhythmia. Patients were considered to have a weaker (class IIb) indication for angiography if they did not meet any of the criteria outlined earlier and if they had received thrombolytic therapy, had experienced a non–Q wave MI or were <45 years old. No patients were included in the present study in whom angiography was categorized as class III (not indicated) according to ACC/AHA criteria.
Angiographic data were obtained from the final procedure report (and from review of angiograms, when necessary) and included the presence and extent of CAD (defined as >50% diameter stenosis) and left ventricular ejection fraction. Performance of percutaneous transluminal coronary angioplasty and coronary artery bypass graft surgery was determined from chart review, catheterization laboratory records and cardiovascular surgery records.
Categoric variables were compared using the chi-square test or Fisher exact test. Continuous variables were compared using two-sided t tests. Multiple logistic regression analysis was performed using all variables with a univariate p value <0.10. A p value <0.05 was considered significant. This study was approved by the Scientific Committee at Cook County Hospital.
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Results
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The clinical characteristics of the patients are shown in Table 1. Women were significantly older than men, and more women were hypertensive or diabetic; a trend toward lower prevalence of smoking was noted in women. No significant differences between men and women were noted in the proportion of patients with Q wave or non–Q wave MIs, in the percentage of patients with anterior infarction or in frequency of thrombolytic use.
There was no significant difference between the proportions of men and women who were classified as having strong (class I/IIa) or weaker (class IIb) indications for coronary angiography according to ACC/AHA guidelines (Table 2), nor were the specific indications for angiography different. Overall angiography rates were nearly identical in men and women (Table 2).
Table 3 summarizes the characteristics, angiographic findings and revascularization rates for patients with ACC/AHA class I/IIa indications for angiography. There were no significant differences in angiography rates between men and women, and there were no differences in the presence or extent of CAD between men and women who underwent angiography. Rates of coronary angioplasty, bypass surgery and overall revascularization were very similar in the men and women found to have significant CAD.
Table 4 summarizes the characteristics, angiographic findings and revascularization rates for patients with ACC/AHA class IIb indications for angiography. The women in this category were significantly older than the men. There were no significant differences in angiography rates between men and women or in the presence or extent of CAD. Finally, there were no significant differences in the rates of coronary angioplasty, bypass surgery or overall revascularization between men and women found to have significant CAD. At the rates of coronary angiography found in this study, the power to detect important differences (>20%) in utilization between men and women was >80% for the overall group and for each ACC/AHA class.
After adjustment for baseline clinical characteristics, there were still no significant differences in catheterization rates between men and women, in the overall group (Table 5) or when the patients were risk stratified according to ACC/AHA criteria (Tables 6 and 7). Although younger patients were less likely to undergo angiography, there was no significant interaction between age and gender; for example, angiography rates in men and women older or younger than age 65 years were not significantly different (p = 0.76).
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Table 6 Predictors of Use of Angiography After Acute Myocardial Infarction in Patients in Class I/IIa According to the American College of Cardiology/American Heart Association
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Table 7 Predictors of Use of Angiography After Acute Myocardial Infarction in Patients in Class IIb According to the American College of Cardiology/American Heart Association
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The overall in-hospital mortality rate was 7.8%. There was no significant difference in mortality between men and women (9.1% vs. 5.7%, p = 0.27). The mortality rate in patients with a class I/IIa indication for angiography was 14.4%, as compared with 1.0% in patients with a class IIb indication (p < 0.0001). There were no significant differences in mortality rates between men and women in class I/IIa (16.5% vs. 11.2%, p = 0.36) or class IIb (1.5% vs. 0%, p = 0.72).
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Discussion
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A number of studies have found that women are less likely than men to undergo coronary angiography and revascularization procedures after AMI. Studies from a national data base of Medicare patients with AMI (1–3,5) and from the National Hospital Discharge Survey (4) found that women admitted to the hospital for AMI were significantly less likely than men to undergo catheterization, coronary angioplasty or bypass surgery.
Angiography has also been demonstrated to be utilized less often in women in other clinical settings as well. One study of nearly 400 patients with suspected CAD undergoing exercise nuclear testing at four different New York City hospitals found that women with abnormal nuclear stress results were only one-tenth as likely as men to be referred for angiography (8), and other studies have also found lower rates of procedures in women as compared with men (7). Large, state-wide studies of hospital discharges (6,16) have found that women were significantly less likely to undergo coronary angioplasty and bypass surgery. In patients without AMI, the gender disparity in angiography rates may be attributed to clinical differences. Women are more likely to present with atypical symptoms (12). Coronary artery disease is less prevalent even in women with typical angina (11), and abnormal stress tests (including abnormal imaging studies) are more likely to be false positives (12). Women develop CAD at a later age than do men and often have more coronary risk factors and comorbid conditions, and age has been shown to be independently associated with rates of procedure utilization (13). Finally, it is possible that women may prefer less invasive treatment strategies (17).
Other, usually more recent studies have found no differences in procedural rates between men and women. After controlling for clinical characteristics, Mark et al. (9) found no differences in referrals for angiography between men and women. Krumholz et al. (10) controlled for age and found no differences in angiography rates between men and women with AMI. Wong et al. (18) found that in-hospital angiography rates were similar for men and women.
In the Survival and Ventricular Enlargement (SAVE) trial, women had lower rates of coronary angiography before the index MI, despite reporting symptoms consistent with greater functional disability (19). However, after the index AMI, rates of angiography and revascularization procedures were similar for women and men (19). This has been termed the "Yentl" syndrome; once a woman has a documented infarct and behaves like a man, she may be treated like a man.
Present study.
The findings of the present study are in agreement with the more recent studies. In 439 consecutive patients with AMI who did not undergo primary angioplasty, we found no differences in the rates of coronary angiography between men and women (80% vs. 82%) or revascularization procedures (55% for both). In addition, revascularization rates in this study of patients in an inner-city public hospital were comparable to those in other reports, including studies which found differences in utilization rates between men and women (10,20).
Although mortality rates for women were significantly higher after an AMI in some reports (20–22), adjustment for clinical characteristics minimizes differences in outcomes between men and women (23). Women in the present study tended to have lower (but not statistically significant) in-hospital mortality rates (5.7% vs. 9.1% p = 0.27), a finding which held in both ACC/AHA class I/IIa and class IIb subgroups, despite the fact that these women were older and had more risk factors for CAD. It is possible that the similarity in angiography and revascularization rates contributed to the similarity in outcomes between men and women.
The major strength of the present study is that procedure utilization was compared in men and women who were classified by a recognized standard of care—the ACC/AHA guidelines. Analyzing procedure utilization according to the same criteria that physicians should apply in making management decisions may provide valuable insight into the appropriateness of clinical conduct; indeed, in the present study, ACC/AHA class was an independent predictor of performance of angiography after AMI. Furthermore, these data represent actual practice in a consecutive, unselected group of patients in a real-world setting, rather than a select patient group, as in multicenter trials (19) or Medicare data base reports (1–3,5). Such studies may include more homogeneous groups of patients that are less complex or older than those seen in a typical clinical environment.
Study limitations.
Although the clinical, angiographic and procedure data were prospectively collected, and the methods and end points were prospectively identified, this is a retrospective analysis, with the attendant limitations. It is possible that studying a larger number of patients might have revealed a difference in procedure utilization between men and women, but no trends in the data suggest that larger numbers might have detected such a difference. Another limitation is that the findings reflect the practice at a single center; demonstrating a lack of bias in this institution does not necessarily mean that the results are generalizable to other institutions. Finally, long-term follow-up with respect to either outcomes or performance of later angiography would provide additional information.
Conclusions.
We found no evidence for gender disparity in utilization of coronary angiography or revascularization procedures in men and women admitted to a large inner-city teaching hospital with AMI. We also found no differences in in-hospital mortality rates, despite the fact that women were older and had more risk factors. It is possible that the similarity in angiography and revascularization rates among patients with ACC/AHA criteria for undergoing angiography contributed to the similarity in outcomes between men and women. These data provide further evidence that although presentations may differ as a function of gender, physicians respond appropriately to the needs of the female population.
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Footnotes
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This work was performed internally with institutional funds.
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References
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Abstract
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