ABSTRACT
OBJECTIVES: To determine whether outcome differences based on the patient’s sex occur after myocardial infarction (MI) at a large private hospital.
STUDY DESIGN: We conducted a large cohort study.
POPULATION: Inclusion required hospital admission between January 1, 1998, and June 30, 1999, and a diagnosis of acute MI or subendocardial infarction. The number of patients included in the study was 1669. Data were collected at discharge on age, sex, race, health insurance, hypercholesterolemia, diabetes, smoking, hypertension, and the extent of coronary artery disease.
OUTCOMES MEASURED: The 8 outcomes analyzed were angiogram, angioplasty, stent placement, coronary artery bypass grafting (CABG), mortality, time in the intensive care unit, total length of stay, and combined catheterization procedures.
RESULTS: After adjusting for 7 confounding variables, we found no significant differences between men and women for mortality, ICU time, total hospital time, stent placement, angiogram, angioplasty, or combined catheterization procedures. Men had significantly more CABG (relative risk [RR] 1.96, P < .01). Among patients who underwent CABG (N = 204), men had significantly more 3-vessel coronary disease (RR 1.44, P < .01) and left main coronary artery disease greater than 50% (RR 1.58, P < .01). Once we had controlled for the extent of coronary artery disease, we found no difference between the sexes for CABG.
CONCLUSIONS: During hospitalization after an MI, most cardiovascular outcomes and process measures are the same for men and women. The greater frequency of CABG in men than in women is explained by men’s greater frequency of 3-vessel and advanced left-main coronary disease.
KEY POINTS FOR CLINICIANS
- Unadjusted data reveal that in patients hospitalized for acute myocardial infarction, women experience higher mortality rates and undergo fewer procedures, particularly coronary artery bypass grafting, than men.
- Controlling for several comorbidities and the extent of coronary artery disease eliminates differences between the sexes in this context.
Recent studies have shown that women aged less than 75 years have a significantly higher rate of in-hospital mortality than men after acute myocardial infarction (MI).1-3 A cohort study involving more than 384,000 patients admitted to the hospital for MI found that women aged 74 years or less had a higher mortality rate than men. The mortality rate in women aged less than 50 years was twice as high as that of men in the same age group.2 The difference in mortality after an acute MI disappears at age 75 years.1,2,4
Although women are as likely as men to have a positive stress electrocardiogram or stress thallium test after an acute MI, women are referred less often for additional noninvasive testing or cardiac catherization.5 In a study of more than 12,000 patients with acute coronary syndromes, fewer women than men underwent cardiac catheterization.3 In hypothetical case studies, physicians shown videotapes of actors playing patients and given hypothetical case studies were less likely to say they would refer the women for catheterization than the men. Black women were referred least.6
Men are also more likely than women to receive angioplasty or coronary artery bypass grafting (CABG) after acute MI.2 Women undergoing CABG have significantly more comorbidities and less favorable patient characteristics preoperatively than do men.7 While women and men undergoing CABG have the same type and extent of symptoms overall, women are more likely to have preserved ventricular function and less likely to possess multivessel disease than are men.3,7,8
The purpose of this study was to determine whether sex-related outcome differences existed after being treated for an MI at a large private hospital. We also evaluated how significantly any difference in the extent of coronary artery disease between the sexes would confound the rate of CABG performed after an acute MI.
Methods
Study design and population
This is a hospitalization cohort study using data obtained from the Acute Myocardial Infarction Registry database at TriHealth hospitals in Cincinnati, Ohio. The TriHealth hospital system consists of 3 private hospitals in the greater Cincinnati area. Inclusion criteria for entering the cohort included admission to a TriHealth hospital during an 18-month period between January 1, 1998, and June 30, 1999, and a discharge diagnosis of acute MI or subendocardial infarction. Exclusion criteria included transfer to another local hospital for some of the patient’s health care or more than 1 hospitalization for an MI during the cohort time period. Double admissions and transferred patients were rare (N = 7). Individuals were included in the cohort only during their hospitalization for the acute MI. Patients exited the cohort at discharge.
Data collection
Data were collected at hospital discharge on age, sex, race, insurance status, and various comorbidities, including smoking, hypercholesterolemia, diabetes, hypertension, and the extent of coronary artery disease. The 8 outcomes available for analysis included hospital mortality, time in the intensive-care unit, total length of stay, angiogram, angioplasty, stent placement, CABG, and the 3 catheterization procedures combined. For patients who underwent CABG, data were collected on the number of bypassed vessels and the presence of advanced left main coronary disease. Data on demographics, disposition, and length of stay were obtained by means of the hospital registry system. The comorbidity and cardiovascular data collection sheet was typically filled out at discharge, usually by the cardiologist and occasionally by a primary care physician. The presence or absence of comorbidities was determined by the physician who provided the patient data. Each comorbidity was listed on the data sheet with a “yes or no” option.