Original article
Prevalence of risk factors, and not gender per se, determines short- and long-term survival after coronary artery bypass surgery

https://doi.org/10.1016/S1053-0770(03)00201-5Get rights and content

Abstract

Objective: Much attention has been directed towards female gender as an independent risk factor for in-hospital mortality after coronary artery bypass grafting surgery; however, the effects of surgery are known to persist for 6 months or more. Studies that have compared postoperative survival in women and men beyond hospital discharge report disparate results with regard to the independent effect of gender per se on ultimate survival.

Design: This investigation was a prospective, observational study.

Setting: The study was a multicenter investigation involving 24 US medical centers.

Participants: There were 2,048 patients undergoing isolated coronary artery bypass graft surgery enrolled between September 1991 and September 1993 and after discharge.

Interventions: There were no interventions with this prospective observational study.

Measurements and main results: Preoperative demographic variables, medical history, and angiographic data were collected for each patient at the time of enrollment. Patients’ vital status through the National Death Index up to August 31, 1998, were added to assess postoperative long-term survival. For survivorship analysis, the Kaplan-Meier product-limit method was used with Cox regression model. Survivorship analyses were performed separately and in combination on mortality within 30 days and 6 months of coronary artery bypass graft surgery and during the entire postoperative follow-up period. Among women, preoperative disease status, as expected, was more severe than that in men. Women were older (p = 0.0001) and had more comorbidity, such as congestive heart failure (p = 0.0019), diabetes (p = 0.0001), anemia, and hypertension (p = 0.0001). After surgery, unadjusted survival of 6 months and 5 years in women was worse than that in men. However, there were no gender-related differences in short- or long-term survival after adjusting for covariates in the multivariate model. Preoperative conditions, such as congestive heart failure, anemia, diabetes, and advanced age, are indicative of greater risk in both women and men for lower survival after coronary artery bypass graft surgery.

Conclusions: Disease prevalence in women, and not gender per se, affects mid- and long-term survival after cardiac surgery. Attention, therefore, should be focused on efforts to reduce or modify such disease prevalence earlier in women, which may in turn allow longer survival after surgical intervention. Differences in postoperative survival between women and men were related to the gender differences in the distribution of preoperative risk factors.

Section snippets

Methods

The authors used a prospective multicenter observational database of patients undergoing CABG surgery. All patients enrolled in the study were undergoing elective CABG surgery and not enrolled in another research study. A total of 100 randomly selected patients were required from each of the 24 medical centers.

Two thousand four hundred seventeen patients who underwent CABG surgery at the 24 United States centers were enrolled into the study between September 1991 and September 1993 and followed

Results

Of the 2,048 patients, 460 (22%) were females and 1,588 (78%) were males. The preoperative variables listed in Table 1 were compared between male and female patients and are presented in Table 2. At the time of surgery, women were older and had more comorbid conditions, including congestive heart failure, higher Canadian classification for angina and New York Heart Association classification for congestive heart failure, diabetes mellitus, anemia, hypertension, vascular disease, and/or prior

Discussion

The authors found that gender per se did not confer risk for adverse outcome after CABG surgery, but the prevalence of risk factors such as advanced age, vascular disease, anemia, prior myocardial infarction, congestive heart failure, and diabetes did equally for both women and men. The implications of the present study suggest that surgical outcome is not determined by gender and therefore irreversible but that there exist potentially modifiable risk factors for women (as there are for men),

Acknowledgements

The authors wish to thank Diane Beatty and Brenda Xavier for their technical assistance. Participating Multicenter Study of Perioperative Ischemia (McSPI) Research Group Institutions and Investigators: Baylor College of Medicine, Houston, TX, Randall Clark, MD, Patrick E. Curling, MD, Salwa Shenaq, MD; Beth Israel Hospital, Boston, MA, Mark E. Communale, MD; Brigham and Women’s Hospital, Boston, MA, Simon Body, MD, Rosemarie Maddi, MD; Cedars-Sinai Medical Center, Los Angeles, CA, Arnold S.

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      These included patient age, gender, body mass index (BMI), estimated preoperative creatinine clearance [2], a preoperative diagnosis of diabetes, hypertension or anaemia, the preoperative left ventricular function estimated from echocardiac or angiographic examination by a cardiologist, a history of previous sternotomy surgery, the number of coronary artery grafts, the occurrence of total arterial re-vascularisation, concurrent surgical procedures, and the patient’s Indigenous status. This chose this set of risk factors because we have consistently recorded them since 1993 and they include factors that have been previously identified as important for long-term survival after cardiac surgery [3–5]. To determine if survival has changed over time, patients were classified into three arbitrary groups of approximately equal size: those undergoing surgery before April 1999, those between April 1999 and July 2006, and those after July 2006.

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    Supported by a grant from the Ischemia Research and Education Foundation, San Francisco, CA.

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