Gender Differences in Diabetic Patients Following Coronary Artery Bypass Graft Surgery

Higher Mortality in Women after Coronary Artery Bypass: Meta-analysis & Bias Analysis of Confounding

BACKGROUND

Some studies suggest the observed higher mortality in women than men after coronary artery bypass grafting (CABG) is due to confounding. Our meta-analysis aimed to 1) summarize the effect of sex on mortality following CABG and 2) identify whether unmeasured confounding likely explains the apparent higher mortality in women.

METHODS

MEDLINE, Embase, and CENTRAL databases were searched for studies examining sex and 30-day mortality following CABG. We used random-effects meta-analysis to estimate the summary odds ratio (OR) of mortality in women versus men using 1) unadjusted study results and 2) adjusted study results. Available confounders data from included studies was identified. Using the OR of measured confounders and the risk of death to inform unmeasured confounding effects, we performed bias analysis simulation to correct potential unmeasured confounding in our summary OR.

RESULTS

From 7138 retrieved studies, 112 were included (N=5,008,262 patients), 25 studies reported adjusted OR (N=770,450 patients). The overall 30-day mortality was 4.9% in women vs. 3.3% in men. The unadjusted summary OR (1.81, 95% CI 1.72 to 1.91) and adjusted summary OR (1.40, 95% CI 1.35 to 1.45) demonstrated that women had an increased risk of 30-day mortality compared to men. Simulations correcting for unmeasured confounding that mostly ranged from 1.05 to 1.80, supporting a higher risk of death in women after CABG.

CONCLUSIONS

The findings of this review suggest confounding is unlikely to account for the increased risk of mortality in women after CABG and that biological factors have a casual effect.

Gender differences in the impact of diabetes on mortality in patients with established coronary artery disease: a report from the eastern Taiwan integrated health care delivery system of Coronary Heart Disease (ET-CHD) registry, 1997-2006

OBJECTIVES

The effect of type 2 diabetes mellitus (DM) on mortality was more pronounced in women than men with coronary artery disease (CAD) in the pre-stent era before 1996. However this relationship is controversial in the post-stent era.

METHODS

We studied a cohort of 1073 patients with angiographically defined CAD from the Eastern Taiwan integrated health care delivery system of Coronary Heart Disease (ET-CHD) registry during 1997-2003 in Tzu-Chi General Hospital, Hualien, Taiwan. To evaluate gender-specific DM effect on mortality, the subjects were divided into 4 groups: diabetic women (n=147), non-diabetic women (n=127), diabetic men (n=239), and non-diabetic men (n=560). At a mean follow-up of 5.4 years, cardiac and all-cause mortality were the primary end points.

RESULTS

Annual total mortality rates were 10.2%, 5.1%, 7.2%, and 4.8%; annual cardiac mortality rates were 8.2%, 3.0%, 4.3%, and 2.6% for diabetic women, non-diabetic women, diabetic men, and non-diabetic men, respectively. Multivariate Cox regression models, adjusted for possible confounders showed that gender-specific hazard ratios (HRs) of DM for total mortality were 2.02 (95% CI: 1.32-3.09), and 1.72 (95% CI: 1.32-2.25) for women and men, respectively. The HRs for total mortality associated with diabetes were not different between women and men (p=0.53). Similarly, adjusted gender-specific HRs of DM for cardiac mortality were 2.46 (95% CI: 1.45-4.19) for women, and 1.83 (95% CI: 1.28-2.62) for men, which were also not significantly different (p=0.36).

CONCLUSIONS

Among patients with CAD, the impact of DM on mortality was consistently higher in women than in men, but the differences across sexes were not statistically significant after 1996 in Taiwan.

Hypertrophied hearts: what of sevoflurane cardioprotection?

BACKGROUND

Recent studies have demonstrated that inhalation anaesthetics, like sevoflurane, confer cardioprotection both experimentally and clinically. However, coexisting cardiac disease might diminish anaesthetic cardioprotection and could partly explain why the clinical results of cardioprotection with anaesthetics remain controversial--in contrast to solid experimental evidence. Concomitant left ventricular hypertrophy is found in some cardiac surgery patients and could change cardioprotection efficacy. Hypertrophy could potentially render the heart less susceptible to sevoflurane cardioprotection and more susceptible to ischaemic injury. We investigated whether hypertrophy blocks sevoflurane cardioprotection, and whether tolerance to ischaemia is altered by left ventricular hypertrophy, in an established experimental animal model of ischaemia-reperfusion.

METHODS

Anaesthetized juvenile pigs (n=7-12/group) were subjected to 45 min distal coronary artery balloon occlusion, followed by 120 min of reperfusion. Controls were given pentobarbital, while sevoflurane cardioprotection was achieved by 3.2% inhalation throughout the experiment. Chronic banding of the ascending aorta resulted in left ventricular hypertrophy development in two further groups and these animals underwent identical ischaemia-reperfusion protocols, with or without sevoflurane cardioprotection. Myocardial infarct sizes were compared post-mortem.

RESULTS

The mean myocardial infarct size (% of area-at-risk) was reduced from mean 55.0 (13.6%) (+/-SD) in controls to 17.5 (13.2%) by sevoflurane (P=0.001). Sevoflurane reduced the infarct size in hypertrophied hearts to 14.6 (10.4%) (P=0.001); however, in hypertrophic controls, infarcts were reduced to 34.2 (10.2%) (P=0.001).

CONCLUSION

Sevoflurane abrogated ischaemic injury to similar levels in both normal and left ventricular hypertrophied hearts.