Sex and mortality associated with coronary artery bypass graft

Sex differences in care complexity and cost of cardiac-related procedures as a basis for improving hospital payments systems

In this study, we estimate sex differences in care complexity and cost of cardiac-related procedures in order to demonstrate the importance of sex as a risk adjuster in a hospital payment system. We use individual visit-level data for all adult Israelis who underwent either heart valve surgery (HVS) or coronary artery bypass graft surgery (CABG) during the period 2014-2018 in publicly funded hospitals. We find that women undergoing a cardiac-related procedure are more likely to die during hospitalization, they have longer hospital stays, and overall, they are more likely to be care-complex than men. Furthermore, the cost of the surgery itself is higher for women than for men in the case of HVS (though not CABG), and the cost of the post-operative hospital stay is higher in the case of CABG (though not HVS). It is concluded that sex differences should be considered in the calculation of payment for cardiac-related procedures in order to reduce incentives for selection and reduce unwarranted variation in cardiac-care utilization and medical practice.

Assignment-Control Plots: A Visual Companion for Causal Inference Study Design

An important step for any causal inference study design is understanding the distribution of the subjects in terms of measured baseline covariates. However, not all baseline variation is equally important. We propose a set of visualizations that reduce the space of measured covariates into two components of baseline variation important to the design of an observational causal inference study: a propensity score summarizing baseline variation associated with treatment assignment, and prognostic score summarizing baseline variation associated with the untreated potential outcome. These assignment-control plots and variations thereof visualize study design trade-offs and illustrate core methodological concepts in causal inference. As a practical demonstration, we apply assignment-control plots to a hypothetical study of cardiothoracic surgery. To demonstrate how these plots can be used to illustrate nuanced concepts, we use them to visualize unmeasured confounding and to consider the relationship between propensity scores and instrumental variables. While the family of visualization tools for studies of causality is relatively sparse, simple visual tools can be an asset to education, application, and methods development.

Update: Gender differences in CABG outcomes-Have we bridged the gap?

Background

Appreciation of unique presentation, patterns and underlying pathophysiology of coronary artery disease in women has driven gender based risk stratification and risk reduction efforts over the last decade. Data regarding whether these advances have resulted in unequivocal improvements in outcomes of CABG in women is conflicting. The objective of our study was to assess gender differences in post-operative outcomes following CABG.

Methods

Retrospective analyses of institutional data housed in the Society of Thoracic Surgeons (STS) database for patients undergoing CABG between 2002 and 2020 were conducted. Multivariable regression analysis was conducted to investigate gender differences in post-operative outcomes. P-values were adjusted using Bonferroni correction to reduce type-I errors.

Results

Our final cohort of 6,250 patients had fewer women than men (1,339 vs. 4,911). more women were diabetic (52.0% vs. 41.2%, p<0.001) and hypertensive (89.1% vs. 84.0%, p<0.001). Women had higher adjusted odds of developing ventilator dependence >48 hours (OR: 1.65 [1.21, 2.45], p = 0.002) and cardiac readmissions (OR: 1.56 [1.27, 2.30], p = 0.003). After adjustment for comorbidity burden, mortality rates in women were comparable to those of age-matched men.

Conclusion

The findings of our study indicate that despite apparent reduction of differences in mortality, the burden of postoperative morbidity is still high among women.

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.