Closing the gender gap in cardiac surgery outcomes: more work to be done

Historically, cardiac surgery outcomes have been worse for women when compared to men [1]. Female sex is a risk factor in both the logistic EuroSCORE, EuroSCOREII and Society for Thoracic Surgery clinical prediction models. Contemporary registry studies have repeatedly identified worse outcomes after cardiac surgery for women despite adjusting for measured confounders [2, 3]. This effect has been observed across coronary, valvular and aortic surgery. Although the gender gap in outcomes after cardiovascular surgery has been apparent for some time, the causes are multifactorial and the underlying mechanisms are poorly understood. However, across all cardiac pathologies a recurring theme is observed of delayed diagnosis and referral of women for intervention. Women are typically older, with more comorbidities and more advanced disease at the time of intervention. This may contribute to a lower physiological reserve and poor early and late outcomes, particularly after valvular surgery. Women with aortic stenosis are less likely to be referred for surgery despite a higher symptom burden and greater risk of death without intervention [4, 5]. In large retrospective studies, women with severe mitral regurgitation were less likely to undergo surgery despite larger atrial and ventricular dimensions; and had greater comorbidities and more advanced symptoms at the time of intervention [6, 7]. If women are higher risk due to more advanced disease could reducing surgical stress help? Minimally invasive cardiac surgery is performed with the aim of reducing surgical trauma, optimizing patient recovery and improving cosmetics. Observational data have suggested that this is the case, although data from randomized trials have been lacking [8]. If women are at an increased risk of worse outcomes, it follows that a less invasive approach may be of particular benefit. Perhaps more widespread adoption of minimally invasive cardiac surgery could be a step in the right direction for improving outcomes in women. In this study, Moscarelli et al. [9] report the outcomes of sternotomy and minimally invasive valve surgery from 9 Italian centres over a 9-year period. They demonstrate an excellent take up of minimally invasive surgery with over half of patients receiving surgery via a minimally invasive approach. Encouragingly, there was no difference in the rate of minimally invasive surgery between men and women. Furthermore, the rates of mitral valve repair, concomitant tricuspid surgery and redo procedures were similar and women generally had shorter cross-clamp times. However, despite undergoing similar treatment, women were older and had more atrial fibrillation at presentation. Details of patients’ ventricular size, function and symptom status at presentation were not available making it challenging to evaluate conclusively whether women presented with more advanced disease at the time of surgery in this cohort. The main finding of the study was that there was no difference in outcomes among female patients undergoing surgery via minimally invasive surgery compared to sternotomy. However, female sex remained an important risk factor for poor outcomes overall, with higher rates of in-hospital mortality after both minimally invasive surgery and sternotomy. Female sex was also identified as an independent risk factor for long-term mortality after adjustment for baseline differences. Once again, female sex has been identified as an important risk factor for worse outcomes after cardiac surgery. If minimally invasive surgery is not the answer, then what is? A multifaceted strategy is inevitably required to improve outcomes in women with cardiovascular disease who require surgical intervention. Firstly, sex bias in basic and clinical research should be addressed, with greater emphasis placed on understanding sex differences in the pathophysiology and progression of disease. Enrolment of women in clinical trials remains poor and strategies are required to improve this. Both observational and prospective studies should have sex-balanced design, analyses and reporting. For valvular disease in particular, sex-neutral thresholds for intervention included in clinical guidelines are problematic and lead to late referral of women for surgery. Cut-off values indicating the need for surgery were developed using predominantly male populations. As a result, women frequently present with greater degrees of ventricular dysfunction and dilatation. Systematic indexing to body surface area and sex-specific guidelines for intervention are crucial to optimize the timing of surgery. While older studies showed worse outcomes for women following aortic valve replacement for aortic regurgitation, studies based on similar indexed end-systolic diameters have shown comparable outcomes [10]. Current indications for intervention for mitral regurgitation are similarly based on absolute diameters and mitral repair rates have historically been lower for women. If guidelines were revised based on indexed thresholds then earlier referral for women may lead to higher repair rates and better early and late outcomes. Moscarelli et al. should be commended for this important sex-based analysis exploring the differential impact of minimally invasive valve surgery on outcomes. Although no differences were seen in outcomes by surgical technique, women again fared worse than men overall. More work is clearly required to close the gender gap in cardiac surgery outcomes. It is likely that improvements in systematic evaluation and earlier referral along with sex-specific guidelines will prove to be more important than modifications to surgical technique in improving cardiac surgery outcomes for women. Conflict of interest: none declared.

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