Background: Cardiovascular disease is the leading cause of mortality for women and men. Prior studies have demonstrated the underrepresentation of women in published clinical trials, but no study to date has assessed inclusion of women in late-breaking clinical trials (LBCTs) presented at national meetings. The objective is to characterize the inclusion of women participants in LBCT presented at the 2021 American College of Cardiology (ACC), American Heart Association (AHA), and European Society of Cardiology (ESC) annual meetings and identify trial characteristics associated with improved inclusion. Methods: LBCT presented at the 2021 ACC, AHA, and ESC meetings were identified and the inclusion of women as participants was assessed. The inclusion to prevalence ratio (IPR) was calculated by dividing the percentage of women participants by the percentage of women in the disease population. IPRs <1 indicate underenrollment of women. Of the 68 LBCT, 3 trials were excluded due to lack of subject matter relevance. Results: Inclusion of women ranged from 0% to 71%. Only 47.1% of trials reported sex-specific analyses. The average IPR was 0.76 for all trials and did not vary based on conference, trial center, geographic region, or funding source. The average IPR varied based on subspecialty, with a statistical difference between interventional cardiology and heart failure (0.65 vs. 0.88, p = 0.02). The average IPR was significantly lower for procedural studies compared with medication trials (0.61 vs. 0.78, p = 0.008), as well as for studies with mean age <65 and trial size <1500 participants. There was no difference in IPR based on female authorship. Conclusions: LBCT can impact novel drug and device approval, intervention indications, and patient management. Nonetheless, most LBCT underenroll women, particularly, procedural LBCT. In 2021, sex-based enrollment disparities persist, highlighting the need to engage key stakeholders, including funding organizations, national governing bodies, editorial board members, and medical societies, in the creation of a coordinated strategic initiative to advance gender parity. These findings warrant further investigation to increase inclusion of women in trials, including potential enrollment requirements for consideration as LBCT by meeting organizers.

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