Coronary CT angiography for suspected acute coronary syndrome: sex-associated differences

There are distinct pathophysiological differences in coronary artery disease (CAD) between men and women. Men are more likely to have obstructive epicardial CAD, while women are more prone to have coronary microvascular dysfunction [1]. In addition, disease perception may differ, both from the physician’s perspective—leading to sex-specific referral bias—and the patient’s own perception of chest discomfort, both of which can result in underrecognition of the burden of CAD in women [2]. The optimal diagnostic test in the work-up of suspected acute coronary syndrome (ACS) may therefore be different for men and women [3].

In this prespecified subanalysis of the Better Evaluation of Acute Chest Pain with Coronary Computed Tomography Angiography (BEACON) trial, we compared the clinical presentation, coronary computed tomography angiography (CCTA) results and the subsequent effect on downstream healthcare utilisation in men and women with suspected ACS.

The study design, the criteria for enrolment and the primary results have been reported previously [4]. Briefly, in the BEACON trial, we randomised 500 patients suspected of having ACS (47% women, 79% of whom were evaluated with a high-sensitivity (hs) troponin assay) at the emergency department of seven hospitals to receive either standard of care (SOC) or a diagnostic strategy supplemented with early CCTA. In the SOC group, the attending physicians made clinical decisions regarding further testing, including repeated cardiac marker assessment, hospital admission, noninvasive tests and referral to invasive coronary angiography, according to relevant guidelines [5, 6]. The results of the main study showed that CCTA, which was applied early in the work-up of suspected ACS, is safe and is associated with less outpatient testing and lower costs. Data concerning particular endpoints, including coronary angiography, coronary revascularisation, hospital admission, length of stay, repeat emergency department visit and outpatient testing, were collected within 30 days of follow-up.

In the current analysis, non–sex-specific 99th percentile upper reference limits of normal were used for all troponin assays, conventional or high-sensitivity, with the exception of the Hs-TnI assay (Abbott ARCHITECT, Abbott Laboratories, Chicago, IL, USA), for which vendor-recommended sex-specific cut-off values were used. ACS was defined as either unstable angina pectoris or myocardial infarction (MI), according to the Third Universal Definition of MI [7].

In the BEACON trial, women were generally older than men (56 ± 10 vs 53 ± 10 years, p < 0.01), less often active smokers and received less pharmacological treatment (Tab. 1). Table S1 in the Electronic Supplementary Material lists all troponin assays used, their characteristics and the algorithm with which they were implemented. ACS was less often diagnosed in women than in men (5% vs 10%, p = 0.03), and obstructive CAD on CCTA (> 50% luminal narrowing) was less frequently seen in women (14% vs 26%, p < 0.02).

Women were admitted less often (33% vs 42%, p = 0.04). The use of invasive coronary angiography (11% vs 17%, p = 0.07) and the rate of coronary revascularisation (6% vs 9%, p = 0.25) were not statistically different between women and men, although referral to invasive coronary angiography was numerically higher in men (Tab. 1).

Tab. 2 shows the study endpoints when comparing both diagnostic groups based on sex. Women underwent less outpatient testing when early CCTA was used in the emergency department evaluation of suspected ACS (p = 0.008).

Tab. 3 shows the study endpoints when comparing both sexes within each diagnostic group. In the CCTA arm, men were more likely to be diagnosed with MI at discharge than women (p = 0.03). Furthermore, although not statistically significant, in the SOC arm, women were less likely to be admitted to hospital (p = 0.07) and had a shorter length of stay (p = 0.08) than men.

In this prespecified analysis of the BEACON trial, women had a lower incidence of obstructive CAD on CCTA and were less often admitted to hospital than men. Women also underwent less outpatient testing when early CCTA was used in the emergency department evaluation of suspected ACS. Although not statistically significant, in the SOC arm, women were less likely to be admitted to hospital and had a shorter length of stay than men.

The presence of sex differences in the pathophysiology of ischaemic heart disease is becoming increasingly apparent [8, 9]. Previously, it has been shown that early CCTA may be a more efficient work-up for suspected ACS, especially in women. In a study by Truong et al., women showed a greater reduction in length of stay and hospital admission than men when early CCTA was used in the emergency department evaluation of suspected ACS [10]. The lower burden of CAD in women was thought to be a likely explanation for this difference, as physicians felt less need to perform downstream tests in patients with non-obstructive CAD on CCTA [10]. Although, we did not see similar reductions in hospital admission and length of stay, women underwent less outpatient testing than men when early CCTA was used. This reduction may also be due to the fact that women had a lower burden of CAD on CCTA, which in turn more often reassured physicians not to perform outpatient testing compared with men.

Although patients with angina without obstructive CAD have a better prognosis than those with obstructive epicardial CAD, they are still at higher risk of cardiovascular disease outcomes than the background population. Therefore, physicians should be vigilant in patients with recurring angina without obstructive epicardial CAD, especially in women, and initiate further evaluation of microvascular disease and treat accordingly.

A novelty in our study was the availability of hs-troponins for clinical decision-making in most of the patients. The introduction of hs-troponin assays has altered our perspective on MI and the way we practice medicine. These new cardiac biomarkers pick up myocardial injury fast and very precisely; serial low values almost certainly exclude MI [11, 12]. In the current study, the majority of the patients with available hs-troponins (> 90%) had normal levels (< 99th percentile of the upper limit of normal), which reassured treating physicians to discharge patients expeditiously, regardless of sex.

However, the improved sensitivity of these new biomarker assays has led to an increasing number of patients being diagnosed with myocardial injury causa ignota. Myocardial injury can be the result of type I MI associated with coronary plaque disruption or other types of MI, non-coronary heart disease or even non-cardiac diseases. Myocardial injury, irrespective of the cause, is associated with a less favourable prognosis and there are also sex-specific differences regarding the cause of injury [13‐15]. Although this type of conclusions cannot be drawn from our own data, it is believed that women more often have other conditions than obstructive epicardial CAD that cause myocardial injury, such as coronary vasospasm or dissection [16, 17]. As a noninvasive anatomical modality, CCTA can serve as a gatekeeper of traditional coronary angiography by discriminating between obstructive and non-obstructive epicardial CAD.

Compared with men, women had a lower incidence of obstructive CAD on CCTA, were less often admitted and underwent less outpatient testing when early CCTA was used in the emergency department evaluation of suspected ACS.