Can CTCA provide health care equity for people in rural Australia with coronary artery disease?

Decades of clinical research have consolidated the evidence that managing high risk acute coronary syndromes with an early invasive strategy — coronary angiography coupled with coronary revascularisation when appropriate — reduces cardiac mortality and the risk of recurrent myocardial infarction.1 Clinical trial evidence also supports coronary anatomic investigation of chest pain that suggests coronary artery disease (CAD), averting future myocardial infarction by facilitating initiation of preventive therapies.2 These insights provide the clinical rationale for coronary angiography.

Unfortunately, translating this evidence into clinical care across geographically diverse Australia is challenging. The enormous burden of the transfers required for managing people with suspected acute coronary syndromes has been documented.3 More recent data from the Australian Institute of Health and Welfare indicate the continuing dearth of diagnostic and procedural services available to people in rural areas and, more importantly, the excess burden of cardiovascular morbidity and mortality they experience.4

The retrospective cohort analysis of rural‐to‐metropolitan transfers for invasive coronary angiography in Western Australia undertaken by Alexander and colleagues and reported in this issue of the MJA5 further illustrates the health service and economic challenges that result from application of the available evidence. Of the 1017 people referred from rural and remote Western Australia to Perth for invasive coronary angiography in 2019, 61% did not require revascularisation and 36% had non‐obstructed coronary arteries (less than 50% stenosis). Given the substantial economic and resource burden of patient transfers, it is not at all surprising that modelling the impact of providing computed tomography coronary angiography (CTCA) in rural centres as a first line investigation for people with suspected CAD indicated that it could mitigate these costs, both in terms of metropolitan hospital bed‐days (43%) and health costs (36%), which include a major transport component.5 However, key insights from the analysis by Alexander and colleagues warrant further consideration.

Only a small proportion of people referred for invasive coronary angiography in Perth subsequently required revascularisation, particularly of those with moderate stenosis (50–69%: nine of 137 patients) or non‐obstructed coronary arteries (none of 365 patients).5 Given that the benefits associated with an early invasive strategy are only realised by the revascularisation of unstable coronary lesions causing type 1 myocardial infarction, the low angiography to revascularisation conversion rate highlights a significant challenge for the clinical selection of patients. The widespread adoption of high sensitivity troponin assays across Australia is likely to exacerbate this clinical dilemma.6

Further, late clinical outcomes resulting from changes in the diagnostic process are only infrequently assessed. CTCA as an alternative to invasive coronary angiography has been examined in a limited number of studies; only a modest impact on the need for invasive coronary angiography has been reported, and none on clinical outcomes.7 The benefits of an invasive coronary strategy for patients with myocardial injury not caused by type 1 myocardial infarction are currently being investigated in Australia, as is the question of whether people for whom the likelihood of type 1 myocardial infarction is low can be identified on the basis of their troponin elevation magnitude with sufficient precision that CTCA can decouple the diagnosis of CAD from revascularisation. Although newer innovations in CTCA, such as the ability to assess coronary physiology, promise to enhance our ability to characterise plaque, non‐invasively assessing plaque instability remains some way off. This is particularly relevant because revascularisation based on plaque characteristics, rather than the severity of ischaemia, appears to be of greater prognostic benefit, particularly for percutaneous coronary interventions.8

Improving diagnostic capabilities in rural areas will require a commensurate increase in clinical decision‐making and therapeutic capacity. Redesigning models of clinical care to link point‐of‐care troponin assessment with senior cardiac decision‐making has been reported to reduce excess cardiac mortality in rural Australia.9 However, this care model depends on improving the rural‐to‐metropolitan transfer and subsequent access to invasive management. While the technology required to remotely pilot CTCA is available, the real questions are whether we can develop clinical models of care and scopes of practice for effectively managing people in rural areas who need high acuity care. In an enhanced digital health environment, where the transmission of clinical information is almost instantaneous, the capacity to remotely pilot patient care may be required to support remote clinicians in the delivery of all components of evidence‐based care, including blood lipid management and therapies for reducing the likelihood of re‐admission, not only with myocardial infarction but also heart failure and cardiac arrhythmias.

The real test for CTCA as a diagnostic tool in rural areas will be whether a model of care and an effective workforce built upon these technological innovations can close the gap in cardiovascular outcomes experienced by regional and rural Australians.