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Ischemic left ventricular dysfunction results from the combination of scar and areas of dysfunctional but viable myocardium that may improve contractile function with revascularization. The traditional paradigm states that an improvement in function after revascularization leads to improved health outcomes and that assessment of myocardial viability has a key role in predicting the benefit of revascularization and, therefore, is a prerequisite for the selection of patients to undergo this treatment option. A range of retrospective observational studies supported this "viability hypothesis". However, randomized prospective trials have not confirmed the interaction between myocardial viability and the treatment effect of revascularization, challenging the recovery of left ventricular function as the principal mechanism by which surgical revascularization improves prognosis. A conceptual shift from the traditional paradigm centered on the assessment of viability as a dichotomous variable to a more comprehensive approach founded on an alternative concept that the main goal of revascularization is to prevent further damage by protecting the residual viable myocardium from subsequent acute coronary events and ventricular arrhythmias is required.

Guidance on the diagnostic approach to coronary artery disease has diverged as the increasing complexity of atherosclerotic clinicopathologic correlations has been revealed. Foundational concepts linking stenosis, the ischaemic cascade and prognosis have been re-evaluated in light of the underwhelming results from the percutaneous revascularization of stenotic vessels. These studies have revealed ischaemia to be an important marker for cardiovascular outcomes, but likely separate from the causal pathway of hard clinical events. Instead, observations from non-invasive anatomical imaging have redefined risk, shifting the focus away from discrete lesions towards total atherosclerotic burden, and with it elevating the role of computed tomography in contemporary diagnostic pathways. As it currently stands, functional and anatomical approaches provide complementary information; stress testing continues to provide guidance for potential revascularization in current guidelines, yet anatomical testing may additionally identify individuals likely to benefit from preventive therapy. While guidelines attempt to keep pace with the advancing technology and expanding literature, clinicians are left to apply clinical acumen to decide on a vast and confusing array of investigative options. This review will deal with strenghts and limitations of the current approach to the diagnosis of coronary artery disease, providing the rationale for both functional and anatomical approaches.