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Coronary anatomy and function: a story of Yin and Yang.

Invasive coronary angiography (ICA) remains an essential component of the diagnostic workup of patients with suspected stable angina. The availability of ICA has increased significantly since it was first performed in the 1960s with remarkable improvements in efficiency and safety. The diagnosis of coronary artery obstruction is readily made anatomically, and its suitability for revascularization by percutaneous or surgical intervention can also be assessed. Therefore, ICA not only provides a diagnosis but it can also be a step towards treatment. Despite being unable to demonstrate atheroma that does not encroach upon the arterial lumen, this invasive procedure is still a common standard for the diagnosis of coronary artery disease (CAD), particularly when assessing the efficacy of alternative diagnostic techniques.

Because treatment decisions partly depend upon the angiographic appearance of disease, ICA is often the initial diagnostic test in suitable patients with a high likelihood of obstructive disease causing their symptoms. However, this may not be appropriate in all cases for several reasons. One of the most important is the low power of the clinical history for predicting the likelihood of obstructive CAD, caused by the complex relation between symptoms, myocardial ischaemia, and coronary luminal narrowing. Classical angina, although highly specific, is reported by only a minority of patients with significant CAD, and atypical features are common.1 Thus, in stable symptomatic patients, routine ICA would result in an unacceptably high number of normal angiograms while denying ICA to patients with less convincing symptoms may lead to misdiagnosis with potentially fatal consequences. When patient selection relies entirely on the clinical history, ICA performs poorly. To refine patient selection, particularly in patients at an intermediate …