The term stable ischemic heart disease (SIHD) often is used synonymously with chronic coronary artery disease (CAD) and encompasses a variety of conditions where the end result is a repetitive mismatch between myocardial oxygen supply and demand. This most frequently is seen when long-standing atherosclerotic obstruction within the epicardial coronary arteries results in poor flow and ischemia distally. However, this is not the only mechanism. Various pathophysiologic processes such as coronary artery vasospasm, microcirculation dysfunction, or congenital anomalies can cause the same supply-demand mismatch and result in chronic repetitive ischemia. Per the American College of Cardiology (ACC)/American Heart Association (AHA) 2012 guidelines, stable ischemic heart disease includes adults with known ischemic heart disease (IHD), who have stable pain syndromes (i.e., chronic angina), or those with new-onset, low-risk chest pain (i.e., low-risk, unstable angina or UA). Asymptomatic patients who were diagnosed through non-invasive methods or who have had their symptoms adequately controlled medically or the following revascularization are also considered to have stable ischemic heart disease. A distinction should be made between stable ischemic heart disease and acute coronary syndrome (ACS), where a more acute presentation with troponin elevation (i.e., myocardial infarction) or high-risk chest pain without troponin elevation (i.e., high-risk, UA) is required for the diagnosis. It also bears mentioning that stable ischemic heart disease patients can develop chronic, slow worsening of their angina symptoms, which is often managed medically, or may go on to develop ACS and require urgent intervention. Therefore, the ability to distinguish stable ischemic heart disease from ACS within the spectrum of atherosclerotic CAD is paramount.