Clinical meaning
Stable ischemic heart disease (SIHD) involves a complex interplay between epicardial coronary stenosis, microvascular dysfunction, and endothelial biology. Coronary flow reserve (CFR), measured as the ratio of hyperemic to resting coronary flow, integrates both epicardial and microvascular disease. FFR (fractional flow reserve) specifically assesses the hemodynamic significance of epicardial stenosis by measuring the pressure gradient across a lesion during maximal hyperemia (adenosine-induced). FFR below 0.80 indicates functionally significant stenosis warranting revascularization (FAME and FAME 2 trials). Instantaneous wave-free ratio (iFR) measured during the diastolic wave-free period provides equivalent diagnostic accuracy without adenosine (iFR below 0.89 is significant). The ISCHEMIA trial demonstrated that among patients with stable SIHD and moderate-to-severe ischemia, an initial invasive strategy did not reduce death or MI compared to optimal medical therapy (OMT) over 3.2 years, shifting the paradigm toward OMT-first approach with catheterization reserved for refractory symptoms or high-risk anatomy. Novel antianginal mechanisms include late sodium current inhibition (ranolazine), If channel inhibition (ivabradine), metabolic modulation (trimetazidine, not available in US), and rho-kinase inhibition (fasudil, for vasospastic angina). The clinician prescribes optimal medical therapy, determines invasive vs conservative management based on risk stratification, manages complex drug interactions, and addresses special populations including women with microvascular disease.