LAUSR

Current Clinical Coronary Physiology Current clinical coronary physiology is based on coronary pressure and flow or perfusion in experimental animals that first demonstrated coronary flow reserve (CFR) for physiological stenosis severity, the fluid dynamic pressure flow equations for coronary stenosis in intact awake canines, pharmacological stress initially experimentally then clinically, pressure-derived fractional flow reserve (FFR) from these 2 steps, cardiac positron emission tomography (PET) with N-13 ammonia in canine coronary stenosis then with generator produced Rb-82 experimentally and clinically, classification of microvascular angina or small vessel disease, and currently quantitative PET-guided revascularization that significantly reduces myocardial infarction (MI) and death. These initial concepts from experimental studies comprise the knowledge base for physiologically guided clinical management that assures ongoing evolution of coronary physiology formerly possible only experimentally. Based on randomized trials, pressure-derived FFR is now the invasive standard for objective, physiologically defining coronary artery disease (CAD) severity to guide revascularization. However, although pressure measurements are precise, FFR is physiologically imprecise with major physiological limitations. Randomized trials of FFR guided revascularization analyzed by intention to treat show no reduction in death or MI; it is invasive and measured at a single point in the coronary tree rather than defining the entire coronary artery system with multiple stenoses, diffuse epicardial, and small vessel disease; it fails to account for mass of myocardium at risk; FFR particularly fails to quantify down stream perfusion or low-risk subendocardial ischemia causing angina versus transmural ischemia associated with high risk of death or MI that is reduced by revascularization. However, like coronary flow meters and microspheres in experimental animals, PET is the best-documented tool for studying human physiology of the entire coronary artery tree. No other imaging technology has the proven record of quantitative PET as extensively detailed in recent reviews, literature, and cardiology textbooks summarized here.