Coronary physiology is widely used to assess epicardial coronary lesions in patients with stable angina. Based on the available evidence, physiology plays a crucial role in diagnosing and treating patients. There have been invasive methods for determining cardiac physiology, such as fractional flow reserve and instantaneous wave-free ratio. Still, new non-invasive approaches provide extra anatomical information, such as fractional flow reserve computed tomography (FFR-CT) based on computed tomography and physiology based on angiography. Even though FFR-guided percutaneous coronary intervention (PCI) is clinically beneficial, one-third of patients retain suboptimal FFR after the procedure, associated with severe adverse events, rendering PCI in diffuse coronary artery disease questionable. Using the pullback pressure gradient (PPG), we can analyze the magnitude and extent of pressure losses; a lower value may indicate diffuse disease, while a high value with an abrupt curve may indicate focal disease. Since PCI is not the best option for treating diffuse coronary disease, current strategies focus on conservatively using medical therapy or bypass surgery. It has been demonstrated that patients with diffuse disease of the left anterior descending (LAD) are at a greater risk of developing occlusion of the left internal mammary artery graft than those with focal disease and that maximal medical therapy may be the most effective treatment for these patients.