Clinical PET Integrated with Current Pathophysiologic Concepts of CAD
Based on current knowledge and technology, the clinical guidelines for applying and interpreting cardiac PET imaging require a radical departure from traditional nuclear cardiology using standard single photon emission computed tomography (SPECT) imaging summarized as follows:
- Due to accurate attenuation correction, high-resolution and improved counting statistics, PET perfusion imaging conducted and viewed correctly is a definitive, stand-alone diagnostic procedure that does not require diagnostic arteriographic confirmation and provides the basis for revascularization decisions.
- Coronary atherosclerosis is a diffuse disease with a graded range of severity of narrowing. PET perfusion imaging shows a corresponding range of abnormalities. Consequently, binary classification as normal or abnormal with an associated binary decision for or against coronary arteriography is inadequate as the basis for managing CAD in view of current knowledge about coronary plaque rupture, diffuse disease, endothelial function, prognosis, vigorous risk factor treatment, and unaltered risk of clinical events after revascularization procedures.
- The severity of perfusion abnormalities quantifies the severity of coronary artery stenosis, its precise anatomic location in the coronary artery tree, diffuse disease and effects of multiple stenoses in addition to diffuse disease that is not possible with any other invasive or non-invasive technology.
- Mild perfusion abnormalities by PET indicate the substrate for plaque rupture and cardiovascular events that requires vigorous, lifelong risk factor management. A mild perfusion defect by PET implies the same long-term risk as a severe defect by virtue of identifying subjects with CAD subject to plaque rupture. Both mild and severe PET perfusion defects mandate equally vigorous cholesterol-lowering and risk factor treatment.
- Changes in perfusion abnormalities by follow-up PET studies indicate progression or regression of CAD with an accuracy greater than the arteriogram due to perfusion reflecting diffuse changes throughout the length of the coronary arteries, depending on radius changes raised to the fourth power and due to altered endothelial mediated vasomotor function.
- Heterogeneity of resting myocardial perfusion outside of the normal limits indicates microvascular dysfunction and is a powerful independent predictor of coronary atherosclerosis requiring vigorous treatment of risk factors.
- Clinical reports of PET perfusion images need to be written in a way that incorporates this new information while still recognizing the traditional viewpoints of most physicians (or patients) reading PET reports who may not be familiar with the implications of this integrated new knowledge about high-quality perfusion imaging, related coronary pathophysiology, and its treatment.