Stress protocol and accuracy of myocardial perfusion imaging: Is it better to start from the end?

The strength of single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is mainly due to the prognostic value also related with the choice of optimal therapeutic strategy. In the current era of comparative effectiveness and outcomes research, we are seeing a progressive shift from a diagnostic approach to a riskand care costs-management of coronary artery disease (CAD). Recent technological advances in SPECT hardware and software, new stressors, and clinical protocols have improved the clinical impact and cost effectiveness of MPI. Particularly, the novel cadmium zinc telluride (CZT) SPECT cameras provide fast high-quality MPI and seem to allow for a more accurate evaluation of myocardial ischemia with lower administered doses. In this issue of the Journal, Gimelli et al assessed with a CZT camera the diagnostic accuracy of MPI for both pharmacologic and exercise stress test, also in patients undergoing sub-maximal exercise. They found an elevated accuracy of MPI, independently on both stress protocol and level of exercise stress testing. The topic is important, and the possibility that enhanced accuracy by CZT cameras could help to partially overcome the limitations of exercise level threshold, usually expressed as 85% of age-predicted maximal heart rate (HR), is of clinical relevance, expanding the indication of exercise test over pharmacologic stressor. However, there are some issues that should be taken into account. THE CONCEPT ‘‘START FROM THE END’’