The frontiers of nuclear cardiology research

Heart disease is the leading cause of death. Each year in the United States, more than 500,000 men and women die from coronary artery disease (CAD). CAD results from the narrowing of blood vessels that supply the heart. The blood vessels become narrow when fatty deposits build up inside the arterial wall. When the arteries become clogged, the blood flow to the myocardium is impaired and a heart attack can occur. Nuclear cardiology studies use noninvasive imaging techniques to assess myocardial blood flow. Among the techniques of nuclear cardiology, single-photon emission tomography (SPECT) myocardial perfusion imaging (MPI) is most widely used to diagnose CAD. The annual number of SPECT MPI procedures is 7-8 million in the United States. The research in the field of nuclear cardiology is everlasting and prosperous. The specific journal that publishes nuclear cardiology research studies is the Journal of Nuclear Cardiology, the official publication of the American Society of Nuclear Cardiology. Readers interested in nuclear cardiology research studies can also find their articles in many other imaging journals as well as cardiology journals. In this issue, the Journal of Biomedical Research publishes a series of reviews on the cutting edges of several research areas in nuclear cardiology. Dr. Hung's article [1] reviews the research efforts in exploring additional markers for diagnosing CAD from the conventional SPECT MPI. SPECT MPI is mainly indicated for the evaluation of patients with suspected or known CAD through the assessment of presence, location, extent, and severity of myocardial ischemia and infarction. However, the diagnostic accuracy of SPECT MPI is limited, especially in patients with a multi-vessel disease. Therefore, extensive research studies have been performed to search for additional markers from SPECT MPI that can provide incremental diagnostic value. There are three quantitative markers reviewed in Dr. Hung's article: transit ischemic dilation, stress-induced stunning, and stress-induced dyssynchrony. These markers compare the parameters of left-ventricular (LV) function between the stress and rest images, based on the concept that stress-induced myocardial ischemia can cause regional and global functional abnormalities. Transit ischemic dilation refers to a significant enlargement in LV size on the stress images as compared to the rest images. Stress-induced stunning refers to a significant reduction in LV ejection fraction (LVEF) from rest to stress. Stress-induced dyssynchrony refers to a significant increase in the LV dyssynchrony parameters measured by phase analysis from rest to stress. These markers have been shown as useful tools …