The Evaluation Criteria in Diagnosing Ischemia with Stress and Rest Myocardial Perfusion Gated SPECT

The study named " The role of myocardial perfusion gated SPECT study in women with coronary artery disease " reveals some current and important issues in diagnosing myocardial ischemia in women (1). Because the obesity is the highest and the death from coronary artery disease (CAD) is the second highest in Turkish women among all European countries, diagnosing CAD in women becomes much more important in daily cardiology and nuclear cardiology practice in our country. We have to pay more attention in clarifying the gender-related differences in nuclear cardiology. This study raises awareness about the issue. On the other hand the evaluation criterion for diagnosing ischemia seems controversial in the study. The question is that: " Do the left ventricular (LV) wall motion abnormality and decreased systolic thickening at the segment with reduced perfusion in gated SPECT study necessarily show true ischemia as it is expressed in the study? This approach considers that wall motion abnormality and perfusion defects occur exactly at the same time in CAD stages, but as it is known, wall motion abnormalities follow quite a bit later after the perfusion defects appear. Myocardial hypoperfusion is first seen in ischemic cascade, and followed by decrease in metabolic activity, relaxation impairment (diastolic dysfunction), reduction in contractility (systolic dysfunction), global LV dysfunction, ECG changes and angina pectoris, respectively (2). So, the evaluation criterion in the study is true for the advanced stages of ischemia, but not in the beginning of the disease. In the beginning, ischemia may be seen with completely normal wall motion and systolic thickening. So, the approach in the study neglects the ischemic patients with normal cardiac wall motions. More importantly, because the imaging begins 30-60 minutes after the radiopharmaceutical injection, stress– gated images with Tc-99m MIBI show stress perfusion at the time of injection, but LV function (wall motion, systolic thickening or ejection fraction) at the time of acquisition. Snapper et al. demonstrated that the combination of a perfusion defect with normal wall motion and thickening in the same segment on stress-gated MIBI images was associated with a high positive predictive value (96%) for detecting ischemia. They concluded that the diagnosis of ischemia could be made confidently in patients with normal wall thickening in a segment with perfusion defect. The lack of wall thickening was found less specific, because only 40% of the cases with perfusion defects and wall motion abnormalities showed reversibility on rest …