RESUMO
UNLABELLED: This study was aimed at assessing the increase in left ventricular cavity volume in patients with induced stress ischemia, by the quantitative analysis of myocardial SPECT perfusion images obtained 30-45 min after 99mTc-Tetrofosmin injection. PATIENTS AND METHODS: 31 consecutive patients with suspected CAD (group A) and 16 low risk CAD subjects (group B) underwent the study. Global (GMPR) and regional myocardial perfusion reserve indices were assessed superimposing a 17 ROI mask on stress and rest bull's eye images. Ventricular cavitation index (VCI) was calculated manually, outlining the left ventricular cavity on stress and rest midventricular SPECT slices. L/H ratio was determined on anterior SPECT images. RESULTS: On the basis of perfusion patterns, group A was divided into two subgroups: subgroup 1 included the patients with reversible perfusion defects (n = 20) and subgroup B those with irreversible perfusion defects (n = 11). Average stress CI was significantly higher in group A than in group B (p < 0.01) and in subgroup 1 than in group B (p < 0.005). Rest CVI, GMPR and L/H ratio showed no significant intergroup differences. The stress VCI to rest VCI ratio (VCI ratio) was higher in subgroup 1 than group B (p < 0.0001) and in subgroup 1 than in subgroup 2 (p < 0.01). Moreover, VCI ratio was higher in group A than in group B. CONCLUSION: These preliminary data show that, in ischemic patients, left ventricular cavity volume increases after stress also in 99mTc-Tetrofosmin images. Since our images were acquired 30-45 min after stress, when the dilatation due to ventricular dysfunction is usually resolved, the volume increase may be caused by a cavitation effect due to reduced intracardiac blood flow.