ASSESSMENT OF MYOCARDIAL VIABILITY IN PAT IENTS WITH CHRONIC MYOCARDIAL-INFARCTION BY F-18 FLUORO-D-GLUCOSE POSITRON EMISSION TOMOGRAPHY AND TC-99M-MIBI-SPECT

The determination of residual viability in regions of myocardial infar cts is of considerable clinical interest. In order to assess residual viability in regions with chronic myocardial infarction, 18 patients w ith anterior myocardial infarcts and 14 patients with inferior myocard ial infarcts as confirmed by ECG and cine ventriculography underwent T c-99m-methoxy-isobutyl-isonitrile single photon emission computed tomo graphy (MIBI-SPECT) and F-18-fluoro-D-glucose positron emission tomogr aphy (FDG-PET). Tracer uptake was quantified in 13 segments for each p atient (a total of 416 segments). MIBI uptake was normalized to the ma ximal uptake in the heart, FDG uptake was normalized to the maximal up take of left ventricular segments with normal contraction by cine vent riculography and without significant stenosis of the coronary artery s upplying this region. MIBI-SPECT scar and FDG-PET scar were defined as tracer uptake of less than 2.5 SD below mean values of a healthy cont rol group. Both methods scored 258 segments concordantly viable and 74 segments concordantly scar; 61 segments were scored scar by MIBI-SPEC T and viable by FDG-PET, 23 segments were scored viable by MIBI-SPECT and scar by FDG-PET (p < 0.0001). In patients with anterior myocardial infarction, 136 segments were scored viable and 53 segments were scor ed scar by both methods, 29 segments were scored scar by MIBI-SPECT an d viable by FDG-PET, 16 were scored discordantly viable by MIBI-SPECT and scar by FDG-PET (p < 0.06). In patients with inferior myocardial i nfarction, 122 segments were scored viable and 21 segments were scored scar by both methods, 32 segments were scored scar by MIBI-SPECT and viable by FDG-PET, 7 segments were scored discordantly viable by MIBI- SPECT and scar by FDG-PET (p < 0.0001). This study demonstrates that M IBI-SPECT and FDG-PET score about 80 % of the analyzed segments concor dantly as viable or scar. However in patients with inferior myocardial infarction MIBI-SPECT considerably underestimates residual viability.