Comparison of 18FDG PET with thallium SPECT in the assessment of myocardial viability. A segmental model analysis.

BACKGROUND In patients with myocardial infarction and left ventricular dysfunction, the evidence of myocardial viability is primordial. There are some methods to detect the presence of myocardial viability, 201 thallium reinjection SPECT protocol represents the most common radioisotopic technique to evaluate it. Positron emission tomography (PET) using FDG is considered the gold standard. The aim of this study was to compare globally and by segments the value of both techniques in the detection of viable myocardium. METHODS Twenty-three consecutive patients with previous myocardial infarction and left ventricular dysfunction were studied. All of them underwent into a SPECT perfusion scan and a FDG PET study to asses myocardial viability. Each study was performed in less than one week between the other. For the analysis, the myocardium was divided into 17 segments. A visual semi-quantitative analysis was carried out according to the following score indicating radiotracer uptake: O = normal to 4 = absent. Myocardial viability was defined as the presence of normal, mildly or moderately reduced radiotracer uptake. The scores obtained by PET were compared to those obtained in SPECT. A statistical analysis was performed using the SPSS v. 10. RESULTS 391 segments were analyzed. PET detected viability in 130 segments that had been defined as non-viable by SPECT. No differences in the analysis by vascular territories were found. Thirty percent of the segments that were defined as non viable by SPECT were viable by PET, meanwhile only 1% of the segments detected viable by SPECT were considered non viable with PET. CONCLUSIONS FDG PET study represents a better technique to detect myocardial viability, compared to thallium reinjection SPECT protocol. By this study we have demonstrated that more of 3 of each 10 studies may be diagnosed as non viable where viability is present.