Could a man with a big belly stomach triggers false positive thalum nuclear stress result and show shadow or false blockage at lower side of heart.?

Doubtful . If dual isotopes are used this should not occur or if sestamibi is used for the stress images this should not occur however nuclear stress studies are only 93% accurate in any event.
Nuclear scan. It is possible for patients with different body shapes and sizes to affect their nuclear scans. For example women with large breasts and men with a large belly can influence the scan. It is best to follow with your cardiologist to review the results for you.