Background: The use of Rb positron emission tomography (PET) for the diagnosis of coronary artery disease (CAD) has increased in recent years but the role of some of the traditional parameters used in SPECT for the diagnosis of CAD, such as transient ischaemic dilation index (TID) of the left ventricle, have not been validated in PET studies.
Methods and results: We studied 95 patients who had undergone rest/pharmacological stress Rb PET scans. Thirty of these patients (18 female and 12 male) who had less than 5% likelihood of CAD (LLK) based on sequential Bayesian analysis, were used to determine the normal limits of TID index in this protocol. The remaining 65 patients (33 female and 32 male) underwent coronary angiography within 15 days of the cardiac PET scan. This second group of patients was used to validate the TID normal limits determined in the first group. In LLK patients mean TID index was 1.01+/-0.07 and there were no significant differences between genders. The TID index upper normal limit was 1.15 and was calculated as mean+2 SD. Using this cut-off point, TID index had high specificity and PPV in the diagnosis of single vessel CAD (100% and 100% respectively) and multiple vessel CAD (93% and 85%, respectively).
Conclusion: Our results indicate that elevated TID index is a specific, although not sensitive marker of single and multiple vessel CAD in pharmacologically stressed Rb PET myocardial perfusion studies.