Can Stress-induced Phase Change be Observed on 99mTc Pharmacological Stress Myocardial Perfusion Imaging?

Background: Phase analysis of left ventricular contraction has incremental value for facilitating the diagnosis of cardiovascular disease using electrocardiography-gated myocardial perfusion imaging (MPI). However, it is unclear whether phase analysis aids the diagnosis of ischemic heart disease using technetium-99m (99mTc)-labeled perfusion agents under pharmacological stress. As pharmacological stress does not usually induce “true” ischemia, and 99mTc MPI is generally performed about one hour after the initiation of stress testing, it is questionable whether phase deterioration can be measured in such conditions.Methods: We retrospectively analyzed the cases of 61 consecutive patients who underwent adenosine stress/rest MPI using 99mTc-labeled perfusion agents. Phase parameters [bandwidth, phase standard deviation (PhaseSD), and entropy] were evaluated using automatic analysis software (cardioREPO). All parameters were assessed both under stress and at rest. The changes (delta) in the phase parameters between the stress and resting conditions were also measured.Results: The patients were separated into those without and with ischemia. Stress bandwidth (46.2±13.0 vs 73.2±41.2, respectively), stress PhaseSD (11.7±3.2 vs 18.2±10.5), stress entropy (0.46±0.06 vs 0.53±0.12), rest PhaseSD (9.4±3.0 vs 12.5±6.4) and rest entropy (0.42±0.07 vs 0.46±0.10) and the delta bandwidth (6.49±11.88 vs 23.58±28.04) and delta PhaseSD (2.29±3.11 vs 5.78±6.89) values exhibited significant differences between the two groups although there were large overlaps between the two groups.Conclusions: On 99mTc MPI performed under pharmacological stress, some minor left ventricular contraction phase changes were observed.