Capabilities of gated myocardial perfusion imaging in detecting decreased myocardial blood flow reserve in patients with non-obstructive coronary artery disease

Introduction: In patients with non-obstructive coronary artery disease, decreased myocardial blood flow reserve (MBFR) is a key pathophysiologic link. Noninvasive assessment of microcirculatory status is available to a very limited number of institutions, in contrast to routine gated myocardial perfusion imaging (gMPI). Mechanical dyssynchrony (MD) is one of the promising additional index of gMPI, but nowadays there are very few data on its comparison with MFR by SPECT. Aim: To evaluate the potential of MD according to gMPI in identifying patients with decreased MBFR according to dynamic SPECT. Material and Methods. The study included 62 patients with non-significant (<50%) coronary artery stenosis according to multislice computed tomography (MSCT) coronary angiography. All patients underwent dynamic SPECT and routine gMPI with 99mTc-technetril. Myocardial blood flow indices at rest and stress, as well as MBFR were evaluated according to dynamic SPECT data. Perfusion indices (SSS, SRS, SDS) and MD indices HBW (phase histogram width, grad.) and PSD (phase histogram standard deviation, grad.) were assessed according to gMPI. Patients were then divided into 2 groups depending on myocardial blood flow reserve indices with a threshold value 2.0. Results. 30 patients were included in the group with reduced MBFR (MBFR<2.0) and 32 patients in the group with preserved MBFR (MFR ≥ 2.0). There was no difference in the main clinical and demographic parameters between the groups. The groups differed in all MD parameters: HBWrest, 64.8 (55.8; 86;4) and 50.4 (42.2; 57.6), p = 0.004; HBWstress, 64.8 (50.4; 93;6) and 50.4 (50.4;63.0), р = 0.03; PSDrest, 17.2 (13.5;22.4) and 12.9 (9.9;14.0), р = 0.01; PSDstress, 15.8 (13.7;23.0) and 12.9 (11.6;15.0), р = 0.01. The only independent predictor of decreased MBFR <2.0 was HBW at rest > 57.6o; OR 1.07; CI (1.01; 1.12); р < 0.001; AUC = 0.810. Conclusion. Mechanical dyssynchrony assessed by gMPI correlates with myocardial blood flow reserve according to dynamic SPECT in patients with non-obstructive coronary artery disease. The most pronounced association with MBFR has phase histogram bandwidth at rest. In patients with non-obstructive coronary artery disease, if HBW at rest is > 57.6o according to ECG-PCM, a reduced myocardial blood flow reserve can be suspected.