Effect of stress testing on left ventricular mechanical synchrony by phase analysis of gated positron emission tomography in patients with normal myocardial perfusion

Purpose There are limited data on whether differences exist in left ventricular (LV) mechanical dyssynchrony indices derived from stress versus rest gated positron emission tomography (PET) in patients with normal myocardial perfusion imaging (MPI). Methods Stress/rest 82Rb gated PET was performed in consecutive patients with normal MPI between 2006 and 2010. Patients were divided into two groups: group 1 [LV ejection fraction (EF) ≥ 55% and QRS < 120 ms] and group 2 (LVEF ≤35%). Images were acquired on a dedicated PET scanner prior to and on a hybrid PET/CT system after November 2008. LV dyssynchrony indices [phase standard deviation (SD)° and SD (ms)] were derived from stress and rest gated images. Results There were 91 patients in group 1 (age 61±13, LVEF 66±8%, normal QRS) and 126 in group 2 (age 66± 12, LVEF 25±7%). The stress derived LVEF were significantly higher than rest for either group (p<0.0001). Patients with cardiomyopathy had significantly higher dyssynchrony indices compared to those with normal LVEF (rest SD° 49.2± 21.5° vs 16.8±7.8° and stress SD° 42.5±19.4° vs 12.4±3.7°, respectively, p<0.0001 for both). The dyssynchrony indices derived from rest gated images were significantly higher than those derived from stress in both groups (p<0.001 by unpaired and paired t test) and irrespective of the type of PET scanner utilized. Finally, 20/87 (23%) patients with normal LVEF and 27/66 (41%) of those with cardiomyopathy but without dyssynchrony based on stress indices were recategorized as having significant dyssynchrony given their resting indices. Conclusion LV mechanical dyssynchrony indices by phase analysis are smaller when derived from peak stress versus rest gated PET imaging in patients with normal MPI, irrespective of the resting LVEF.