Left ventricular function in response to dipyridamole stress: head-to-head comparison between (82)Rubidium PET and Tc-99m-sestamibi SPECT ECG-gated myocardial perfusion imaging

Myocardial perfusion imaging (MPI) with Tc-99m-sestamibi (sestamibi) SPECT and rubidium-82 (Rb-82) PET both allow for combined assessment of perfusion and left ventricular (LV) function. We sought to compare parameters of LV function obtained with both methods using a single dipyridamole stress dose. A group of 221 consecutive patients (65.2 +/- 10.4 years, 52.9% male) underwent consecutive sestamibi and Rb-82 MPI after a single dipyridamole stress dose. Sestamibi and Rb-82 summed rest (SRS), stress (SSS) and difference (SDS) scores, and LV end-diastolic (EDV) and end-systolic (ESV) volumes and left ventricular ejection fraction (LVEF) were compared. Bland-Altman analysis showed that with increasing ESV and EDV the difference between the two perfusion tracers increased both at rest and post-stress. The mean difference in EDV and ESV between the two perfusion tracers at rest could both be independently explained by the Rb-82 SDS and the sestamibi SRS. The combined models explained approximately 30% of the variation in these volumes between the two perfusion tracers (R-2 = 0.261, p = 0.005; R-2 = 0.296, p <0.001, for EDV and ESV respectively). However, the mean difference in LVEF between sestamibi and Rb-82 showed no significant trend post-stress (R-2 = 0.001, p = 0.70) and only a modest linear increase with increasing LVEF values at rest (R-2 = 0.032, p = 0.009). Differences in left ventricular volumes between sestamibi and Rb-82 MPI increase with increasing volumes. However, these differences did only marginally affect LVEF between sestamibi and Rb-82. In clinical practice these results should be taken into account when comparing functional derived parameters between sestamibi and Rb-82 MPI