Comparison of left ventricular function at rest and post-stress in patients with myocardial infarction: Evaluation with gated SPECT

Background. Quantitative electrocardiogram-gated single photon emission com puted tomography (SPECT) myocardial imaging (QGS) is a means of providing f unctional information about the left ventricle and myocardial perfusion. Ho wever, the functional information derived 30 minutes post-stress may be dif ferent from the left ventricular (LV) function determined at rest. This stu dy determined whether LV function post-stress would be different from LV fu nction at rest in patients with an earlier myocardial infarction. Methods and Results. LV perfusion and ejection fraction (LVEF), were determ ined by means of both the rest and post-stress acquisition in 58 patients w ith an earlier myocardial infarction and in 23 patients with a low likeliho od of coronary artery disease by using technetium-99m tetrofosmin and the Q GS program. The interobserver and intraobserver variability of LVEF was exc ellent, within a margin of 2%. No significant differences in LVEF were obse rved between post-stress and rest in the 23 patients with a low likelihood of disease (Delta LVEF, 0.04 % +/- 3.2%, P = not significant). Conversely, the patients with an earlier myocardial infarction showed a significantly l ower LVEF post-stress, compared with that at rest (Delta LVEF; -1.9% +/- 4. 2%, P =.002). In 33 patients (57%), the LVEF post-stress was 2% or more low er than the LVEF at rest. Furthermore, reversible ischemia, which was prese nt in 16 patients (28 %), did not interact with the Delta LVEF post-stress, compared with the Delta LVEF at rest (P = not significant). Parameters suc h as the stress modality (adenosine stress or exercise), the number of sten osed vessels, or the perfusion defect severity score did not influence the Delta LVEF post-stress, compared with the Delta LVEF at rest. Conclusions. In patients with an earlier myocardial infarction, LV function post-stress may not represent the true resting LV function. Consequently, this result justifies the stratification of patients before starting the ga ted SPECT study. In patients with an earlier myocardial infarction, the gat ed acquisition should be performed during the rest study.