Post stress normal resting ejection fraction: a true normal resting ejection fraction?

Full text: Myocardial function parameters acquired 30-40 minutes post stress are generally regarded as being representative of resting myocardial function. In this paper we investigate the difference in the left ventricular ejection fraction between post stress gated acquisition and a true rest gated acquisition in patients with an otherwise normal myocardial perfusion study. In 16 patients gated myocardial perfusion SPECT images were acquired at rest and also at 30-40 minutes post stress (physical or pharmacological). All data was processed and analysed using automated quantitative gated SPECT software. Analysis of the difference in overall ejection fraction and in patient sub-groups was performed. Overall no significant difference was demonstrated between the rest and post stress ejection fraction (54.8% Vs 55.7%). Bland-Altman analysis did not demonstrate any absolute bias however there was a mean absolute variation of 4.4% in ejection fraction between rest and post stress. In a small subset (6 patients) who had undergone a stress test using exercise (5) or Dobutamine (1), there was a significant (P<0.01) reduction in ejection fraction (mean +/- SD) following stress (55.2 +/- 8.1) compared to rest (51.9 +/- 8.2). In patients with otherwise normal myocardial perfusion there is no significant difference in post stress and resting ejection although mean absolute variation of about 4.5% may be expected. In patients undergoing stress test which is likely to involve a significant change in haemodynamic parameters there appears to be some degree of post stress stunning evident at 30-40 minutes post stress. Copyright (2002) The Australian and New Zealand Society of Nuclear Medicine Inc