Stunning and left ventricular function—How long is the ventricle knocked out?: Left ventricular function correlated with ischemic burden and recovery time after stress

Purpose Little is known about the relation between severity of ischemia and duration of myocardial stunning. The aim of this study was therefore to characterize the impact of ischemia on myocardial stunning and on its duration. Methods 310 patients (pts) who underwent myocardial perfusion SPECT (MPS) were evaluated. MPS acquired with a rest Thallium/stress Technetium-99m sestamibi protocol were scored with respect to % myocardium ischemic. Left ventricular post-stress ejection fraction (psEF) was evaluated by the widely used QGS™ algorithm. Resting LVEF (rEF) was assessed by invasive ventriculography. Patient groups were then compared with respect to different extents of ischemia and different time intervals between stress and imaging (≤ 60 min and > 60 min after stress). Results 21% of pts had a normal MPS, 8% had evidence of scar, 37% had evidence of ischemia, and 34% had evidence of scar plus ischemia. Pts with normal MPS had a significantly higher psEF than pts with ischemia, 61 ± 8% and 56 ± 8%, respectively (p = 0.006), whereas rEF was not different. Overall, pts with ≤ 10% myocardium ischemic had significantly higher psEF than pts with >10% myocardium ischemic, 53 ± 11% and 49 ± 9%, respectively (p = 0.006), whereas rEF was not different. In pts with evidence of ischemia who underwent imaging ≤ 60 min after stress testing, pts with ≤ 10% myocardium ischemic had higher psEF than pts with > 10% myocardium ischemic, 60 ± 7% and 53 ± 8%, respectively (p = 0.037). In contrast, pts with evidence of ischemia who underwent imaging > 60 min after stress testing had similar psEF irrespective of extent of ischemia (53% ± 8 in pts with ≤ 10% ischemia and 54% ± 8 in pts with > 10% myocardium ischemic, p = 0.12). Conclusions Ischemia had a significant impact on psEF in patients who underwent imaging less than 1 h after stress. More than one hour after stress testing stunning seems to be less relevant in the interpretation of psEF.