Impact of accelerated washout of Technetium-99m-sestamibi on exercise tolerance in patients with acute coronary syndrome: single-center experience.

Technetium-99m-sestamibi (99mTc-sestamibi) single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) in patients with acute coronary syndrome (ACS) could be used to assess area-at-risks, as well as myocardial infarct or saved sizes. In patients with ACS, accelerated washout of 99mTc-sestamibi during early and delayed imaging in the acute phase may suggest mitochondrial dysfunction in the injured but salvaged myocardium. However, the link between 99mTc-sestamibi accelerated washout and exercise tolerance is unknown. The purpose of this study was to investigate a possible association between 99mTc-sestamibi accelerated washout and exercise tolerance in acute ACS patients as they progressed into the chronic phase. One hundred and sixty-five patients with ACS who underwent 99mTc-sestamibi SPECT MPI during the acute phase were recruited. On this basis, we calculated the total perfusion deficits (TPDs) for early (1 h after tracer injection) and delayed (4 h after tracer injection) images using automated quantification software. We then subtracted the early TPDs from the delayed TPDs to calculate the ΔTPD. We conducted a cardiopulmonary exercise test in acute and chronic phases. We divided two groups according to the median ΔTPD (the ΔTPD ≥ 4 group and the ΔTPD < 4 group) and compared anaerobic threshold (AT; ml/kg/min) between the groups. For anaerobic threshold (AT) improvement in data analysis, we employed multivariate logistic regression analysis. A total of 101 ST-segment elevation myocardial infarctions, 36 non-ST-elevation myocardial infarctions, and 28 unstable angina pectoris events were reported as ACS. From acute phase (10.8 ± 4.2 ml/kg/min) to chronic phase (11.9 ± 2.3 ml/kg/min), the AT in the ΔTPD ≥ 4 group was significantly increased (p < 0.0001). This trend was also seen in the ΔTPD < 4 group from acute (11.4 ± 1.8 ml/kg/min) to chronic phase (12.1 ± 2.2 ml/kg/min, p = 0.015). AT was lower in the ΔTPD ≥ 4 group in the acute phase (p = 0.027), but there was no difference in AT between the two groups in the chronic phase (p = 0.60). ΔTPD and the absence of diabetes were both independent predictors of AT improvement in multivariate logistic regression analysis. Receiver-operating characteristic curve analysis determined that ΔTPD = 6 was the best cut-off value, with 60.0% sensitivity and 71.4% specificity, respectively. The accelerated washout of 99mTc-sestamibi in patients with ACS during the acute phase could help to predict improvement in exercise tolerance in the chronic phase.