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

Abstract

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 (1h after tracer injection) and delayed (4h 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.