A perfect tool for comprehensive evaluation of myocardial perfusion and function: Stress PET imaging

Abstract

Pharmacologic stress cardiac positron emission tomography (PET) is a highly advanced technique for myocardial perfusion imaging (MPI). In comparison with traditional single-photon emission computed tomography (SPECT), MPI with PET provides faster acquisition, better quality, less attenuation artifact, lower radiation burden, and more accurate quantitation of myocardial blood flow (MBF) and perfusion reserve (MPR). With all the advantages, MPI with PET brings higher diagnostic accuracy and more accurate risk stratification and decision-making to patients with known or suspected coronary artery disease (CAD). In addition, applying ECG-gating technique further enables MPI with PET to simultaneously assess left ventricular (LV) functions and synchrony not only at resting but also at peak-stress status. All of these myocardial substrates produce additional values in diagnosis and prognosis and also provide wonderful opportunities for researches on the pathophysiology mechanisms in patients with CAD and heart failure. In this issue of journal of nuclear cardiology, Juarez-Orozco et al used adenosine-stress N-13 ammonia PET to retrospectively study the relationship between traditional perfusion estimate with summed rest score (SRS, a surrogate of myocardial scar) and quantitative perfusion estimates with stress MBF (sMBF), rest MBF (rMBF), MPR, and peak-stress ventricular synchrony expressed as bandwidth (BW), standard deviation (SD), and entropy (E) in chronic heart failure patients referred for MPI with PET due to suspected myocardial ischemia. The authors found an inverse relationship between perfusion estimates and ventricular synchrony. However, quantitative estimates with sMBF, rMBF, and MPR were inferior to SRS for predicting ventricular mechanical synchrony in these patients. The authors further proposed that characterizing the fixed perfusion defects with SRS might be a more convenient approach for treatment in order to improve ventricular mechanical dyssynchrony. Interestingly, the same group had a similar study in which the enrolled patients were also referred for N-13 ammonia PET due to suspected myocardial ischemia but not limited to chronic heart failure; however, sMBF is better than MPR, SSS, and SRS in predicting peak-stress ventricular synchrony independently from other relevant cardiovascular risk factors and clinical covariates. The different results between the authors’ two studies might be caused by the more complicated mechanism of ventricular synchrony in patients with chronic heart failure and the further study is needed to answer this question. The relationship between myocardial perfusion status and LV mechanical synchrony had been well described in previous studies. Our previous study with SPECT showed that stress-induced myocardial ischemia caused dyssynchronous contraction in the ischemic region, deteriorating LV mechanical synchrony. Moreover, our study showed that LV dyssynchrony at stress was more significantly reduced than that at rest in Reprint requests: Guang-Uei Hung, MD, FANMB, Department of Nuclear Medicine, Chang Bing Show Chwan Memorial Hospital, No. 6, Lukong Road, Lukang Town, Changhua 505, Taiwan; [email protected] J Nucl Cardiol 2020;27:2243–6. 1071-3581/$34.00 Copyright 2019 American Society of Nuclear Cardiology.