Left ventricular regional asynchrony: Earliest marker for ischemic cardiomyopathy?
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Division of Cardiology, Cook County Health, Chicago, IL Division of Cardiology, Rush Medical College, Chicago, IL
Received Aug 16, 2020; accepted Aug 17, 2020 doi:10.1007/s12350-020-02355-2
See related article, https://doi.org/10.10 07/s12350-020-02251-9 Left ventricular asynchrony (LVAS) refers to abnormal myocardial activation during a cardiac cycle resulting in non-homogeneous left ventricular contraction. Phase analysis of gated radionuclide tomography is an established technique to assess global and segmental LVAS.1,2 Two validated indices of LVAS include: histogram band width (HBW) which is the range (in degrees) during which 95% of the myocardium initiates contraction and phase standard deviation (PSD) which is the standard deviation (in degrees) of the timing of contraction of all the myocardial samples.3 LVAS is common in patients with heart failure and has been established as a prognostic marker of adverse outcomes.4 LVAS has the ability to predict clinical response to cardiac resynchronization therapy,5,6 and also predicts the risk of ventricular arrhythmias in patients with heart failure.7 Recent reports have assessed the diagnostic value of LVAS for predicting coronary artery disease (CAD) and associated myocardial hypoperfusion. Chen et al reported stress-induced myocardial ischemia to be associated with early poststress LVAS on gated rest/dipyridamole Thallium-201 SPECT.8 Huang et al further showed an incremental value of stress-induced LVAS on gated SPECT, to standard visual interpretation of myocardial perfusion. In their study the extent of LVAS was related to extent of epicardial coronary artery disease.9 Additional studies
Reprint requests: Saurabh Malhotra, MD, MPH, FASNC, Division of Cardiology, Cook County Health, Chicago, IL; saurabh.malhotra@ cookcountyhhs.org J Nucl Cardiol 1071-3581/$34.00 Copyright Ó 2020 American Society of Nuclear Cardiology.
have shown an improvement in LVAS with medical therapy10 and with revascularization.11 These observational studies provide evidence for relationship of LVAS with CAD and myocardial ischemia. Much of the experience with LVAS by phase analysis stems from gated SPECT, though extrapolation of these principles has led to application of phase analysis to gated positron emission tomography (PET).12 PET offers better spatial resolution, allows for list-mode acquisition, along with the assessment of myocardial blood flow. Real time imaging, immediately after vasodilator administration (as opposed to SPECT, where imaging is performed 4560 minutes after the vasodilator injection) allows for the determination of both rest and stress function and thus rest and stress LVAS. Van Tosh et al have previously studied the change in LVAS between rest and stress gated perfusion PET, and the presence of LVAS, improvement in LVAS and induction of LVAS to be related with myocardial blood flow (MBF) and myocardial flow reserve (MFR).13 In the current issue of the Journal, Van Tosh and colleagues have further investigated the presence and severity of LVAS on rest/stress
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