LAUSR

Left ventricular (LV) mechanical dyssynchrony (MD) represents dyskinetic myocardium or myocardial scar tissue which ‘‘pushes outwards’’ during systole, and has been shown previously to be and independent marker of poor outcome. Dyssynchronous myocardium is deleterious twice over—the reduction in ejection fraction is further complicated by the inability of the myocardium to effectively increase LV end systolic pressure, accelerating negative remodeling and straining the remaining healthy muscle tissue. It is often associated with a prolonged QRS duration such as Left Bundle Branch Block, but as has been shown previously in the VALIANT study concentrating on heart failure patients, LVMD is associated with a poor prognosis even in patients with QRS duration \ 120 ms.In the post-MI population, LVMD was more closely associated with a poor prognosis than QRS width. It is a finding which is often described in Echocardiography (via 2D\3D speckle tracking), but can be quantified via analysis of phase histograms in gated SPECT myocardial perfusion imaging, in both rest and stress perfusion imaging. Regional samples of thickening and movement are obtained throughout the cardiac cycle, and the phase angle of initiation of contraction of the myocardium is calculated for each region and presented as distribution on a phase histogram. The bandwidth (width of the histogram, BW) represents synchrony or dyssynchrony—the higher the bandwidth, the more dyssynchronous the mechanical contraction. Dyssynchrony could also be represented on a phase polar map by the distribution the angles of initiation of contraction—the more heterogeneous are the angles (represented as SD), the greater the dyssynchrony. It is an automatic process which is highly reproducible and independent of the operator, unlike echocardiography. In this issue of the journal is published a small retrospective study by Xia Lu et al., in which the authors sought to demonstrate the prognostic capabilities of LVMD by SPECT imaging in a cohort of post-MI patients with LV aneurysm. Despite the small cohort, dyssynchrony, measured by histogram bandwidth ([ 90 ), was significantly associated with a poor outcome and a marker for cardiovascular mortality in patients with LV aneurysm. The authors further sought to better define the subgroup of patients who would most likely benefit from aneurysm resection surgery, a high-risk procedure which is rarely performed today due to perioperative mortality and morbidity. The authors have shown benefit in LV aneurysm patients who previously demonstrated LVMD per gated SPECT. They found that patients with LVEF B 25% and LVMD had higher mortality rate than patients with LVEF[ 25% and without LVMD. However, in this study it ought to be emphasized that none of the patients underwent CRT or CRTD during follow up which may influence outcome. Second, in most of the studies and publications regarding LVMD, the main predictor of outcome was increased SD and not HB as shown in this study. This may be related to wall motion variability in patients with LV aneurysm, who were the focus in this article. Reprint requests: Nili Zafrir, MD, FESC, FASNC, Department of Cardiology, Rabin Medical Center, Tel Aviv University, Petah Tikva, Israel; [email protected] J Nucl Cardiol 2022;29:661–2. 1071-3581/$34.00 Copyright 2020 American Society of Nuclear Cardiology.