Repeatability and reproducibility of phase analysis of gated single-photon emission computed tomography myocardial perfusion imaging used to quantify cardiac dyssynchrony

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confidence: 99%

Left ventricular dyssynchrony assessment by phase analysis from gated PET-FDG scans

Pazhenkottil

Buechel

Nkoulou

et al. 2011

“…These indices are derived retrospectively from prior acquired and saved images, with no additional radiation burden or cost. They are automated, reproducible with small inter and intra-observer variability, 8 repeatable, 9 and have been validated against two 10 and three-dimensional echocardiography. 11 The initial application of the technique was in identifying the optimal patients with cardiomyopathy who would derive most benefit from cardiac resynchronization therapy.…”

Section: See Related Article Pp 1048-1056mentioning

confidence: 99%

Early post-stress LV dyssynchrony: A new marker for significant CAD

AlJaroudi

2014

Single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) remains one of the most commonly ordered tests for the detection of ischemia and significant coronary artery disease (CAD). 1 A coronary artery territory perfused by a significantly narrowed vessel has limited coronary flow reserve; hence, during peak stress, there are less blood flow and tracer uptake in that region as compared to normal myocardial. The detection of reversible perfusion defect, therefore, depends on the relative flow between myocardial territories. 2 In patients with multivessel disease, the coronary flow reserve is reduced in all territories leading to what has been described as balanced ischemia phenomenon. 3 The latter poses a challenge as patients with multi-vessel CAD may have ''normal'' MPI and could be miss-diagnosed or more commonly assumed to have less extensive CAD. 3 However, other complementary tools have helped recognize the presence of high ischemic burden even when the perfusion images say otherwise. Among them, transient ischemic dilation (TID), 4 increased lung uptake of 5 and left ventricular (LV) stunning (i.e., decrease in early post-stress LV ejection fraction [EF]). These tools, nevertheless, have limitations: the diagnostic accuracy of TID is low; Tl-201 is rarely used and has been replaced by Tc-99m; and LV stunning is often missed or underestimated since imaging with SPECT does not occur at peak stress giving enough time for LV recovery. 6 LV mechanical dyssynchrony indices have been proposed as additional tools to help detect myocardial stunning and ischemia-induced dyssynchronous contraction. The technique was developed by Chen 7 almost a decade ago. It calculates a phase value for each of sampled regions ([600) that represent the onset of mechanical contraction. The standard deviation (phase SD) and 95% bandwidth (histogram bandwidth) represent the LV dyssynchrony indices: the bigger the numbers, the greater the dyssychrony. These indices are derived retrospectively from prior acquired and saved images, with no additional radiation burden or cost. They are automated, reproducible with small inter and intra-observer variability, 8 repeatable, 9 and have been validated against two 10 and three-dimensional echocardiography. 11 The initial application of the technique was in identifying the optimal patients with cardiomyopathy who would derive most benefit from cardiac resynchronization therapy. 12 Since then, the technique proved not only to be a valuable tool in detecting mechanical dyssynchrony, but also providing prognostic information and risk stratifying patients with various co-morbidities (ischemic, 13 non-ischemic cardiomyopathy, 14 implantable defibrillators, 15 end-stage renal disease 16,17 ). More recently, the technique has been used to detect ischemiainduced myocardial dyssynchrony and multi-vessel CAD by comparing stress and rest indices [18][19][20] (Table 1).The concept of stress-induced changes in LV dyssynchrony is not new. In patients with normal MPI undergoing gated...

“…17 GMPI phase SD and BW have the advantage of being highly reproducible and repeatable. 18,19 Single center studies indicated GMPI phase parameters can help identify patients likely to respond to CRT, with GMPI SPECT providing additional information on location and extent of myocardial infarction/scarring, which together with location of the LV pacing lead predicts CRT response with positive predictive value of 96%. 20 Evaluation of RV function has been more difficult than the LV because of RV anatomy.…”

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confidence: 99%

“…Reproducibility of these RV techniques needs to be established, including inter-and intra-observer reproducibility, as has been done for LV parameters. 18,19 The longer half-life of F-18, relative to other PET tracers, is well suited to performing two acquisitions from a single injection. Also, correlations in this study between the time differential of RV septal to free wall contraction for PET versus echo is significant, but moderate at best.…”

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confidence: 99%

Ventricular asynchrony: A shift to the right?

Tosh

Nichols

2017

Evaluation of ventricular function has been a focus of nuclear medicine since 1971, when Zaret et al demonstrated that abnormalities of left ventricular (LV) wall motion and ejection fraction (EF) could be determined by injection of Tc-99m human serum albumen and acquiring images at end-diastole and end-systole. Multi-gated equilibrium radionuclide ventriculography (RNV) and first-pass imaging further refined characterization of LV asynergy and performance.2,3 Clinical trials soon showed that noninvasively determined LVEF was a strong predictor of survival in a broad range of heart diseases. 4,5 Further work demonstrated that synchronicity of LV contraction could be derived from RNV by Fourier analysis of pixel by pixel labeled RBC time-activity curves, assigning a phase to each pixel (percent of the R-R interval from 0°-360°) to identify time of maximum contraction.6 Synchronicity has important effects on LV performance: patients with inter-or intra-ventricular asynchrony have lower LVEF relative to normal control subjects.7 Mechanisms for reduced ventricular performance resulting from dyssynchrony remain unclear, but Sweeney et al suggested early-contracting segments stretch and deform later-contracting ones, and vice versa, expending energy in the process, resulting in lower rate of pressure rise, lower developed pressure, prolonged ejection, and reduced EF. 8 The most ubiquitous methods to measure asynchrony are by tissue doppler echocardiographic techniques, which use low frequency signals to measure myocardial wall deformation, and calculate strain, strain rate, delay in contraction of opposing LV walls (four basal LV segments on 4-chamber view), and dispersion of time to peak systolic contraction. 9Cardiac resynchronization therapies (CRT) were designed to improve LV synchronicity through optimally timed pacing (as determined by echo) of right ventricle (RV) and LV lateral walls. CRT promotes reverse remodeling, with improved EF and survival in heart failure patients. 10 However, clinical response to CRT (defined hemodynamically or as decrease in NYHA CHF class) occurs in only two-thirds of patients, prompting efforts to identify variables that would prospectively predict a positive CRT response. Multicenter studies (''Prospect'' and ''Rethinq'' trials) demonstrated large variability in performance of echo parameters, and their failure to predict CRT response, 11,12 which fostered the development of nuclear cardiology methods for dyssynchrony assessment.One nuclear approach to quantifying asynchrony used gated myocardial perfusion imaging (GMPI) SPECT data. 13 Because of partial volume effects, myocardial wall thickening varies linearly with systolic counts, 14 so that onset of mechanical contraction (OMC) in each LV myocardial pixel was defined as increase of systolic counts from baseline. Fourier analysis generated curves of OMC phase per pixel, plotted as frequency histograms, the standard deviation (SD) and bandwidth (BW) of which were quantified. A slightly different approach that imposes constant my...