Assessment of left ventricular ejection fraction with quantitative gated SPECT: Accuracy and correlation with first-pass radionuclide angiography

BACKGROUND: Quantitative gated single photon emission computed tomography (SPECT [QGS]) software is widely used for the assessment of left ventricular ejection fraction (LVEF). Potentially confounding variables that may affect the accuracy of quantitative analysis of LVEF remain undefined. This study evaluated the accuracy of QGS as a means of determining LVEF in a wide range of LVEF values; evaluated the effect of extracardiac activity, count statistics, heart size, and perfusion defects on the accuracy of QGS LVEF; and compared QGS LVEF obtained at rest with that obtained after stress. METHODS AND RESULTS: QGS-derived LVEF was compared with rest first-pass radionuclide angiography (FPRNA) LVEF in 400 electrocardiographic-gated SPECT studies. The overall correlation between QGS and FPRNA LVEF was only fair (r = 0.66, SEE = 11.85%). In 35 of the patient studies (9%) with high extracardiac activity, the automated software failed, and no correlation was obtained. In the remaining 365 patient studies (91%), left ventricular contours were successfully identified. In these studies, correlation was better (r = 0.74, SEE = 9.77%). Agreement was better for images with high counts (r = 0.81, SEE = 8.66%) than for images with low counts (r = 0.61, SEE = 11.17%). Patient studies with abnormal LVEF had better correlation (r = 0.77, SEE = 6.4%) than studies with normal LVEF (r = 0.46, SEE = 10.2%). Agreement between QGS LVEF and FPRNA LVEF was better in hearts with large end diastolic volumes (>104 mL) than in hearts with small volumes. Overall, mean QGS LVEF was lower than mean FPRNA LVEF (54%+/-14% vs. 58%+/-14%, P<.0001). There was no difference between mean rest and stress QGS LVEF in the same patients, even in patients with stress-induced ischemia. CONCLUSIONS: QGS is a valuable method for assessing resting LVEF. However, QGS LVEF is often lower than FPRNA LVEF. Accuracy is affected by high extracardiac activity, low count density, and small size of the left ventricle.     

Comparison of interstudy reproducibility of equilibrium electrocardiography-gated SPECT radionuclide angiography versus planar radionuclide angiography for the quantification of global left ventricular function

BACKGROUND: Electrocardiography-gated single photon emission computed tomography (SPECT) radionuclide angiography (RNA) provides accurate measurement of both left ventricular (LV) ejection fraction (EF) and end-diastolic and end-systolic volumes. In this study we studied the interstudy precision and reliability of SPECT RNA as compared with planar RNA for the measurement of global systolic LV function. METHODS AND RESULTS: The population included 10 patients with chronic coronary artery disease having 2 sets of acquisitions, each consisting of planar and SPECT RNA. SPECT RNA was processed with SPECT-QBS and SPECT-35%. (For SPECT-35%, a manual segmentation method based on the 35% threshold of the maximum LV cavity activity is used to provide estimates of the number of voxels and the activity included in the LV cavity. The calculated LV number of voxels is then used to calculate LV volume measurement. The LV EF is calculated as the ratio of LV end-diastolic and end-systolic activity.) For LV EF, end-diastolic volume, and end-systolic volume, the interstudy precision, as reflected by the correlation coefficient, coefficient of variability, coefficient of repeatability, and within-subject coefficient of variation, and the interstudy reliability, as reflected by the intraclass correlation coefficient, were best with SPECT-35%, followed by planar RNA and then SPECT-QBS, respectively. The sample size needed to objectify a change in a parameter of LV function is lowest with SPECT-35%, followed by planar RNA and then SPECT-QBS, respectively. CONCLUSIONS: The SPECT-35% processing method provides excellent interstudy precision and reliability for LV function measurement. In this aspect it seems to be better than planar RNA and SPECT-QBS. These results need to be confirmed in a larger patient population.     

Stress-related variations in left ventricular function as assessed with gated myocardial perfusion SPECT

BACKGROUND: There is inconsistency in reported patient characteristics associated with differences in basal and poststress left ventricular function (delta ejection fraction [DeltaEF]) assessed by gated single photon emission computed tomography (SPECT). This inconsistency may therefore hamper adequate interpretation. In this study we first determined the reproducibility of serial gated SPECT-assessed left ventricular function. Second, we determined whether left ventricular ejection fraction (LVEF) assessed directly after stress reflects basal LVEF and, if not, what patient characteristics were associated with this discrepancy in LVEF. METHODS AND RESULTS: Serial reproducibility of technetium 99m tetrofosmin gated SPECT-assessed LVEF in 22 patients showed a mean difference between two sequential measurements at rest of 0.09% EF units, with a 95% limit of agreement (2 SDs) at 5.8% EF units. In 229 patients Tc-99m tetrofosmin gated SPECT was performed after stress and at rest. Independent predictors of DeltaEF were the presence of scintigraphically proven ischemia (standardized coefficient, -1.256; P =.003) and difference in heart rate at the time of acquisition (standardized coefficient, 0.121; P =.001). CONCLUSIONS: Gated SPECT-assessed LVEF at rest is reproducible under standard clinical conditions. However, LVEF assessed after stress does not represent LVEF at rest in patients with scintigraphically proven ischemia and in patients with increased heart rate after stress compared with heart rate at rest.     

Identification of exercise-induced left ventricular systolic and diastolic dysfunction using gated SPECT in patients with coronary artery disease

BACKGROUND: We investigated whether poststress left ventricular dysfunction in patients with coronary artery disease may be confirmed at 30 minutes after exercise using newly modified quantitative gated single photon emission computed tomography (QGS) software that can evaluate systolic and diastolic function. METHODS AND RESULTS: In this study 28 control subjects, 26 patients with angina pectoris (AP), and 27 patients with old myocardial infarction (MI) who had undergone revascularization were included. Same-day exercise/rest gated technetium 99m tetrofosmin single photon emission computed tomography was performed. QGS was used with a temporal resolution of 32 frames per R-R interval, and a left ventricular volume curve was reconstructed. From the fitted volume curve and its first derivative curve, we derived the ejection fraction (EF), peak ejection rate (PER), peak filling rate (PFR), and time to PFR (TPFR). In patients with AP and MI, the values for EF, PER, and PFR were lower after stress than at rest. TPFR was significantly prolonged in patients with MI after stress. In control subjects, EF, PER, PFR, and TPFR were not changed. CONCLUSIONS: Modified QGS software successfully indicated the changes in systolic and diastolic function. In patients with AP and MI, poststress systolic and diastolic dysfunction was identified 30 minutes after exercise.     

Gated SPECT assessment of left ventricular function is sensitive to small patient motions and to low rates of triggering errors: A comparison with equilibrium radionuclide angiography

BACKGROUND: Patient displacements and errors in R-wave detection are the main causes of inaccurate acquisition for gated single photon emission computed tomography (SPECT) and equilibrium radionuclide angiography (RNA). This study aimed to compare the influences of both factors between gated SPECT and RNA determinations of left ventricular ejection fraction. METHODS AND RESULTS: On gated SPECT and RNA acquisitions, recorded in 20 patients with coronary artery disease, we simulated the consequences of (1) 3-dimensional patient displacements of low (6.7 mm), moderate (13.4 mm), and high amplitude (20.1 mm) and (2) an erroneous triggering on T waves in 10% to 40% of recorded beats. Absolute values of left ventricular ejection fraction changes from baseline were higher with gated SPECT compared with RNA for patient displacements of low amplitude (5.0% +/- 3.8% vs 1.2% +/- 0.9%, P < .001) or moderate amplitude (10.0% +/- 6.2% vs 3.0% +/- 2.3%, P = .001) but not for patient displacements of high amplitude (12% +/- 9% vs 9% +/- 7%, P = not significant) and inaccurate triggering (for 20% T-wave triggering, 8.9% +/- 3.6% vs 7.9% +/- 3.0%; P = not significant). CONCLUSION: Contrary to RNA, gated SPECT is vulnerable to small patient displacements, and thus, specific efforts might be useful for limiting this potential cause of erroneous results. Both techniques may be affected by low rates of triggering errors, suggesting that small acceptance windows on cycle length should be recommended not only for RNA but also for gated SPECT.     

Assessment of left ventricular function by ECG-gated myocardial perfusion scintigraphy with image inversion technique: Comparison with equilibrium radionuclide angiography

BACKGROUND: Inversion of gated myocardial perfusion imaging has been proposed for the evaluation of left ventricular function. This study compared the results of inversion technique of gated left anterior oblique 45 degrees images (G-LAO 45 degrees) with those provided by equilibrium radionuclide angiography in the assessment of global left ventricular function in the same patients with suspected or known coronary artery disease. METHODS AND RESULTS: A total of 107 patients (85 men and 22 women, mean age 59 +/- 9 years) with suspected or documented coronary artery disease were studied. Eighty-seven underwent a 2-day stress/rest technetium-99m sestamibi single photon emission computed tomography with acquisition of G-LAO 45 degrees images on the day of rest, and 20 underwent thallium-201 stress/redistribution single photon emission computed tomography with G-LAO 45 degrees image acquisition immediately after redistribution imaging. An excellent correlation (P < .001) with no significant differences was found between left ventricular ejection fraction values provided by inversion G-LAO 45 degree and radionuclide angiography in 87 patients studied with Tc-99m sestamibi and 20 patients studied with TI-201. The Bland-Altman analysis demonstrated the difference in absolute ejection fraction values obtained by inversion G-LAO 45 degree images and radionuclide angiography as <8%. The inversion G-LAO 45 degrees left ventricular ejection fraction distinguishes the patients with myocardial infarction (ejection fraction = 43% +/- 13%) and without myocardial infarction (ejection fraction = 60% +/- 5%) (P < .001). In patients with left ventricular ejection fraction <40%, inversion G-LAO 45 degree images provide evaluation of left ventricular function comparable with that obtained by RNA. CONCLUSIONS: Semiautomated myocardial perfusion gated inversion technique analyzed with a count-based method is useful in the evaluation of left ventricular function and provides similar results to those of radionuclide angiography.     

Monitoring left ventricular function in small animals

Small animals such as mice and rats are extensively used to investigate the mechanisms and treatment of human cardiac diseases in vivo. The monitoring of left ventricular function is a key factor in this research. The measurement should be rapid, reproducible, and repeatable and allow the detection of subtle differences in function. Currently, echocardiography is most widely used in cardiac research laboratories for measuring left ventricular dimensions and function in small animals. Although the technique is rapid, the reproducibility of the calculations of left ventricular volumes is limited in some circumstances as a result of assumptions that do not necessarily hold true, such as in the setting of dilated, failing ventricles.     

Comparison of left ventricular function at rest and post-stress in patients with myocardial infarction: Evaluation with gated SPECT

BACKGROUND. Quantitative electrocardiogram-gated single photon emission computed tomography (SPECT) myocardial imaging (QGS) is a means of providing functional information about the left ventricle and myocardial perfusion. However, the functional information derived 30 minutes post-stress may be different from the left ventricular (LV) function determined at rest. This study determined whether LV function post-stress would be different from LV function at rest in patients with an earlier myocardial infarction. METHODS AND RESULTS. LV perfusion and ejection fraction (LVEF), were determined by means of both the rest and post-stress acquisition in 58 patients with an earlier myocardial infarction and in 23 patients with a low likelihood of coronary artery disease by using technetium-99m tetrofosmin and the QGS program. The interobserver and intraobserver variability of LVEF was excellent, within a margin of 2%. No significant differences in LVEF were observed between post-stress and rest in the 23 patients with a low likelihood of disease (DeltaLVEF, 0.04% +/- 3.2%, P = not significant). Conversely, the patients with an earlier myocardial infarction showed a significantly lower LVEF post-stress, compared with that at rest (DeltaLVEF, -1.9% +/- 4.2%, P =.002). In 33 patients (57%), the LVEF post-stress was 2% or more lower than the LVEF at rest. Furthermore, reversible ischemia, which was present in 16 patients (28%), did not interact with the DeltaLVEF post-stress, compared with the DeltaLVEF at rest (P = not significant). Parameters such as the stress modality (adenosine stress or exercise), the number of stenosed vessels, or the perfusion defect severity score did not influence the DeltaLVEF post-stress, compared with the DeltaLVEF at rest. CONCLUSIONS. In patients with an earlier myocardial infarction, LV function post-stress may not represent the true resting LV function. Consequently, this result justifies the stratification of patients before starting the gated SPECT study. In patients with an earlier myocardial infarction, the gated acquisition should be performed during the rest study.     

Serial assessment of left ventricular function during dobutamine stress by means of electrocardiographygated myocardial SPECT: Combination with dual-isotope myocardial perfusion SPECT for detection of ischemic heart disease

BACKGROUND: Technetium-labeled myocardial perfusion tracers allow simultaneous assessment of myocardial perfusion and left ventricular function by electrocardiography (ECG)-gated myocardial single photon emission computed tomography (SPECT). The purpose of this study was to evaluate left ventricular performance during dobutamine stress by means of ECG-gated myocardial perfusion SPECT with short-time data collection. METHODS AND RESULTS: After administration of Tc-99m sestamibi or tetrofosmin (600-740 MBq), 67 patients with ischemic heart disease, including 35 with prior myocardial infarction, were examined by ECG-gated myocardial perfusion SPECT at rest and during dobutamine stress (at dosages of 4, 8, 12, 16, and 20 microg/kg/min, with increments every 8 minutes). The ECG-gated data collection time was 5 minutes for each dobutamine dosage. After acquisition of gated SPECT data at the highest dose, thallium 201 chloride (111 MBq) was injected, and dual-isotope SPECT was also performed to assess the myocardial ischemia. In 32 patients without prior myocardial infarction, the sensitivity of individual stenosed-vessel detection with dual-isotope perfusion SPECT, with wall motion abnormality obtained from gated SPECT, and with the combined method was 55.9%, 52.9%, and 73.5%, respectively, based on coronary angiography. ECG-gated SPECT during dobutamine infusion revealed regional wall motion abnormalities (worsening or biphasic response) in 19 (57.6%) of 33 infarcted areas with culprit coronary arterial stenosis. The prevalence of reversible perfusion defects on dual-isotope SPECT was higher in segments with wall motion abnormalities than in segments with normal wall motion response (89.5% vs 42.9%, P <.02). CONCLUSIONS: Myocardial perfusion and left ventricular function during dobutamine infusion were analyzed in a single examination by means of the combined method. This procedure has the potential to provide comprehensive information with which to evaluate patients with ischemic heart disease.     

Three-dimensional registration of myocardial perfusion SPECT and CT coronary angiography

OBJECTIVE: In this study, we describe a new technique for three-dimensional registration of CT coronary angiography (CTCA) and gated myocardial perfusion SPECT. METHODS: Twelve patients with known or suspected CAD who underwent CTCA and gated SPECT were enrolled retrospectively. Coronary arteries and their branches were traced using CTCA data manually and reconstructed in three-dimensions. Gated SPECT data were registered and mapped to a left ventricle binary model extracted from CTCA data using manual, rigid and nonrigid registration methods. RESULTS: Three-dimensional reconstruction and volume visualization of both modalities were successfully achieved for all patients. All 3 registration methods gave better quality based on visual inspection, and nonrigid registration gave significantly better results than the other registration methods (p < 0.05). The cost function for three-dimensional registration using nonrigid registration (235.3 +/- 13.9) was significantly better than those of manual and rigid registration (218.5 +/- 15.3 and 223.7 +/- 17.0, respectively). Inter-observer reproducibility error was within acceptable limits for all methods, and there were no significant difference among the methods. CONCLUSION: This technique of image registration may assist the integration of information from gated SPECT and CTCA, and may have clinical application for the diagnosis of ischemic heart disease.     

Evaluation of left ventricular mechanical dyssynchrony as determined by phase analysis of ECG-gated SPECT myocardial perfusion imaging in patients with left ventricular dysfunction and conduction disturbances

Background  Cardiac resynchronization therapy (CRT) is approved for the treatment of patients with advanced systolic heart failure and evidence of dyssynchrony on electrocardiograms. However, a significant percentage of patients do not demonstrate improvement with CRT. Echocardiographic techniques have been used for more accurate determination of dyssynchrony. Single photon emission computed tomography (SPECT) myocardial perfusion imaging has not previously been used to evaluate cardiac dyssynchrony. The objective of this study is to evaluate mechanical dyssynchrony as described by phase analysis of gated SPECT images in patients with left ventricular dysfunction, conduction delays, and ventricular paced rhythms. Methods and Results  A novel count-based method is used to extract regional systolic wall thickening amplitude and phase from gated SPECT images. Five indices describing the phase dispersion of the onset of mechanical contraction are determined: peak phase, phase SD, bandwidth, skewness, and kurtosis. These indices were determined in consecutive patients with left ventricular dysfunction (n=120), left bundle branch block (n=33), right bundle branch block (n=19), and ventricular paced rhythms (n=23) and were compared with normal control subjects (n=157). Phase SD, bandwidth, skewness, and kurtosis were significantly different between patients with left ventricular dysfunction, left bundle branch block, right bundle branch block, and ventricular paced rhythms and normal control subjects (all P<.001) Peak phase was significantly different between patients with right ventricular paced rhythms and normal control subjects (P=.001). Conclusions  A novel SPECT technique for describing left ventricular mechanical dyssyn-chrony has been developed and may prove useful in the evaluation of patients for CRT. This study was funded in part by a research grant from the Medtronic-Duke Strategic Alliance, of which Dr Borges-Neto is the primary investigator.     

Comparison between ECTb and QGS for assessment of left ventricular function from gated myocardial perfusion SPECT

BACKGROUND: The most widely distributed software packages to compute left ventricular (LV) volume and ejection fraction (EF) from gated perfusion tomograms are QGS and the Emory Cardiac Toolbox (ECTb). Because LV modeling and time sampling differ between the algorithms, it is necessary to document relationships between values produced by them and to establish normal limits individually for each software package in order to interpret results obtained for individual patients. METHODS AND RESULTS: Gated single photon emission computed tomography technetium 99m sestamibi myocardial perfusion studies were collected and analyzed for 246 patients evaluated for coronary artery disease. QGS and ECTb values of ejection fraction (EF), end-diastolic volume (EDV), and end-systolic volume were found to correlate linearly (r = 0.90, 0.91, and 0.94, respectively), but EF and EDV were significantly lower for QGS than with ECTb (53% +/- 13% vs 61% +/- 13 and 102 +/- 45 mL vs 114 +/- 50 mL, respectively). To compare calculations for healthy subjects between the two software packages, data were also selected for 50 other patients at low likelihood for coronary artery disease, for whom EF and EDV were significantly lower for QGS compared with ECTb (62% +/- 9% vs 67% +/- 8% and 84 +/- 26 mL vs 105 +/- 33 mL, respectively). The ECTb lower limit was 51% for EF and the upper limits were 171 mL for EDV and 59 mL/m(2) for mass-indexed EDV, compared with limits of 44%, 137 mL, and 47 mL/m(2) for QGS. CONCLUSIONS: Although correlations were strong between the two methods of computing LV functional values, statistical scatter was substantial and significant biases and trends observed. Therefore, when both software packages are used at the same site, it will be important to take these differences into consideration and to apply normal limits specific to each set of algorithms.     

Impact of photon energy recovery on the assessment of left ventricular volume using myocardial perfusion SPECT

BACKGROUND: Photon energy recovery (PER) is a spectral deconvolution technique validated for scatter removal in patients and phantom studies. The purpose of this study was to examine the impact of PER on left ventricular volume measurement based on myocardial perfusion single photon emission computed tomography (SPECT). METHODS AND RESULTS: SPECT acquisitions were performed by use of a static cardiac phantom and in 25 patients after a rest injection of technetium 99m sestamibi by use of multiple energy windows (126-136, 137-144, and 145-154 keV). Data were successively reconstructed with and without PER, by use of iterative reconstruction and post-processing filtering (Butterworth filter; order, 5; cutoff, 0.30 cycles/pixel). Image contrast was evaluated in reconstructed data, and volumes were calculated by use of QGS. PER increased reconstructed image contrast from 62% +/- 2.7% to 84.3% +/- 5.7% in the phantom studies (P <.0001) and from 49% +/- 2% to 73% +/- 2% in patients (P <.0001). Although it remained underestimated (P <.0001), phantom volume was higher after PER correction compared with uncorrected data (50.9 +/- 0.8 mL vs 44.6 +/- 1 mL, P <.0001). The error in volume measurement was decreased by PER correction (16.6% +/- 1.3% vs 27% +/- 1.7% [uncorrected data], P <.0001). In patients, left ventricular volume increased from 83 +/- 10 mL to 91 +/- 10 mL (P <.0001), and the PER-induced volume increase was correlated with the image contrast increase (r = 0.61, P =.001). Finally, the percentage of volume increase was higher in patients with small left ventricular volumes. CONCLUSIONS: PER has a significant impact on image contrast and left ventricular volume measurement by use of perfusion SPECT. PER improves the accuracy of phantom volume assessment. In patients, volume increase is correlated to image contrast increase and is higher in those with small ventricles.     

Operator-interactive method for simultaneous measurement of left and right ventricular volumes and ejection fraction by tomographic electrocardiography-gated blood pool radionuclide ventriculography

BACKGROUND: A method that uses single photon emission computed tomography (SPECT) equilibrium radionuclide angiocardiography (ERNA) to measure right ventricular (RV) and left ventricular (LV) volumes (in milliliters) and ejection fraction (EF) is described. METHODS AND RESULTS: We recorded 35 paired SPECT ERNA and electron beam computed tomography (EBCT) cardiac studies in 27 patients; for comparison with EBCT, a method for measurement of RV and LV volumes and EF with SPECT ERNA was developed in 18 paired studies and was validated and assessed for reproducibility in 17. Validation indicated that SPECT ERNA and EBCT were similar for measurement of RV volume (end-systolic and end-diastolic volumes in a combined analysis) and EF (180+/-74 mL vs 182+/-80 mL and 0.44+/-0.11 vs 0.43+/-0.11, respectively) and for measurement of LV volume and EF (88+/-36 mL vs 84+/-43 mL and 0.53+/-0.081 vs 0.59+/-0.07, respectively). The SPECT ERNA method was quite reproducible. CONCLUSIONS: RV and LV volumes and EF can be measured readily via SPECT ERNA.     

Accuracy of the automated assessment of left ventricular function with gated perfusion SPECT in the presence of perfusion defects and left ventricular dysfunction: Correlation with equilibrium radionuclide ventriculography and echocardiography

BACKGROUND: Gated single photon emission computed tomography (SPECT) with automated methods allows the quantitative assessment of left ventricular function and perfusion; however, its accuracy must be defined for patients with large earlier infarctions and severe rest perfusion defects, in whom the estimation of endocardial and epicardial borders might be more difficult, even with automated edge-detection techniques. METHODS AND RESULTS: We prospectively compared the automated measurements of left ventricular ejection fraction (LVEF) and volumes from rest-injected gated Technetium 99m (Tc99m) perfusion SPECT with equilibrium radionuclide angiocardiography (ERNA) in 62 patients and the assessment of regional function with echocardiography in 22 patients. Forty-six patients had an earlier myocardial infarction (mean defect size, 34% of left ventricle; SD, 12.7%; range, 8% to 56%); 27 patients had large defects (> or = 20% of left ventricle; LVEF range, 8% to 75%). LVEF, as determined with Cedars-Sinai software (quantitative gated SPECT), correlated well with ERNA (r = 0.941; y = 1.003x + 1.15; P<.0001; SE of the estimate = 6.3%; mean difference -1.3% for LVEF) in the entire study population and in the subgroups of patients with an earlier infarction, severe defects, and large infarctions (> or = 20% of the left ventricle). A correlation existed between gated SPECT and ERNA volumes (r = 0.882, y = 1.040x - 14.7, P<.0001 for end-diastolic volume; r = 0.954, y = 1.147x - 13.9, P<.0001 for end-systolic volumes with the count-ratio technique), but with wider limits of agreement. The exact segmental score agreement between gated SPECT and echocardiography for regional function was 79.8% (281 of 352, kappa = 0.682). CONCLUSIONS: Automated gated SPECT provides an accurate assessment of ejection fraction and regional function, even in the presence of an earlier myocardial infarction with large perfusion defects and significant left ventricular dysfunction.     

Assessment of left ventricular mechanical dyssynchrony by phase analysis of ECG-gated SPECT myocardial perfusion imaging

Cardiac resynchronization therapy (CRT) has shown benefits in patients with severe heart failure. However, at least 30% of patients selected for CRT by use of traditional criteria (New York Heart Association class III or IV, depressed left ventricular [LV] ejection fraction, and prolonged QRS duration) do not respond to CRT. Recent studies with tissue Doppler imaging have shown that the presence of LV dyssynchrony is an important predictor of response to CRT. Phase analysis has been developed to allow assessment of LV dyssynchrony by gated single photon emission computed tomography myocardial perfusion imaging. This technique uses Fourier harmonic functions to approximate regional wall thickness changes over the cardiac cycle and to calculate the regional onset-of-mechanical contraction phase. Once the onset-of-mechanical contraction phases are obtained 3-dimensionally over the left ventricle, a phase distribution map is formed that represents the degree of LV dyssynchrony. This technique has been compared with other methods of measuring LV dyssynchrony and shown promising results in clinical evaluations. In this review the phase analysis methodology is described, and its up-to-date validations are summarized.     

Accuracy and repeatability of left ventricular systolic and diastolic function measurements using an ambulatory radionuclide monitor

The accuracy and repeatability of a new ambulatory radionuclide detector (VEST) for left ventricular systolic (ejection fraction) and diastolic (peak filling rate) measurements were assessed. Seventeen patients underwent equilibrium radionuclide angiography immediately before and immediately after a VEST study. The accuracy was evaluated at the beginning and at the end of the VEST studies. Limits of agreement for the ejection fraction were –1%: 2% at the beginning of the VEST study and –4% at the end. Limits of agreement for the peak filling rate were –0.6: 0.6 at the beginning of the VEST study and –0.7: 0.5 at the end. For both measurements the limits of agreement were well within the clinical range. Repeatability was evaluated in a second group of 11 patients who underwent VEST studies in 2 separate days. The coefficient of repeatability (twice the standard deviation of the differences between the 2 studies) was 13 for the ejection fraction and 0.4 for the peak filling rate. Thus, the VEST is an accurate and repeatable method to measure both the ejection fraction and peak filling rate. Offprint requests to: L. Pace, Sanseverino 5/A, 1-80128 Napoli, Italy     

彩色M型多普勒评价室壁肥厚患者左室舒张功能的临床研究

目的：探讨应用M型彩色多普勒评价室壁肥厚患者左室舒张功能的临床价值。方法：研究32例左室肥厚患者，包括肥厚型心脏病（HCM）10例、高血压性心脏病（HHD）Ⅱ期左室肥厚22例，正常对照（NC）20例，分别测量左室舒张早期血流播散速度（Vp）、E峰与Vp的比值（E／Vp）等指标。结果：室壁肥厚患者不论E／A〉1，还是E／A〈1，其Vp和E／Vp与对照值相比，均有显著性差异（P〈0．01）。结论：彩色M型多普勒无“假性正常化”现象，是评价左室舒张功能的可靠指标。     

Evaluation of left ventricular endocardial volumes and ejection fractions computed from gated perfusion SPECT with magnetic resonance imaging: Comparison of two methods

BACKGROUND: Two methods of computing left ventricular volumes and ejection fraction (EF) from 8-frame gated perfusion single photon emission computed tomography (SPECT) were compared with each other and with magnetic resonance (MR) imaging. METHODS AND RESULTS: Thirty-five subjects underwent 8-frame gated dual-isotope SPECT imaging and 12- to 16-frame gated MR imaging. Endocardial boundaries on short-axis MR images were hand traced by experts blinded to any SPECT results. Volumes and EF were computed with the use of Simpson's rule. SPECT images were analyzed for the same functional variables with the use of 2 automatic programs, Quantitative Gated SPECT (QGS) and the Emory Cardiac Toolbox (ECTb). The mean difference between MR and SPECT EF was 0.008 for ECTb and 0.08 for QGS. QGS showed a slight trend toward higher correlation for EF (r = 0.72, SE of the estimate = 0.08) than ECTb (r = 0.70, SE of the estimate = 0.09). For both SPECT methods, left ventricular volumes were similarly correlated with MR, although SPECT volumes were higher than MR values by approximately 30%. CONCLUSIONS: QGS and ECTb values of cardiac function computed from 8-frame gated perfusion SPECT correlate very well with each other and correlate well with MR. Averaged over all subjects, ECTb measurements of EF are not significantly different from MR values but QGS significantly underestimates the MR values.     

Left ventricular shape index assessed by gated stress myocardial perfusion SPECT: Initial description of a new variable

Background  Ventricular remodeling is predictive of congestive heart failure (CHF). We aimed to automatically quantify a new myocardial shape variable on gated myocardial perfusion single photon emission computed tomography (SPECT) (MPS) and to evaluate the association of this new SPECT parameter with the risk of hospitalization for CHF. Methods and Results  A computer algorithm was used to measure the 3-dimensional (3D) left ventricular (LV) shape index (LVSI), derived as the ratio of maximum 3D short- and long-axis LV dimensions, for end systole and end diastole. LVSI normal limits were obtained from stress technetium 99m sestamibi MPS images of 186 patients (60% of whom were men) (control subjects) with a low likelihood of CAD (<5%). These limits were tested in a consecutive series of 93 inpatients (85% of whom were men) having MPS less than 1 week after hospitalization, of whom 25 were hospitalized for CHF exacerbation. Variables associated with CHF hospitalization were tested by receiver operating characteristic curve and multivariate logistic regression analyses. LVSI repeatability was assessed in 52 patients with ischemic cardiomyopathy who had sequential stress MPS within 60 days after the initial MPS without clinical events in the interval between MPS studies. Control subjects had lower end-systolic and end-diastolic LVSIs compared with patients with CHF and those without CHF (P <.001). Receiver operating characteristic curve areas for the prediction of hospitalization as a result of CHF were similar for LV ejection fraction and end-systolic LVSI. End-systolic and end-diastolic LVSIs were independent predictors of CHF hospitalization by multivariate analysis; however, end-systolic LVSI had the greatest added value among all tested variables. Repeatability was excellent for both end-systolic LVSI (R2 = 0.85, P < .0001) and end-diastolic LVSI (R2 = 0.82, P < .001). Conclusion  LVSI is a promising new 3D variable derived automatically from gated MPS providing highly repeatable ventricular shape assessment. Preliminary findings suggest that LVSI might have clinical implications in patients with CHF. Supported in part by grants from Bristol-Myers Squibb Medical Imaging, Inc, Billerica, Mass, and Astellas Pharma US, Deerfield, Ill.