Prognostic value of gated spect in patients with left bundle branch block

Background  The aim of this study was to assess the prognostic value of quantitative gated technetium 99m tetrofosmin single photon emission computed tomography (SPECT) imaging in patients with left bundle branch block (LBBB). Methods and Results  We followed up 101 consecutive patients with LBBB using Tc-99m tetrofosmin gated SPECT imaging. The mean follow-up was 1.24 years (maximum, 2.48 years). Hard endpoints were all-cause death and acute myocardial infarction. Event-free survival curves were obtained. Optimal cutoff points for left ventricular (LV) volumes and LV ejection fraction (EF) to predict outcome were determined by receiver operating characteristic curve analysis. Of the patients, 94 had an abnormal study. Fifteen hard events occurred (thirteen deaths). Perfusion abnormalities were similar for patients with or without events. For LV function parameters, the survival curves were maximally separated when we used cutoff values of 160 mL or greater for end-diastolic volume (P ± .019 and hazard ratio [HR] of 1.04 for hard events, P ± .024 and HR of 1.04 for all-cause death), 100 mL or greater for end-systolic volume (P ± .043 and HR of 1.04 for hard events, P ± .062 and HR of 1.04 for all-cause death), and lower than 35% for LVEF (P ± .013 and HR of 0.81 for hard events, P ± .047 and HR of 0.81 for all-cause death). Conclusion  By use of quantitative gated SPECT imaging, LBBB patients with an end-diastolic volume of 160 mL or greater, end-systolic volume of 100 mL or greater, or LVEF lower than 35% are at increased risk for subsequent cardiac events. (J Nucl Cardiol 2007;14: 75–81.)     

Decreased septal wall thickening in patients with left bundle branch block

OBJECTIVES: Septal wall motion abnormalities are frequently observed in patients with left bundle branch block (LBBB). However, septal wall thickening in LBBB patients has not been thoroughly evaluated. METHODS AND RESULTS: To investigate the relationship between septal wall motion and wall thickening, we studied 31 normal control subjects, 24 LBBB patients with normal wall motion (LBBB-NWM), and 24 LBBB patients with septal dyssynchrony (LBBB-SDS), all with a low likelihood (<15%) of coronary artery disease. The septal and lateral quadrants of the left ventricle were analyzed in stress 8-frame gated technetium 99m sestamibi tomograms. The percent wall thickening was calculated by use of a 25-segment polar map with the p-FAST software program by two independent methods: the regional count density increase from end diastole to end systole (CD method) and the geometric increase in the distance between the 50% thresholded endocardial and epicardial borders from end diastole to end systole (GD method). In addition, the ratio of septal/lateral percent wall thickening was calculated. The relative septal wall thickening in the entire LBBB population was decreased as compared with the normal control subjects (0.35 +/- 0.37 vs 0.81 +/- 0.17, P <.001). Decreased wall thickening was observed in not only LBBB-SDS patients but also to a lesser degree in LBBB-NWM patients (0.12 +/- 0.35, P <.001; 0.57 +/- 0.24, P =.005, respectively). This abnormality was most apparent when the CD method was used. CONCLUSIONS: Septal wall thickening is decreased in patients with LBBB even with normal wall motion. LBBB per se may compromise septal wall thickening, and dyssynchronous wall motion results in further deterioration of wall thickening.     

Left bundle branch block and coronary artery disease: Accuracy of dipyridamole thallium-201 single-photon emission computed tomography in patients with exercise anteroseptal perfusion defects

Background  Reduced septal or anteroseptal uptake of thallium-201 during exercise is frequently observed in patients with left bundle branch block (LBBB) even in the absence of left anterior descending (LAD) coronary artery disease. The purpose of this study was to evaluate prospectively the accuracy of dipyridamole²⁰¹TI single-photon emission computed tomography (SPECT) in detecting LAD coronary artery disease in patients with LBBB and septal or anteroseptal perfusion defects on exercise²⁰¹TI SPECT. Methods and Results  Twelve consecutive patients (10 men and two women) with complete LBBB and septal or anteroseptal perfusion defects on exercise²⁰¹TI SPECT underwent dipyridamole²⁰¹TI SPECT. The delay between dipyridamole and exercise was 2 to 30 days. Coronary angiography was performed during this period in all patients. Six (50%) of 12 patients with exercise perfusion defects showed normal perfusion after dipyridamole; all had normal coronary angiograms. The remaining six patients also had positive results of dipyridamole studies, two with moderate and four with severe septal or anteroseptal perfusion defects. Coronary angiography showed significant (>50%) LAD coronary artery stenosis in three patients; three patients with severe septal or anteroseptal perfusion defects after dipyridamole had normal coronary angiograms. Neither the evaluation of apical involvement nor the presence of dilated ventricles, decreased left ventricular ejection fraction, or wall motion abnormalities could help to identify (or explain) false-positive results. Conclusion  This study confirms that dipyridamole is more accurate than exercise in excluding LAD coronary artery disease. However, there are still false-positive results and the severity of the septal or anteroseptal perfusion defect does not add additional information to identify LAD coronary artery disease. Coronary angiography is thus necessary for positive dipyridamole study results to identify coronary artery disease as a major prognostic factor in patients with LBBB.     

The expanding role of left ventricular functional assessment using gated myocardial perfusion SPECT: the supporting actor is stealing the scene

Background Gating of single-photon emission computed tomography (SPECT) has significantly improved the reliability and diagnostic accuracy of myocardial perfusion imaging. The functional parameters derived from this technique, mainly left ventricular volumes and ejection fraction, have been demonstrated to be accurate and reproducible. They are able to increase the detection of severe and extensive coronary artery disease and show a significant incremental prognostic power over perfusion abnormalities. Therefore, the importance given to gated SPECT functional data has progressively grown. Discussion This circumstance has further expanded the indications for myocardial perfusion imaging and strengthened its position among the different imaging modalities. Moreover, several studies show that the evaluation of ventricular function may have a leading part in justifying the execution of perfusion scintigraphy in various clinical conditions. Aim Aim of this review is to describe this evolution of gated SPECT functional assessment from a supporting rank with respect to perfusion, to a main actor position in the field of cardiac imaging.     

Prognostic value of stress myocardial perfusion single photon emission computed tomography imaging in patients with left bundle branch block

Background. Left bundle branch block (LBBB) may occur with or without structural heart disease. In patients with coronary artery disease the presence of LBBB is associated with an increased risk of cardiovascular events.Methods and Results. This study examined the outcome of 293 medically treated patients with LBBB and symptoms who were undergoing stress thallium-201 single photon emission computed tomography imaging. One hundred seventy-three men and 120 women with an age range of 67 ± 9 years and a pretest probability of coronary artery disease of 77% ± 28% were studied. During a mean follow-up of 33 months 58 hard cardiac events (death or nonfatal myocardial infarction) and 112 total events (hard events, coronary angioplasty, coronary bypass surgery, or cardiac transplantation) occurred. Univariate and multivariate Cox survival analysis with clinical, stress, hemodynamic, and single photon emission computed tomography variables identified the perfusion defect size (chi SQUARE = 27, p = 0.0001) and increased lung thallium uptake as the most important independent predictors of hard or total cardiac events. The hard event-free survival rate was 91% in patients with no or small defects (<15% of left ventricular myocardium) and 72% in patients with large defects (p = 0.0001, RR = 3.2, 95% CI 1.7 to 5.9). The total event-free survival rate was 81% in patients with small defects and 48% in patients with large defects (p = 0.0001, RR = 2.7, 95% CI 1.9 to 4.0). The total event rate was 54% in patients with large perfusion defects and increased lung uptake and 17% in patients with no or small abnormality and normal lung thallium uptake (p = 0.0001).Conclusion. Single photon emission computed tomography perfusion imaging is useful in predicting outcome in patients with LBBB and intermediate pretest probability of coronary artery disease. The size of perfusion abnormality and lung thallium uptake stratified patients into high and low risk groups with a threefold difference in hard and total cardiac events.     

Prognosis in patients with left bundle branch block and normal dipyridamole thallium-201 scintigraphy

Background  The presence of complete left bundle branch block (LBBB) is commonly associated with a poorer prognosis, especially in patients with coronary artery disease (CAD). In the general population with suspected CAD and normal intraventricular conduction, a normal dipyridamole-thallium scintigraphy is a strong marker of a favorable outcome. Objective  Our objective was to assess the prognosis in patients with LBBB and a normal dipyridamole thallium-201 scintigram. Population and methods  Patients with complete LBBB and normal myocardial perfusion on dipyridamole SPECT thallium-201 scintigraphy performed in our center for suspected CAD between 1988 and 1995 were monitored for clinical events. Results  Sixty-nine patients (36 women and 33 men) with a mean age of 59 years (range 56 to 61) were monitored for a mean period of 33 months (range 25 to 35). During this period, 4 patients had unstable angina, 2 of whom underwent myocardial revascularization. There were no deaths or myocardial infarction. All events occurred at least 2 years after the thallium-201 scintigraphy. Conclusion  The presence of a normal myocardial perfusion with dipyridamole thallium-201 scintigraphy in this group of patients with suspected CAD and LBBB was associated with a very good prognosis, a low rate of clinical events occurring only 2 years after the myocardial scintigraphy, and no hard events.     

Compared with 3-dimensional analysis, 2-dimensional gated SPECT analysis overestimates left ventricular ejection fraction in patients with regional dyssynchrony

BACKGROUND: Left ventricular (LV) ejection fraction (EF) is a powerful prognostic predictor in patients with heart disease. However, LVEF calculated by 2-dimensional (2D) modalities such as echocardiography by use of the "modified" Simpson's rule may be incorrect in patients with regional dyssynchrony, presumably because regions of dyssynchrony are excluded from analysis. METHODS AND RESULTS: To elucidate the difference between 2D and 3-dimensional (3D) methods with regard to LVEF calculation in patients with regional dyssynchrony, we compared LVEF derived from 8-frame gated technetium 99m sestamibi stress perfusion tomograms using commercially available 2D single photon emission computed tomography (SPECTEF) software that uses the modified Simpson's rule, 3D QGS, and investigational 3D p-FAST software in 136 left bundle branch block patients. Twenty-four patients had normal wall motion, whereas one hundred twelve showed septal dyssynchrony. Bland-Altman plots demonstrated that compared with QGS and p-FAST, SPECTEF overestimated LVEF in patients with septal dyssynchrony systemically by 8.6% and 11.3%, respectively. CONCLUSIONS: We conclude that compared with 3D modalities, 2D modalities that use the modified Simpson's rule, such as SPECT EF, overestimate LVEF in patients with dyssynchronous septal wall motion. Therefore 3D modalities are preferred to evaluate patients with regional dyssynchrony.     

Thallium-201 myocardial SPECT in a patient with mirror-image dextrocardia and left bundle branch block

A 53-year-old male patient with a previous diagnosis of situs inversus with mirror-image dextrocardia underwent thallium-201 (Tl-201) stress-redistribution myocardial perfusion single photon emission computed tomography (SPECT). Electrocardiogram (ECG) obtained on right hemithorax revealed constant complete left bundle branch block. Tl-201 stress-redistribution SPECT images revealed abnormal perfusion with reversible ischemia in the anteroseptal, septal and inferoseptal walls. Coronary angiography performed 1 month after SPECT study was normal. This case illustrates that false positive reversible perfusion defects can be seen in patients with mirror-image dextrocardia associated with constant complete left bundle branch block. To our knowledge, this is the first reported case of mirror-image dextrocardia and constant complete left bundle branch block with false positive Tl-201 SPECT findings.     

Thallium-201 myocardial SPECT in left bundle branch block: Diagnosis of myocardial ischemia with a disease-specific reference database

Background  The aim of this study was to assess the value of a myocardial perfusion single photon emission computed tomography (SPECT) reference file for patients with left bundle branch block (LBBB). Methods and Results  Tl-201 stress-redistribution myocardial perfusion SPECT studies of patients with complete, permanent LBBB were reviewed retrospectively. To develop a reference database, 18 patients with a low likelihood of coronary artery disease (CAD) were selected. Left ventricular regional average and standard deviation (SD) values of the reference file images were calculated. The diagnostic performance was tested on perfusion images of 49 patients with LBBB, undergoing both scintigraphic and coronary angiographic evaluation, and was compared with a commercial quantitative analysis system using a general reference database. The LBBB reference file performed significantly better in detecting epicardial CAD than did the general reference database (receiver operating characteristic area under the curve 0.835 ± 0.06 vs 0.580 ± 0.08, p < .01). Disease localization also was improved significantly in the territory of the left anterior descending and of the right coronary arteries. Conclusions  The use of a reference file of patients with LBBB and a low likelihood of CAD aids the detection and the localization of myocardial ischemia on Tl-201 myocardial SPECT images of this patient group. The authors thank Professor Mátyás Keltai MD and István Szilvási MD for valuable discussions. The authors also thank József Turák (Mediso Ltd., Budapest, Hungary) for providing technical information on the Interview image processing system.     

Segmental myocardial velocities in dilated cardiomyopathy with and without left bundle branch block

Purpose:

To quantify three‐directional left ventricular (LV) myocardial velocities and intraventricular synchrony in dilated cardiomyopathy (DCM) with and without left bundle branch block (LBBB) using MR tissue phase mapping (TPM).

Materials and Methods:

Regional velocities were assessed by TPM (spatial/temporal resolution = 1.3 × 1.3 mm² × 8 mm/14 ms) in DCM patients with (n = 12) and without LBBB (n = 7) compared with age‐matched volunteers (n = 20). For the evaluation the AHA 16‐segment and an extended LV visualization model was used.

Results:

Radial velocities in DCM patients were reduced in 75% (systole) and in 94% (diastole) (P = 0.0001 – P = 0.0360), long‐axis velocities in 31% (systole) and in 75% (diastole) of the 16 segments compared with controls (P = 0.0001 – P = 0.0310). LBBB resulted in inferolaterally delayed diastolic long‐axis velocities (P = 0.0012 – P = 0.0464) and shortened TTP for septal systolic radial velocities (P = 0.0002). Intra‐ventricular radial systolic TTP differed up to 150 ms between segments in patients with LBBB (89 ms without LBBB, 34 ms in volunteers) reflecting an increased dyssynchrony. LV twist was altered in all patients with reduced and delayed systolic and diastolic peak velocities.

Conclusion:

TPM identified previously not described alterations of the spatial distribution and timing of all myocardial velocities in patients with DCM and LBBB. This may help to optimize therapy management in future. J. Magn. Reson. Imaging 2013;37:119–126. © 2012 Wiley Periodicals, Inc.     

Intravenous dipyridamole thallium-201 SPECT imaging in patients with left bundle branch block

Tl-201 exercise imaging in patients with left bundle branch block (LBBB) has proven to be indeterminate for significant left anterior descending (LAD) coronary artery stenosis because of the presence of immediate septal perfusion defects with redistribution on delayed images in almost all cases. Tl-201 redistribution occurs regardless of the presence or absence of LAD stenosis. Nineteen patients having LBBB were evaluated with dipyridamole Tl-201 SPECT. Fourteen of these subjects had normal dipyridamole Tl-201 SPECT imaging. Three patients had normal coronary angiograms. None of the remaining 11 patients with normal dipyridamole Tl-201 SPECT images was found to have clinical coronary artery disease in a 5-11 month follow-up period. Five patients had abnormal septal perfusion. Four underwent coronary angiography. One had a significant LAD stenosis. The single patient with septal redistribution who refused to undergo coronary angiography died shortly thereafter of clinical coronary artery disease. This preliminary work suggests that dipyridamole Tl-201 SPECT may be more useful for excluding LAD stenosis in patients with LBBB than Tl-201 exercise imaging.     

Myocardial scintigraphy with thallium-201 and technetium-99m-hexakis-methoxyisobutylisonitrile in left bundle branch block: a study in patients with and without coronary artery disease

In left bundle branch block (LBBB) thallium-201 myocardial scintigraphy frequently reveals septal abnormalities in the absence of coronary artery disease (CAD) and gives rise to false-positive results in patients with suspected CAD. It has not yet been clarified which pathophysiological mechanism is responsible for these perfusion abnormalities. A total of 66 patients with constant LBBB were investigated with ²⁰¹T1 or technetium-99m-hexakis-methoxyisobutylisonitrile (MIBI), 62 underwent coronary angiography. Of 12 patients without left anterior descending artery (LAD) or right coronary artery (RCA) stenoses, 11 had a reversible septal activity deficit after ²⁰¹T1 stress injection, whereas 20 of 22 patients without relevant CAD showed a constant stress/rest septal deficit using MIBI. Regarding patients with significant LAD and/or RCA stenoses, both radiopharmaceuticals almost always showed a reversible septal deficit: with ²⁰¹T1 in 15 of 16 individuals and with MIBI in 14 of 15. In 12 patients ²⁰¹T1 was reinjected at rest. In those who had LAD or RCA stenoses (n = 5), early septal activity uptake after stress injection was poorer than that after rest injection; in the absence of CAD (n = 7), septal stress uptake corresponded with that of rest injection. It is concluded that septal perfusion abnormalities in LBBB and the absence of CAD are characterized by an exercise-independent reduction of septal blood flow per mass of viable myocardium and that stress/rest injection protocols of myocardial perfusion tracers are able to differentiate between LBBB with and without CAD.Dedicated to Prof. Dr. Dr. h.c. H. Hundeshagen on the occasion of his 65th birthday Correspondence to: W.H. Knapp     

Thallium-201 gated single-photon emission tomography for the assessment of left ventricular ejection fraction and regional wall motion abnormalities in comparison with two-dimensional echocardiography

Simultaneous assessment of myocardial perfusion and function by gated single-photon emission tomography (GS) after a single tracer injection provides incremental information and is feasible with technetium-99m sestamibi. The present study validated the use of GS with thallium-201 for the assessment of left ventricular ejection fraction (LVEF) and regional wall motion by comparison with two-dimensional (2D) echocardiography (echo), which has not been done before. After injection of 111 MBq ²⁰¹Tl at peak bicycle exercise (n=55) or pharmacological stress (n=17), GS was acquired 15 (post stress) and 120 min post injection (rest) on a double-head camera. An automatic algorithm (QGS) was used for processing. Echo (Acuson Sequoia C256) was performed immediately after rest GS. LVEFs assessed by GS and echo were correlated. The overall and segmental sensitivity and specificity of GS for the detection of regional wall motion abnormalities (WMAs) were calculated, echo serving as the gold standard. Perfusion abnormalities were scored. The success rate of the automatic algorithm was 100%, and visually assessed image quality was good to excellent in 88% of cases. Post-stress and rest LVEF as assessed by GS were highly correlated (r=0.91). Good correlations were obtained between post-stress LVEF (GS) and rest LVEF (echo) and between rest LVEF (GS) and rest LVEF (echo) (r=0.76 and 0.86 respectively). In patients with a reduced LVEF of less than 50% (n=23), these correlations were even better (r=0.84 and 0.89 respectively). Regional wall motion abnormalities (WMAs) were identified by GS with high sensitivity and specificity (88%–100% and 82%–98% respectively) and were directly related to the extent and severity of stress as well as of resting perfusion defects. It is concluded that GS with ²⁰¹Tl is a feasible and reliable tool for the evaluation of patients with compromised left ventricular function in the context of coronary artery disease, and thus improves diagnosis and prognostic stratification. Regional WMAs were identified with high diagnostic accuracy and the method may prove helpful for the detection of myocardial viability. Received 20 February and in revised form 12 June 1999     

Tc-99m sestamibi gated SPECT in patients with left bundle branch block

PURPOSE: The purpose of this study was to assess the diagnostic role of a Tc-99m sestamibi gated SPECT technique in patients with left bundle branch block (LBBB) without known coronary artery disease. MATERIALS AND METHODS: Twenty consecutive patients with constant complete LBBB were included. A same-day rest-stress protocol was used, and dipyridamole stress (14 patients) or treadmill exercise (6 patients) was applied. Electrocardiograph (ECG)-gated SPECT images were acquired 15 minutes after the administration of 0.31 mCi/kg Tc-99m sestamibi at peak stress. Regional myocardial perfusion was analyzed in relation to the cardiac cycle. RESULTS: Eleven of 14 patients who underwent a dipyridamole stress test had hypoactivity in the left anterior descending (LAD) artery territory in the ungated (summed) stress-rest images (abnormality ratio, 78%). On the ungated images, the abnormality was completely reversible in one patient (9%), partially reversible in five patients (46%), irreversible in two patients (18%), and reverse perfusion was identified in three patients (27%). Abnormality ratios of end-systolic and end-diastolic data were 93% and 29%, respectively. Conversely, the ungated rest-stress and end-systolic images of all the patients who performed treadmill exercise were abnormal despite the presence of normal or nearly normal end-diastolic myocardial perfusion. The angiographic findings correlated best with those of end-diastolic images. In 13 patients without coronary artery disease, normal or nearly normal regional perfusion was observed on end-diastole, but four patients with abnormal end-diastolic perfusion, which involved the LAD territory in all but one, had substantial coronary artery disease. The number of the involved segments was similar on the end-systolic and ungated data. Most of these artifactual defects were localized to the anteroseptal, septal, and inferoseptal segments. CONCLUSIONS: These preliminary data indicate that end-diastolic images can significantly reduce artifactual defects in patients with LBBB. The resolution of an LBBB pattern on end-diastolic data would significantly improve the diagnostic role of myocardial perfusion studies in these patients.     

Differential effects comparing exercise and pharmacologic stress on left ventricular function using gated Tc-99m sestamibi SPECT

OBJECTIVE: Although post-ischemic stunning has emerged as an important marker for severe coronary artery disease (CAD), differences in stress methods may have different effects on left ventricular (LV) volumes and function. METHODS: To assess differential effects comparing exercise and pharmacologic stress on the LV measurements, (99m)Tc-sestamibi gated single-photon emission computed tomography (SPECT) acquired more than 30 min after stress and at rest was evaluated in 38 patients undergoing adenosine triphosphate (ATP) stress (ATP group) and 38 age-and sex-matched patients subjected to exercise stress (Ex group) among 268 patients with normal SPECT findings. RESULTS: Coronary risk factors and LV volumetric measurements at baseline were similar in the two groups. Compared with volumetric measurements at rest, end-diastolic volume (EDV) increased (72 +/- 21 ml to 74 +/- 21 ml; P = 0.01), end-systolic volume increased (25 +/- 12 ml to 28 +/- 13 ml; P = 0.001), and ejection fraction (EF) decreased after stress (66% +/- 8% to 63% +/- 9%; P < 0.002) in the ATP group. In the Ex group, by contrast, no such change was observed. In addition, changes in EDV (3 +/- 6 vs. -1 +/- 5 ml; P = 0.01) and the stress-to-rest ratio of EDV (1.04 +/- 0.09 vs. 0.99 +/- 0.08; P < 0.02) after stress were greater in the ATP than in the Ex group. CONCLUSIONS: Differential effects of stress methods on LV volumes persist more than 30 min after the stress. These findings should be kept in mind when interpreting post-ischemic stunning.     

Clinical impact of arrhythmias on gated SPECT cardiac myocardial perfusion and function assessment

BACKGROUND. We reported previously that mean quantified cardiac functional parameters computed by one gated single photon emission computed tomography (SPECT) technique were not significantly altered by common gating errors. However, it is not known to what extent other gated SPECT approaches that are based on different ventricular modeling assumptions are influenced by arrhythmias, nor are the effects of gating errors on visual analyses and their subsequent clinical implications known. METHODS. Projection data for 50 patients (aged 64 +/- 12 years; 68% men; 76% with myocardial perfusion defects) undergoing technetium-99m sestamibi gated SPECT who were in sinus rhythm during data acquisition were altered to simulate common arrhythmias. To determine quantitative effects, we performed calculations for original control and altered images by Gaussian myocardial detection (Quantitative Gated SPECT [QGS] program) and by wall thickening derived from gated perfusion polar maps (Emory Cardiac Toolbox program). To evaluate visual assessment in control and simulated-arrhythmia tomograms, 2 experienced blinded observers independently interpreted perfusion from polar maps and wall motion and thickening from tomographic cines, using a 4-point scale. RESULTS. Although mean functional parameters were scarcely altered, paired t tests showed ejection fraction fluctuations to be significantly different from control values, causing patients to change between abnormal and normal ejection fraction categories (2% of patients by QGS and 14% by Emory Cardiac Toolbox). Visual examination of QGS polar perfusion and function maps showed changes for 72% of cases, although in only 4% were these considered to have potential clinical consequences. The kappa statistic for visual analysis of concordance between control and arrhythmia readings showed that agreement was "excellent" for perfusion, "good" for motion, and "marginal" for thickening. CONCLUSIONS. As with quantitative measurements, thickening is the parameter most prone to error in the presence of arrhythmias. It is important to test data for gating errors to avoid potentially erroneous measurements and visual readings.     

Effects of low-dose dobutamine on left ventricular function in normal subjects as assessed by gated single-photon emission tomography myocardial perfusion studies

Electrocardiography gated single-photon emission tomography (gated SPET) allows the assessment of regional perfusion and function simultaneously and in full spatial congruency. In this study changes in global and regional left ventricular function in response to dobutamine infusion were assessed in ten healthy volunteers using sequential gated SPET myocardial perfusion acquisitions. Four consecutive gated SPET images were recorded 60 min after injection of 925 MBq technetium-99m tetrofosmin on a three-head camera equipped with focussing collimators. Two acquisitions were made at rest (baseline 1 and 2), and the third and fourth acquisitions were started 5 min after the beginning of the infusion of 5 and 10 μg kg^–1 min^–1 dobutamine, respectively. Systolic wall thickening (WT) was quantified using a method based on circumferential profile analysis. Left ventricular ejection fraction (LVEF) and volumes were calculated automatically using the Cedars-Sinai program. Nine of the ten subjects presented a definite increase in WT during dobutamine infusion. WT increased on average from 46%±14% at baseline to 71%±23% (range: 37%–106%; P<0.05) during 5 μg kg^–1 min^–1 dobutamine infusion and to 85%±25% (range: 62%–123%; P<0.05 with respect to WT at 5 μg kg^–1 min^–1) during 10 μg kg^–1 min^–1 dobutamine infusion. Apical segments showed the largest WT at baseline. The average WT response to dobutamine was similar for all parts of the myocardium. It is concluded that changes in WT induced by infusion of low-dose dobutamine can be assessed by sequential gated SPET myocardial perfusion studies. The ”stress gated SPET” protocol proposed in this study might be helpful to distinguish viable from scar tissue in patients with coronary artery disease, by demonstrating a preserved inotropic response in hypoperfused myocardium. Received 6 March and in revised form 6 May 1999     

Gated 99mTc-MIBI single-photon emission computed tomography for the evaluation of left ventricular ejection fraction: comparison with three-dimensional echocardiography

Objective  Parameters of left ventricular systolic function directly influence the management of patients with suspected coronary artery disease (CAD). Quantitative gated single-photon emission computed tomography (QGS; Cedars-Sinai Medical Center, Los Angeles, CA, USA) allows the computation of left ventricular ejection fraction (LVEF) from myocardial perfusion imaging studies which are frequently performed on patients with suspected CAD. Three-dimensional (3D) echocardiography is considered to be the echocardiographic “gold standard” for the quantification of LVEF. We sought to compare QGS with 3D echocardiography in the evaluation of EF in patients with suspected CAD. Methods  Ninety-one consecutive patients with suspected CAD, scheduled for coronary angiography, underwent rest electrocardiographic-gated technetium-99m methoxyisobutylisonitrile SPECT (G-SPECT) with measurement of LVEF by QGS and transthoracic 3D echocardiography with off-line measurement of LVEF (Tomtec 4D LV Analysis 1.1). The diagnosis of CAD was based on coronary angiography, performed on every patient. Results  Nine patients were excluded from the analysis owing to unsuitability for 3D echocardiography (8 patients) or G-SPECT (1 patient). In the remaining group of 82 patients, 71 (87%) had significant CAD, 34 (42%) had a history of myocardial infarction, and 50 (61%) had perfusion defects at rest G-SPECT images. The mean LVEF measured by QGS and 3D echocardiography was 53 ± 13% and 53 ± 10%, respectively. The mean difference in LVEF between 3D echocardiography and QGS was 0.1 ± 6.0% (P = 0.87), and the correlation between the values obtained by both methods was high (r = 0.88, P < 0.001). The largest discrepancies were observed in patients with small ventricular volumes. Conclusions  In patients undergoing diagnostic work-up for CAD, the measurement of LVEF by QGS algorithm provides high correlation and satisfactory agreement with the results of reference ultrasound method-3D echocardiography.     

Heterogeneity of myocardial wall motion and thickening in the left ventricle evaluated with quantitative gated SPECT

BACKGROUND: Global and regional ventricular function may be evaluated by using gated myocardial perfusion single photon emission computed tomography (SPECT). This study investigated two parameters of regional contraction of the left ventricle, segmental wall motion (WM) and wall thickening (WT), to determine their similarity and disparity in each myocardial segment in patients with normal myocardial perfusion. METHODS AND RESULTS: Thirty-five patients with normal myocardial perfusion and cardiac function (mean left ventricular ejection fraction, 62.6%+/-8.8%) were included in this study. A 1-day stress/rest protocol was used as a means of acquiring technetium 99m (Tc-99m) sestamibi gated SPECT protocol for each patient. A commercially available software package for quantitative gated SPECT (QGS) was used to generate cine loop three-dimensional surface display and SPECT images. The left ventricle was divided into 9 segments to score WM and WT (on a scale of 0 to 4, with 0 being normal and 4 being severely reduced) by 6 independent observers. The WM score was significantly higher than the WT score in the septum, whereas the WM score was lower than the WT score in the inferior segment. Similar WM and WT scores were observed in the remaining segments. CONCLUSIONS: Heterogeneous myocardial WM and WT were observed by using QGS software. These findings suggest that different criteria are required in each segment to evaluate segmental WM and WT by means of gated myocardial perfusion SPECT.     

Comparison of gated N-13 ammonia PET and gated Tc-99m sestamibi SPECT for quantitative analysis of global and regional left ventricular function

Background  The aim of this study was to compare global and regional left ventricular function in patients with coronary artery disease (CAD), obtained by use of Cedars-Sinai quantitative gated single photon emission computed tomography (QGS), for gated nitrogen 13 ammonia (NH₃) positron emission tomography (PET) and technetium 99m sestamibi (MIBI) single photon emission computed tomography (SPECT). Methods and Results  Fifty-one patients with CAD underwent gated N-13 NH₃ PET and gated MIBI SPECT. The end-diastolic volume, end-systolic volume, and ejection fraction were calculated by use of QGS. The quantitative regional wall motion (WM) and wall thickening (WT) scores for 20 segments in the myocardium were also measured by QGS. The end-diastolic volume, end-systolic volume, and ejection fraction measured by N-13 NH₃ PET showed highly significant correlation with those measured by MIBI SPECT (r=0.97, r=0.97, and r=0.84, respectively). The mean correlation of WM and WT on an individual patient basis between N-13 NH₃ PET and MIBI SPECT was 0.81 and 0.84, respectively. The circumferential variation of WM and TT in 20 segments showed a similar pattern with N-13 NH₃ PET and MIBI SPECT. Conclusion  Gated N-13 NH₃ PET combined with QGS provides information on both global and regional left ventricular function comparable to that obtained by gated Tc-99m perfusion myocardial SPECT in CAD patients.