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.     

QRS complex duration and dipyridamole gated SPECT findings in the left bundle branch block

OBJECTIVE: The aim of this study was to investigate the relationship between QRS duration, artifactual perfusion abnormalities, and left ventricular function in patients with left bundle branch block (LBBB) using dipyridamole technetium-99m sestamibi electrocardiography-gated single-photon emission computed tomography (SPECT). METHODS: Twenty-three patients (62 +/- 12.2 years, 18 women, 5 men) with complete LBBB were analyzed. All patients underwent rest-dipyridamole gated SPECT (1-day protocol). To exclude patients with true myocardial ischemia and clearly define artifactual abnormalities owing to LBBB, only patients with normal end-diastolic stress images were involved. Four sets of SPECT images representing ungated rest, ungated stress, and end-diastolic and end-systolic stress images were generated, and the summed defect scores were obtained for each [summed rest score (SRS), summed stress score (SSS), end-diastolic score (EDS), and end-systolic score (ESS), respectively]. QRS durations were measured for both rest and dipyridamole stress. RESULTS: The patients with perfusion abnormalities on ungated rest, ungated stress, or end-systolic stress images had significantly longer minimum QRS duration at rest. These QRS values correlated with SRS and SSS (r: 0.528, P: 0.01 and r: 0.47, P: 0.024, respectively). Analysis of perfusion and functional data demonstrated an inverse correlation between left ventricular ejection fraction (LVEF) and ESS (r: -0.671, P < 0.0001). The patients with end-systolic perfusion abnormalities had significantly lower LVEF rates when compared with the patients with normal perfusion on end-systolic images. CONCLUSIONS: Our results demonstrated that the presence and severity of artifactual perfusion abnormalities owing to LBBB were significantly related to minimum QRS duration. The magnitude of perfusion abnormalities especially on the end-systolic phase seems to adversely affect systolic function of the left ventricle.     

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.     

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.     

Thallium-201 SPECT in coronary artery disease patients with left bundle branch block

Fourteen patients with left bundle branch block (LBBB) underwent immediate postexercise and 3-hr delayed 201Tl single photon emission computed tomography (SPECT) with quantitative analysis using bullseye polar maps. Test performance in detecting individual coronary artery stenosis greater than or equal to 50% demonstrated 100% sensitivity. Specificity was 100% for circumflex stenosis, 78% for right coronary stenosis, but only 10% for left anterior descending coronary stenosis. This very low specificity was due to the fact that 3/4 (75%) patients with left anterior descending stenosis and also 9/10 (90%) patients with normal left anterior descending coronary arteries had immediate septal perfusion defects with redistribution in all cases at 3 hr. Septal abnormalities were most marked in patients who achieved high peak heart rates (greater than 170 bpm). Thus, with LBBB, 201Tl SPECT is indeterminate for left anterior descending coronary disease.     

Early and delayed Tc-99m-tetrofosmin myocardial SPECT in patients with left bundle branch block

To determine the utility of the myocardial tracer Tc-99m-tetrofosmin in the examination of patients with left bundle branch block (LBBB) and to investigate Tc-99m-tetrofosmin uptake and retention in the myocardium, early and delayed Tc-99m-tetrofosmin SPECT was performed in 10 patients having LBBB without coronary stenosis.Methods: After 740 MBq of Tc-99m-tetrofosmin injection in the resting state, the early and delayed SPECT imaging was done at 30 min and 180 min, respectively.Results: Decreased Tc-99m-tetrofosmin uptake in the septal segments was observed in 4 patients (40%) at 30 min and in 9 (90%) at 180 min. Reverse redistribution was seen in 9 of 10 patients. In patients with LBBB, the septal-to-lateral uptake ratio was lower in the delayed images than in the early images (0.80 ± 0.09 vs. 0.89 ± 0.09, p < 0.001). In patients with LBBB, the washout rate of Tc-99m-tetrofosmin was higher in the septal segments than in the lateral segments (28.3 ±4.3% vs. 22.8 ± 3.3%, p < 0.001).Conclusion: The SPECT data indicate that in LBBB without coronary stenosis, the uptake of Tc-99m-tetrofosmin is decreased in the septal wall, and that reverse redistribution occurs frequently. Our results contribute to the elucidation of both the cellular biokinetics of Tc-99m-tetrofosmin in the myocardium and the hemodynamics of the septum in LBBB, and indicate the possible clinical utility of Tc-99m-tetrofosmin.     

False-positive Tl-201 SPECT studies in patients with left bundle branch block. Frequency and clinical significance.

This study reports on the frequency and clinical significance of false-positive thallium studies in the interventricular septum in patients with left bundle branch block. In a 3-year period, 93 studies were performed on patients with complete left bundle branch block and sinus rhythm. Of these, 29 had a reversible septal defect; 17 are scored false-positive although only six had angiographic proof of normal left anterior descending coronary arteries. We conclude that thallium scintigraphy is indicated in patients with left bundle branch block, but caution is justified when reversible ischemia is demonstrated scintigraphically.     

Standard provocative manoeuvres in patients with and without left bundle branch block studied with myocardial SPECT

BACKGROUND: The objective of this study was to determine the prevalence of anterior and septal defects in patients with left bundle branch block (LBBB), and to assess the diagnostic accuracy of myocardial single photon emission computed tomography (SPECT) with technetium compounds in patients with and without LBBB using standard provocative manoeuvres. METHODS: Five hundred and nine consecutive patients (456 without LBBB and 53 with LBBB) without previous infarction who had a coronary angiography performed within <3 months of the scintigraphic study were retrospectively evaluated. The same stress procedures were followed in all patients. (1) Only exercise when it was sufficient; and (2) exercise + simultaneous administration of dypiridamole if exercise was insufficient. Only reversible defects were considered positive and > or =50% of coronary stenosis was considered significant. RESULTS: Prevalence of reversible anterior and septal defects was low (33% and 12%, respectively) in patients with LBBB. Although lower values of global sensitivity (81%) and specificity (73%) were obtained in these patients, there were no significant differences with respect to the patients without LBBB (89% and 86%, respectively). Specificity values for the diagnosis of stenosis of left anterior descending (78%), left circumflex (96%) and right coronary artery (74%) in patients with LBBB were lower, but without significant statistical differences with respect patients without LBBB (90%, 96% and 82%, respectively). CONCLUSIONS: Myocardial SPECT with technetium compounds, using standard provocation manoeuvres, can be used in patients with LBBB with only a mild decrease in diagnostic accuracy as compared to patients without LBBB.     

Is septal glucose metabolism altered in patients with left bundle branch block and ischemic cardiomyopathy?

Left bundle branch block (LBBB) is common in patients with heart failure (HF) and contributes to left ventricular (LV) dysfunction. The abnormal septal motion may alter septal metabolic demand but this has not been well characterized in patients with ischemic cardiomyopathy (ICM) and LV dysfunction. The aim of this study was to determine the effect of LBBB on septal metabolism in patients with ICM, LV dysfunction, and LBBB. METHODS: Fifty-three patients with LV dysfunction and ICM were identified: 34 with LBBB, 19 with normal QRS (30% of this patient population. Absence of this finding was often associated with lateral wall perfusion defects, suggesting an alteration in the metabolic demand on the septum. This may have implications for HF therapies such as resynchronization and requires further study.     

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.     

Association between left ventricular mechanical dyssynchrony with myocardial perfusion and functional parameters in patients with left bundle branch block

Objective

To identify predictors of left ventricular mechanical dyssynchrony (LVMD) in patients with known left bundle branch block (LBBB) using gated single-photon emission computed tomography (SPECT) phase analysis.

Methods

81 patients (74% male, 70 ± 10 years) with LBBB and suspected or known coronary artery disease underwent ECG-gated myocardial perfusion SPECT. LV perfusion and functional parameters were measured, and phase analysis was performed to quantify LV-dyssynchrony.

Results

35/81 patients (42%) had prior myocardial infarction (MI), and the mean left ventricular ejection fraction (LVEF) was 49% ± 16%. LVMD was present in 58/81 (72%) patients. The summed thickening score (STS) (P < .001; odds ratio 1.22) emerged as independent predictor for the presence of LVMD in a multivariate regression model. In addition, prior MI, low LVEF, summed stress score, summed rest score, summed motion score, and LAD rest extent were identified as predictors of LVMD in a univariate model. Clinical baseline characteristics, cardiac risk factors, and QRS duration (P = .051) had no influence on the presence of LVMD.

Conclusion

In patients with LBBB, the occurrence of LVMD as assessed by gated SPECT phase analysis is mainly influenced by reduced myocardial contractility as expressed by the STS. Proper discrimination between LVMD arising from known electrical conduction delay as opposed to areas of MI causing reduced regional contractility seems to be mandatory for therapy planning in patients with LVMD.     

Automatic global and regional phase analysis from gated myocardial perfusion SPECT imaging: application to the characterization of ventricular contraction in patients with left bundle branch block

Although many patients with heart failure benefit from cardiac resynchronization therapy (CRT), predicting which patients will respond to CRT remains challenging. Recent evidence suggests that the analysis of mechanical dyssynchrony using gated myocardial perfusion SPECT (MPS) may be an effective tool. The aim of this study was to evaluate global and regional gated MPS dyssynchrony measurements by comparing parameters obtained from patients with a low likelihood (LLk) of conduction abnormalities and coronary artery disease and patients with left bundle branch block (LBBB). METHODS: A total of 86 consecutive patients with LLk and 72 consecutive patients with LBBB, all without prior myocardial infarction or sternotomy, were studied using gated MPS. Global (histogram SD [sigma], bandwidth [beta], and entropy [epsilon]) and regional (wall- and segment-based differences of means [Deltamicro(W) and Deltamicro(S), respectively] or modes [DeltaM(W) and DeltaM(S), respectively]) dyssynchrony measures were calculated by Fourier harmonic phase-angle analysis of local myocardial count variations over the cardiac cycle for each patient, and then unpaired t tests were used to determine which parameters were sex-specific and how well they discriminated between the LLk and LBBB populations. Receiver-operating-characteristic analysis was also performed to calculate the area under the curve (AUC), sensitivity (Ss), specificity (Sp), and optimal threshold (Th). RESULTS: Global parameters were found to be sex-specific, whereas regional differences were sex-independent. All parameters studied showed statistically significant differences between the groups (all global, P < 0.05; all regional, P < 0.0001). Receiver-operating-characteristic analysis yielded higher AUC, Ss, and Sp for epsilon and regional parameters (epsilon: AUC = 0.95/0.96, Ss = 94%/88%, Sp = 89%/91%, and Th = 53.9%/60.6% for women/men; Deltamicro(W): AUC = 0.93, Ss = 88%, Sp = 86%, and Th = 10.5 degrees ; Deltamicro(S): AUC = 0.94, Ss = 90%, Sp = 94%, and Th = 9.2 degrees ; DeltaM(W): AUC = 0.95, Ss = 90%, Sp = 94%, and Th = 15 degrees ; and DeltaM(S): AUC = 0.95, Ss = 88%, Sp = 90%, and Th = 10.5 degrees ) than for global parameters (sigma: AUC = 0.75/0.67, Ss = 81%/66%, Sp = 63%/64%, and Th = 16.5 degrees /22.2 degrees for women/men; beta: AUC = 0.80/0.72, Ss = 71%/71%, Sp = 79%/64%, and Th = 69 degrees /81 degrees for women/men). CONCLUSION: The computed parameters all discriminate effectively between LLk and LBBB populations. Measurements that are less dependent on the shape of the phase-angle distribution histogram provided higher sensitivity and specificity for this purpose. Further study is needed to evaluate these parameters for the purpose of predicting response to CRT.     

False-positive results obtained with stress myocardial SPECT in patients with right bundle branch block

PURPOSE: Right bundle branch block (RBBB) is a conduction defect that often is accompanied by nonspecific patient symptoms. The objective of this study was to evaluate the false-positive results obtained with TI-201 myocardial SPECT in patients with RBBB. METHODS: Thirty-one patients (24 men, 7 women; age range, 35 to 78 years; mean age, 39 +/- 14 years) had nonspecific chest pain and electrocardiograph-proved RBBB, normal results of echography, and normal results of coronary angiography. None of them had a previous history or evidence of myocardial infarction. All patients underwent stress-rest TI-201 myocardial SPECT; 24 had normal images but 7 showed hypoperfusion in the inferolateral segments, both visually and quantitatively. RESULTS: TI-201 myocardial perfusion scintigraphs must be evaluated carefully in RBBB because false-positive results are likely to occur as a result of functional changes produced by dissynchronous activation between the ventricles.     

Myocardial perfusion SPECT identifies patients with left bundle branch block patterns at high risk for future coronary events

Background  

The value of myocardial perfusion SPECT (MPS) for patients with left bundle branch block (LBBB) or right ventricular apical (RVA) pacing seems reduced. The prognosis of patients with only abnormal activation related perfusion defects (AARD) due to LBBB or RVA-pacing is similar to those with a normal MPS. We assessed the prognostic value of MPS in patients with LBBB or RVA pacing.     

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.     

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.