Global Washout Rate Research Articles

Accuracy of washout rate analysis for thallium-201 single-photon emission computed tomography myocardial perfusion imaging using cadmium zinc telluride detectors: A phantom study.

ObjectiveThe aim of this study was to assess the accuracy of washout rate (WOR) analysis for thallium-201 chloride (201Tl) single-photon emission computed tomography myocardial perfusion imaging data acquired using cadmium zinc telluride detectors and a myocardial phantom.MethodsA myocardial phantom was injected with 10.5 MBq 201Tl, and 10-min acquisitions were performed at 0, 24, 46, and 62 h to accommodate natural radioactive decay over time. Global myocardial WOR (global-WOR) and regional WOR (regional-WOR, left anterior descending artery [LAD], right coronary artery [RCA], and left circumflex artery [LCX]) were analyzed between 0 and 24 h (infarction model), 0 and 46 h (ischemia model), and 0 and 62 h (normal model), respectively. We compared the calculated radioactive decay-rate as a reference standard and phantom imaging WOR (phantom-WOR).ResultsDecay-rate versus phantom-WOR were 20.4% vs. 20.8% (global-WOR), 21.3% (LAD), 21.2% (RCA), and 19.7% (LCX) for the infarction model; 35.4% vs. 35.6% (global-WOR), 35.5% (LAD), 36.2% (RCA), and 35.2% (LCX) for the ischemia model; and 44.5% vs. 45.1% (global-WOR), 45.4% (LAD), 44.7% (RCA), and 43.5% (LCX) for the normal model.ConclusionWOR analysis for 201Tl single-photon emission computed tomography myocardial perfusion imaging using cadmium zinc telluride detectors is a reliable analysis method.

An Exploratory Study of Washout Rate Analysis for Thallium-201 Single-Photon Emission Computed Tomography Myocardial Perfusion Imaging Using Cadmium Zinc Telluride Detectors

The aim of this study was to assess the washout rate (WOR) for thallium-201-chloride single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) using cadmium zinc telluride detectors for SPECT (CZT SPECT) versus conventional Anger-type SPECT (conventional SPECT). A total of 52 Japanese patients were examined using CZT SPECT and conventional SPECT, and the global WORs were compared. Additionally, the MPI WORs were compared for patients with a normal MPI versus those in whom MPI reflected the patients’ multivessel disease (MVD) MPI. Washout rates were similar when approximated by CZT SPECT versus conventional SPECT 12.59 ± 2.26%/h vs 12.57 ± 2.27%/h (P = .997), respectively. The WOR values for CZT SPECT versus conventional SPECT were 13.42%/h (1.53%/h) vs 13.93%/h (1.24%/h) (P = .337), respectively, for 7 normal MPI patients, and 10.64 ± 2.20%/h vs 10.84 ± 2.26%/h (P = .848), respectively, for 7 MVD-MPI patients. The WOR values for normal MPI versus MVD-MPI patients for CZT SPECT were 13.42 ± 1.53%/h vs 10.64 ± 2.20%/h (P = .025), respectively. Thallium-201-chloride WOR values obtained with high-efficiency CZT SPECT, which enabled significantly reduced imaging times and use of a low-dose protocol, were similar to those obtained with conventional SPECT.

Prediction of sudden cardiac death in patients with chronic heart failure by regional washout rate in cardiac MIBG SPECT imaging

BackgroundThe sympathetic nervous system provides an important trigger for major arrhythmic events through regional heterogeneity of sympathetic activity, which could be evaluated by SPECT imaging as the regional MIBG washout rate (WR). There is little information available on the prognostic value of regional WR in SPECT imaging for the prediction of sudden cardiac death (SCD) in patients with chronic heart failure (CHF). MethodsWe studied 73 CHF outpatients with LVEF < 40%. At study entry, the regional WR was measured in 17 segments on the polar map. We defined abnormal regional WR as both the regional WR range (maximum − minimum regional WR) and maximum regional WR > mean value + 2SD obtained in 15 normal controls. ResultsDuring a mean follow-up of 7.5 ± 4.1 years, 15 of 73 patients had SCD. The abnormal regional WR and abnormal global WR on planar images were significantly and independently associated with SCD. Patients with both the abnormal regional WR and global WR had a significantly higher risk of SCD than those with none of these criteria. ConclusionsThe analysis of regional MIBG WR on SPECT imaging provides additional prognostic value to global WR on planar images for SCD prediction in CHF patients.

Dynamic 3D analysis of myocardial sympathetic innervation: an experimental study using 123I-MIBG and a CZT camera.

Data on the in vivo myocardial kinetics of (123)I-metaiodobenzylguanidine ((123)I-MIBG) are scarce and have always been obtained using planar acquisitions. To clarify the normal kinetics of (123)I-MIBG in vivo over time, we designed an experimental protocol using a 3-dimensional (3D) dynamic approach with a cadmium zinc telluride (CZT) camera. We studied 6 anesthetized pigs (mean body weight, 37 ± 4 kg). Left ventricular myocardial perfusion and sympathetic innervation were assessed using (99m)Tc-tetrofosmin (26 ± 6 MBq), (123)I-MIBG (54 ± 14 MBq), and a CZT camera. A normal perfusion/function match on gated SPECT was the inclusion criterion. A dynamic acquisition in list mode started simultaneously with the bolus injection of (123)I-MIBG, and data were collected every 5 min for the first 20 min and then at acquisition steps of 30, 60, 90, and 120 min. Each step was reconstructed using dedicate software and reframed (60 s/frame). On the reconstructed transaxial slice that best showed the left ventricular cavity, regions of interest were drawn to obtain myocardial and blood pool activities. Myocardial time-activity curves were generated by interpolating data between contiguous acquisition steps, corrected for radiotracer decay and injected dose, and fitted to a bicompartmental model. Time to myocardial maximum signal intensity (MSI), MSI value, radiotracer retention index (RI, myocardial activity/blood pool integral), and washout rate were calculated. The mediastinal signal was measured and fitted to a linear model. The myocardial MSI of (123)I-MIBG was reached within 5.57 ± 4.23 min (range, 2-12 min). The mean MSI was 0.426% ± 0.092%. Myocardial RI decreased over time and reached point zero at 176 ± 31 min (range, 140-229 min). The ratio between myocardial and mediastinal signal at 15 and 125 min and extrapolated at 176 and 4 h was 5.45% ± 0.61%, 4.33% ± 1.23% (not statistically significant vs. 15 min), 3.95% ± 1.46% (P < 0.03 vs. 125 min), and 3.63% ± 1.64% (P < 0.03 vs. 176 min), respectively. Mean global washout rate at 125 min was 15% ± 14% (range, 0%-34%), and extrapolated data at 176 min and 4 h were 18% ± 18% (range, 0.49%-45%) and 25% ± 23% (range, 1.7%-56.2%; not statistically significant vs. 176 min), respectively. 3D dynamic analysis of (123)I-MIBG suggests that myocardial peak uptake is reached more quickly than previously described. Myocardial RI decreases over time and, on average, is null about 3 h after injection. The combination of an early peak and variations in delayed myocardial uptake could result in a wide physiologic range of washout rates. Mediastinal activity appears to be constant over time and significantly lower than previously described in planar studies, resulting in a higher heart-to-mediastinum ratio.

Myocardial washout rate of resting 99mTc-Sestamibi (MIBI) uptake to differentiate between normal perfusion and severe three-vessel coronary artery disease documented with invasive coronary angiography

Patients with severe coronary artery disease (CAD) may present impaired mitochondrial function to enhance (99m)Tc-sestamibi (MIBI) washout from ischemic myocardium. In this study, we aimed to study the MIBI washout rate (WR) between patients with three-vessel CAD (3V-CAD) confirmed by invasive coronary angiography and healthy normal volunteers (HNV) to evaluate the potential utility of MIBI WR to differentiate between these two populations and to stratify the CAD severity. Ten HNV (male = 5, age = 56 ± 10 years) and eight 3V-CAD patients (male = 4, age = 62 ± 8 years) with 3V lumen stenosis ≥50% were enrolled for this study. Each study subject had a resting MIBI perfusion scan at 90 min and a repeated scan at 4 h post the MIBI injection. Global WR (GWR) and regional WR (RWR) were quantified with the percentage difference of decay-corrected polar maps obtained from the two scans and compared between the HNV and 3V-CAD groups. For the 3V-CAD group, the severity of CAD was assessed with CAD severity scores (CADSS) utilizing degree and location of obstructive lesions (stenosis ≥50%) for quantification and compared with WR to evaluate the correlation between these two variables. Significantly higher GWR was observed in the 3V-CAD (21.1 ± 4.6 %) group than the HNV group (9.5 ± 4.9%) (p < 0.001). RWR values in left anterior descending (LAD), right coronary artery (RCA) and left circumflex (LCX) in the 3V-CAD group were also higher than those of the HNV group (LAD 20.7 ± 5.9 vs 9.4 ± 5.6, p < 0.001; RCA 21.3 ± 4.8 vs 9.2 ± 5.8, p < 0.001; LCX 20.5 ± 7.2 vs 10.1 ± 4.4, p = 0.002). Additionally, the linear correlation of GWR and total CADSS for the whole myocardium was strong and statistically significant (y = 0.86x - 1.12, r (2) = 0.73, p = 0.006). Patients with impaired mitochondrial function due to 3V-CAD had consistently higher global and regional rest (99m)Tc-sestamibi washout rates than those of healthy normal volunteers. The global rest (99m)Tc-sestamibi washout rate is a sensitive indicator to stratify the severity of 3V-CAD and to differentiate between severe 3V-CAD and normal perfusion populations.

Myocardial washout rate of technetium-99m-sestamibi in the chronic phase predicts myocardial damage in patients with previous myocardial infarction

This study aimed to clarify the correlation between the myocardial washout rate (WR) of technetium-99m hexakis 2-methoxy-isobutyl-isonitrile ((99m)Tc-sestamibi) and cardiac enzyme levels in patients with acute myocardial infarction (AMI) 6 months after the onset. Sixty-one consecutive AMI patients (mean age, 66.2 ± 9.7 years) who underwent percutaneous coronary intervention (PCI) on admission were enrolled. Creatinine kinase MB isoenzyme (CK-MB) levels were measured every 3 h. (99m)Tc-sestamibi myocardial scintigraphic images were obtained at the early (30 min) and delayed (4 h) phases after tracer injection for calculating heart-to-mediastinum (H/M) ratios and global WRs at 2 weeks (0 M) and 6 months (6 M) after the onset of AMI. Regional WRs in the culprit lesions (culprit WR) and the extent score (ES) and severity score (SS) of myocardial damage were also calculated. PCI was performed 8.3 ± 7.7 h after AMI onset. At 6 M, the early H/M ratio (p = 0.04), delayed H/M ratio (p = 0.02), global WR (p = 0.01), culprit WR (p = 0.002), and delayed ES (p = 0.008) were alleviated. At 0 M, the peak CK-MB level correlated with the delayed H/M ratio (p = 0.003), global WR (p = 0.003), culprit WR (p < 0.001), early ES (p = 0.03), delayed ES (p = 0.01), early SS (p = 0.001), and delayed SS (p < 0.001). At 6 M, the peak CK-MB level correlated with the delayed H/M ratio (p < 0.001), global WR (p = 0.005), culprit WR (p = 0.001), early ES (p = 0.001), delayed ES (p < 0.001), early SS (p < 0.001), and delayed SS (p < 0.001). These results demonstrated that (99m)Tc-sestamibi WR in the chronic phase as well as that in the acute phase reflects the extent of initial myocardial damage in AMI patients after PCI. Moreover, it might indicate the myocardial condition in the clinical course.

Relevance of 123 I-BMIPP delayed scintigraphic imaging for patients with angina pectoris – a pilot study

IntroductionThe study was designed to clarify the role of 123I-β-methyl-iodophenylpentadecanoic acid (123I-BMIPP) in the evaluation of myocardial fatty acid metabolism in patients with stable angina pectoris (AP) before and after percutaneous coronary intervention (PCI).Material and methodsTen controls (mean age: 70.4 ±10.5 years) and 12 patients with AP (mean age: 67.4 ±11.6 years) and single vessel coronary artery disease participated in the radionuclide cardiac study. Scintigraphic images were acquired at 30 min and at 4 h after 123I-BMIPP injection to determine early and delayed BMIPP uptake, respectively. The heart-to-mediastinum (H/M) ratio and the washout rate (WR) were calculated from the planar images. All patients underwent scintigraphy one day before PCI and again 1 month after successful PCI.ResultsNo significant differences in the early or delayed H/M ratios were observed between the patients and the controls before PCI (early: 2.70 ±0.36 vs. 2.73 ±0.57; delayed: 2.26 ±0.33 vs. 2.40 ±0.43; p > 0.2 for both). The early and delayed H/M ratios remained unchanged with the comparison with before PCI (early: 2.72 ±0.27, delayed: 2.23 ±0.22; p > 0.2 for both). The global WR before PCI was significantly higher in the patients than in the control group (36.7 ±9.3%, vs. 28.1 ±8.2%, p = 0.02). However, the WR after PCI did not significantly differ between the patients and the controls (34.3 ±7.8% vs. 28.1 ±8.2%, p = 0.1).ConclusionsThese data may suggest that the WR of 123I-BMIPP determined from the planar images enhances the presence of myocardial ischaemia.

The washout rate of 123I-BMIPP and the evolution of left ventricular function in patients with successfully reperfused ST-segment elevation myocardial infarction: comparisons with the echocardiography

The evolution of the oxidative metabolism of (11)C acetate parallels the recovery of left ventricular(LV) contraction following acute myocardial infarction(AMI). This study was designed to unravel, for the first time, the impact of the global washout rate(WR) of (123)I-beta-methyl-p-iodophenylpentadecanoic acid (BMIPP) on the recovery of LV function followingAMI, as evidenced from conventional echocardiography.Twenty consecutive patients (age: 58 +/- 13 years; 16 males and 4 females) with ST-segment elevation myocardial infarction (STEMI) were enrolled and all of them underwent successful percutaneous coronary intervention (PCI). (123)I-BMIPP cardiac scintigraphy was performed at 7 +/- 3 days after admission. The WR was calculated from the polar map and the regional BMIPP defect score was calculated using a 17 segment model. Echocardiography was performed within 24 h of admission and at 3 months to record the ejection fraction (EF), the wall motion score index (WMSI), the ratio of the mitralinflow velocity to the early diastolic velocity (E/E0)and the myocardial performance index (MPI). The mean global WR of the BMIPP was 22.12 +/- 7.22%, and it was significantly correlated with the improvement of the WMSI (r = 0.61, P\0.004). However,the relative changes of the EF, E/E0 and MPI were not correlated with the WR. The BMIPP defect score (18 +/- 10) was significantly correlated with the WMSI on admission (r = 0.74, P = 0.0002), but the defect score was not correlated with the relative changes of any of the echocardiographic parameters. We proved that the WR of the BMIPP is a promising indicator of improvement of the LV wall motion (WMSI) following ST-segment elevation myocardial infarction and successful reperfusion.

Regional quantitative analysis of small animal myocardial sympathetic innervation and initial application in streptozotocin induced diabetes

In several disease models it is known that heterogeneous dysinnervation occurs in the sympathetic nervous system. We therefore adapted the (123)I-MIBG imaging procedure in small animals to allow quantification of both global and regional uptake and wash-out rate using high specific activity (123)I-MIBG in the myocardium of rats. After evaluation of the image procedure in normal animals, we then applied our imaging protocol to visualize the regional dysinnervation in cardiac autonomic neuropathy occurring in streptozotocin-induced diabetes. Seven normal Lewis rats underwent (123)I-MIBG pinhole SPECT with low specific activity (123)I-MIBG (lsa MIBG) and high specific activity (123)I-MIBG (hsa MIBG) with a 2 week interval. Twelve normal rats and 12 rats 8 weeks after streptozotocin injection underwent the same hsa MIBG imaging protocol. The imaging protocol consisted of two SPECT acquisitions for every animal. The imaging sequence started at 20 min after tracer injection. The percentage of injected activity (%IA) and the wash-out rate in the global myocardium were measured. Left ventricular regional MIBG kinetics were analyzed in the six midventricular segments of the 17 segment model. Compared with lsa MIBG, the wash-out rate of hsa MIBG was significantly slower, in association with a higher cardiac uptake. Regional analysis showed a maximal uptake in the anterolateral segment, without significant differences between segments. We noted a significantly higher global wash-out rate in the streptozotocin group compared to controls (p < 0.05). Regional analysis confirmed the increased wash-out rate, reaching statistical significance in the inferior and the inferoseptal walls. High-quality (123)I-MIBG images and accurate measurements can be obtained using hsa (123)I-MIBG with image acquisitions performed at relatively early time points. Small animal MIBG SPECT imaging allows for regional analysis of the myocardium. In the streptozotocin group, wash-out of MIBG is globally increased, compatible with a higher sympathetic tonus or decreased reuptake of MIBG. The highest increase is located in the inferior, inferoseptal and anteroseptal walls. These findings further suggest the occurrence of diabetic cardiomyopthy after streptozotocin injection.

Brain Natriuretic Peptide (BNP) Level is Closely Related to the Extent of Left Ventricular Sympathetic Overactivity in Chronic Ischemic Heart Failure

Both brain natriuretic peptide (BNP) and cardiac sympathetic activity are useful surrogate markers of congestive heart failure. BNP is known to be secreted in response to sympathetic tone. This study examined the relationship between the cardiac sympathetic system and BNP. Sixty patients with chronic ischemic heart failure (mean age,72 years-old; 46 males and 14 females) who had undergone cardiac catheterization and were classified as NYHA II underwent resting (99m)Tc-sestamibi quantitative gated imaging (MIBI) and (123)I-metaiodobenzylguanidine imaging (MIBG). MIBI was used to obtain left ventricular (LV) dimension. MIBG was used to obtain the washout rate and the H/M ratios as well as the extent of LV washout rate abnormality (RSNA), which was defined as the number of regions with a regional washout rate of more than mean+2SD of 15 normal subjects on a two-dimensional polar map divided into 20 regions. Blood samples were obtained to measure neurohormones such as BNP, renin activity, noradrenaline, and angiotensin II. Simple linear regression analysis showed that BNP had significant correlations to age, LVEF, LV end diastolic volume, LV end systolic volume, RSNA, global washout rate, myocardial ischemia, and LV end diastolic pressure. Among them, multiple linear regression analysis showed that only RSNA (partial regression coefficient =0.618, p<0.002) had a significant positive correlation with BNP. This study suggested that the extent of cardiac sympathetic overactivity in the LV could enhance BNP release.

123I-BMIPP delayed scintigraphic imaging in patients with chronic heart failure

The objective of the present study was to clarify the ability of 123I-beta-methyl-iodophenylpentadecanoic acid (123I-BMIPP) to evaluate the heart-to-mediastinum (H/M) ratio and myocardial global washout rate (WR) in patients with chronic heart failure (CHF). The severity of CHF was evaluated on the basis of the New York Heart Association (NYHA) classification. Twenty patients with CHF (13 with idiopathic dilated cardiomyopathy and 7 with ischemic cardiomyopathy) and 11 age-matched controls underwent myocardial radionuclide imaging. Scintigraphic images were obtained from each participant at the early (30 min following radio-isotope injection) and late (4 h) phases using 123I-BMIPP. The H/M ratio and WR were calculated from planar images. Concentrations of plasma brain natriuretic peptide (BNP) were measured prior to the scintigraphic study. The 123I-BMIPP uptake of early H/M and global WR did not significantly differ among groups, but uptake of delayed H/M was significantly lower in patients with NYHA class III than in controls (control 2.47 +/- 0.39; class III 1.78 +/- 0.28, P < 0.05). The uptake of delayed H/M and global WR correlated with plasma log BNP in all participants (r = -0.38, P < 0.05; 0.43, P < 0.05, respectively). These data suggest that 123I-BMIPP uptake of delayed H/M enhances the image of CHF severity. The myocardial WR of 123I-BMIPP also effectively depicted the severity of CHF.

Cardiac sympathetic nerve activity in patients with hypertrophic cardiomyopathy with malignant ventricular tachyarrhythmias

Background Malignant ventricular tachyarrhythmia (VT) and sudden death are serious events in hypertrophic cardiomyopathy (HCM). However, the pathophysiology of this condition is not well understood. The objective of this study was to evaluate the relationship between cardiac sympathetic nerve activity and the occurrence of VT in HCM patients. Methods and results We studied iodine 123 metaiodobenzylguanidine scintigraphy and 24-hour ambulatory electrocardiographic monitoring in 44 HCM patients, 15 with VT (group A) and 29 without VT (group B). With planar I-123 metaiodobenzylguanidine imaging, the heart-to-mediastinum ratio for early and delayed acquisition and washout rate were calculated. Polar maps of left ventricular myocardium were divided into 20 segments, and the SD of uptake and washout rate in 20 segments were calculated as indices of regional variation. The global washout rate was significantly higher in group A than in group B (26.8 ± 6.4% vs 17.4 ± 5.7%, P < .0001), although other parameters including heterogeneity indices did not differ. The logistic multiple regression analysis also determined that washout rate was the most powerful predictor of VT in patients with HCM. Conclusions The occurrence of malignant VT in HCM may be associated with global cardiac sympathetic nerve activity rather than with the heterogeneity of this activity.

Relationship between cardiac sympathetic function and baroreceptor sensitivity after acute myocardial infarction.

The relationship between baroreceptor sensitivity (BRS) and cardiac sympathetic nerve function after acute myocardial infarction (AMI) was investigated in 34 patients. BRS was measured during the Valsalva maneuver and cardiac sympathetic function was assessed by the washout rate (WR) of I-123 meta-iodo-benzyl guanidine (123I-MIBG) with planar image (global WR) and polar map analysis (regional WR). Gated left ventricular ejection fraction (LVEF) measured by left ventriculography as a parameter of ventricular function was measured with quantitative gated SPECT (QGS). The gated LVEF correlated with global WR (r=-0.36, p=0.034) and regional WR of normal area (r=-0.46, p=0.006), but not with BRS, although BRS correlated with global WR (r=-0.43, p=0.015) and regional WR of normal area (r=-0.72, p<0.0001). After AMI, baroreceptor function is linked to sympathetic activation, as elucidated by the regional WR of normal area, which suggests that separation of the infarcted area from the non-infarcted myocardium is necessary for evaluating sympathetic activation after AMI and that the regional kinetics of 123I-MIBG in the normal area are a more suitable marker of activated cardiac nerve function than global 123I-MIBG kinetics.

Evaluation of regional cardiac sympathetic innervation in congenital long QT syndrome using 123I-MIBG scintigraphy.

The aim of this study was to determine whether sympathetic imbalance in congenital long QT syndrome (LQTS) can be identified by cardiac sympathetic neuronal dysinnervation. 123I-metaiodobenzylguanidine (MIBG) is a tracer of the norepinephrine analogue which reflects the regional innervation and norepinephrine kinetics in cardiac sympathetic nerves. Sixteen patients with LQTS, who were members of 12 families, and 7 normal controls underwent MIBG scintigraphy. Myocardial SPET and planar images were obtained 15 min and 4 h after the injection of MIBG in each patient. The relative regional uptake (RRU) and regional washout rate (rWR) of MIBG at 4 h in each of nine regions were compared with those in the control group. The heat-to-mediastinum ratio (H/M) and global washout rate (GWR) were also calculated. The RRU, rWR, H/M and GWR showed no significant difference between LQTS patients and normal controls. Furthermore, the RRU in 96% of all regions in LQTS was within the mean +/- 2 standard deviations of that in the control group. Patients with LQTS have normal cardiac sympathetic innervation, as assessed by MIBG. The sympathetic imbalance hypothesis is unlikely to be attributed to an abnormal distribution and different regional norepinephrine kinetics of cardiac sympathetic nerves.