Decreased 123I-MIBG uptake and increased clearance in various cardiac diseases

Cardiac sympathetic "morbidity" might reflect the neurobiology of early Parkinson's disease

BACKGROUND

An appropriate extracranial biomarker that delineates endophenotypes of Parkinson's disease (PD) at an early stage and reflects the neurodegenerative process is lacking. An evaluation of myocardial sympathetic nerve terminals could be a good candidate. This study aimed to explore subtypes of PD patients that showed cardiac catecholaminergic vesicular defect and their characteristics.

METHODS

This study included 122 early drug-naïve PD patients who were followed for approximately 4-5 years. All patients were examined with 18F-N-(3-fluoropropyl)-2beta-carbon ethoxy-3beta-(4-iodophenyl) nortropane positron-emission tomography and 123I-meta-iodobenzylguanidine myocardial scintigraphy. Cardiac scans were reexamined two or three times. Patients were subgrouped into the sympathetic denervated group at the initial scan, those without evidence of denervated myocardium in the first and subsequent scans, and the converters whose myocardium was initially normal but became impaired in the subsequent scans. Cognition in 99 patients was initially assessed with neuropsychological tests. Any associations between cardiac denervation subtypes and presynaptic dopamine transporter densities were investigated. Cognitive status relevant to cardiac sympathetic denervation status was evaluated.

RESULTS

This study found that cross-sectional comparisons of presynaptic monoamine transporter availability with a predefined order of cardiac denervation groups revealed parallel degeneration. A quadratic correlation between cardiac catecholamine capacity and cognition was observed. This association was interpreted to reflect the early neurobiology of PD.

CONCLUSION

An observed cardiac catecholaminergic gradient was to mirror the central neurobiology of early PD.

Cardiac sympathetic burden reflects Parkinson disease burden, regardless of high or low orthostatic blood pressure changes

Reduced uptake of ¹²³I-meta-iodobenzylguanidine (¹²³I-MIBG) and orthostatic hypotension (OH) are independently associated with worse clinical outcomes of Parkinson's disease (PD). However, their interactive influence on PD has not been studied. The role of ¹²³I-MIBG myocardial uptake, as a biomarker of PD severity, was investigated, conditional on the mediating effects of OH. A total of 227 PD patients were enrolled. Their motor and nonmotor aspects were assessed with standardized tools. Global disease burden was estimated by averaging the scaled z-scores of the assessment tools. Every patient went through ¹²³I-MIBG scan, and OH was evaluated with the head-up tilt-test. The mediating role of orthostatic blood pressure changes (ΔBP) on the association between cardiac sympathetic denervation and disease burden was investigated. Low heart-to-mediastinum (H/M) ratio with less than 1.78 was seen in 69.6% of the patient population, and 22.9% of patients had OH. Low H/M ratio was associated with OH, and these patients had worse disease burden than subjects with normal ¹²³I-MIBG uptake (global composite z-score: normal ¹²³I-MIBG vs. abnormal ¹²³I-MIBG; -0.3 ± 0.5 vs. 0.1 ± 0.7; p < 0.001). The mediation models, controlled for age and disease duration, revealed that the delayed H/M ratio and global composite score were negatively associated, irrespective of orthostatic ΔBP. Adverse relationship between cardiac sympathetic denervation and disease burden was shown without any interference from orthostatic blood pressure fluctuations. This result suggested that extracranial cardiac markers might reflect disease burden, regardless of labile blood pressure influence.

Calibrated scintigraphic imaging procedures improve quantitative assessment of the cardiac sympathetic nerve activity

The ¹²³I-labeled meta-iodobenzylguanidine (MIBG) is an analogue of noradrenaline that can evaluate cardiac sympathetic activity in scintigraphy. Quantitative analysis of ¹²³I-MIBG images has been verified in patients with heart failure and neurodegenerative diseases. However, quantitative results differ due to variations in scintigraphic imaging procedures. Here, we created and assessed the clinical feasibility of a calibration method for ¹²³I-MIBG imaging. The characteristics of scintigraphic imaging systems were determined using an acrylic calibration phantom to generate a multicenter phantom imaging database. Calibration factors corresponding to the scintigraphic imaging procedures were calculated from the database and applied to a clinical study. The results of this study showed that the calibrated analysis eliminated inter-institutional differences among normal individuals. In summary, our standardization methodology for ¹²³I-MIBG scintigraphy could provide the basis for improved diagnostic precision and better outcomes for patients.

How do we establish cardiac sympathetic nervous system imaging with 123I-mIBG in clinical practice? Perspectives and lessons from Japan and the US

Cardiac denervation is associated with progressive left ventricular (LV) dysfunction, ventricular arrhythmias, and sudden cardiac death (SCD) in heart failure (HF). In this regard, it is important to evaluate cardiac-specific sympathetic nervous system (SNS) function. The radiotracer Iodine-123 meta-iodobenzylguanidine (123I-mIBG) can noninvasively evaluate pre-synaptic SNS function. Recent multicenter trials have shown 123I-mIBG to have strong predictive value for fatal arrhythmias and cardiac death in HF. 123I-mIBG was initially developed in the USA in the 1970s. In 1992, the Japanese Ministry of Health and Labour approved 123I-mIBG for the assessment of cardiac function. Following approval, the Japanese nuclear cardiology community developed 123I-mIBG imaging services in various medical centers. Japanese groups have been trying to establish the clinical utility of 123I-mIBG and standardize parameters for data acquisition and image analysis. The US Food and Drug Administration (FDA) has approved clinical use of 123I-mIBG for cardiac and non-cardiac imaging. However, clinical use of 123I-mIBG in the US has been very limited. The number of 123I-mIBG studies in Japan has also been limited. There are similarities and differences between the two countries. To establish the clinical utility of 123I-mIBG in both countries, it is important to characterize the situations of 123I-mIBG in each.

Initial Versus Follow-up Sequential Myocardial 123I-MIBG Scintigraphy to Discriminate Parkinson Disease From Atypical Parkinsonian Syndromes

PURPOSE

Previous single-center or meta-analysis studies analyzed myocardial I-metaiodobenzylguanidine (I-MIBG) scintigraphy in a single image session and demonstrated low sensitivity and high specificity for discriminating Parkinson disease (PD) from atypical Parkinsonian syndromes (APS). This study aimed to assess diagnostic ability of myocardial I-MIBG scintigraphy at 2 phases to discriminate PD from APS.

PATIENTS AND METHODS

This hospital-based prospective study enrolled 162 PD and 26 APS patients who underwent 2 sequential I-MIBG scintigraphy evaluations. Patients were stratified into normal and decreased I-MIBG groups according to early and delayed heart-to-mediastinum (H/M) ratios. Patients with PD and normal I-MIBG uptake (initial delayed H/M ratio, ≥1.78) were considered scans without evidence of cardiac norepinephrine deficit (SWEND). Early and delayed H/M ratios on the initial and 2-year follow-up scintigraphs were studied. The diagnostic sensitivity and specificity were calculated from these confusion matrices and were analyzed according to receiver-operating characteristic curve analysis. A repeated-measures general linear model was used to investigate differences among groups over time in H/M ratio changes and washout rates.

RESULTS

Follow-up I-MIBG scintigraphy analysis had a higher diagnostic sensitivity (89.5%) than the initial imaging (72.2%). The improved sensitivity was associated with a steeper decrease in H/M ratio in the SWEND group than in the APS group.

CONCLUSIONS

Follow-up I-MIBG scintigraphy can identify cardiac sympathetic denervation and its progression in patients with PD and may be effective in discriminating PD from APS. A later decrease in myocardial I-MIBG uptake in the group with SWEND meets the Braak staging threshold hypothesis for synucleinopathy.

Variability in Heart-to-Mediastinum Ratio from Planar 123I-MIBG Images of a Thorax Phantom for 6 Common γ-Camera Models

A heart-to-mediastinum (H/M) ratio of 1.6 or greater on planar ¹²³I-iobenguane (¹²³I-MIBG) images identifies heart failure patients at low risk of experiencing an adverse cardiac event. This phase-4 study used standardized phantoms to assess the intercamera, intracamera, and interhead variability in H/M ratio determinations from planar cardiac ¹²³I-MIBG imaging using commercially available, dual-head γ-cameras. Methods: A fillable thorax phantom was developed to simulate the typical uptake of ¹²³I-MIBG. The phantom had a nominal H/M ratio of 1.6 on the reference camera. Commercial cameras used in the study were dual-head and capable of 90° configuration for cardiac imaging. The target sample size was 8 units (examples) per camera model. Two imaging technologists independently analyzed planar images of simulated ¹²³I-MIBG uptake from the thorax phantom. H/M was the ratio of the average counts per pixel of the heart and mediastinum regions of interest. The primary endpoint, intercamera variability in H/M ratio from head 1, was determined for each camera model via comparison with the H/M ratio on the reference camera. Only cameras with at least 8 units tested (n ≥ 8) were included in the primary analysis. Intracamera and interhead variability in the H/M ratio were also evaluated. Results: Nine camera models were studied. The mean H/M ratio ranged from 1.342 to 1.677. The primary analysis (6 camera models) using a mixed-model, repeated-measures analysis showed no significant difference in H/M ratio between any camera model and the reference camera. Intracamera variability (head 1) in the H/M ratio among camera models with 8 units or more was high, with SDs ranging from 0.0455 to 0.1193. Interhead variability was low (SDs of the interhead difference, 0.017-0.074). Conclusion: Commonly used γ-cameras produced H/M ratios from simulated ¹²³I-MIBG phantom images that were not significantly different from those on the reference camera. This finding indicates that the results of previous clinical trials of ¹²³I-MIBG, involving many different clinical sites and camera models, are valid. The assessment of the performance of a given camera unit using an ¹²³I planar phantom before H/M results from ¹²³I-MIBG imaging are used for classifying risk in heart failure patients is encouraged.

Cardiac sympathetic activity in hypertrophic cardiomyopathy and Tako-tsubo cardiomyopathy

¹²³I-meta-iodobenzylguanidine (¹²³I-mIBG) scintigraphy has been established as an important technique to evaluate cardiac sympathetic function and it has been shown to be of clinical value, especially for the assessment of prognosis, in many cardiac diseases. The majority of ¹²³I-mIBG scintigraphy studies have focused on patients with cardiac dysfunction due to hypertension, ischemic heart disease, or valvular disease. However less is known about the role of ¹²³I-mIBG scintigraphy in primary cardiomyopathies. This overview shows the clinical value of ¹²³I-mIBG scintigraphy in two types of primary cardiomyopathy: The genetic hypertrophic cardiomyopathy (HCM) and the acquired Tako-tsubo cardiomyopathy (TCM). Cardiac sympathetic activity is increased in HCM and correlates to the septal wall thickness and consequently to the LVOT obstruction. Moreover, increased cardiac sympathetic activity correlates with impaired diastolic and systolic LV function. In addition, ¹²³I-mIBG scintigraphy may be useful for determining the risk of developing congestive heart failure and ventricular tachycardia in these patients. In TCM ¹²³I-mIBG scintigraphy can be used to assess cardiac sympathetic hyperactivity. In addition, ¹²³I-mIBG scintigraphy may identify those patients who are prone to TCM recurrence and may help to identify responders to individual (pharmacological) therapy.

Combination of ¹²³I-metaiodobenzylguanidine scintigraphy and flow-mediated dilation for the detection of patients with coronary spastic angina

BACKGROUND

This study evaluated the usefulness of cardiac sympathetic nerve activity, estimated by (123)I-MIBG scintigraphy, and endothelial function, estimated by flow-mediated dilation (FMD), in the detection of coronary spastic angina (CSA).

METHODS AND RESULTS

We compared 78 consecutive patients suspected of CSA with ten age-matched controls. On the basis of a spasm provocation test with acetylcholine, 53 patients were diagnosed as CSA and 25 patients were considered to have chest-pain syndrome (CPS). The total defect score (TDS) by delayed (123)I-MIBG scintigraphy was significantly higher in both patient groups than in controls (P < 0.05), and was significantly higher in CSA than in CPS patients (P = 0.02). The heart/mediastinum activity (H/M) ratio by delayed (123)I-MIBG scintigraphy and FMD were significantly lower in both patient groups than in controls (P < 0.05), and were lower in CSA than in CPS patients (P = 0.04). In receiver-operating curve analysis, the areas under the curve for TDS, H/M, and FMD were 0.78, 0.72, and 0.70, respectively. The combination of delayed (123)I-MIBG scintigraphy and FMD showed a higher diagnostic value than either method alone.

CONCLUSIONS

(123)I-MIBG scintigraphy and FMD can distinguish CSA patients among patients complaining of chest pain at rest, with good sensitivity and specificity.

A pooled analysis of multicenter cohort studies of (123)I-mIBG imaging of sympathetic innervation for assessment of long-term prognosis in heart failure

OBJECTIVES

The study objectives were to create a cardiac metaiodobenzylguanidine (mIBG) database using multiple prospective cohort studies and to determine the quantitative iodine-123-labeled mIBG indices for identifying patients with chronic heart failure (HF) at greatest and lowest risk of lethal events.

BACKGROUND

Although the prognostic value of cardiac mIBG imaging in patients with HF has been shown, clinical use of this procedure has been limited. It is required to define universally accepted quantitative thresholds for high and low risk that could be used as an aid to therapeutic decision-making using a large cohort database.

METHODS

Six prospective HF cohort studies were updated, and the individual datasets were combined for the present patient-level analysis. The database consisted of 1,322 patients with HF followed up for a mean interval of 78 months. Heart-to-mediastinum ratio (HMR) and washout rate of cardiac mIBG activity were the primary cardiac innervation markers. The primary outcome analyzed was all-cause death.

RESULTS

Lethal events were observed in 326 patients, and the population mortality rate was 5.6%, 11.3%, and 19.7% at 1, 2, and 5 years, respectively. Multivariate Cox proportional hazard model analysis for all-cause mortality identified age (p < 0.0001), New York Heart Association (NYHA) functional class (p < 0.0001), late HMR of cardiac mIBG activity (p < 0.0001), and left ventricular ejection fraction (LVEF) (p = 0.0029) as significant independent predictors. Analysis of the 512-patient subpopulation with B-type natriuretic peptide (BNP) results showed BNP (p < 0.0001), greater NYHA functional class (p = 0.0002), and late HMR (p = 0.0011) as significant predictors, but LVEF was not. The receiver-operating characteristic-determined threshold of HMR (1.68) identified patients at significantly increased risk in any LVEF category. Survival rates decreased progressively with decreasing HMR, with 5-year all-cause mortality rates >7% annually for HMR <1.25, and <2% annually for HMR ≥1.95. Addition of HMR to clinical information resulted in a significant net reclassification improvement of 0.175 (p < 0.0001).

CONCLUSIONS

Pooled analyses of independent cohort studies confirmed the long-term prognostic value of cardiac mIBG uptake in patients with HF independently of other markers, such as NYHA functional class, BNP, and LVEF, and demonstrated that categoric assessments could be used to define meaningful thresholds for lethal event risk.

Cardiac applications of 123I-mIBG imaging

Cardiac autonomic innervation plays a key role in maintaining hemodynamic and electrophysiologic harmony. Cardiac sympathetic function is adversely altered in many disease states, such as congestive heart failure, myocardial ischemia, and diabetes. (123)I-mIBG, a sympathetic neurotransmitter radionuclide analog, aids in the detection of sympathetic innervation abnormalities and can be imaged with planar and single-photon emission computed tomographic techniques. Cardiac (123)I-mIBG uptake can be assessed by the heart mediastinal ratio (H/M), tracer washout rate, and focal uptake defects. These parameters have been widely studied and shown to correlate strongly and independently with congestive heart failure progression, cardiac arrhythmias, cardiac death, and all-cause mortality. There is accumulating evidence that (123)I-mIBG imaging can help to monitor a patient's clinical course and response to therapy. The ability to predict potentially lethal ventricular arrhythmias promises to help more accurately select patients for implantable cardioverter defibrillators, limiting unnecessary devices and identifying additional patients at risk who do not meet current guidelines. (123)I-mIBG shows potential to help determine whether greater risk and usually more expensive ventricular assist device therapies or cardiac transplantation might be needed. Although more investigation in larger populations is needed to strengthen previous findings, cardiac (123)I-mIBG imaging shows promise as a new technique for recognizing and following potentially life-threatening cardiac conditions.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Semi-automated algorithm for calculating heart-to-mediastinum ratio in cardiac Iodine-123 MIBG imaging

BACKGROUND

We have developed novel software for semi-automatically measuring heart-to-mediastinum (H/M) ratio in cardiac Iodine-123 (¹²³I)-labeled meta-iodobenzylguanidine (MIBG) imaging. Our aim is to improve the reproducibility of the H/M ratio using the semi-automated method as opposed to the manual method.

METHODS AND RESULTS

The software algorithm automatically determined the mediastinal region of interest (ROI) using information from ¹²³I-MIBG uptake of the heart, lung, liver, and thyroid after a cardiac circular ROI was manually set. A total of 37 patients who underwent both early and delayed ¹²³I-MIBG imaging was retrospectively selected. The heart-to-mediastinum (H/M) ratios were calculated by both semi-automated and manual methods and assessed for the intra- and inter-observer variability. All H/M ratios were classified into three groups: normal, slight abnormality, and severe abnormality. The H/M ratios with the new method were higher than those obtained manually (P < .001). In the test-retest reliability, the intra-class correlation coefficient from the semi-automated method showed excellent reproducibility for early (0.99) and delayed (0.99) imaging. The Bland-Altman plots demonstrated better agreement using the semi-automated method (a range of 95% limits -0.11 to 0.10) than that in the manual method (-0.34 to 0.27). The inter-observer agreement was also good using the semi-automated method (κ = 0.866).

CONCLUSIONS

The H/M ratio using the semi-automated method showed high reproducibility in both early and delayed imaging.

Determination of the survival rate in patients with congestive heart failure stratified by ¹²³I-MIBG imaging: a meta-analysis from the studies performed in Japan

BACKGROUND

The goals of this meta-analysis were to determine survival rates in patients with heart failure (HF) assessed by ¹²³I-MIBG imaging results using recently published studies and to determine the prognostic value of ¹²³I-MIBG imaging.

METHODS

We reviewed published cohort studies carried out in Japan that compared the prognosis of patients with their ¹²³I-MIBG activity quantified as late heart-to-mediastinum ratio (H/M) or washout rate by performing a PubMed search for articles in English up to December 2006. Studies were selected if they analyzed a clearly defined lethal outcome (cardiovascular death) using life tables to estimate the odds ratio at 24 months after enrollment.

RESULTS

Of 158 articles related to cardiac ¹²³I-MIBG, seven referred to studies that met the inclusion criteria: 5 evaluated H/M via ¹²³I-MIBG in a total of 866 patients and 4 calculated washout rate in a total of 491 patients. A low H/M indicated a high risk of cardiac death: pooled odds ratio, 5.2; 95% confidence interval (CI) of 3.1-5.7. A high washout was also associated with lethal events with a pooled odds ratio of 2.8 (CI: 1.6-5.0). The association between washout and cardiac death was heterogeneous (Chi-square = 11.0, P < 0.02), whereas that between late H/M and fatal events was homogeneous (Chi-square = 2.3, P = no significance).

CONCLUSION

This meta-analysis of published studies of ¹²³I-MIBG studies conducted in Japan indicated that both a decreased cardiac ¹²³I-MIBG activity (H/M) and an increased washout rate are indicative of a poor prognosis in patients with chronic heart failure.

Norepinephrine spillover during exercise as a novel parameter to evaluate the severity of heart failure

BACKGROUND

The washout rate (WR) of (123)I-metaiodobenzylguanidine (MIBG) is now widely used for assessing the severity of heart failure. Although the WR of MIBG is usually measured at rest, the assessment of WR of MIBG during exercise might have a different clinical relevance. In this study, we measured the WR rate of MIBG during low-grade exercise and studied the clinical importance of this novel index.

METHODS

Twenty-four patients with dilated cardiomyopathy (DCM) were enrolled in this study. Planar images were obtained 20 minutes after MIBG injection (first image) and after 270 minutes (second image); the third image was obtained after 15 minutes of low-grade (10 W) bicycle ergometer exercise (300 minutes after MIBG injection). The decay of the specific counts was calculated from the first two images. The estimated third counts were calculated from the resting decay and were compared with the actual third counts.

RESULTS

In the receiver operating characteristic (ROC) curve analysis, we set a 10% decrease from the estimated counts as a cut-off value for severe heart failure (New York Heart Association [NYHA] Class IIm or worse). In 15 patients, the actual third count value was within 10% of the estimated count (N-group). In nine patients, the WR during exercise was high, and the actual third count values showed more than a 10% decrease from the estimated count value (H-group). In the H-group, 78% of the patients were in NYHA class IIm or III. In contrast, in the N-group, no patient had NYHA class III, and only 20% of the patients were in class IIm. The brain natriuretic peptide (BNP) level was significantly higher in the H-group than in the N-group (525 ± 263 pg/mL vs 176 ± 144 pg/mL; P < .01). No significant differences were observed in heart/mediastinal (H/M) activity ratio, the regular WR, and left ventricular ejection fraction values between the two groups.

CONCLUSIONS

The WR of MIBG during exercise may be an independent prediction variable, with a clinical relevance different from that of the WR at rest. This measurement could be used as a new index for assessing the severity of heart failure.

Identification of myocardial damage in systemic sclerosis: a nuclear cardiology approach

Myocardial involvement is an important prognostic factor in patients with systemic sclerosis, and early diagnosis and staging of the disease have been sought after. Since myocardial damage is characterized by connective tissue disease, including fibrosis and diffuse vascular lesions or microcirculation, nuclear myocardial perfusion imaging has been a promising option for evaluating myocardial damages in early stages. In addition to the conventional stress-rest perfusion imaging, the current use of quantitative electrocardiographic gated imaging has contributed to more precise evaluation of cardiac perfusion, ventricular wall motion, and diastolic function, all of which have enhanced diagnostic ability of evaluating myocardial dysfunction. Abnormal sympathetic imaging with Iodine-123 metaiodobenzylguanidine might be another option for identifying myocardial damage. This paper deals with approaches from nuclear cardiology to detect perfusion and functional abnormality as an early sign of myocardial involvement as well as possible prognostic values in patients with abnormal imaging results. The role of nuclear cardiology in the era of multiple imaging modalities is discussed.

Validation of cardiac (123)I-MIBG scintigraphy in patients with Parkinson's disease who were diagnosed with dopamine PET

PURPOSE

The aim of this study was to evaluate the diagnostic potential of cardiac (123)I-labelled metaiodobenzylguanidine ((123)I-MIBG) scintigraphy in idiopathic Parkinson's disease (PD). The diagnosis was confirmed by positron emission tomography (PET) imaging with (11)C-labelled 2beta-carbomethoxy-3beta-(4-fluorophenyl)-tropane ((11)C-CFT) and (11)C-raclopride (together designated as dopamine PET).

METHODS

Cardiac (123)I-MIBG scintigraphy and dopamine PET were performed for 39 parkinsonian patients. To estimate the cardiac (123)I-MIBG uptake, heart to mediastinum (H/M) ratios in early and delayed images were calculated. On the basis of established clinical criteria and our dopamine PET findings, 24 patients were classified into the PD group and 15 into the non-PD (NPD) group.

RESULTS

Both early and delayed images showed that the H/M ratios were significantly lower in the PD group than in the NPD group. When the optimal cut-off levels of the H/M ratio were set at 1.95 and 1.60 in the early and delayed images, respectively, by receiver-operating characteristic analysis, the sensitivity of cardiac (123)I-MIBG scintigraphy for the diagnosis of PD was 79.2 and 70.8% and the specificity was 93.3 and 93.3% in the early and delayed images, respectively. In the Hoehn and Yahr 1 and 2 PD patients, the sensitivity decreased by 69.2 and 53.8% in the early and delayed images, respectively.

CONCLUSION

In early PD cases, cardiac (123)I-MIBG scintigraphy is of limited value in the diagnosis, because of its relatively lower sensitivity. However, because of its high specificity for the overall cases, cardiac (123)I-MIBG scintigraphy may assist in the diagnosis of PD in a complementary role with the dopaminergic neuroimaging.

Decreased cardiac MIBG uptake, its correlation with clinical symptoms in dementia with Lewy bodies

Recent studies have demonstrated the usefulness of 123I-meta-iodobenzylguanidine (MIBG) myocardial scintigraphy for the diagnosis of dementia with Lewy bodies (DLB). In this study, we investigated the relationship between decreased cardiac MIBG uptake and clinical symptoms in DLB. Thirty-six patients with probable DLB and six normal controls underwent MIBG scintigraphy. We measured the early and delayed heart-to-mediastinum (H/M) ratios, and the results between subgroups based on the presence and absence of clinical symptoms were compared. The mean early and delayed H/M ratios were 1.55+/-0.29 and 1.42+/-0.30, and 30 (83.3%) and 33 (91.7%) subjects showed lower values compared to the cutoff, respectively. A statistically significant difference was found only between groups with and without orthostatic hypotension (OH). Among 10 DLB subjects without Parkinsonism, nine patients had a decreased H/M ratio in the delayed image. To our knowledge, this is the first study to correlate decreased MIBG uptake with the clinical symptoms of DLB, and to show a significantly lower H/M ratio in subjects with OH. Furthermore, we found that MIBG scintigraphy could detect cardiac sympathetic denervation regardless of clinically evident Parkinsonism. These results suggest that MIBG myocardial scintigraphy could be a valuable diagnostic test in the clinical diagnosis of DLB.

Impact of mediastinal, liver and lung (123)I-metaiodobenzylguanidine ( (123)I-MIBG) washout on calculated (123)I-MIBG myocardial washout

PURPOSE

In planar (123)I-metaiodobenzylguanidine ((123)I-MIBG) myocardial imaging mediastinum (M) activity is often used as a background correction in calculating "washout" (WO). However, the most likely sources for counts that might produce errors in estimating myocardial (Myo) activity are lung (Lu) and liver (Li), which typically have higher counts/pixel (cpp) than M. The present study investigated the relationship between changes in Lu, Li and Myo activity between early and late planar (123)I-MIBG images, with comparison to M as the best estimator of non-specific background activity.

METHODS

Studies on 98 subjects with both early (e) and late (l) planar (123)I-MIBG images were analysed. There were 68 subjects with chronic heart failure (CHF), 14 with hypertension (HTN) but no known heart disease and 16 controls (C). For each image, regions of interest (ROIs) were drawn: an irregular whole Myo, Lu, upper M and Li. For each ROI, WO was calculated as [(cpp(e)-cpp(l:decay corrected))/cpp(e)]x100%.

RESULTS

Multivariable forward stepwise regression analysis showed that overall a significant proportion of the variation in Myo WO could be explained by a model containing M WO and Lu WO (37%, p < 0.001). Only in controls was M WO the sole variable explaining a significant proportion of the variation in Myo WO (27%, p = 0.023).

CONCLUSION

Although increased Myo WO in CHF subjects reflects disease severity, part of the count differences measured on planar (123)I-MIBG myocardial images likely reflects changes in the adjacent and surrounding Lu tissue. The results for the controls suggest that this is the only group where a mediastinum correction alone may be appropriate for cardiac WO calculations.

Cardiac sympathetic activity in the asymmetrically hypertrophied septum in patients with hypertension or hypertrophic cardiomyopathy

BACKGROUND

In patients with essential hypertension (HT), proportional (symmetric) left ventricular hypertrophy (LVH) is common. In contrast, hypertrophic cardiomyopathy (HCM) is characterized by disproportional LVH and, in particular, asymmetric septal hypertrophy (ASH); however, some hypertensive patients also develop ASH. It has not been determined whether such cases represent a distinct type of hypertensive LVH or HCM combined with hypertension.

HYPOTHESIS

The study was undertaken to evaluate sympathetic activity in the interventricular septum in patients with HT and ASH or in patients with HCM.

METHODS

The patients were evaluated by I-123 meta-iodobenzylguanidine (MIBG) and thallium-201 (201Tl) single-photon emission computed tomography (SPECT), respectively. They were divided into three groups: patients with essential HT and symmetric septal hypertrophy (Group A), patients with HT and ASH (Group B), and patients with HCM and ASH (Group C).

RESULTS

Compared with the lateral wall, early uptake of MIBG in the septum was significantly higher in Group B than in Group A, but not significantly different between Groups A and C. Compared with the lateral wall, early uptake of 201Tl in the septum did not differ among the three groups. No significant difference in the MIBG clearance in the lateral wall was seen among the three groups. By contrast, MIBG clearances in the septum and apex were significantly greater in Group C than in Groups A and B. There was an inverse correlation between systolic thickening and MIBG clearance in the septum.

CONCLUSION

These findings suggest that sympathetic activity in the septum differs between patients with HT and ASH and patients with HCM.

123I-mIBG scintigraphy to predict risk for adverse cardiac outcomes in heart failure patients: design of two prospective multicenter international trials

BACKGROUND

ADMIRE-HF (AdreView Myocardial Imaging for Risk Evaluation in Heart Failure) consists of two identical prospective open-label, multicenter, phase 3 studies (MBG311 and MBG312) evaluating the prognostic usefulness of (123)I-mIBG scintigraphy for identifying subjects with heart failure who will experience a major adverse cardiac event.

METHODS

Subjects with NYHA class II and III heart failure and left ventricular ejection fraction < or = 35% were eligible for the trials. Subjects underwent planar and SPECT (123)I-mIBG myocardial imaging, as well as echocardiography and gated SPECT (99m)Tc-tetrofosmin myocardial perfusion imaging. Subjects are then monitored on a regular basis for 2 years. Time to first occurrence of one of the following--NYHA class progression; potentially life-threatening arrhythmic event (including ICD discharge); or cardiac death, as verified by an independent adjudication panel---will be analyzed in comparison to quantitative parameters derived from (123)I-mIBG imaging. The primary efficacy analysis will employ the heart/mediastinum ratio on 4-hour delayed planar imaging, while secondary efficacy analyses will examine quantitative results from both planar and SPECT (123)I-mIBG images, as well as from (99m)Tc-tetrofosmin SPECT and echocardiography.

CONCLUSION

The results of the ADMIRE-HF trials will provide prospective validation of the potential role of (123)I-mIBG scintigraphy in assessing prognosis and developing management strategies for patients with heart failure.

Significance of 123I-MIBG scintigraphy as a pathophysiological indicator in the assessment of Parkinson's disease and related disorders: it can be a specific marker for Lewy body disease

Recently, reliable and clear evidence for the usefulness of 123I-MIBG scintigraphy in the diagnosis of Parkinson's disease (PD) has been accumulated and it has become increasingly popular as one of the most accurate means of diagnosing the disease. PD, one of the most common neurodegenerative disorders, is characterized by resting tremor, rigidity, bradykinesia or akinesia, and postural instability. The disease is characterized pathologically by distinctive neuronal inclusions called Lewy bodies in many surviving cells of dopaminergic neurons of the substantia nigra pars compacta and other specific brain regions. Furthermore Lewy body type degeneration in the cardiac plexus has been observed in PD. In PD, cardiac MIBG uptake is reduced markedly even in the early disease stages; therefore, MIBG imaging can be used as an indicator of the presence of PD rather than disease severity. Other parkinsonian syndromes such as multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration demonstrate normal cardiac MIBG uptake or only mild reduction of MIBG uptake, indicating that MIBG imaging is a powerful method to differentiate PD from other parkinsonian syndromes. Dementia with Lewy bodies (DLB) also shows severe reduction of MIBG uptake, whereas Alzheimer's disease (AD) demonstrates normal MIBG uptake, permitting differentiation of DLB from AD using MIBG scintigraphy. In pure autonomic failure, which shares similar pathological findings with PD and is thought to be associated with diffuse loss of sympathetic terminal innervation, cardiac MIBG uptake also decreases markedly. Considering all the data together, marked reduction of cardiac MIBG uptake seems to be a specific marker of Lewy body disease and thus extremely useful in the differentiation from other diseases with similar symptoms without Lewy bodies.

Cardiac neurotransmission SPECT imaging

The sympathetic nervous system has great influence on cardiovascular physiology. Cardiac neurotransmission single photon emission computed tomography (SPECT) imaging allows in vivo noninvasive assessment of presynaptic reuptake and storage of neurotransmitters, which offers characterization of the cardiac neuronal function in different diseases of the heart and other altered metabolic or functional conditions. Therefore assessment of the integrity of cardiac sympathetic innervation may help in the diagnosis of these disorders, as well as in prognostication, and will result in better therapy and outcome. At present, the most widely available SPECT tracer by which to assess cardiac neurotransmission is metaiodobenzylguanidine labeled with iodine 123. This article focuses on reviewing the characteristics of cardiac SPECT imaging with I-123 metaiodobenzylguanidine and its role in the assessment of pathophysiologic changes during relevant clinical conditions.

[123 I-MIBG myocardial sympathetic innervation scintigraphy and Parkinson's disease. Preliminary results]

OBJECTIVES

Cardiac sympathetic function in patients with Parkinson's disease (PD) is significantly impaired. Cardiac scintigraphy with 123I-metaiodobenzylguanidine (123I-MIBG) is used to assess cardiac sympathetic function.

METHODS

A total of 29 consecutive patients with PD and 10 control subjects without neurological disease were studied. Myocardial imaging with 123I-MIBG was performed to evaluate cardiac sympathetic function. Early and delayed images of the anterior view were obtained at 15 min. and 4 h. after injection of 123I-MIBG, respectively. 123I-MIBG uptake was quantified qualitatively and semiquantitatively by calculating a heart-to-mediastinum (H/M) ratio.

RESULTS

The heart/mediastinum ratio was markedly reduced in patients with PD (I to IV on the Hoehn and Yahr scale) when compared to the control subjects (p < 0.05). This finding was independent of the length and severity of the disease or the pharmacological treatment of the patients. None of the control subjects showed decrease in myocardial 123I-MIBG uptake.

CONCLUSIONS

Our findings indicate that a decrease in myocardial accumulation of 123I-MIBG was observed in the early stages of PD. This suggests that the measurement of 123I-MIBG may help the early diagnosis of PD, and can be used to detect cardiac autonomic dysfunction, especially in patients without typical signs and symptoms.

123I-MIBG radioaerosol lung clearance in COPD patients with fixed and partially reversible obstruction to evaluate the functional status of pulmonary adrenergic innervation

In order to test the hypothesis that a greater sympathetic activity underlies partial reversibility of the bronchial obstruction in selected patients with chronic obstructive pulmonary disease (COPD), we assessed the pulmonary clearance of inhaled I-meta-iodobenzylguanidine ( I-MIBG) radioaerosol in 10 patients with fixed and nine with reversible obstruction. The clearance of inhaled I-MIBG is known to be inversely related to I-MIBG uptake by adrenergic terminals. Groups were matched for age and judged free from confounding comorbidity. The penetration index did not distinguish between the groups (fixed obstruction, 97.39+/-14.59%; reversible obstruction, 89.09+/-19.95%; P=0.659); this excludes the possibility that the inequality of tracer penetration could affect I-MIBG clearance. The I-MIBG clearance was 140.92+/-7.67 min in patients with fixed obstruction and 151.08+/-31.54 min in patients with reversible obstruction ( P=0.604). In conclusion, COPD patients with fixed and reversible obstruction show comparable binding of the tracer to adrenergic pulmonary receptors. Thus, a greater receptor responsiveness or post-receptor mechanism probably underlies the partial reversibility of bronchial obstruction.

A clinical role for [(123)I]MIBG myocardial scintigraphy in the distinction between dementia of the Alzheimer's-type and dementia with Lewy bodies

OBJECTIVE

Scintigraphy with [(123)I]metaiodobenzyl guanidine ([(123)I]MIBG) enables the quantification of postganglionic sympathetic cardiac innervation. Recently, myocardial [(123)I]MIBG scintigraphy has been found to be useful in distinguishing Parkinson's disease, a Lewy body disease, from other akinetic rigid syndromes. Some patients initially diagnosed with dementia of the Alzheimer's type (DAT) are discovered to have an alternative disease such as dementia with Lewy bodies (DLB), despite the application of stringent diagnostic criteria. In the present study, examinations were performed to clarify the usefulness of myocardial [(123)I]MIBG scintigraphy in improving the differential diagnosis between patients with DLB and DAT.

METHODS

Fourteen patients with DLB and 14 patients with DAT underwent scintigraphy with [(123)I]MIBG, combined with orthostatic tests and cardiac examinations.

RESULTS

In all patients with DLB, the heart to mediastinum (H/M) ratio of MIBG uptake was pathologically impaired in both early and delayed images, independently of the duration of disease and autonomic failure. All patients with DAT had successful MIBG uptake in the heart regardless of duration of disease and autonomic failure. Orthostatic hypotension was seen in four patients with DAT and 13 patients with DLB.

CONCLUSIONS

[(123)I]MIBG myocardial scintigraphy might detect early disturbances of the sympathetic nervous system in DLB and might provide useful diagnostic information to discriminate DLB from DAT. The distinction between DLB and DAT may be improved by greater emphasis on cardiac sympathetic disturbances.

Pulmonary involvement in Behçet's disease: evaluation of 123 I-MIBG retention

Pulmonary involvement in Behçet's disease (BD) is reported to indicate poor prognosis and high mortality. Our aim was to evaluate the pulmonary vascular status in BD. As 123I-meta-iodobenzylguanidine (123I-MIBG) shares the same uptake, storage and release mechanisms as norepinephrine, associated with the functional state of pulmonary endothelium, it may reflect endothelial injury. Twenty-five patients (13 males, 12 females; mean age, 36.44 years) and 12 age-matched controls were included. After intravenous injection of 123I-MIBG, thorax images were taken at 15 min and 4 h. Appropriate regions of interest were drawn, and heart to mediastinum (H/M) ratios and lung retention indices (LRI) were calculated. The difference between the LRI of controls (75.6+/-4%) and patients (87.7+/-10%) was found to be extremely significant (P<0.005). The LRIs of active (92.85+/-12%) and inactive (83.65+/-5%) states of BD were significantly different (P<0.05) from each other. There was no significant difference between the H/M ratios of controls (2.4+/-0.27) and patients (2.39+/-0.31) or between patients in active and inactive disease states. Our study revealed prolonged lung retention of 123I-MIBG in BD, probably reflecting the severity of the disease. In conclusion, 123I-MIBG lung retention is a valuable finding in the evaluation of pulmonary vascular status and may be a potential marker of prognosis in BD.

Increased QT dispersion does not reflect the increased regional variation of cardiac sympathetic nervous activity in hypertrophic cardiomyopathy

BACKGROUND

QT dispersion (QTD) reflects regional variation of ventricular repolarization. However, the relationship between QTD and the regional variation of cardiac sympathetic nerve activity in hypertrophic cardiomyopathy (HCM) is not yet elucidated.

METHODS

Cardiac sympathetic nerve activity was evaluated in 25 patients with HCM by iodine 123 metaiodobenzylguanidine (MIBG) myocardial scintigraphy. With planar MIBG imaging, heart and mediastinum ratios (H/M) at early (20 minutes) and delayed (3 hours) acquisition and the washout rate (WR) were calculated. Polar maps of left ventricular myocardium were divided into 20 segments. The SD of early uptake (EU-SD), delayed uptake (DU-SD), and WR (WR-SD) in 20 segments as indices of regional variation were calculated. QT intervals were corrected by use of the Bazett formula.

RESULTS

Maximum QTc correlated positively with H/M early, WR, and left ventricular wall thickness (LVWT). Minimum QTc correlated positively with WR and LVWT. Corrected QTD (QTDc) correlated negatively with EU-SD, DU-SD, and WR-SD and positively with the interventricular septal thickness/posterior wall thickness ratio. Stepwise regression analysis revealed that the most powerful determinants for maximum QTc, minimum QTc, and QTDc were WR, LVWT, and EU-SD, respectively.

CONCLUSIONS

QTD correlated negatively rather than positively with the regional variability index of cardiac sympathetic nerve activity. These results suggest that increased QTD in patients with HCM may not reflect increased heterogeneity of cardiac sympathetic nerve activity.

Effects of reduced sympathetic activity on myocardial metaiodobenzylguanidine (MIBG) washout

1. Increase in myocardial sympathetic activity contributes markedly to the pathophysiology of conditions such as congestive heart failure and is also associated with myocardial infarction. However, measurement of myocardial sympathetic activity in vivo is difficult. 2. The present study assesses the effectiveness of metaiodobenzylguanidine (MIBG) imaging to characterize modulation of sympathetic activity, as induced by dexmedetomidine, a highly specific alpha-2 adrenoceptor agonist. 3. We imaged washout of [125I]-MIBG from rabbit heart before and during two consecutive 45-min intravenous infusions of dexmedetomidine (10 microg kg(-1) followed by 16 microg kg(-1)) (n=9) or of saline (n=9). 4. Heart rate (HR), and mean blood pressure (BP) were measured before and at the end of each study period. Plasma noradrenaline (NA) was measured before and after study drug infusion. The hearts were then excised and biopsied for MIBG tissue concentration [MIBG] (% kg-dose g(-1)). 5. Relative to saline controls, dexmedetomidine significantly decreased HR, BP, plasma NA and MIBG washout. There was an inverse correlation between MIBG washout and residual [MIBG] in the myocardium (r= -0.75, P < 0.01). 6. These data suggest that a reduction of sympathetic nervous system activity causes a decrease in myocardial MIBG washout in vivo in rabbits, and confirms the usefulness of MIBG scintigraphy as a non-invasive tool to measure changes in myocardial sympathetic activity.

Prognostic value of iodine-123-metaiodobenzylguanidine imaging and cardiac natriuretic peptide levels in patients with left ventricular dysfunction resulting from cardiomyopathy

This study assessed the prognostic value of Iodine-123-metaiodobenzylguanidine (MIBG) imaging and of the plasma level of cardiac natriuretic peptides in patients with left ventricular dysfunction resulting from cardiomyopathy. Predictors of cardiac death or hospitalization related to progressive heart failure were examined in 171 patients with chronic heart failure (96 patients with idiopathic cardiomyopathy and 75 patients with ischemic cardiomyopathy). All patients underwent MIBG imaging at rest and other hemodynamic studies. During a mean (+/-SD) follow-up period of 27+/-11 months, 11 patients died from heart failure and 16 required hospitalization. High MIBG washout was an independent predictor of cardiac death (relative risk [RR] = 1.158, p<0.0001) whereas the plasma level of brain natriuretic peptide (BNP: relative risk [RR] = 1.005, p<0.0001) and high MIBG washout (relative risk [RR] = 1.094, p<0.0001) were predictors of progressive heart failure (ie, combined cardiac death and hospitalization). Accelerated myocardial adrenergic nerve activity as assessed by MIBG imaging and the plasma levels of BNP are powerful predictors of the patient's prognosis.

Autonomic dysfunction in Machado-Joseph disease assessed by iodine123-labeled metaiodobenzylguanidine myocardial scintigraphy

Iodine123-labeled metaiodobenzylguanidine, a radioiodinated analogue of norepinephrine, is a tracer for evaluating sympathetic function. We used iodine123-labeled metaiodobenzylguanidine myocardial scintigraphy and sympathetic skin response to study autonomic nervous functions in 19 patients with Machado-Joseph disease (MJD) and 20 control subjects. Planar imaging of all the participants was done to evaluate myocardial scintigraphy. The ratio of average counts in the heart to average counts in the mediastinum was calculated for both early and delayed images, the latter of which reflects the cardiac neural uptake of the tracer. Single photon emission computed tomography also was done on 12 patients with MJD to examine regional tracer uptake to the heart. The mean ratio of counts in the heart to counts in the mediastinum in the delayed images was lower for the patients with MJD than for the control subjects (p <0.01). Abnormal sympathetic skin response was present in 6 patients with MJD whose mean ratio of counts in the heart to counts in the mediastinum was lower than that of patients with MJD who had normal sympathetic skin response (p <0.01). A single photon emission computed tomography study showed significantly lower accumulation of the tracer in patients with MJD than in the control subjects in the anterior lateral sectors predominantly innervated by sympathetic nerves but not in the inferior septal sectors reported to be under main innervation by parasympathetic fibers. These results show that MJD is accompanied by cardiac sympathetic dysfunction, as detected by iodine123-labeled metaiodobenzylguanidine myocardial scintigraphy, which appears to be correlated with sudomotor sympathetic dysfunction.

Abnormality of left ventricular sympathetic nervous function assessed by (123)I-metaiodobenzylguanidine imaging in patients with COPD

BACKGROUND

Cardiac and systemic autonomic nervous function may be impaired in patients with COPD. Few reports, however, have described sympathetic nervous function of the left ventricle (LV) in COPD patients.

STUDY OBJECTIVE

To assess the LV sympathetic nervous function in patients with COPD using (123)I-metaiodobenzylguanidine (MIBG) imaging of the heart.

DESIGN

Prospective comparison of (123)I-MIBG imaging results in COPD patients and normal subjects.

PARTICIPANTS

Twenty-eight patients with COPD without manifest right ventricular overload and 7 volunteers without cardiopulmonary disease (control subjects).

MEASUREMENTS

(123)I-MIBG imaging results and plasma norepinephrine concentration were compared between the COPD and control groups. In the COPD group, pulmonary function tests were performed and all subjects were interviewed about their symptoms.

RESULTS

(123)I-MIBG uptake, assessed as the cardiac to mediastinal activity ratio in the delayed image, was significantly lower in the COPD group than in the control group (p < 0.05). (123)I-MIBG turnover, expressed as the washout rate (WR) of (123)I-MIBG from 15 to 240 min, was significantly higher in the COPD group than in the control group (p < 0.01). In the COPD group, patients with dyspnea showed lower cardiac to mediastinal activity ratios and higher WRs compared with patients who had mild dyspnea. The WR correlated negatively with the vital capacity/predicted value ratio, correlated negatively with the maximal voluntary ventilation volume/predicted value ratio, and correlated positively with the residual volume/total lung capacity ratio in the COPD group. The plasma norepinephrine concentration in COPD patients was higher than that in the control subjects.

CONCLUSION

Patients with COPD have significant sympathetic nervous impairment of the LV myocardium as a result of generalized sympathetic overactivity.

Relationship between insulin resistance and cardiac sympathetic nervous function in essential hypertension

BACKGROUND

It has been suggested that hyperinsulinemia and insulin resistance participate in the pathogenesis of hypertension, in part by activating sympathetic activity.

OBJECTIVE

We aimed to examine the relationship between insulin resistance and cardiac sympathetic nervous function in patients with essential hypertension using 123I-metaiodobenzylguanidine (MIBG) cardiac scintigraphy.

METHODS AND RESULTS

Twenty-eight patients (18 men) with essential hypertension and 11 (seven men) control individuals with a mean age of 55.8+/-3.3 years were recruited. Patients with diabetes mellitus, congestive heart failure or coronary artery disease were excluded from this study. To evaluate insulin resistance, we used steady-state plasma glucose (SSPG; mg/dl) levels measured by the SSPG method. To evaluate cardiac sympathetic nervous function, we calculated the heart-to-mediastinum ratio from the delayed MIBG image (H:M-D) and the mean washout rate (WOR, %). There were significant differences (P<0.01) in SSPG, H:M-D and WOR between the essential hypertension and control individual groups (125 versus 103 mg/dl, 2.2 versus 2.4, and 32 versus 23%, respectively). Stepwise regression analysis showed that SSPG and plasma norepinephrine level are independent predictors for the cardiac sympathetic nervous function obtained from MIBG scintigraphy.

CONCLUSIONS

These findings indicate that insulin resistance is significantly related to activation of the cardiac sympathetic nervous function associated with left ventricular hypertrophy in patients with essential hypertension.

(123)I-metaiodobenzylguanidine myocardial scintigraphy in Parkinson's disease

OBJECTIVES

(123)I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy is clinically used to estimate local myocardial sympathetic nerve damage in some forms of heart disease, autonomic nerve disturbance in diabetic neuropathy, and disturbance of the autonomic nervous system in neurodegenerative disease. In the present study, examinations were performed to clarify (1) the proportion of cardiac sympathetic nerve disturbance in Parkinson's disease, (2) the usefulness of (123)I-MIBG myocardial scintigraphy to detect sympathetic nerve disturbances compared with autonomic function tests, (3) cardiac function in patients who have a decreased MIBG uptake in (123)I-MIBG myocardial scintigraphy, (4) the usefulness of (123)I-MIBG myocardial scintigraphy to differentiate Parkinson's disease from the other neurological diseases mimicking it.

METHODS

(123)I-MIBG myocardial scintigraphy was performed, together with autonomic function tests and cardiac examinations in 46 patients with Parkinson's disease and 25 patients with vascular parkinsonism, essential tremor, or multiple system atrophy.

RESULTS

In an anterior image study, the average count per pixel in heart to mediastinum (H/M) ratio decreased in 80% of the patients with Parkinson's disease in the early phase and 84% in the late phase. The mean H/M ratio in Parkinson's disease was significantly lower than that in controls and the other diseases. The H/M ratio tended to decrease with the disease progression. In almost half of the patients in Hoehn and Yahr stage I, the H/M ratio was already decreased. The sympathetic skin response in upper and lower limbs, head up tilt test, and coefficient of variation of R-R interval were abnormal in 17%, 31%, 30%, and 17% of the patients, respectively. All the patients with abnormal autonomic functions were in Hoehn and Yahr stage III, IV, or V. Echocardiography showed normal left ventricular function. Twenty four hour Holter electrocardiography detected no serious arrhythmias except for one patient with non-sustained ventricular tachycardia.

CONCLUSION

(123)I-MIBG myocardial scintigraphy might detect early disturbances of the sympathetic nervous system in Parkinson's disease and might give useful diagnostic information to differentiate vascular parkinsonism, essential tremor, and multiple system atrophy from Parkinson's disease.

Cardiac metaiodobenzylguanidine uptake in patients with moderate chronic heart failure: relationship with peak oxygen uptake and prognosis

OBJECTIVES

This prospective study was undertaken to correlate early and late metaiodobenzylguanidine (MIBG) cardiac uptake with cardiac hemodynamics and exercise capacity in patients with heart failure and to compare their prognostic values with that of peak oxygen uptake (VO2).

BACKGROUND

The cardiac fixation of MIBG reflects presynaptic uptake and is reduced in heart failure. Whether it is related to exercise capacity and has better prognostic value than peak VO2 is unknown.

METHODS

Ninety-three patients with heart failure (ejection fraction <45%) were studied with planar MIBG imaging, cardiopulmonary exercise tests and hemodynamics (n = 44). Early (20 min) and late (4 h) MIBG acquisition, as well as their ratio (washout, WO) were determined. Prognostic value was assessed by survival curves (Kaplan-Meier method) and uni- and multivariate Cox analyses.

RESULTS

Late cardiac MIBG uptake was reduced (131+/-20%, normal values 192+/-42%) and correlated with ejection fraction (r = 0.49), cardiac index (r = 0.40) and pulmonary wedge pressure (r = -0.35). There was a significant correlation between peak VO2 and MIBG uptake (r = 0.41, p < 0.0001). With a mean follow-up of 10+/-8 months, both late MIBG uptake (p = 0.04) and peak VO2 (p < 0.0001) were predictive of death or heart transplantation, but only peak VO2 emerged by multivariate analysis. Neither early MIBG uptake nor WO yielded significant insights beyond those provided by late MIBG uptake.

CONCLUSIONS

Metaiodobenzylguanidine uptake has prognostic value in patients with wide ranges of heart failure, but peak VO2 remains the most powerful prognostic index.

Effect of exercise-induced activation of sympathetic nerve activity on clearance of 123I-MIBG from the myocardium

The effect of exercise on the cardiac kinetics of 123I-MIBG was investigated in the present study. 123I-MIBG was administered intravenously at rest in 6 healthy male volunteers, and anterior planar and SPECT images were obtained 15 minutes, and 2 and 4 hours after administration (protocol A). After 4 weeks, 123I-MIBG was again administered intravenously at rest, and images were obtained 15 minutes later. After imaging, the subjects ran 10 km in approximately 1 hour, and anterior planar and SPECT images were obtained 2 and 4 hours after administration of 123I-MIBG (protocol B). The heart-to-mediastinum uptake ratio (H/M) was calculated from each anterior planar image, and the mean 123I-MIBG clearance from 15 minutes to 2 hours, and from 2 hours to 4 hours was calculated with a bull's eye display. The H/M was much lower after exercise. The mean clearance rate between 15 minutes and 2 hours in protocol B was significantly higher than that between 2 hours and 4 hours, and that between 15 minutes and 2 hours in protocol A. It was concluded that the clearance rate of 123I-MIBG may be a useful index of cardiac sympathetic nerve activity.

Decreased myocardial 123I-MIBG uptake in Parkinson's disease

We studied myocardial 123I-metaiodobenzylguanidine (MIBG) accumulation in 12 patients with Parkinson's disease (PD). MIBG is an analog of norepinephrine (NE) and a tracer for sympathetic neuron integrity and function. MIBG uptake of the myocardium was significantly lower in PD than in controls. The heart to mediastinum ratio (H/M) was calculated by using the average count per pixel for the heart and mediastinum. In PD, H/M was lower than in controls (P<0.0001), while the washout ratio of the heart was higher (P<0.001). A decrease in myocardial accumulation of MIBG was observed in the early stage of PD. This suggests that the measurement of MIBG may help the diagnosis of early PD, and the causative factor underlying in PD may be operating the NE neuron as well as dopamine neuron.

Differentiation of idiopathic Parkinson's disease from striatonigral degeneration and progressive supranuclear palsy using iodine-123 meta-iodobenzylguanidine myocardial scintigraphy

Iodine-123 meta-iodobenzylguanidine ([123I]MIBG), an analogue of norepinephrine, is a tracer for functioning of sympathetic neurons. To investigate cardiac sympathetic function in PD, SND, and PSP, [123I]MIBG myocardial scintigraphy was performed in 25 patients with PD, 15 patients with SND, 14 patients with PSP, and 20 control subjects. In planar imaging studies, the heart-to-mediastinum average count ratio (H/M) was calculated for both early and delayed images. The mean value of H/M in patients with PD was significantly lower than those with SND, PSP, or no disease. Regardless of disease severity or intensity of anti-Parkinsonian pharmacotherapy, mean values for H/M were always low in patients with PD. The mean value of H/M in SND with orthostatic hypotension (OH) was lower than that in SND without OH. Although the mean value of H/M in PSP with amitriptyline treatment was significantly lower than that in PSP patients without amitriptyline treatment, there was no significant difference between the mean value of H/M in PSP patients without amitriptyline treatment and that in control. Thus, PD may have a abnormality of cardiac sympathetic function which has not been detected by previous cardiovascular autonomic studies. Moreover, particularly in early stages, [123I]MIBG myocardial scintigraphy may provide helpful diagnostic information in these akinetic-rigid syndromes.

Increased cardiac sympathetic activity in patients with hypothyroidism as determined by iodine-123 metaiodobenzylguanidine scintigraphy

Clinical manifestations of hypothyroidism, such as bradycardia, suggest decreased sympathetic tone. However, previous studies in patients with hypothyroidism have suggested that increased plasma noradrenaline (NA) levels represent enhanced general sympathetic activity. As yet, cardiac sympathetic activity (CSA) in hypothyroidism has not been clarified. To evaluate CSA in patients with hypothyroidism, iodine-123 metaiodobenzylguanidine (MIBG) scintigraphy was performed in eight patients with hypothyroidism before therapy and in ten normal control patients. Planar images were obtained at 15 min and 4 h after injection of MIBG. The ratio of early myocardial uptake to the total injected dose (MU) and myocardial clearance of MIBG within 4 h p.i. (MC) were calculated. Plasma NA was also measured, and echocardiography was performed in all patients. Those patients with hypothyroidism in the euthyroid state after medical therapy were also evaluated in a similar manner. Left ventricular ejection fraction, measured by echocardiography, did not differ significantly between the groups. NA, MU and MC were significantly higher in patients with hypothyroidism than in controls, and all parameters were decreased after therapy. MC was well correlated with NA in hypothyroidism (r=0.86) before therapy. We conclude that CSA is increased in patients with hypothyroidism, in parallel with the enhanced general sympathetic activity.

Influence of prolonged exercise on myocardial distribution of 123I-MIBG in long-distance runners

BACKGROUND

A study was conducted to determine if prolonged exercise could provoke sympathetic neuronal alteration in an athlete's heart through assessment of myocardial distribution of 123I-metaiodobenzylguanidine (MIBG) in nine ultramarathon runners at baseline and after a 4-hour race.

METHODS AND RESULTS

After injection of 370 MBq of 123I-MIBG, the athletes ran for 4 hours, covering 45 +/- 8 km. Planar and single-photon emission computed tomography (SPECT) images of the thorax were acquired at the end of the race. Two weeks later, studies at baseline were performed. A heart:mediastinum ratio (HMR) was calculated to quantify MIBG uptake. Basal MIBG studies showed normal myocardial tracer uptake, on both planar and SPECT images, and the HMR was 1.84 +/- 0.16. After the 4-hour race, MIBG studies showed decreased myocardial uptake in all athletes, and the HMR was 1.70 +/- 0.18 (p < 0.005). A positive correlation between the percentage of decrease of HMR after the race and the distance covered was observed (r = .910, p < 0.001).

CONCLUSIONS

Myocardial MIBG activity is decreased by prolonged exercise in long-distance runners. The degree of reduction of myocardial MIBG activity is related to the distance covered. Prolonged exercise, as sustained sympathetic stimulus, may alter myocardial distribution of MIBG.

123I-MIBG myocardial imaging in hypertensive patients: abnormality progresses with left ventricular hypertrophy

Twenty-seven patients with essential hypertension were prospectively studied with 123I-labeled metaiodobenzyl-guanidine (123I-MIBG) to assess the presence and location of impaired sympathetic innervation in hypertrophied myocardium. Thirteen patients had left ventricular hypertrophy on echocardiography, and 14 had normal echocardiograms. The wash out ratio of 123I-MIBG in these two groups did not differ significantly (35.3 +/- 6.1 and 35.4 +/- 5.1) but was higher than in control subjects (29.4 +/- 6.7). The delayed heart-to-mediastinum count ratio was lower in the patients with hypertrophy than in the patients without hypertrophy (1.93 +/- 0.28 and 2.22 +/- 0.21; p < 0.05) and the control subjects (1.93 +/- 0.28 and 2.33 +/- 0.25; p < 0.05). On SPECT imaging, abnormalities in segmental uptake were frequent at the posterior and postero-lateral wall in both groups, although the hypertrophic group had more significant impairment. Our results lead to the hypothesis that hypertension in more advanced stages may be associated not only with hypertrophic changes but also with more advanced regional impairment of cardiac sympathetic innervation.