Iodine-123 Metaiodobenzylguanidine Research Articles

The Potential Role of Iodine-123 Metaiodobenzylguanidine Imaging for Identifying Sustained Ventricular Tachycardia in Patients with Cardiomyopathy

Implantable cardioverter-defibrillators (ICDs) significantly reduce mortality in patients with depressed left ventricular ejection fraction (LVEF) and heart failure (HF). However, shortcomings of LVEF to accurately identify those at greatest risk of ventricular tachyarrhythmias have led to the pursuit of alternative means to refine qualification criteria for ICD implantation. It is well established that imaging the cardiac nervous system with123I meta-iodobenzylguanidine (123I-mIBG) provides incremental prognostic value in patients with HF beyond LVEF. Whether 123I-mIBG will also play an important role for identifying and/or predicting sustained ventricular tachyarrhythmias in patients with cardiomyopathy and determining those who may benefit from ICD implantation is currently under investigation. Novel imaging approaches that pinpoint the site of ventricular arrhythmias and guide ventricular tachycardia ablation are presented.

Iodine-123 Metaiodobenzylguanidine Scintigraphy Scoring Allows Prediction of Outcome in Patients With Stage 4 Neuroblastoma: Results of the Cologne Interscore Comparison Study

Radioiodinated metaiodobenzylguanidine ((123)I-mIBG) scintigraphy is an established imaging method in neuroblastoma. Semiquantitative scoring systems have been developed to assess the extent of disease and response to chemotherapy. We present the results of the comparison between the SIOPEN [International Society of Pediatric Oncology Europe Neuroblastoma Group] score and the modified Curie score. We retrospectively analyzed 147 mIBG scans of 58 patients older than 1 year of age with stage 4 neuroblastoma from German Neuroblastoma Trial NB97 that were assessed according to the SIOPEN and the Curie scoring method. mIBG examinations were performed at diagnosis and after four and six cycles of chemotherapy. Scoring results were highly correlated between both methods, and interobserver reliability was excellent. A Curie score ≤ 2 and a SIOPEN score ≤ 4 (best cutoff) at diagnosis were correlated to significantly better event-free and overall survival compared with higher scores. After four cycles of chemotherapy, overall survival was significantly better for mIBG-negative patients compared with those with any residual mIBG-positive metastases. After six cycles of chemotherapy, there was no difference in survival between mIBG-negative patients and patients with residual mIBG-positive metastases. Patients without mIBG-positive metastases after four and six cycles of chemotherapy had a better overall survival, but late clearance of mIBG-positive metastases did not improve outcome. Higher mIBG scores at diagnosis and occurrence of any residual mIBG-positive metastases after four cycles of chemotherapy predicted unfavorable outcome for patients with stage 4 neuroblastoma. Later clearance of metastases did not improve prognosis. The Curie and the SIOPEN score were equally reliable and predictive.

パーキンソン病の障害評価とリハビリテーション

Hoehn and Yahr (H-Y) staging and the Unified Parkinson's Disease Rating Scale (UPDRS) are commonly used for clinical evaluation of Parkinson's disease (PD). Iodine-123 metaiodobenzylguanidine (MIBG) myocardial scintigraphy and single photon emission computed tomography (SPECT) are useful for the differential diagnosis of PD from other Parkinsonism. Additionally, gravicorders or gait analysis systems and upper limb voluntary movement analyzing systems may be helpful for the quantitative evaluation of parkinsonian symptoms. From the early stage of H-Y, PD patents should be informed and coached about rehabilitation programs by expert therapists. Educational and health promotional gymnastics are the main programs used in stage I and II. Muscle stretching exercises, postural exercises, balance training and activity/instrumental-activity training are needed in stage III and IV. Finally, preventing changes due to disuse and lightening the caregiver load are the main purpose of rehabilitation in stage V. It is very important to understand not only the patients' clinical stages but also their personal situations such as their life-stage and life-style and their family situation. Home visit rehabilitation is useful to discover the actual daily living problems faced by patients and their families. Then, evaluation according to the International Classification of Functioning, Disability and Health (ICF) is available to clarify and solve the problems. With the progression of the clinical stage, patients need many social resources. Therefore, medical social workers (MSW) should be a part of the rehabilitation team to support the home care of patients from their incipient stage.

MIBG Myocardial Scintigraphy can Predict the Occurrence of Wearing-off Phenomenon in Early-stage Parkinson’s Disease

Background: Iodine-123 metaiodobenzylguanidine ( ¹²³ I-MIBG) myocardial scintigraphy has been accepted as one of the most useful methods for the diagnosis of Parkinson’s disease (PD). Moreover, the accumulated evidence has indicated that the heart-to-mediastinum (H/M) ratio correlates with the disease severity of hypokinesia/ bradykinesia and rigidity. The present report describes the wearing-off predictions obtained from MIBG in patients with early-stage PD. Methods: 13 males and 10 females with PD whose onset ages between 45 and 70 years were enrolled. They were separated into two groups according to their H/M ratios (less than 1.7 or 1.7 or higher). We generated Kaplan- Meier survival curves for the times of the onset of the wearing-off phenomenon, and survival differences were analyzed by the log-rank test. The onset of the wearing-off phenomenon was defined as an event during the 71- month observation. Results: There was a significant difference in the wearing-off occurrence between the 2 groups that were divided by the H/M ratio (P=0.016). This result might reflect the existence of PD patients who do not show reductions in the H/M ratios at earlier stages and who do not manifest the wearing-off phenomenon later. Conclusions: Our study suggests the possibility that patients with good prognoses represent those with almost normal H/M ratios, even though they are affected with PD. MIBG could be a valuable method for predicting prognoses as well as for diagnoses

I-131 MIBG post-therapy scan is more sensitive than I-123 MIBG pretherapy scan in the evaluation of metastatic neuroblastoma

Iodine-123 metaiodobenzylguanidine (I-123 MIBG) scintigraphy is gradually replacing I-131 MIBG scans in the diagnostic workup of neuroblastoma. High-dose I-131 MIBG, however, is commonly used for subsequent therapy in patients with proven MIBG-avid lesions. The objective of this study was to compare the sensitivities of pretherapy I-123 MIBG and post-therapy I-131 MIBG scans for detecting metastatic lesions of neuroblastoma and determine the suitability of post-therapy scans for detecting new metastases. Pretherapy I-123 MIBG scans and post-therapy I-131 MIBG scans of 126 patients with neuroblastoma were analyzed retrospectively and the number of detected lesions was compared. In 70 patients (55.6% cases), the pretherapy and post-therapy scans were concordant, showing similar MIBG-avid foci. In the remaining 56 patients (44.4% cases), the post-therapy I-131 MIBG scans revealed additional lesions (i.e. a total of 716 lesions) compared with pretherapy I-123 MIBG scans (only 532 lesions). All lesions detected on pretherapy I-123 MIBG scans were revisualized on the post-therapy I-131 MIBG scans, the latter also revealing 184 new MIBG-avid lesions. Post-therapy I-131 MIBG scans demonstrate new lesions in almost half of the patients when compared with pretherapy I-123 MIBG scans and therefore are essential to delineate the disease extent.

Iodine-123 metaiodobenzylguanidine imaging can predict future cardiac events in Japanese patients with Parkinson’s disease

Iodine-123 metaiodobenzylguanidine (123I-MIBG) myocardial scintigraphy provides useful diagnostic information in differentiating Parkinson's disease (PD) from other neurological diseases. Moreover, a number of studies have reported that 123I-MIBG imaging provides powerful diagnostic and prognostic information in congestive heart failure (HF) patients. The aim of the present study was to investigate the cardiovascular predictive value of cardiac 123I-MIBG imaging in patients with PD. Seventy-eight patients with PD were retrospectively studied. All patients underwent 123I-MIBG imaging at 30 min (early) and 240 min (delayed) after the tracer injection, and clinical parameters were also investigated. During a mean follow-up of 27 ± 12 months, 5 patients required hospitalization for HF. There were no occurrences of myocardial infarction, fatal arrhythmia or sudden death. There was no significant coronary artery stenosis, significant valvular heart disease, or cardiomyopathy in the HF patients. The left ventricular ejection fraction (LVEF) was normal in the HF patients. (123)I-MIBG delayed heart to mediastinal ratio (delayed H/M) was lower and washout rate (WR) was higher in HF patients than non-HF patients (1.62 ± 0.21 vs. 1.34 ± 0.08, p = 0.019; 31.9 ± 5.5 vs. 38.2 ± 3.3, p = 0.005, respectively). Both WR and delayed H/M did not correlate with Hoehn and Yahr stage. The WR showed a weak negative correlation with delayed H/M (R = -0.357, p < 0.001) upon simple linear regression analysis. A multivariate Cox regression analysis revealed that WR and delayed H/M were independently associated with HF (p = 0.014, p = 0.029, respectively). Kaplan-Meier analysis revealed that patients with abnormal WR (> 37%) and delayed H/M (< 1.48) had a higher incidence of HF than those with normal WR and delayed H/M (p = 0.014, p = 0.04, respectively). WR showed stronger predictive power than delayed H/M in Kaplan-Meier analysis. WR has more useful cardiovascular predictive value than delayed H/M in Japanese patients with PD. Further studies are needed to clarify the significance of abnormal MIBG uptake in PD patients.

Can Combined Assessment of Baroreflex Sensitivity and Iodine-123 Metaiodobenzylguanidine Imaging Be Used for Risk Stratification of Patients With Type 2 Diabetes Mellitus?

Can Combined Assessment of Baroreflex Sensitivity and Iodine-123 Metaiodobenzylguanidine Imaging Be Used for Risk Stratification of Patients With Type 2 Diabetes Mellitus?

Selective improvement in Seattle Heart Failure Model risk stratification using iodine-123 meta-iodobenzylguanidine imaging

BackgroundThe Seattle Heart Failure Model (SHFM) is a multivariable model that uses demographic and clinical markers to predict survival in patients with heart failure. Inappropriate activation of the sympathetic nervous system, which contributes to the progression of heart failure and increased mortality, can be assessed using iodine-123 meta-iodobenzylguanidine (MIBG) cardiac imaging. This study investigated the incremental value of MIBG cardiac imaging when added to the SHFM for prediction of all-cause mortality. MethodsSurvival data from 961 NYHA II-III subjects in the ADMIRE-HFX trial were included in this analysis. The predictive value of the SHFM alone and in combination with MIBG heart-to-mediastinum ratio (H/M) was compared for all-cause mortality (101 deaths during a median follow-up of 2 years). ResultsThe addition of H/M to the SHFM in a Cox model significantly improved risk prediction (P < .0001), with a greater utility in higher risk SHFM patients. The observed 2-year mortality in the highest-risk SHFM subjects (rounded SHFM score of 1) was 24%, but varied from 46% with H/M <1.2 to 0% with H/M >1.8. Net reclassification improvement was 22.7% (P < .001), with 14.9% of subjects who died reclassified into a higher risk category than suggested by SHFM score alone (P = .01) and 7.9% of subjects who survived reclassified into a lower risk category (P < .0001). The 2-year integrated discrimination improvement (+4.14%, P < .0001) and the 1-year area under the receiver-operator characteristic curve (+0.04, P = .026) both showed significant improvement for the combined model with H/M compared to the SHFM alone. ConclusionThe addition of MIBG imaging to the SHFM improves risk stratification, especially in higher risk patients. MIBG may have clinical utility in higher risk patients who are being considered for devices such as ICD, CRT-D, LVAD, and cardiac transplantation.

Cardiac iodine-123 metaiodobenzylguanidine imaging predicts ventricular arrhythmia in heart failure patients receiving an implantable cardioverter-defibrillator for primary prevention

ObjectiveTo assess the prognostic value of cardiac iodine-123 metaiodobenzylguanidine (123I-MIBG) scintigraphy to predict ventricular arrhythmias in patients with heart failure (HF) listed for implantable cardioverter-defibrillator (ICD) devices as primary prevention.Design,...

Unusually increased metaiodobenzylguanidine uptake in a gastrointestinal stromal tumor of the stomach

A 70-year-old woman with a submucosal gastric tumor was referred to our hospital for surgical treatment. Upon examination, it was found that she had hypertension, and abdominal computed tomography revealed swelling on both adrenal glands. The patient was examined with gamma camera imaging and iodine-123 metaiodobenzylguanidine (MIBG), because her hypertension was thought to be due to a suspected adrenomedullary tumor. The planar image showed an unexpected abnormal uptake of MIBG in the upper abdomen. On single-photon emission computed tomographic images, the area of abnormal tracer uptake was thought to correspond to the known gastric tumor. The surgical procedure and histological assessments revealed that the gastric tumor was a gastrointestinal stromal tumor (GIST). MIBG can accumulate in GISTs as well as in neuroendocrine tumors of the medulla of the adrenal glands. Although the cause of radiolabeled MIBG uptake in GISTs is uncertain, further studies are necessary to establish the significance of MIBG scintigraphy in GIST imaging.

The role of autonomic testing in the differentiation of Parkinson's disease from multiple system atrophy

Differentiation of idiopathic Parkinson's disease (PD) from multiple system atrophy (MSA) can be difficult. Methods devised to help distinguish the two disorders include standardized autonomic testing and cardiac imaging with iodine-123 meta-iodobenzylguanidine myocardial scintigraphy. MSA patients had more severe adrenergic and overall autonomic dysfunction when compared to control and PD patients. Area of anhidrosis on thermoregulatory sweat test was greater in MSA (67.4±12.42, p<0.001) versus PD patients (area of anhidrosis, 1.7±2.96). Postganglionic cardiac sympathetic innervation (iodine-123 meta-iodobenzylguanidine) expressed as heart to mediastinal ratio was significantly lower in Parkinson's disease patients (1.4±0.40, p=0.025) compared to controls (2.0±0.29), but not in multiple system atrophy (2.0±0.76). These findings indicate that autonomic dysfunction is generalized and predominantly preganglionic in multiple system atrophy, and postganglionic in Parkinson's disease. In our hands the thermoregulatory sweat test provides the best distinction between MSA and PD. However further confirmatory studies using larger patient numbers are required. Currently a combination of clinical judgment and autonomic testing is recommended to help differentiate MSA and PD.

Relationship of haemodialysis therapy duration and cardiac adrenergic system function assessed by iodine-123 metaiodobenzylguanidine imaging in haemodialysed nondiabetic patients

The aim of the study was to evaluate the relationship of haemodialysis therapy duration with the function of the cardiac adrenergic system in nondiabetic patients. Thirty haemodialysed male patients were enrolled in this study; all patients were evaluated by myocardial perfusion imaging at rest and after dynamic stress, with the assessment of left ventricular ejection fraction (LVEF) at rest and after stress and summed stress score (SSS). Single photon emission computed tomography and planar iodine-123 metaiodobenzylguanidine myocardial scintigraphy were also performed in all the patients. Semiquantitative analysis of iodine-123 metaiodobenzylguanidine myocardial uptake was expressed as the routine heart-to-mediastinum ratio (HMR): 15 min [early HMR (eHMR)] and 4 h [delayed HMR (dHMR)] post administration as well as the washout rate. Twenty-four hours of Holter studies were carried out and heart rate variability was evaluated. Significant correlations (Spearman's tests) were found between the duration of haemodialysis treatment and the following ratios: eHMR (P=0.03; r=-0.378), dHMR (P=0.04; r=-0.367) and washout rate (P=0.05; r=0.352). Further significant correlations were found between eHMR and LVEFs (P=0.03; r=0.379), SSS (P=0.01; r=-0.429) and between dHMR and LVEFs (P=0.005; r=0.496), LVEFr (P=0.03; r=0.379) and SSS (P=0.02; r=-0.404). The duration of haemodialysed patients appears to be an important factor influencing the cardiac sympathetic nervous system.

Glucose hypometabolism in primary visual cortex is commonly associated with clinical features of dementia with Lewy bodies regardless of cognitive conditions

Although metabolic reduction in the primary visual cortex on [(18) F]-fluoro-d-glucose (FDG) positron emission tomographic (PET) scans is the hallmark of dementia with Lewy bodies (DLB) for differential diagnosis from Alzheimer's disease, the clinical significance of the metabolic pattern in patients without dementia remains unknown. The purpose of this study was to investigate the clinical profiles of patients without dementia with the metabolic pattern and its relevance to DLB. Of 145 individuals who underwent (18) F-FDG PET, 25 patients with glucose hypometabolism in the primary visual cortex were identified based on three-dimensional stereotactic surface projection images through comparison with a normative database. The frequency of core and suggestive clinical features of DLB was compared between the groups with and without the metabolic pattern. Of 25 patients with glucose hypometabolism in the primary visual cortex, 12 exhibited more than two core features of DLB (probable DLB group) and 6 had rapid eye movement sleep behavior disorder (possible DLB group). Three patients exhibited memory loss without any core or suggestive features but with reduced cardiac iodine-123 metaiodobenzylguanidine uptake. Ten of these 21 patients exhibited no dementia. The proportion of individuals in the probable and possible DLB groups was significantly higher in the group with glucose hypometabolism in the primary visual cortex. Glucose hypometabolism in the primary visual cortex is commonly associated with the clinical features of DLB regardless of cognitive conditions. Continued follow-up of these patients without dementia with the metabolic pattern is warranted to determine if they represent the prodromal state of DLB.

Iodine-131 meta-iodobezylguanidine single photon emission computed tomography/computerized tomography in diagnosis of neuro-endocrine tumors

Metaiodobenzyl guanidine (MIBG) is a derivative of guanethidine and acts as an analogue of nor-epinephrine and is widely used in the imaging of tumors of neuro-endocrine origin. Iodine-123 MIBG has ideal imaging characteristics but is expensive with limited availability. Iodine-131 MIBG is widely used in India and is cheap. Hybrid single photon emission computed tomography (SPECT)/computerized tomography (CT) allows for anatomico-functional imaging and is being tried in MIBG studies. However, the experience with I-131 MIBG is limited. We present a pictorial assay of I-131 MIBG SPECT/CT findings in various MIBG avid tumors.

Takotsubo syndrome in a patient after renal transplantation

SummaryBackgroundTakotsubo syndrome (TTS) is a transient cardiomyopathy of unknown origin, clinically manifesting as acute coronary syndrome (ACS). This syndrome mainly occurs in postmenopausal women and has a temporary relationship with emotional or physical stress.Case ReportTTS occurred in 46-year-old female patient on the first day after renal transplantation. The predominant symptoms were connected with ACS, performed with low grade troponin elevation and characteristic shape of left ventricle depicted in echocardiography. Taking into consideration the risk of the development of contrast-induced nephropathy, coronary angiography (CA) was delayed; myocardial perfusion scintigraphy and iodine-123 metaiodobenzylguanidine (123I-mIBG) myocardial uptake were performed to confirm the clinical suspicion. Myocardial perfusion scintigraphy (MPS) performed in rest condition showed normal perfusion but myocardial uptake of 123I-mIBG was impaired. Within 6 months after surgery, full recovery of all biochemical and functional parameters of the left ventricle were observed. At that time CA was done, depicting normal coronary arteries.ConclusionsTTS could be diagnosed by the use of non-nephrotoxic tests – 123I-mIBG myocardial scintigraphy, MPS and echocardiography.

Does Reducing Unnecessary Right Ventricular Pacing Improve Sympathetic Activity and Innervation of Heart in Sinus Node Disease Patients?

Ventricular desynchronization imposed by ventricular pacing causes regional disturbances of adrenergic innervation in the left ventricular myocardium and increases the risk of heart failure and atrial fibrillation (AF) in patients with sinus node disease (SND). As a result, decreased iodine-123 metaiodobenzylguanidine (I-(123 )MIBG) uptake occurs in patients with an implanted permanent pacemaker. Fourteen SND patients with an implanted pacemaker equipped with an algorithm for reducing unnecessary right ventricular pacing (RURVP) were enrolled. Pacemakers were programmed to RURVP mode for the first 12 weeks, and then reprogrammed to DDD for the last 12 weeks. At the end of each mode, data on cumulative percent ventricular pacing (%Vp), atrial high rate episodes (%AHR), I-(123 )MIBG myocardial scintigraphy, brain natriuretic peptide (BNP), human atrial natriuretic peptide (hANP), and myocardial damage indices typified by troponin T and C-reactive protein (CRP) were collected. %Vp was lower in RURVP than in DDD (0.2% versus 95.7%, P = 0.00098). BNP, hANP, troponin T, and CRP did not differ significantly between the pacing modes. However, I-(123 )MIBG findings of patients with full ventricular pacing in DDD improved in RURVP. In contrast, among patients without full ventricular pacing in DDD, their I-(123 )MIBG findings did not differ significantly between the pacing modes. In SND patients with normal cardiac function and intact atrioventricular conduction, the reduction of %Vp in RURVP was due to the reduction of ineffective pacing and fusion pacing in DDD. Therefore, these 2 types of pacing do not affect cardiac pump function.

Cardiac Iodine-123 Metaiodobenzylguanidine (123I-MIBG) Scintigraphy Parameter Predicts Cardiac and Cerebrovascular Events in Type 2 Diabetic Patients Without Structural Heart Disease

Cardiac iodine-123 metaiodobenzylguanidine ((123)I-MIBG) scintigraphy is an established method of assessment of cardiovascular sympathetic function. The aim of the present study was to investigate the long-term cardiovascular predictive value of cardiac (123)I-MIBG scintigraphy parameters in Japanese type 2 diabetic patients without structural heart disease. Cardiac (123)I-MIBG scintigraphy in 108 patients with type 2 diabetes who did not have structural heart disease, was evaluated. The washout rate (WR) was considered enhanced if it was ≥40%. Accurate follow-up information for 4.6 years was obtained in 54 enhanced WR patients (27 male; mean age, 61 ± 11 years) and in 54 sex- and age-matched preserved WR patients (27 male; mean age, 61 ± 10 years). Major adverse cardiac and cerebrovascular events (MACCE) were investigated. During follow-up, 10 enhanced WR patients developed MACCE including cardiac death, coronary revascularization, stroke, and congestive heart failure, while MACCE occurred in only 3 male patients. The Kaplan-Meier curves indicated that enhanced WR patients had higher incidence of MACCE than those with preserved WR (P<0.05). Cox proportional hazards regression analysis showed that age and enhanced WR were independently associated with the incidence of MACCE (hazard ratio, 4.06; 95% confidence interval: 1.194-18.76, P = 0.0237). Abnormal WR of cardiac (123)I-MIBG scintigraphy at baseline has long-term cardiovascular predictive value in Japanese patients with type 2 diabetes without structural heart disease.

False-negative 123I-MIBG SPECT is most commonly found in SDHB-related pheochromocytoma or paraganglioma with high frequency to develop metastatic disease

The purpose of this study was to present the characteristics and outcome of patients with proven pheochromocytoma or paraganglioma who had false-negative iodine-123 metaiodobenzylguanidine single photon emission computed tomography ((123)I-MIBG SPECT). Twenty-one patients with false-negative (123)I-MIBG SPECT (7 males, 14 females), aged 13-55 years (mean: 41.40 years), were included. We classified them as nonmetastatic or metastatic according to the stage of the disease at the time of false-negative (123)I-MIBG SPECT study, the location and size of the tumor, plasma and urinary catecholamine and metanephrine levels, genetic mutations, and outcome in terms of occurrence and progression of metastases and death. Thirteen patients were evaluated for metastatic tumors, while the remaining eight were seen for nonmetastatic disease. All primary tumors and multiple metastatic foci did not show avid (123)I-MIBG uptake regardless of the tumor diameter. The majority of patients had extraadrenal tumors with hypersecretion of normetanephrine or norepinephrine. SDHB mutations were present in 52% (n=11) of cases, RET mutation in 4% (n=1), and the rest were apparently sporadic. Twenty-four percent (n=5) had metastatic disease on initial presentation. Fourteen patients were followed for 3-7 years. Of them, 71% (n=10) had metastatic disease and the majority had SDHB mutations. Nine are still alive, while five (four with SDHB) died due to metastatic disease. We concluded that false-negative (123)I-MIBG SPECT is frequently related to metastatic tumors and usually due to SDHB mutations with unfavorable prognosis. We therefore recommend that patients with false-negative (123)I-MIBG SPECT be tested for SDHB mutations and undergo more regular and close follow-up.

Iodine-123 Metaiodobenzylguanidine Cardiac Imaging as a Method to Detect Early Sympathetic Neuronal Dysfunction in Chagasic Patients With Normal or Borderline Electrocardiogram and Preserved Ventricular Function

The indeterminate form of Chagas disease represents the most common chronic presentation. The aim of this study was to assess cardiovascular autonomic system function with I-123 metaiodobenzylguanidine (MIBG) scintigraphy in chagasic patients with normal or "borderline" electrocardiographic alterations and preserved left ventricular function evaluated by echocardiography. A total of 40 chagasic patients and 19 control subjects were included in this study. Patients had normal echocardiogram and chest radiography; no arrhythmias or myocardial ischemia; and normal exercise performance for age, gender, and body mass index. I-123 MIBG scintigraphy was performed and the heart-to-mediastinum (H/M) uptake was used as the primary predictor in the present analysis. The data analysis was performed by using Nonparametric Regression Trees and the Survival Agreement Plot. We included only patients with preserved right and left ventricular function assessed by echocardiographic methods. Variables analyzed in the regression tree were age, sex, 20 minutes and 3 hours H/M uptake after injection of I-123 MIBG, washout rate, and single photon emission computed tomography imaging. The 3 hours H/M ratio was the only significant variable (P<0.001) and for 95% of chagasic patients, this value was less than 2.19. This study presents evidence that cardiac autonomic sympathetic modulation may be affected in chagasic subjects with preserved ventricular function evaluated by echocardiography, especially in those with "borderline" electrocardiogram.

Sympathetic Reinnervation 1 Year After Heart Transplantation, Assessed Using Iodine-123 Metaiodobenzylguanidine Imaging

Complete allograft denervation occurs during heart transplantation (HT). Partial ventricular sympathetic reinnervation that may develop after transplantation can be measured using iodine-123 meta iodobenzylguanidine (MIBG) uptake. Previous studies have suggested that reinnervation is likely to be a slow process, only occurring after 1 year posttransplantation. However, the reinnervation prevalence at 1 year after HT remains unknown. This study sought to determine sympathetic reinnervation measured by MIBG at 12 months after surgery. We performed serial cardiac MIBG imaging in 45 cardiac transplant recipients, including 32 males and 13 females, early (2 months) and late (12 months) after the operation. The intensity of myocardial MIBG uptaken was quantified by heart-to-mediastinum ratios (HMR). Reinnervation was considered when the HMR was >1.3. HMR was significantly higher at 12 months: 1.16 ± 0.10 at 2 vs 1.30 ± 0.15 at 12 months (P < .001). Eighteen (40%) of 45 subjects developed visible cardiac MIBG uptake at 1 year after transplantation with HMR >1.3. In conclusion, partial sympathetic reinnervation increases with time after HT; it was seen in 40% of patients at 1 year after the operation.