Cardiac autonomic neuropathy in patients with diabetes and no symptoms of coronary artery disease: comparison of 123I-metaiodobenzylguanidine myocardial scintigraphy and heart rate variability

Functional and 123I-MIBG scintigraphy assessment of cardiac adrenergic dysfunction in diabetes

OBJECTIVES

To assess the agreement between clinical cardiovascular adrenergic function and cardiac adrenergic innervation in type 2 diabetes patients (T2D).

METHODS

Thirty-three patients with T2D were investigated bimodally through (1) a standardized clinical cardiovascular adrenergic assessment, evaluating adequacy of blood pressure responses to the Valsalva maneuver and (2) 123I-meta-iodobenzylguanidine (MIBG) scintigraphy assessing myocardial adrenergic innervation measured as early and delayed heart heart/mediastinum (H/M) ratio, and washout rate (WR).

RESULTS

T2D patients had significantly lower early and delayed H/M-ratios, and lower WR, compared to laboratory specific reference values. Thirteen patients had an abnormal adrenergic composite autonomic severity score (CASS > 0). Patients with abnormal CASS scores had significantly higher early H/M ratios (1.76 [1.66-1.88] vs. 1.57 [1.49-1.63], p < 0.001), higher delayed H/M ratios (1.64 [1.51:1.73] vs. 1.51 [1.40:1.61] (p = 0.02)), and lower WR (-0.13(0.10) vs -0.05(0.07), p = 0.01). Lower Total Recovery and shorter Pressure Recovery Time responses from the Valsalva maneuver was significantly correlated to lower H/M early (r = 0.55, p = 0.001 and r = 0.5, p = 0.003, respectively) and lower WR for Total Recovery (r = -0.44, p = 0.01).

CONCLUSION

The present study found impairment of sympathetic innervation in T2D patients based on parameters derived from MIBG cardiac scintigraphy (low early H/M, delayed H/M, and WR). These results confirm prior studies. We found a mechanistically inverted relationship with favourable adrenergic cardiovascular responses being significantly associated unfavourable MIBG indices for H/M early and delayed. This paradoxical relationship needs to be further explored but could indicate adrenergic hypersensitivity in cardiac sympathetic denervated T2D patients.

Cardiac innervations in diabetes mellitus-Anatomical evidence of neuropathy

The extensive innervations of the heart include a complex network of sympathetic, parasympathetic, and sensory nerves connected in loops that serve to regulate cardiac output. Metabolic dysfunction in diabetes affects many different organ systems, including the cardiovascular system; it causes cardiac arrhythmias, silent myocardial ischemia, and sudden cardiac death, among others. These conditions are associated with damage to the nerves that innervate the heart, cardiac autonomic neuropathy (CAN), which is caused by various pathophysiological mechanisms. In this review, the main facts about the anatomy of cardiac innervations and the current knowledge of CAN, its pathophysiological mechanisms, and its diagnostic approach are discussed. In addition, anatomical evidence for CAN from human and animal studies has been summarized.

Thyroid [123I]MIBG uptake in Parkinson’s disease and diabetes mellitus

Thyroid [¹²³I]MIBG uptake is proposed as a tool for differentiating between Parkinson's disease (PD) and diabetes mellitus (DM) on [¹²³I]MIBG scintigraphies since both patient groups show decreased cardiac uptake. One study compared thyroid [¹²³I]MIBG uptake in DM and PD patients and reported reduced [¹²³I]MIBG uptake only in the PD group. Here, we investigated thyroid [¹²³I]MIBG uptake in patients with PD and DM and found severely reduced thyroid [¹²³I]MIBG uptake in DM. Larger studies are needed to substantiate whether DM patients are more or less likely to exhibit decreased thyroid MIBG uptake compared to controls and PD patients.

Ventricular Arrhythmia Substrate Distribution and Its Relation to Sympathetic Innervation in Nonischemic Cardiomyopathy Patients

BACKGROUND

Nonischemic cardiomyopathy patients referred for catheter ablation of ventricular arrhythmias (VAs) typically have either inferolateral (ILS) or anteroseptal (ASS) VA substrate locations, with poorer outcomes for ASS. Sympathetic denervation is an important determinant of arrhythmogenicity. Its relation to nonischemic fibrosis in general and to the different VA substrates is unknown.

OBJECTIVES

This study sought to evaluate the association between VA substrates, myocardial fibrosis, and sympathetic denervation.

METHODS

Thirty-five patients from the Leiden Nonischemic Cardiomyopathy Study, who underwent electroanatomic voltage mapping and iodine-123 metaiodobenzylguanidine imaging between 2011 and 2018 were included. Late gadolinium-enhanced cardiac magnetic resonance data were collected when available. The relation between global cardiac sympathetic innervation and area-weighted unipolar voltage (UV) as a surrogate for diffuse fibrosis was evaluated. For regional analysis, patients were categorized as ASS or ILS. The distribution of low UV, sympathetic denervation, and late gadolinium enhancement (LGE) scar were compared using the 17-segment model.

RESULTS

Median area-weighted UV was 12.3 mV in patients with normal sympathetic innervation and 8.7 mV in patients with sympathetic denervation. Global sympathetic denervation correlated with diffuse myocardial fibrosis (R = 0.53; P = 0.02). ILS (n = 13) matched with low UV, sympathetic denervation, and LGE scar in all patients, whereas ASS (n = 11) matched with low UV in all patients, with LGE scar in 63% (P = 0.20), but with sympathetic denervation in only 27% of patients (P = 0.0002).

CONCLUSIONS

Global cardiac sympathetic denervation is related to fibrosis in nonischemic cardiomyopathy patients with VA. The mismatch between regional fibrosis and preserved innervation for ASS may contribute to a VA substrate difficult to control by catheter ablation.

Role of Autonomous Neuropathy in Diabetic Bone Regeneration

Diabetes mellitus has multiple negative effects on regenerative processes, especially on wound and fracture healing. Despite the well-known negative effects of diabetes on the autonomous nervous system, only little is known about the role in bone regeneration within this context. Subsequently, we investigated diabetic bone regeneration in db−/db− mice with a special emphasis on the sympathetic nervous system of the bone in a monocortical tibia defect model. Moreover, the effect of pharmacological sympathectomy via administration of 6-OHDA was evaluated in C57Bl6 wildtype mice. Diabetic animals as well as wildtype mice received a treatment of BRL37344, a β3-adrenergic agonist. Bones of animals were examined via µCT, aniline-blue and Masson–Goldner staining for new bone formation, TRAP staining for bone turnover and immunoflourescence staining against tyrosinhydroxylase and stromal cell-derived factor 1 (SDF-1). Sympathectomized wildtype mice showed a significantly decreased bone regeneration, just comparable to db−/db− mice. New bone formation of BRL37344 treated db−/db− and sympathectomized wildtype mice was markedly improved in histology and µCT. Immunoflourescence stainings revealed significantly increased SDF-1 due to BRL37344 treatment in diabetic animals and sympathectomized wildtypes. This study depicts the important role of the sympathetic nervous system for bone regenerative processes using the clinical example of diabetes mellitus type 2. In order to improve and gain further insights into diabetic fracture healing, β3-agonist BRL37344 proved to be a potent treatment option, restoring impaired diabetic bone regeneration.

Cardiac sympathetic dysfunction in left ventricular hypertrophy caused by arterial hypertension and degenerative aortic stenosis

BACKGROUND

To evaluate cardiac sympathetic innervation in hypertensive patients with left ventricular (LV) hypertrophy (H) and aortic stenosis (AS) submitted to transcatheter aortic valve implantation (TAVI).

METHODS AND RESULTS

Twenty-two hypertensive elders (82 ± 5 years) with severe AS and significant LVH (> 122 g·m-2 in women and > 149 g·m-2 in men) were compared with 14 patients with uncomplicated essential hypertension (HT) with similar degree of LVH and 10 controls. 123I-metaiodobenzylguanidine (MIBG) and 99mTc-tetrofosmin SPECT acquisitions were obtained to assess sympathetic innervation and LV perfusion. The innervation/perfusion mismatch score was taken as an indicator of cardiac sympathetic dysfunction. The imaging protocol was repeated 6 months after TAVI. Regional MIBG uptake was more heterogeneous in HT and AS patients than controls, and therefore, innervation/perfusion mismatch score was higher in both AS (9 ± 8) and HT (5 ± 2) than controls (1 ± 1, P < .001). On multivariate analysis, significant LVH was the major predictor of impaired LV sympathetic innervation (OR 19.45, 95% CI 1.87-201.92; P = .013). After TAVI, no differences in measures of LV sympathetic innervation were evident, although only a marginal LV mass reduction was observed (- 5.4 ± 2.4 g).

CONCLUSIONS

Cardiac sympathetic innervation is impaired in patients with LVH, either with AS or not, and is not impacted significantly by TAVI procedure.

The role of myocardial innervation imaging in different clinical scenarios: an expert document of the European Association of Cardiovascular Imaging and Cardiovascular Committee of the European Association of Nuclear Medicine

Cardiac sympathetic activity plays a key role in supporting cardiac function in both health and disease conditions, and nuclear cardiac imaging has always represented the only way for the non-invasive evaluation of the functional integrity of cardiac sympathetic terminals, mainly through the use of radiopharmaceuticals that are analogues of norepinephrine and, in particular, with the use of 123I-mIBG imaging. This technique demonstrates the presence of cardiac sympathetic dysfunction in different cardiac pathologies, linking the severity of sympathetic nervous system impairment to adverse patient's prognosis. This article will outline the state-of-the-art of cardiac 123I-mIBG imaging and define the value and clinical applications in the different fields of cardiovascular diseases.

Cardiovascular autonomic neuropathy in diabetes: Pathophysiology, clinical assessment and implications

Cardiovascular autonomic neuropathy (CAN) is a debilitating condition that mainly occurs in long-standing type 2 diabetes patients but can manifest earlier, even before diabetes is diagnosed. CAN is a microvascular complication that results from lesions of the sympathetic and parasympathetic nerve fibers, which innervate the heart and blood vessels and promote alterations in cardiovascular autonomic control. The entire mechanism is still not elucidated, but several aspects of the pathophysiology of CAN have already been described, such as the production of advanced glycation end products, reactive oxygen species, nuclear factor kappa B, and pro-inflammatory cytokines. This microvascular complication is an important risk factor for silent myocardial ischemia, chronic kidney disease, myocardial dysfunction, major cardiovascular events, cardiac arrhythmias, and sudden death. It has also been suggested that, compared to other traditional cardiovascular risk factors, CAN progression may have a greater impact on cardiovascular disease development. However, CAN might be subclinical for several years, and a late diagnosis increases the mortality risk. The duration of the transition period from the subclinical to clinical stage remains unknown, but the progression of CAN is associated with a poor prognosis. Several tests can be used for CAN diagnosis, such as heart rate variability (HRV), cardiovascular autonomic reflex tests, and myocardial scintigraphy. Currently, it has already been described that CAN could be detected even during the subclinical stage through a reduction in HRV, which is a non-invasive test with a lower operating cost. Therefore, considering that diabetes mellitus is a global epidemic and that diabetic neuropathy is the most common chronic complication of diabetes, the early identification and treatment of CAN could be a key point to mitigate the morbidity and mortality associated with this long-lasting condition.

Current View of Diagnosing Small Fiber Neuropathy

Small fiber neuropathy (SFN) is a disorder of the small myelinated Aδ-fibers and unmyelinated C-fibers [5, 6]. SFN might affect small sensory fibers, autonomic fibers or both, resulting in sensory changes, autonomic dysfunction or combined symptoms [7]. As a consequence, the symptoms are potentially numerous and have a large impact on quality of life [8]. Since diagnostic methods for SFN are numerous and its pathophysiology complex, this extensive review focusses on categorizing all aspects of SFN as disease and its diagnosis. In this review, sensitivity in combination with specificity of different diagnostic methods are described using the areas under the curve. In the end, a diagnostic work-flow is suggested based on different phenotypes of SFN.

Early therapeutic effects of adaptive servo-ventilation on cardiac sympathetic nervous function in patients with heart failure evaluated using a combination of 11C-HED PET and 123I-MIBG SPECT

RATIONALE

Adaptive servo-ventilation (ASV), a novel respiratory support therapy for sleep disorders, may improve cardiac function in heart failure (HF). However, the reasons that ASV improves cardiac function have not been fully studied especially in sympathetic nervous function (SNF). The purpose of the present study was to investigate the effects of ASV therapy on cardiac SNF in patients with HF.

METHODS

We evaluated ASV therapeutic effects before and 6 months after ASV therapy in 9 HF patients [57.3 ± 17.3 years old, left ventricular ejection fraction (LVEF) 36.1 ± 16.7%]. We performed echocardiography, polysomnography, biomarkers, 11C-hydroxyephedrine (HED) PET as a presynaptic function marker and planar 123I-metaiodobenzylguanidine (MIBG) to evaluate washout rate.

RESULTS

ASV therapy reduced apnea-hypopnea index (AHI) and improved plasma brain natriuretic peptide (BNP) concentration. In 123I-MIBG imaging, the early heart/mediastinum (H/M) ratio increased after ASV therapy (2.19 ± 0.58 to 2.40 ± 0.67; P = 0.045). Washout rate did not change (23.8 ± 7.3% to 23.8 ± 8.8%; P = 0.122). Global 11C-HED retention index (RI) improved from 0.068 ± 0.033/s to 0.075 ± 0.034/s (P = 0.029).

CONCLUSIONS

ASV reduced AHI and improved BNP. ASV might initially improve presynaptic cardiac sympathetic nervous function in HF patients after 6 months of treatment.

Iodine-123 metaiodobenzylguanidine scintigraphy for the assessment of cardiac sympathetic innervation and the relationship with cardiac autonomic function in healthy adults using standardized methods

BACKGROUND

Global iodine-123 metaiodobenzylguanidine (I-MIBG) uptake is predictive of cardiovascular events and mortality in patients with heart failure. Normal variations in global and regional uptake, however, are not well defined and few studies have addressed the functional relevance of I-MIBG uptake and distribution in healthy individuals.

MATERIALS AND METHODS

We performed I-MIBG scintigraphy and cardiac autonomic function testing using the standardized methodology in 15 healthy individuals (mean age 54.6±5.3 years, male : female 10 : 5) with no evidence of previous myocardial infarction or ischaemic heart disease.

RESULTS

Early heart to mediastinum ratio (HMR) was 1.67±0.13, late HMR was 1.73±0.16 and washout rate was 19.09±7.63% (4.20-31.30). Regional analysis showed reduced tracer uptake at the apex, base and inferior wall in all individuals. Early and late HMR correlated negatively with RFa (r=-0.603; P=0.05 and r=-0.644; P=0.033) and expiration and inspiration ratio (r=-0.616; P=0.043 and r=-0.676; P=0.022) and positively with LFa/RFa (r=0.711; P=0.014 and r=0.784; P=0.004). Washout rate correlated only with RFa (r=0.642; P=0.033).

CONCLUSION

Healthy adults show a heterogeneous pattern of cardiac innervation with reduced regional uptake of I-MIBG. Furthermore, HMR correlates with indices of cardiac sympathetic function, suggesting that it might not only be a useful prognostic marker but may also provide insight into the functional integrity of the cardiac autonomic nervous system.

Cardiac Autonomic Function Is Associated With the Coronary Microcirculatory Function in Patients With Type 2 Diabetes

Cardiac autonomic dysfunction and cardiac microvascular dysfunction are diabetic complications associated with increased mortality, but the association between these has been difficult to assess. We applied new and sensitive methods to assess this in patients with type 2 diabetes mellitus (T2DM). In a cross-sectional design, coronary flow reserve (CFR) assessed by cardiac (82)Rb-positron emission tomography/computed tomography, cardiac autonomic reflex tests, and heart rate variability indices were performed in 55 patients with T2DM, without cardiovascular disease, and in 28 control subjects. Cardiac (123)I-metaiodobenzylguanidine scintigraphy was conducted in a subgroup of 29 patients and 14 control subjects and evaluated as the late heart-to-mediastinum ratio and washout rate. Impaired function of all the cardiac autonomic measures (except the washout rate) was associated with reduced CFR. A heart rate variability index, reflecting sympathetic and parasympathetic function (low-frequency power), and the late heart-to-mediastinum ratio, reflecting the function of adrenergic receptors and sympathetic activity, were positively correlated with CFR after adjustment for age and heart rate. The late heart-to- mediastinum ratio remained correlated with CFR after further adjustment. In patients with T2DM without cardiovascular disease, we demonstrate an independent association between cardiac autonomic function and CFR. We suggest that a reduced cardiac autonomic function and damage to the adrenergic receptors may contribute to the development of cardiac microvascular dysfunction.

Mercury Exposure and Heart Rate Variability: a Systematic Review

BACKGROUND

Mercury affects the nervous system and has been implicated in altering heart rhythm and function. We sought to better define its role in modulating heart rate variability, a well-known marker of cardiac autonomic function.

DESIGN

This is a systematic review study.

METHODS

We searched PubMed, Embase, TOXLINE, and DART databases without language restriction. We report findings as a qualitative systematic review because heterogeneity in study design and assessment of exposures and outcomes across studies, as well as other methodological limitations of the literature, precluded a quantitative meta-analysis.

RESULTS

We identified 12 studies of mercury exposure and heart rate variability in human populations (ten studies involving primarily environmental methylmercury exposure and two studies involving occupational exposure to inorganic mercury) conducted in Japan, the Faroe Islands, Canada, Korea, French Polynesia, Finland, and Egypt. The association of prenatal mercury exposure with lower high-frequency band scores (thought to reflect parasympathetic activity) in several studies, in particular the inverse association of cord blood mercury levels with the coefficient of variation of the R-R intervals and with low-frequency and high-frequency bands at 14 years of age in the Faroe Islands birth cohort study, suggests that early mercury exposure could have a long-lasting effect on cardiac parasympathetic activity. Studies with later environmental exposures to mercury in children or in adults were heterogeneous and did not show consistent associations.

CONCLUSIONS

The evidence was too limited to draw firm causal inferences. Additional research is needed to elucidate the effects of mercury on cardiac autonomic function, particularly as early-life exposures might have lasting impacts on cardiac parasympathetic function.

(123)I-Metaiodobenzylguanidine Myocardial Scintigraphy in Lewy Body-Related Disorders: A Literature Review

Lewy body-related disorders are characterized by the presence of Lewy bodies and Lewy neurites, which have abnormal aggregations of α-synuclein in the nigral and extranigral areas, including in the heart. ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy is a well-known tool to evaluate cardiac sympathetic denervation in the Lewy body-related disorders. MIBG scintigraphy showed low uptake of MIBG in the Lewy body-related disorders, including Parkinson’s disease, dementia with Lewy bodies, pure autonomic failure and rapid eye movement sleep behavior disorder. This review summarizes previous results on the diagnostic applications of MIBG scintigraphy in Lewy body-related disorders.

Diabetes causes bone marrow autonomic neuropathy and impairs stem cell mobilization via dysregulated p66Shc and Sirt1

Diabetes compromises the bone marrow (BM) microenvironment and reduces the number of circulating CD34(+) cells. Diabetic autonomic neuropathy (DAN) may impact the BM, because the sympathetic nervous system is prominently involved in BM stem cell trafficking. We hypothesize that neuropathy of the BM affects stem cell mobilization and vascular recovery after ischemia in patients with diabetes. We report that, in patients, cardiovascular DAN was associated with fewer circulating CD34(+) cells. Experimental diabetes (streptozotocin-induced and ob/ob mice) or chemical sympathectomy in mice resulted in BM autonomic neuropathy, impaired Lin(-)cKit(+)Sca1(+) (LKS) cell and endothelial progenitor cell (EPC; CD34(+)Flk1(+)) mobilization, and vascular recovery after ischemia. DAN increased the expression of the 66-kDa protein from the src homology and collagen homology domain (p66Shc) and reduced the expression of sirtuin 1 (Sirt1) in mice and humans. p66Shc knockout (KO) in diabetic mice prevented DAN in the BM, and rescued defective LKS cell and EPC mobilization. Hematopoietic Sirt1 KO mimicked the diabetic mobilization defect, whereas hematopoietic Sirt1 overexpression in diabetes rescued defective mobilization and vascular repair. Through p66Shc and Sirt1, diabetes and sympathectomy elevated the expression of various adhesion molecules, including CD62L. CD62L KO partially rescued the defective stem/progenitor cell mobilization. In conclusion, autonomic neuropathy in the BM impairs stem cell mobilization in diabetes with dysregulation of the life-span regulators p66Shc and Sirt1.

Effect of intramyocardial bone marrow-derived mononuclear cell injection on cardiac sympathetic innervation in patients with chronic myocardial ischemia

Intramyocardial bone marrow cell injection has been associated with improvements in myocardial perfusion and left ventricular function. The current substudy of a randomized, placebo-controlled, double-blinded study, investigated the effect of intramyocardial bone marrow cell injection on myocardial sympathetic innervation in patients with chronic myocardial ischemia. In a total of 16 patients (64 ± 8 years, 13 men), early and late iodine-123 metaiodobenzylguanidine (MIBG) imaging was performed before and 3 months after intramyocardial bone marrow cell injection. No improvements were observed in global early H/M ratio (P = 0.40), late H/M ratio (P = 0.43) and cardiac washout rate (P = 0.98). However, late 123-I MIBG SPECT defect score showed a trend to improvement in the bone marrow cell group (from 31.0 ± 7.1 to 28.1 ± 14.9) as compared to the placebo group (from 33.6 ± 8.5 to 34.5 ± 9.8, P = 0.055 between groups). This trend was mainly driven by a substantial improvement in three bone marrow cell-treated patients, which all had diabetes and severe MIBG defects. In these patients, the extent and severity of MIBG defects improved substantially independent of myocardial perfusion and cell injection sites. The present study does not demonstrate improvements in global cardiac sympathetic nerve innervation after intramyocardial bone marrow cell injection in patients with chronic myocardial ischemia. However, regional analysis of sympathetic nerve innervation reveals improvements in three diabetic patients independent of myocardial perfusion, suggestive of a therapeutic effect on diabetic cardiac sympathetic dysinnervation.

Cardiovascular manifestations of neurologic disease

Cardiac manifestations of neurologic diseases are common in clinical practice. There are numerous anatomic and pathophysiologic links between the normal and abnormal function of both systems. There are a number of brain-heart interactions which affect the care of patients as well as help guide therapeutic development. This is exemplified in the area of vascular neurology where knowledge of the brain-heart connection is essential not only for bedside management but where collaborative efforts between neurology and cardiology are key in developing new strategies for ischemic stroke prevention and treatment, atrial fibrillation, and interventional techniques. This chapter will focus on cardiac manifestations of neurologic disease, with special emphasis on vascular and intensive care neurology, epilepsy, and neurodegenerative and peripheral nervous system diseases.

Impact of diabetes on cardiac sympathetic innervation in patients with heart failure: a 123I meta-iodobenzylguanidine (123I MIBG) scintigraphic study

OBJECTIVE

Impaired parasympathetic and sympathetic nervous system activity have been demonstrated in patients with diabetes mellitus (DM) and correlated with worse prognosis. Few data are available on the effect of DM on cardiac neuropathy in heart failure (HF). The aim of the current study was to assess cardiac sympathetic activity in HF patients with and without DM.

RESEARCH DESIGN AND METHODS

Patients with severe HF (n = 75), with (n = 37) and without DM (n = 38), and 14 diabetic patients with normal cardiac function underwent (123)I meta-iodobenzylguanidine scintigraphy from which early and late heart-to-mediastinum (H/M) ratios were calculated. Clinical, echocardiographic, and biochemical data were measured.

RESULTS

DM compared with non-DM patients showed significantly lower early (1.65 ± 0.21 vs. 1.75 ± 0.21; P < 0.05) and late H/M ratios (1.46 ± 0.22 vs. 1.58 ± 0.24; P < 0.03). Early and late H/M were significantly higher in DM patients without HF (2.22 ± 0.35 and 1.99 ± 0.24, respectively) than HF patients with (P < 0.0001) and without (P < 0.0001) DM. In HF patients, an inverse correlation between early or late H/M ratio and hemoglobin A1c (HbA1c) (Pearson = -0.473, P = 0.001; Pearson = -0.382, P = 0.001, respectively) was observed. In DM, in multivariate analysis, HbA1c and ejection fraction remained significant predictors of early H/M; HbA1c remained the only significant predictor of late H/M. No correlation between early or late H/M and HbA1c was found in non-DM patients.

CONCLUSIONS

Diabetic patients with HF show lower cardiac sympathetic activity than HF patients not having DM or than DM patients with a similar degree of autonomic dysfunction not having HF. HbA1c correlated with the degree of reduction in cardiac sympathetic activity.

Thyroid MIBG uptake in Parkinson's disease with diabetes mellitus

In our work, we investigated thyroid and cardiac MIBG uptake as potential differential markers. We observed reduced cardiac uptake of MIBG in PD and diabetic CAN, in agreement with the previous studies. However, there was a significant difference between the PD and diabetic cardiac autonomic neuropathy groups with respect to early and delayed thyroid MIBG uptake, in that reduced thyroid MIBG uptake was seen in PD but not in diabetic autonomic neuropathy. We therefore propose that this parameter could be a marker for identifying parkinsonism when it presents together with DM.

Prevalence and clinical implication of microbleeds in dementia with lewy bodies in comparison with microbleeds in Alzheimer's disease

Background

Cerebral microbleeds (MBs) have been well investigated in Alzheimer's disease (AD), but not very extensively in non-AD dementias or in dementia with Lewy bodies (DLB).

Aims

To elucidate the clinical significance of MBs in DLB.

Methods

We compared the prevalence, locations and risk factors for MBs in 59 DLB and 81 AD patients. We visually counted MBs in each of the cortical and subjacent areas (frontal, temporal, parietal and occipital), the basal ganglia and the thalamus, and the brainstem and the cerebellar hemispheres on 1.5-tesla T2*-weighted gradient-recalled-echo MRI images. White matter lesions were semiquantified in fluid-attenuated inversion recovery images according to the Fazekas rating scale.

Results

While the prevalence of MBs was comparable, MBs tended to be more abundant in DLB than in AD in all brain areas with the exception of the occipital lobes. The number of MBs was positively associated with the severity of white matter lesions but not with other vascular risk factors in either AD or DLB. The presence of MBs could be associated with cognitive impairment at onset. MB-positive DLB patients showed less impairment on ¹²³I-metaiodobenzylguanidine myocardial scintigraphy (MIBG scintigraphy) images, supporting the notion of an inverse relationship between vascular lesions and Lewy body pathology.

Conclusion

It was suggested that an intricate association between Lewy body pathology, AD-type pathologies and vascular lesions seems to be related to the initial symptoms and results of MIBG scintigraphy in DLB.

Heart rate complexity and cardiac sympathetic dysinnervation in patients with type 2 diabetes mellitus

Cardiovascular autonomic neuropathy (CAN) is one of the most severe complications of type 2 diabetes mellitus (T2DM). The aim of this study was to investigate associations of cardiac sympathetic dysinnervation (CSD; by (123)I-MIBG scintigraphy) with short-term heart rate variability (HRV) measured by traditional vs. complexity markers. ECG was measured in 31 diabetic patients during rest over a period of 5 minutes and HRV quantified in different domains (time and frequency domain, scaling properties, symbolic dynamics). (123)I-MIBG scintigraphy identified 16 patients with CSD. Resting heart rate was increased and HRV reduced in these patients. In a subgroup of 16 patients ECG was also measured during standing. Changes in several HRV measures upon standing demonstrated cardiac responsiveness to orthostatic stress. Strong correlations between HRV, measured during standing, and CSD were observed with metrics based on symbolic dynamics. In conclusion, HRV assessment during standing may be useful for assessing cardiac sympathetic dysinnervation in patients with type 2 diabetes mellitus.

QT interval variability in type 2 diabetic patients with cardiac sympathetic dysinnervation assessed by 123I-metaiodobenzylguanidine scintigraphy

QT Variability and Sympathetic Dysinnervation. 

INTRODUCTION

The mechanism of adverse prognosis attributable to proarrhythmic cardiac sympathetic dysinnervation in patients with type 2 diabetes is incompletely understood. This study sought the association of cardiac sympathetic dysinnervation with temporal instability of ventricular repolarization assessed by beat-to-beat QT interval variability.

METHODS AND RESULTS

 (123) I-metaiodobenzylguanidine ((123) I-MIBG) scintigraphy was analyzed in 31 type 2 diabetic patients for cardiac sympathetic dysinnervation (4-hour heart-to-mediastinum ratio <1.8) and regional sympathetic integrity and washout rate (from 15-minute (123) I-MIBG uptake). Relative QT variability was defined from a continuous 5-minute ECG in the supine position (n = 31) and standing position (subgroup; n = 15) by the log ratio of absolute QT variability (QT variance divided by the mean QT interval squared) to heart rate (HR) variability (HR variance divided by the mean HR squared). Patients with (n = 16; 52%) versus without cardiac sympathetic dysinnervation demonstrated higher relative QT variability in the supine position (P < 0.001), owing to lower HR variability. However, on standing, absolute QT variability was significantly raised in these patients (P = 0.009) despite similar HR variability in the 2 groups. Correlations of heart-to-mediastinum ratio with standing QT variability (relative [r =-0.63, P = 0.013] and absolute [r =-0.79, P = 0.001]) were superior to corresponding supine measures (relative [r =-0.47, P = 0.008] and absolute [P = NS]). No associations of QT variability with washout rate or regional (123) I-MIBG uptake were identified.

CONCLUSION

Elevated QT variability is associated with cardiac sympathetic dysinnervation in type 2 diabetes and may contribute to adverse prognosis. Moreover, QT variability may be more specific for cardiac sympathetic innervation when measured in the context of sympathetic activation. (J Cardiovasc Electrophysiol, Vol. 24, pp. 305-313, March 2013).

Assessment of global cardiac I-123 MIBG uptake and washout using volumetric quantification of SPECT acquisitions

BACKGROUND

Assessment of cardiac innervation using single-photon emission computer tomography (SPECT) is less established than planar imaging, but may be more suitable for quantification. Therefore, a volumetric quantification of I-123 MIBG SPECT acquisitions was performed. Reproducibility, the effects of extra cardiac I-123 MIBG uptake and the relation with conventional planar indices were evaluated.

METHODS

54 patients referred for planar and SPECT I-123 MIBG acquisitions were included. Ellipsoidal or box-shaped volumes of interest were placed on the left ventricle, cardiac lumen, mediastinum, lung and liver. SPECT segmentation was performed twice in all patients. Indices were determined based on the heart-to-mediastinum (HM), myocardial wall-to-mediastinum and myocardial wall-to-lumen regions. HM ratios and washout rates were also determined based on anterior planar images.

RESULTS

Cardiac count densities were highly reproducible (CV 1.5-5.4, ICC 0.96-0.99) and inter-rater variability was low (CV 1.8-6.8, ICC 0.94-0.99). Mediastinal uptake was an important explanatory variable of uptake in the entire heart (early R(2) = 0.36; delayed R(2) =0.43) and myocardial wall (early R(2) = 0.28; delayed R(2) = 0.37). Lung washout was an explanatory variable of organ washout of the heart (heart R(2) = 0.38; myocardial wall R(2) = 0.33). In general, SPECT indices showed moderate-to-good correlations with the planar uptake (PCC 0.497-0.851).

CONCLUSION

By applying a volumetric segmentation method we were able to segment the heart in all patients. SPECT I-123 MIBG quantification was found to be highly reproducible and had a moderate to good correlation with the planar indices.

Radionuclide imaging in stage B heart failure

This article discusses currently available radionuclide techniques in the diagnostic and prognostic evaluation of patients with chronic heart failure, with a focus on stage B/asymptomatic left ventricular dysfunction. Radionuclide imaging is promising for such patients because it can simultaneously determine left ventricular function, evaluate for the presence of obstructive coronary disease, determine the extent of viable myocardium, and evaluate dyssynchronous left ventricular contraction. Radionuclide imaging can thus provide important noninvasive insights into the pathophysiology, prognosis, and management of patients with asymptomatic left ventricular dysfunction as well as more advanced heat failure.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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).

CONCLUSION

The duration of haemodialysed patients appears to be an important factor influencing the cardiac sympathetic nervous system.

[Incidence and prognostic value of ischemic heart disease in high risk cardiovascular asymptomatic diabetic patients detected by gated myocardial perfusion SPECT study]

AIM

To determine the clinical utility of the gated myocardial perfusion SPECT to detect silent ischemia in asymptomatic diabetic patients without previous coronary events and to evaluate the prognosis of this population.

MATERIAL AND METHODS

A retrospective study of 56 asymptomatic diabetics referred for a gated myocardial perfusion SPECT for diagnosis of ischemic disease was performed. The criteria for ischemia were: mild SDS<4, moderate SDS 4-8, severe SDS>8. A multivariable statistical analysis was carried out to identify possible predictive variables of an abnormal SPECT. The cardiovascular events were recorded up to December-2010.

RESULTS

A high proportion of the 56 patients had an abnormal perfusion study (46.4%), there being moderate-severe ischemia in 10.7%, necrosis with ischemia in 5.4% and necrosis in 7.1%. We found no statistical differences in the type of stress used (treadmill or dipyridamole). The patients had a high combination of cardiovascular risk factors. In the multivariate analysis, diabetic nephropathy was the only factor related to an abnormal SPECT (p=0.043). The events recorded in the follow-up were: 2 early revascularizations, 5 cardiology admissions, 10 non-cardiac related deaths. The existence of ischemia in the SPECT was significantly related to the appearance of cardiovascular events (p<0.05).

CONCLUSION

A gated myocardial perfusion SPECT in asymptomatic diabetics with high combination of cardiovascular risk factors detects silent ischemia in a significant proportion and this seems to be related to future coronary events. Diabetic nephropathy implies a greater likelihood of abnormal studies. However, the screening criteria in this population still need to be established for better performance and lower cost.