Comparison of [123I]metaiodobenzylguanidine kinetics with heart rate variability and plasma norepinephrine level

Pathways and morphologic pattern of blood supply of epicardial ganglionated nerve plexus

Detailed cardiac neuroanatomy is critical for understanding cardiac function and its pathology. However, there remains a significant gap in knowledge regarding the blood supply to the intrinsic cardiac ganglionated plexus (GP). This study addresses this by mapping the routes and morphological pattern of blood supply to the epicardial GP in a large-animal pig model (Sus scrofa domesticus). Twenty-five domestic pigs were used in the study. We demonstrate that the epicardial ganglionated nerves receive blood from both coronary and extra-cardiac arteries. The coronary arterial branches supply blood to all five subplexuses constituting the epicardial GP. In contrast, the branches of extra-cardiac arteries supply blood to target heart areas: 1) the venous part of the heart hilum on the left atrium, 2) the walls of the sinuses of the right cranial (superior cava) and 3) pulmonary veins. Uniformly, epicardial nerves and ganglia are supplied with blood via a sole epineurial arteriole which, in most cases, is the fifth/sixth-order branch of the coronary arteries. The extra-cardiac arteries supplying blood to the epicardial GP accompanied the mediastinal nerves entering the epicardium within the limits of the heart hilum. Together, the dual and triple blood supply of the epicardial nerves and ganglia suggests a protective role from an ischemic event and/or ischemic heart disease. STUCTURED ABSTRACT: This study details the anatomy of the blood supply of epicardial ganglionated nerve plexus, from which nerve fibres extend to the myocardium, heart conduction system, coronary vessels, and endocardium, in the most popular animal model of experimental cardiology and cardiac surgery - the domestic pig. Our observations demonstrate that the epicardial nerves and ganglia receive blood from both coronary and extra-cardiac arteries. The multi-source blood supply to the cardiac nerves and ganglia may offer protection against myocardial infarction ant other ischemic heart disorders.

F-18 meta-fluorobenzylguanidine PET imaging of myocardial sympathetic innervation

BACKGROUND

I-123 meta-iodobenzylguanidine (MIBG) imaging has long been employed to noninvasively assess the integrity of human norepinephrine transporter-1 and, hence, myocardial sympathetic innervation. Positron-emitting F-18 meta-fluorobenzylguanidine (MFBG) has recently been developed for potentially superior quantitative characterization. We assessed the feasibility of MFBG imaging of myocardial sympathetic innervation.

METHODS

16 patients were imaged with MFBG PET (30-minute dynamic imaging of chest, followed by 3 whole-body acquisitions between 30 minutes and 4-hour post-injection). Blood kinetics were assessed from multiple samples. Pharmacokinetic modeling with reversible 1- and 2-compartment models was performed. Kinetic rate constants were re-calculated from truncated datasets. All patients underwent concurrent MIBG SPECT.

RESULTS

MFBG myocardial uptake was rapid and sustained; the mean standardized uptake value (SUV (mean ± standard deviation)) was 5.1 ± 2.2 and 3.4 ± 1.9 at 1 hour and 3-4-hour post-injection, respectively. The mean K1 and distribution volume (VT) were 1.1 ± 0.6 mL/min/g and 34 ± 22 mL/cm3, respectively. Both were reproducible when re-calculated from truncated 1-hour datasets (Intraclass Correlation Coefficient of 0.99 and 0.91, respectively). Spearman's ϱ = 0.86 between MFBG SUV and VT and 0.80 between MFBG PET-derived VT and MIBG SPECT-derived heart-to-mediastinum activity concentration ratio.

CONCLUSION

MFBG is a promising PET radiotracer for the assessment of myocardial sympathetic innervation.

Power spectral analysis of heart rate variability is useful as a screening tool for detecting sympathetic and parasympathetic nervous dysfunctions in Parkinson’s disease

Background

Parkinson’s disease (PD) is a progressive neurodegenerative disorder that causes motor symptoms and autonomic dysfunction. However, autonomic function tests commonly performed in PD can only evaluate either the sympathetic or parasympathetic nervous system. Therefore, the purpose of this pilot study is to investigate whether power spectral analysis of heart rate variability could detect both sympathetic and parasympathetic nervous dysfunctions in patients with PD.

Methods

Seventeen patients with PD and 11 healthy control subjects underwent electrocardiogram recording for the spectral analysis of heart rate variability to obtain values of low-frequency (LF) (0.04–0.15 Hz) and high-frequency (HF) (0.15–0.4 Hz) powers. Moreover, we examined the coefficient of variation of R–R intervals (CVRR) as a parameter of parasympathetic function in all participants and performed ¹²³I-metaiodobenzylguanidine scintigraphy to measure the heart-to-mediastinum ratio as a parameter of cardiac sympathetic innervation in patients with PD.

Results

The median age of control subjects and PD patients was 63 and 66 years old, respectively. The median Hoehn and Yahr scale of PD patients was stage 2. The values of resting LF and HF powers widely varied. The median values of resting LF powers of control subjects and PD patients and those of HF powers were 169 and 70 ms², 279 and 65 ms², respectively, the difference was statistically insignificant. Approximately 41% of patients with PD had values below the first quartile of resting LF powers (< 58 ms²) or HF powers (< 50 ms²); however, no control subject had such low values. Positive correlations were found between resting LF powers and heart-to-mediastinum ratios of ¹²³I-metaiodobenzylguanidine uptake (r = 0.6) and between resting HF powers and CVRRs (r = 0.7). The resting LF power was also associated with CVRRs and constipation. Furthermore, a positive correlation was observed between resting LF powers and resting HF powers in patients with PD (r = 0.8).

Conclusions

The power spectral analysis of heart rate variability may be useful as a screening tool for detecting autonomic dysfunctions by detecting low resting LF and HF powers in patients with PD. Sympathetic and parasympathetic nerves may be concurrently damaged in patients with PD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02872-2.

Whole-body evaluation of MIBG tissue extraction in a mouse model of long-lasting type II diabetes and its relationship with norepinephrine transport protein concentration

Accelerated cardiac washout of (123)I-metaiodobenzylguanidine (MIBG), which is clinically used as an index of cardiac neuropathy in diabetes, is ascribed to decreased norepinephrine reuptake into synaptic vesicles. However, accelerated washout frequently contrasts with preserved early tracer uptake, whose significance remains undetermined. The aim of this study was to investigate in a mouse model of long-lasting type II diabetes whether the mismatch between MIBG early uptake and washout is the consequence of a more generalized disorder of the autonomic nervous system.

METHODS

Nine mice were given low doses of streptozotocin by intraperitoneal injection for 5 consecutive days. At 7 mo after streptozotocin, MIBG kinetics were evaluated by heart and liver time-activity curves and by tracer accumulation in the bladder. Data were compared with those obtained in 10 sham mice and correlated with the cardiac and hepatic tissue expression of norepinephrine transporter (NET) as assessed with a (3)H-desipramine saturation binding assay.

RESULTS

In diabetic mice, myocardial and liver MIBG retention was reduced at 2 h and was associated with both increased tracer washout and reduced NET density. The rate of myocardial washout correlated with the degree of urinary MIBG excretion.

CONCLUSION

The paradoxic observation of preserved early uptake associated with accelerated washout of MIBG in diabetes seems to be explained by a generalized disorder in NET function leading to reduced whole-body tracer removal from the blood and increased tracer availability for early myocardial uptake.

Cardiac sympathetic dysautonomia in children with chronic kidney disease

BACKGROUND

The pathophysiology of cardiovascular disease (CVD) in chronic kidney disease (CKD) remains uncertain, but autonomic dysfunction seems to be involved. The aim of the study is to investigate the cardiac dysautonomia in uremic pediatric individuals through iodine 123 metaiodobenzylguanidine (MIBG) scintigraphy and heart rate variability (HRV) analysis.

METHODS AND RESULTS

We divided 40 CKD patients (aged 5-21 years) into 4 groups according to the treatment for CKD: conservative (n = 7), continuous ambulatory peritoneal dialysis (n = 5), hemodialysis (n = 13), and kidney transplantation (n = 15). Planar and tomographic I-123 MIBG images were acquired, and early and late cardiac uptake, cardiac and lung washout, and regional I-123 MIBG uptake were evaluated. Hemodialysis patients showed increased cardiac washout (P = .002), a heterogeneous pattern of I-123 MIBG distribution (P = .036), and lower values of the low-frequency (LF) component of HRV (P = .040). Subjects undergoing continuous ambulatory peritoneal dialysis had reduced lung washout (P = .030). The cardiac washout correlated positively with parathyroid hormone levels and negatively with creatinine clearance. There was a significant negative association between the LF component and cardiac washout.

CONCLUSIONS

Uremic cardiac dysautonomia may be characterized by a decreased LF component of HRV, increased I-123 MIBG washout, and a heterogeneous distribution pattern in the left ventricular walls; these abnormalities were not present after kidney transplantation.

Higher heart rate and reduced heart rate variability persist during sleep in chronic fatigue syndrome: a population-based study

Autonomic nervous system (ANS) dysfunction has been suggested in patients with chronic fatigue syndrome (CFS). In this study, we sought to determine whether increased heart rate (HR) and reduced heart rate variability (HRV) parameters observed in CFS patients during wakefulness persist during sleep. To this end, we compared heart rate (HR) and HRV as indicators of ANS function in CFS subjects and non-fatigued (NF) controls in a population-based, case-control study. Thirty subjects with CFS and 38 NF controls, matched for age-, sex- and body mass index, were eligible for analysis. Main outcome measures included mean RR interval (RRI), HR, and HRV parameters derived from overnight ECG. Plasma aldosterone and norepinephrine levels, medicines with cardiovascular effect, and reported physical activity were examined as covariates. General Linear Models were used to assess significance of associations and adjust for potential confounders. Compared to controls, CFS cases had significantly higher mean HR (71.4 vs 64.8 bpm), with a shorter mean RRI [840.4 (85.3) vs 925.4(97.8) ms] (p<0.0004, each), and reduced low frequency (LF), very low frequency (VLF), and total power (TP) of HRV (p<0.02, all). CFS cases had significantly lower plasma aldosterone (p<0.05), and tended to have higher plasma norepinephrine levels. HR correlated weakly with plasma norepinephrine (r=0.23, p=0.05) and moderately with vitality and fatigue scores (r=-0.49 and 0.46, respectively, p<0.0001). Limitation in moderate physical activity was strongly associated with increased HR and decreased HRV. Nevertheless, among 42 subjects with similar physical activity limitations, CFS cases still had higher HR (71.8 bpm) than respective controls (64.9 bpm), p=0.023, suggesting that reduced physical activity could not fully explain CFS-associated differences in HR and HRV. After adjusting for potential confounders case-control differences in HR and TP remained significant (p<0.05).

CONCLUSION

the presence of increased HR and reduced HRV in CFS during sleep coupled with higher norepinephrine levels and lower plasma aldosterone suggest a state of sympathetic ANS predominance and neuroendocrine alterations. Future research on the underlying pathophysiologic mechanisms of the association is needed.

Prognostic value of iodine-123-metaiodobenzylguanidine myocardial uptake and heart rate variability in chronic congestive heart failure secondary to ischemic or idiopathic dilated cardiomyopathy

Autonomic nervous system dysfunction is common in congestive heart failure (CHF) and is believed to predispose patients to an increased risk of death. This study aimed to assess the prognostic significance of heart rate variability (HRV) measurements in conjunction with scintigraphic imaging using metaiodobenzylguanidine (MIBG) labeled with iodine-123 (I-123-MIBG), which detects abnormalities in autonomic nervous activity, in patients with stable CHF during optimal medical treatment. The study population included 52 patients (56 +/- 12 years of age) with a mean left ventricular ejection fraction of 31 +/- 12%. All underwent I-123-MIBG scanning and 24-hour ambulatory electrocardiographic monitoring for the analysis of HRV on entrance into the study. The heart/mediastinum MIBG uptake ratio was calculated. HRV analysis included the assessment of time- and frequency-domain variables. During the 2-year follow-up, 14 patients (27%) died. MIBG uptake at 1 hour was less (1.39 +/- 0.10) in nonsurvivors than in survivors (1.50 +/- 0.16; p = 0.013). In univariate Cox regression analysis, MIBG uptake was a significant prognostic factor (p = 0.038, hazard ratio [HR] 0.017, 95% confidence interval [CI] 0.00 to 0.79). Time- and frequency-domain variables were similar in survivors and nonsurvivors. However, high-frequency power was associated with an increased risk for sudden death (HR 0.310, 95% CI 0.101 to 0.954, p = 0.041) but not with all-cause mortality. In conclusion, cardiac I-123-MIBG imaging identifies patients with CHF at high risk of dying and may be a more reliable predictor of overall mortality than HRV.

MYOCARDIAL IMAGING WITH123I-METAIODOBENZYLGUANIDINE IN ESSENTIAL HYPERTENSION AND RENOVASCULAR HYPERTENSION

Iodine-123 metaiodobenzylguanidine (MIBG) myocardial imaging is considered to reflect cardiac sympathetic function. We performed myocardial MIBG scintigraphy and echocardiography in 27 patients with essential hypertension (EHT), 7 patients with renovascular hypertension (RVHT), and 8 normotensive subjects (NT) to investigate alterations in MIBG myocardial imaging in the presence of hypertension and left ventricular hypertrophy (LVH). EHT were divided into two groups based on LV wall thickness; EHT with LVH group (> or = 13 mm, n = 15) and EHT without LVH group (< 13 mm, n = 12). The delayed uptake of MIBG was decreased, and the washout rate of MIBG was greater in the EHT with LVH group than EHT without LVH group or NT group. The washout rate was correlated with LV mass and LV diastolic function (as assessed by mitral flow). In RVHT group, the MIBG washout rate increased even without LVH, compared with NT and EHT without LVH groups. In summary, the washout rate of MIBG increased in parallel with the development of LVH in EHT and increased independently of the LV mass in RVHT. Cardiac sympathetic function could be altered in hypertensive LVH and in renovascular hypertension.

Diabetic cardiac autonomic dysfunction: parasympathetic versus sympathetic

BACKGROUND

Diabetic cardiac autonomic dysfunction often causes lethal arrhythmia and sudden cardiac death. 123I-Metaiodobenzylguanidine (MIBG) can evaluate cardiac sympathetic dysfunction, and analysis of heart rate variability (HRV) can reflect cardiac parasympathetic activity. We examined whether cardiac parasympathetic dysfunction assessed by HRV may correlate with sympathetic dysfunction assessed by MIBG in diabetic patients.

METHODS AND RESULTS

In 24-hour electrocardiography, we analyzed 4 HRV parameters: high-frequency power (HF), HF in the early morning (EMHF), rMSSD and pNN50. MIBG planar images and SPECT were obtained 15 minutes (early) and 150 minutes (late) after injection and the heart washout rate was calculated. The defect score in 9 left ventricular regions was scored on a 4 point scale (0 = normal approximately 3 = severe defect). In 20 selected diabetic patients without congestive heart failure, coronary artery disease and renal failure, parasympathetic HRV parameters had a negative correlation with the sum of defect scores (DS) in the late images (R = -0.47 approximately -0.59, p < 0.05) and some parameters had a negative correlation with the washout rate (R = -0.50 approximately -0.55, p < 0.05). In a total of 64 diabetic patients also, these parameters had a negative correlation with late DS (R = -0.28 approximately -0.35, p < 0.05) and early DS (R = -0.27 approximately -0.32, p < 0.05).

CONCLUSIONS

The progress of diabetic cardiac parasympathetic dysfunction may parallel the sympathetic one.

Metaiodobenzylguanidine and heart rate variability in heart failure

It is assumed that the low-frequency power (LF) of heart rate variability (HRV) increases with progress of congestive heart failure (CHF), therefore positively correlating with cardiac 123I-metaiodobenzylguanidine (MIBG) washout. It is demonstrated here that HRV, including normalized LF, correlated inversely with MIBG washout and positively with the ratio of heart-to-mediastinum MIBG activity in controls and CHF patients, whereas these correlations were not observed within CHF patients. Thus MIBG washout may increase and HRV including normalized LF may decrease with CHF, although the HRV and MIBG measures may not similarly change in proportion to the severity of the cardiac autonomic dysfunction in CHF.