Iodine-123-metaiodobenzylguanidine scintigraphy in risk stratification of sudden death in heart failure

Carotid Artery Revascularization Improves Cardiac Sympathetic Nerve Activity in Patients With Carotid Artery Stenosis

BACKGROUND

The carotid sinus baroreceptor reflex controls the neural regulation of blood pressure. Baroreceptor disorders due to carotid sinus atherosclerosis have detrimental cardiovascular effects. This study investigated the medium-term effects of carotid artery revascularization (CAR) on sympathetic and cardiac function and systemic blood pressure variability in patients with carotid artery stenosis.

METHODS

This study included 21 consecutive patients (median age 70 years, 18 men) with carotid artery stenosis scheduled for CAR. ¹²³I metaiodobenzylguanidine (MIBG) scintigraphy, echocardiography, brain natriuretic peptide levels, 24-h Holter electrocardiography (ECG), and ambulatory blood pressure monitoring assessed approximately 3 months postoperatively were compared to preoperative data.

RESULTS

All 21 enrolled patients underwent CAR. Carotid artery stenting was done in three patients with cardiovascular risk or anatomical difficult for carotid endarterectomy. The mean common carotid artery end-diastolic velocity improved significantly (P < 0.01) by 1.6-fold, from 10.8 ± 3.2 to 16.1 ± 7.1 cm/s. In ¹²³I-MIBG scintigraphy, the heart-to-mediastinum (H/M) count ratio was significantly higher than preoperatively (from 2.66 ± 0.48 to 2.86 ± 0.56, P = 0.03). Holter ECG analysis revealed a significant decrease in the low-frequency/high-frequency (LF/HF) ratio compared to preoperatively (from 2.17 ± 1.20 to 1.62 ± 0.68, P = 0.04). These findings suggest decreased myocardial sympathetic activation. In echocardiography, the tissue Doppler-derived e' increased, and E/e' decreased significantly (P < 0.05) from 11.7 ± 5.1 to 10.1 ± 4.0, suggesting an improved left ventricular diastolic capacity. The mean 24-h and nighttime blood pressures were unchanged.

CONCLUSIONS

CAR in patients with carotid stenosis may provide medium-term improvement in cardiac sympathetic nerve activity and left ventricular diastolic dysfunction.

[123I]Metaiodobenzylguanidine (MIBG) Cardiac Scintigraphy and Automated Classification Techniques in Parkinsonian Disorders

PURPOSE

To provide reliable and reproducible heart/mediastinum (H/M) ratio cut-off values for parkinsonian disorders using two machine learning techniques, Support Vector Machines (SVM) and Random Forest (RF) classifier, applied to [¹²³I]MIBG cardiac scintigraphy.

PROCEDURES

We studied 85 subjects, 50 with idiopathic Parkinson's disease, 26 with atypical Parkinsonian syndromes (P), and 9 with essential tremor (ET). All patients underwent planar early and delayed cardiac scintigraphy after [¹²³I]MIBG (111 MBq) intravenous injection. Images were evaluated both qualitatively and quantitatively; the latter by the early and delayed H/M ratio obtained from regions of interest (ROIt₁ and ROIt₂) drawn on planar images. SVM and RF classifiers were finally used to obtain the correct cut-off value.

RESULTS

SVM and RF produced excellent classification performances: SVM classifier achieved perfect classification and RF also attained very good accuracy. The better cut-off for H/M value was 1.55 since it remains the same for both ROIt₁ and ROIt_2. This value allowed to correctly classify PD from P and ET: patients with H/M ratio less than 1.55 were classified as PD while those with values higher than 1.55 were considered as affected by parkinsonism and/or ET. No difference was found when early or late H/M ratio were considered separately thus suggesting that a single early evaluation could be sufficient to obtain the final diagnosis.

CONCLUSIONS

Our results evidenced that the use of SVM and CT permitted to define the better cut-off value for H/M ratios both in early and in delayed phase thus underlining the role of [¹²³I]MIBG cardiac scintigraphy and the effectiveness of H/M ratio in differentiating PD from other parkinsonism or ET. Moreover, early scans alone could be used for a reliable diagnosis since no difference was found between early and late. Definitely, a larger series of cases is needed to confirm this data.

Machine learning for prediction of sudden cardiac death in heart failure patients with low left ventricular ejection fraction: study protocol for a retroprospective multicentre registry in China

INTRODUCTION

Left ventricular ejection fraction (LVEF) ≤35%, as current significant implantable cardioverter-defibrillator (ICD) indication for primary prevention of sudden cardiac death (SCD) in heart failure (HF) patients, has been widely recognised to be inefficient. Improvement of patient selection for low LVEF (≤35%) is needed to optimise deployment of ICD. Most of the existing prediction models are not appropriate to identify ICD candidates at high risk of SCD in HF patients with low LVEF. Compared with traditional statistical analysis, machine learning (ML) can employ computer algorithms to identify patterns in large datasets, analyse rules automatically and build both linear and non-linear models in order to make data-driven predictions. This study is aimed to develop and validate new models using ML to improve the prediction of SCD in HF patients with low LVEF.

METHODS AND ANALYSIS

We will conduct a retroprospective, multicentre, observational registry of Chinese HF patients with low LVEF. The HF patients with LVEF ≤35% after optimised medication at least 3 months will be enrolled in this study. The primary endpoints are all-cause death and SCD. The secondary endpoints are malignant arrhythmia, sudden cardiac arrest, cardiopulmonary resuscitation and rehospitalisation due to HF. The baseline demographic, clinical, biological, electrophysiological, social and psychological variables will be collected. Both ML and traditional multivariable Cox proportional hazards regression models will be developed and compared in the prediction of SCD. Moreover, the ML model will be validated in a prospective study.

ETHICS AND DISSEMINATION

The study protocol has been approved by the Ethics Committee of the First Affiliated Hospital of Nanjing Medical University (2017-SR-06). All results of this study will be published in international peer-reviewed journals and presented at relevant conferences.

TRIAL REGISTRATION NUMBER

ChiCTR-POC-17011842; Pre-results.

123I-ioflupane brain SPECT and 123I-MIBG cardiac planar scintigraphy combined use in uncertain parkinsonian disorders

We evaluated the clinical usefulness of the combined use of I-ioflupane brain single photon emission computed tomography (SPECT) and I-metaiodobenzylguanidine (MIBG) cardiac scintigraphy in discriminating uncertain parkinsonism with vascular lesions in striatal nuclei at magnetic resonance imaging (MRI). Forty-three consecutive patients with uncertain parkinsonism and vascular lesions at MRI in striatal nuclei were retrospectively evaluated; the uncertain differential diagnosis was between Parkinson's disease and vascular parkinsonism (PD/VP) in 22 patients, between PD and other neurodegenerative parkinsonism (PD/PS) in 11 patients and between Lewy body dementia and Alzheimer disease (LBD/AD) in the remaining 10 cases. All patients underwent I-ioflupane SPECT with striatal dopaminergic activity determination as binding potentials (BP; cut-off: 3.3). I-MIBG cardiac planar scintigraphy was performed 2 weeks later, in early (15 minutes) and delayed (240 minutes) phases also calculating heart to mediastinum (H/M) ratio (cut-off: 1.56). I-Ioflupane uptake was normal in 9 patients with BP values >3.3, while it was reduced in 34/43 cases with BP values <3.3 at least in one of the striatal nuclei. I-MIBG uptake was normal in 21/43 patients (5 of whom with normal and 16 with I-ioflupane striatal defects) showing the H/M ratio >1.56 in all cases; the uptake was reduced in 22/43 cases, (4 of whom were normal and 18 were with I-ioflupane striatal defects) with the H/M ratio <1.56 in all cases. No statistical differences were found when early and delayed H/M ratios were mutually compared. Combining the 2 radioisotopic procedures, a more reliable diagnosis was achieved in 39/43 cases properly classifying 13 PD, 10 VP, 7 PS, 5 LBD, and 4 AD. However, the diagnosis remained uncertain in four patients with normal I-ioflupane and reduced I-MIBG uptake. The results of the present study confirmed that in uncertain parkinsonian syndromes associated with vascular lesions in striatal nuclei, brain I-ioflupane SPECT alone did not prove able to discriminate between the different forms of disease. Only the association with I-MIBG cardiac scintigraphy, also with the early acquisition alone, allowed the most appropriate diagnosis in 90.7% of our cases. However, patients with normal I-ioflupane and reduced I-I-MIBG uptakes need a close clinical and instrumental follow-up as sympathetic damage could precede striatal disorders in the early stage of PD and LBD.

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.

Preoperative iodine-123 meta-iodobenzylguanidine imaging is a novel predictor of left ventricular reverse remodeling during treatment with a left ventricular assist device

Although left ventricular reverse remodeling (LVRR) is accompanied with an improved clinical course during LV assist device (LVAD) treatment, its preoperative prediction remains uncertain. Twenty-seven heart failure patients with dilated cardiomyopathy were enrolled in this study. Patients underwent (123)I-meta-iodobenzylguanidine (MIBG) scintigraphy before LVAD implantation, and were monitored at our institute from 2010 to 2014. This study investigated the prognostic value of preoperative (123)I-MIBG parameters for predicting postoperative LVRR. Of the preoperative variables studied, including (123)I-MIBG data, washout rate (WR) ≤ 39 % was the only significant, independent predictor of LVRR (defined as LV ejection fraction ≥35 % at 6 months post-LVAD implant using univariate and multivariate logistic regression analyses) (p = 0.036, odds ratio [OR]:14.45). Improved exercise capacity and more frequent opening of the native aortic valve, as well as lower B-type natriuretic peptide plasma levels, were observed in LVRR patients (p < 0.05 for all), although β-blocker doses were comparable with those of non-LVRR patients throughout the 6-month LVAD support period. In conclusion, preoperative (123)I-MIBG is a novel predictive tool of LVRR during LVAD support.