Prognostic significance of cardiac (123)I metaiodobenzylguanidine imaging for mortality and morbidity in patients with chronic heart failure: a prospective study

Optimal Protocol and Clinical Usefulness of 123I-MIBG Cardiac Scintigraphy for Differentiation of Parkinson's Disease and Dementia with Lewy Body from Non-Parkinson's Diseases

Purpose

123I-metaiodobenzylguanidine (MIBG) cardiac scintigraphy was a useful imaging modality for the diagnosis of Parkinson's disease, but its diagnostic performances were variably reported. This retrospective study compared the diagnostic performances and investigated the optimal imaging protocol of 123I-MIBG cardiac scintigraphy at various imaging time points in patients suspected of Parkinson's disease in clinical practice.

Methods

In patients suspected of Parkinson's disease, clinical records, autonomic function tests, and 123I-MIBG cardiac scintigraphy were retrospectively reviewed. Semi-quantitative parameters such as heart-to-mediastinum ratio (HMR) and washout rate (WR) were calculated and compared at 15 min, 1 h, 2 h, 3 h, and 4 h post-injection (p.i.). of 123I-MIBG cardiac scintigraphy. Group A consisted of Parkinson's disease (PD), Parkinson's disease dementia (PDD), and dementia with Lewy body (DLB), and group B consisted of non-Parkinson's diseases such as multiple system atrophy (MSA), progressive supranuclear palsy (PSP), drug-induced parkinsonism (DIP), essential tremor (ET), Parkinson-plus syndrome (PPS), and unspecified secondary parkinsonism (NA). The diagnostic performances of HMR and WR were compared for differentiation of group A from group B, and their clinical usefulness and optimal imaging time points were explored.

Results

Seventy-eight patients were included in group A (67 PD, 7 PDD, 4 DLB), and 18 patients were included in group B (5 MSA, 3 PSP, 2 DIP, 2 ET, 1 PPS, and 1 NA). Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value of HMR and WR were maximized at 4 h p.i., (82.1%, 85.7%, 82.6%, 97.0%, and 46.2%; cutoff threshold < 1.717; area under curve 0.8086) and at the time interval between 1 and 4 h p.i. (65.4%, 85.7%, 68.5%, 96.2%, and 30.8%; cutoff threshold > 24.1%; area under curve 0.8246), respectively, and PPVs of both HMR and WR persistently showed greater than 92.7% at earlier time points and shorter time intervals.

Conclusion

This study reassured that 4-h-delayed imaging is recommended for the best diagnostic performances in 123I-MIBG cardiac scintigraphy. Although it showed suboptimal diagnostic performances to differentiate PD, PDD, and DLB from non-Parkinson's diseases, it can be useful as an auxiliary measure for the differential diagnosis in usual clinical practice.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13139-023-00790-w.

Left-atrial volume reduction reflects improvement of cardiac sympathetic nervous function in patients with severe aortic stenosis after transcatheter aortic valve replacement

Trans-catheter aortic valve replacement (TAVR) is an excellent alternative intervention for surgical aortic valve replacement. Cardiac sympathetic nervous (CSN) function and left atrial (LA) volume are both important prognostic factors in patients with aortic stenosis (AS) after TAVR. The relationship between the two clinical factors is unknown, however. This retrospective observational study aimed to assess the correlation between CSN function and LA volume in 48 symptomatic patients with severe AS (median age: 85 years, IQR 82-88 years; 81% female) before and after TAVR. CSN function was assessed by performing ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy before and 6 months after TAVR, and the delayed heart-to-mediastinum ratio (dHMR) and washout rate (WR) were calculated. We also performed transthoracic echocardiography near the same time. TAVR improved the dHMR, WR, and LA volume index (LAVI) (dHMR: median 2.89 [IQR 2.62-3.23] vs. 2.98 [2.49-3.25], p = 0.0182; WR: 28% [24-38] vs. 23% [16-32], p < 0.0001; LAVI: 47.7 mL/m² [37.8-56.3] vs. 41.2 mL/m² [33.7-56.1], p = 0.0024). In multiple linear regression analysis, the percentage change in LAVI from baseline to post-TAVR (∆LAVI%) was an independent predictor of change in dHMR from baseline to post-TAVR (β =  - 0.35, p = 0.0110). In conclusion, LA volume reduction reflected CSN functional improvement after TAVR. In patients with TAVR, ∆LAVI% might be a valuable parameter for evaluating CSN functional recovery.

Complementary Role of Combined Indirect and Direct Cardiac Sympathetic (Hyper)Activity Assessment in Patients with Heart Failure by Spectral Analysis of Heart Rate Variability and Nuclear Imaging: Possible Application in the Evaluation of Exercise Training Effects

In chronic heart failure (CHF), abnormalities in cardiac autonomic control, characterized by sympathetic overactivity, contribute to the progression of the disease and are associated with an unfavorable prognosis. Assessing cardiac autonomic status is clinically important in the management of patients with CHF. To this aim, heart rate variability (HRV) analysis has been extensively used as a non-invasive tool for assessing cardiac autonomic regulation, and has been shown to predict the clinical outcome in patients with CHF. Adrenergic nerve activity has also been estimated using iodine-123 (I-123) metaiodobenzylguanidine (MIBG), a noradrenaline analogue. MIBG is an analogue of norepinephrine sharing the same cellular mechanism of uptake, storage, and release in presynaptic sympathetic neurons. As an innervation tracer, 123I-MIBG allows for the evaluation of cardiac sympathetic neuronal function. Cardiac MIBG imaging has also been reported to predict a poor clinical outcome in CHF. MIBG provides direct information on the function of the presynaptic sympathetic nerve endings, whereas HRV, which depends on postsynaptic signal transduction, reflects the end-organ response of the sinus node. The aim of this brief review is to provide the reader with some basic concepts regarding the spectral analysis of HRV and MIBG, highlighting what is known about their respective roles in detecting cardiac sympathetic hyperactivity in CHF and, in perspective, their possible combined use in assessing non-pharmacological treatments in patients with CHF and reduced ejection fraction, with a particular focus on the effects of exercise training.

Usefulness of the 2-year iodine-123 metaiodobenzylguanidine-based risk model for post-discharge risk stratification of patients with acute decompensated heart failure

PURPOSE

A four-parameter risk model that included cardiac iodine-123 metaiodobenzylguanidine (MIBG) imaging and readily available clinical parameters was recently developed for prediction of 2-year cardiac mortality risk in patients with chronic heart failure. We sought to validate the ability of this risk model to predict post-discharge clinical outcomes in patients with acute decompensated heart failure (ADHF) and to compare its prognostic value with that of the Acute Decompensated Heart Failure National Registry (ADHERE) and Get With The Guidelines-Heart Failure (GWTG-HF) risk scores.

METHODS

We studied 407 consecutive patients who were admitted for ADHF and survived to discharge, with definitive 2-year outcomes (death or survival). Cardiac MIBG imaging was performed just before discharge. The 2-year cardiac mortality risk was calculated using four parameters, namely age, left ventricular ejection fraction, New York Heart Association functional class, and cardiac MIBG heart-to-mediastinum ratio on delayed images. Patients were stratified into three groups based on the 2-year cardiac mortality risk: low- (< 4%), intermediate- (4-12%), and high-risk (> 12%) groups. The ADHERE and GWTG-HF risk scores were also calculated.

RESULTS

There was a significant difference in the incidence of cardiac death among the three groups stratified using the 2-year cardiac mortality risk model (p < 0.0001). The 2-year cardiac mortality risk model had a higher C-statistic (0.732) for the prediction of cardiac mortality than the ADHERE and GWTG-HF risk scores.

CONCLUSION

The 2-year MIBG-based cardiac mortality risk model is useful for predicting post-discharge clinical outcomes in patients with ADHF.

TRIAL REGISTRATION NUMBER

UMIN000015246, 25 September 2014.

Prognostic significance of cardiac I-123-metaiodobenzylguanidine imaging in patients with reduced, mid-range, and preserved left ventricular ejection fraction admitted for acute decompensated heart failure: a prospective study in Osaka Prefectural Acute Heart Failure Registry (OPAR)

AIMS

Cardiac 123I-metaiodobenzylguanidine (123I-MIBG) imaging provides prognostic information in patients with chronic heart failure (HF). However, there is little information available on the prognostic role of cardiac 123I-MIBG imaging in patients admitted for acute decompensated heart failure (ADHF), especially relating to reduced ejection fraction [HFrEF; left ventricular ejection fraction (LVEF) < 40%], mid-range ejection fraction (HFmrEF; 40% ≤ LVEF < 50%) and preserved ejection fraction (HFpEF; LVEF ≥ 50%).

METHODS AND RESULTS

We studied 349 patients admitted for ADHF and discharged with survival. Cardiac 123I-MIBG imaging, echocardiography, and venous blood sampling were performed just before discharge. The cardiac 123I-MIBG heart-to-mediastinum ratio (late H/M) was measured on the chest anterior view images obtained at 200 min after the isotope injection. The endpoint was cardiac events defined as unplanned HF hospitalization and cardiac death. During a follow-up period of 2.1 ± 1.4 years, 128 patients had cardiac events (45/127 in HFrEF, 28/78 in HFmrEF, and 55/144 in HFpEF). On multivariable Cox analysis, late H/M was significantly associated with cardiac events in overall cohort (P = 0.0038), and in subgroup analysis of each LVEF subgroup (P = 0.0235 in HFrEF, P = 0.0119 in HFmEF and P = 0.0311 in HFpEF). Kaplan-Meier analysis showed that patients with low late H/M (defined by median) had significantly greater risk of cardiac events in overall cohort (49% vs. 25% P < 0.0001) and in each LVEF subgroup (HFrEF: 48% vs. 23% P = 0.0061, HFmrEF: 51% vs. 21% P = 0.0068 and HFpEF: 50% vs. 26% P = 0.0026).

CONCLUSION

Cardiac sympathetic nerve dysfunction was associated with poor outcome in ADHF patients irrespective of HFrEF, HFmrEF, or HFpEF.

Incremental prognostic value of cardiac metaiodobenzylguanidine imaging over the co-morbid burden in acute decompensated heart failure

Aims

Co‐morbidities are associated with poor clinical outcomes in patients with chronic heart failure, while cardiac iodine‐123 (I‐123) metaiodobenzylguanidine (MIBG) imaging provides prognostic information in such patients. We sought to prospectively investigate the incremental prognostic value of cardiac MIBG imaging over the co‐morbid burden, in patients admitted for acute decompensated heart failure (ADHF).

Methods and results

In 433 consecutive ADHF patients with survival to discharge, we measured the co‐morbidity using age‐adjusted Charlson co‐morbidity index (ACCI), commonly employed to evaluate a weighted and scored co‐morbid condition, adding additional points for age. In cardiac MIBG imaging, the cardiac MIBG heart‐to‐mediastinum ratio (late HMR) was measured on the delayed image. Over a follow‐up period of 2.9 ± 1.5 years, 160 patients had a cardiac event (a composite of cardiac death and unplanned hospitalization for worsening heart failure). Patients with high ACCI (≥6: median value) had a significantly greater risk of a cardiac event. In multivariate Cox analysis, the ACCI and late HMR were significantly and independently associated with a cardiac event. In both high and low ACCI subgroups (ACCI ≥ 6 and <6, respectively), patients with low late HMR had a significantly greater risk of a cardiac event (high ACCI: 51% vs. 34% P = 0.0026, adjusted HR 1.74 [1.21–2.51]; low ACCI: 34% vs. 17%, P = 0.0228, adjusted HR 2.19 [1.10–4.37]).

Conclusions

Cardiac MIBG imaging could provide additional prognostic information over ACCI, which was also promoted to be a useful risk model, in patients admitted for ADHF.

Assessment of right ventricular sympathetic dysfunction in patients with arrhythmogenic right ventricular cardiomyopathy: An 123I-metaiodobenzylguanidine SPECT/CT study

PURPOSE

The purpose of the study was to evaluate a novel approach for the quantification of right ventricular sympathetic dysfunction in patients diagnosed with ARVC/D through state-of-the-art functional SPECT/CT hybrid imaging.

METHODS

Sympathetic innervation of the heart was assessed using 123I-MIBG-SPECT/CT in 17 patients diagnosed with ARVC according to the modified task force criteria, and in 10 patients diagnosed with idiopathic ventricular fibrillation (IVF). The 123I-MIBG-uptake in the left (LV) and right ventricle (RV) was evaluated separately based on anatomic information derived from the CT scan, and compared to the uptake in the mediastinum (M).

RESULTS

There was a significant difference in the LV/M ratio between the ARVC/D and the IVF groups (3.2 ± 0.5 vs. 3.9 ± 0.8, P = 0.014), with a cut-off value of 3.41 (77% sensitivity, 80% specificity, AUC 0.78). There was a highly significant difference in the mean RV/M ratios between both groups (1.6 ± 0.3 vs. 2.0 ± 0.2, P = 0.001), with optimal cut-off for discrimination at 1.86 (88% sensitivity, 90% specificity, AUC 0.93).

CONCLUSION

Employing state-of-the-art functional SPECT/CT hybrid imaging, we could reliably assess and quantify right and left ventricular sympathetic innervation. The RV/M ratio was significantly lower in patients diagnosed with ARVC/D and provided sensitive and specific discrimination between patients with ARVC/D and IVF patients.

Structural and Physiological Imaging to Predict the Risk of Lethal Ventricular Arrhythmias and Sudden Death

Identifying patients at risk of sudden cardiac death remains a major challenge in cardiovascular medicine. Advances in cardiovascular imaging have identified several anatomic and functional variables that can be quantified as continuous variables to predict the risk of developing lethal ventricular tachyarrhythmias in patients with depressed left ventricular (LV) systolic function. Some, such as LV mass, volume, and the dyssynchrony of contraction, can be derived from currently available echocardiographic and nuclear imaging modalities. Others require advanced cardiac imaging modalities with quantification of myocardial scar with gadolinium-enhanced cardiac magnetic resonance and myocardial sympathetic denervation using norepinephrine analogs and positron emission tomography or single-photon emission computed tomography offering the most promise. There is an immediate need to develop a sequential cost-effective approach that capitalizes on readily available clinical information complemented with advanced imaging modalities in selected patients to improve risk stratification for arrhythmic death beyond LV ejection fraction.

Impact of adjunctive tolvaptan on sympathetic activity in acute heart failure with preserved ejection fraction

AIMS

Acute decompensated heart failure (ADHF) is generally treated by decongestion using diuretic therapy. However, the use of loop diuretics is associated with increased cardiac sympathetic nerve activity (CSNA). We aimed to evaluate the effect of adjunctive tolvaptan therapy on CSNA in ADHF patients with preserved left ventricular ejection fraction (LVEF).

METHODS AND RESULTS

We enrolled 51 consecutive ADHF patients with LVEF ≥45%. Patients were randomly assigned to receive either tolvaptan add-on (n = 25) or conventional diuretic therapy (n = 26). Cardiac iodine-123 metaiodobenzylguanidine (MIBG) imaging was performed after stabilisation of heart failure symptoms, and the cardiac MIBG heart-to-mediastinum ratio (HMR) and washout rate (WR) were calculated. There were no significant differences in the body weight change and total urine volume during 2 days after randomisation or in the HMR on delayed image (HMR(d)) and WR between the tolvaptan and conventional groups. After stratification based on the median change in body weight, the patients with higher weight reduction had a significantly lower HMR(d) (P = 0.0128) and tended to have a higher WR (P = 0.0786) in the conventional group, whereas the cardiac MIBG imaging results were not influenced by body weight reduction in the tolvaptan group.

CONCLUSIONS

Adjunctive tolvaptan therapy may provide rapid decongestion without a harmful effect on CSNA in ADHF patients with preserved LVEF.

123I-MIBG for detection of subacute doxorubicin-induced cardiotoxicity in patients with malignant lymphoma

BACKGROUND

Doxorubicin is the mainstay of curative lymphoma treatment but is associated with a dose-dependent cardiotoxicity that is often recognized too late to avoid substantial irreversible cardiac injury. Iodine-123 metaiodobenzylguanidine (123I-MIBG) is a gamma-emitting tracer that mimics noradrenaline uptake, storage, and release mechanisms in adrenergic presynaptic neurons. 123I-MIBG scintigraphy can be used for assessment of doxorubicin-induced injury to myocardial adrenergic neurons during treatment and could be the tool for early detection of doxorubicin cardiotoxicity, which is currently lacking.

METHODS AND RESULTS

A total of 37 lymphoma patients scheduled for doxorubicin treatment were included in our study. 123I-MIBG imaging was performed prior to chemotherapy and after a median of 4 cycles of doxorubicin. Early and late heart-to-mediastinum ratios (H/Mearly and H/Mlate) and washout rate (WOR) were used for evaluation of cardiotoxicity. The prognostic value of 123I-MIBG results was assessed using left ventricular ejection fraction (LVEF) as measured by cardiac magnetic resonance at 1-year follow-up. We found a post-therapy increase in WOR (including nine patients with > 10% increase), which was not statistically significant (18.6 vs 23.4%, P = 0.09). The difference appeared to be driven by an increase in H/Mearly. LVEF decreased from baseline to 1-year follow-up (64 vs 58%, P = 0.03). LVEF change was not associated with changes in WOR (P = 0.5).

CONCLUSION

The present study does not provide evidence for 123I-MIBG imaging as a clinically applicable tool for early detection of doxorubicin-induced cardiotoxicity.

Prediction of sudden cardiac death in chronic heart failure patients with reduced ejection fraction by ADMIRE-HF risk score and early repolarization pattern

BACKGROUND

AdreView myocardial imaging for risk evaluation in heart failure (ADMIRE-HF) risk score is a novel risk score to predict serious arrhythmic risk in chronic heart failure patients with reduced ejection fraction (HFrEF). Moreover, early repolarization pattern (ERP) has been shown to be associated with an increased risk of sudden cardiac death (SCD) in HFrEF patients. We sought to investigate the prognostic value of combining ADMIRE-HF risk score and ERP to predict SCD in HFrEF patients.

METHODS

We studied 90 HFrEF outpatients with LVEF< 40% in our prospective cohort study. In cardiac MIBG imaging, the heart-to-mediastinum (H/M) ratio was measured on the delayed planar image. ADMIRE-HF risk score was derived from the sum of the point values of LVEF, H/M ratio, and systolic blood pressure. We also assessed ERP on the standard electrocardiogram.

RESULTS

During a median follow-up of 7.5(4.5-12.0) years, 22 patients had SCD. At multivariate Cox analysis, ADMIRE-HF risk score and ERP were independently associated with SCD. Patients with both intermediate/high ADMIRE-HF score and ERP had a higher SCD risk than those with either and none of them.

CONCLUSION

The combination of ADMIRE-HF risk score and ERP would provide the incremental prognostic information for predicting SCD in HFrEF patients.

Renal iodine123-metaiodobenzylguanidine scintigraphy relates to muscle sympathetic nervous activity in heart failure with reduced ejection fraction

BACKGROUND

Renal denervation is effective for modulating augmented sympathetic nerve activity (SNA) in heart failure with reduced ejection fraction (HFrEF). We have demonstrated that renal iodine¹²³-metaiodobenzylguanidine (¹²³I-MIBG) scintigraphy is associated with muscle sympathetic nerve activity (MSNA) in patients with hypertension. However, it is unclear whether renal ¹²³I-MIBG scintigraphy is useful for assessment of SNA in HFrEF.

METHODS

The study population consisted of 24 HFrEF patients and 11 healthy subjects as controls. Patients with HFrEF underwent ¹²³I-MIBG scintigraphy and hemodynamics using a Swan-Ganz catheter (SGC). HFrEF was defined as echocardiography with left ventricular ejection fraction (LVEF) < 50%. MSNA was measured from the peroneal nerve for direct evaluation of SNA. Renal ¹²³I-MIBG scintigraphy was performed simultaneously with cardiac scintigraphy. The early and delayed kidney-to-mediastinum ratio (K/M), early and delayed heart-to-mediastinum ratio (H/M), and washout rate (WR) were calculated.

RESULTS

LVEFs were 35% ± 11% in patients with HFrEF and 63% ± 10% in the controls (p < 0.01). The WR of cardiac ¹²³I-MIBG showed no relation to MSNA, but was related to stroke volume (r = 0.45, p < 0.05). In contrast, the WR of renal ¹²³I-MIBG scintigraphy (average of both sides) showed a strong correlation with MSNA (BI, r = 0.70, p < 0.01; BF, r = 0.66, p < 0.01); however, no significant correlations were detected between renal ¹²³I-MIBG scintigraphy and SGC results.

CONCLUSIONS

The WR of renal ¹²³I-MIBG scintigraphy may reflect MSNA. Further studies are needed to clarify the relationship between renal ¹²³I-MIBG imaging and renal SNA.

Cardiac Imaging With 123I-meta-iodobenzylguanidine and Analogous PET Tracers: Current Status and Future Perspectives

Autonomic innervation plays an important role in proper functioning of the cardiovascular system. Altered cardiac sympathetic function is present in a variety of diseases, and can be assessed with radionuclide imaging using sympathetic neurotransmitter analogues. The most studied adrenergic radiotracer is cardiac ¹²³I-meta-iodobenzylguanidine (¹²³I-mIBG). Cardiac ¹²³I-mIBG uptake can be evaluated using both planar and tomographic imaging, thereby providing insight into global and regional sympathetic innervation. Standardly assessed imaging parameters are the heart-to-mediastinum ratio and washout rate, customarily derived from planar images. Focal tracer deficits on tomographic imaging also show prognostic utility, with some data suggesting that the best approach to tomographic image interpretation may differ from conventional methods. Cardiac ¹²³I-mIBG image findings strongly correlate with the severity and prognosis of many cardiovascular diseases, especially heart failure and ventricular arrhythmias. Cardiac ¹²³I-mIBG imaging in heart failure is FDA approved for prognostic purposes. With the robustly demonstrated ability to predict occurrence of potentially fatal arrhythmias, cardiac ¹²³I-mIBG imaging shows promise for better selecting patients who will benefit from an implantable cardioverter defibrillator, but clinical use has been hampered by lack of the randomized trial needed for incorporation into societal guidelines. In patients with ischemic heart disease, cardiac ¹²³I-mIBG imaging aids in assessing the extent of damage and in identifying arrhythmogenic regions. There have also been studies using cardiac ¹²³I-mIBG for other conditions, including patients following heart transplantation, diabetic related cardiac abnormalities and chemotherapy induced cardiotoxicity. Positron emission tomographic adrenergic radiotracers, that improve image quality, have been investigated, especially ¹¹C-meta-hydroxyephedrine, and most recently ¹⁸F-fluorbenguan. Cadmium-zinc-telluride cameras also improve image quality. With better spatial resolution and quantification, PET tracers and advanced camera technologies promise to expand the clinical utility of cardiac sympathetic imaging.

Left-ventricular innervation assessed by 123I-SPECT/CT is associated with cardiac events in inherited arrhythmia syndromes

AIMS

Impaired myocardial sympathetic innervation assessed by ¹²³Iodine-Metaiodobenzylguanidine (¹²³I-MIBG) scintigraphy is associated with cardiac events. Since regional disparities of structural abnormalities are common in inherited arrhythmia syndromes (iAS), a chamber-specific innervation assessment of the right (RV) and left ventricle (LV) could provide important insights for a patient-individual therapy. Aim of this study was to evaluate chamber-specific patterns of autonomic innervation by Single-photon emission computed tomography/computed tomography (SPECT/CT) in patients with iAS with respect to clinical outcome regarding cardiac events.

METHODS AND RESULTS

We assessed ventricular sympathetic innervation (LV, RV and planar heart/mediastinum-ratios, and washout-rates) by ¹²³I-MIBG-SPECT/CT in 48 patients (arrhythmogenic right ventricular cardiomyopathy [ARVC], n = 26; laminopathy, n = 8; idiopathic ventricular fibrillation [iVF], n = 14) in relation to a composite clinical endpoint (ventricular arrhythmia; cardiac death; cardiac hospitalization). RV tracer uptake was lower in patients with ARVC than in laminopathy and iVF patients (1.7 ± 0.4 vs. 2.1 ± 0.7 and 2.1 ± 0.5, respectively). Over a median follow-up of 2.2 years, the combined endpoint was met in 18 patients (n = 12 ventricular tachyarrhythmias, n = 5 hospitalizations, n = 1 death). LV, but not RV H/M ratio was associated with the combined endpoint (hazard-ratio 2.82 [1.30-6.10], p < 0.01). After adjustment for LV and RV function, LV H/M-ratio still remained a significant predictor for cardiac events (hazard-ratio 2.79 [1.06-7.35], p = 0.04).

CONCLUSION

We demonstrated that chamber-specific ¹²³MIBG-SPECT/CT imaging is feasible and that reduced LV sympathetic innervation was associated with worse outcome in iAS. These findings provide novel insights into the potential role of regional autonomic nervous system heterogeneity for the evolution of life-threatening cardiac events in iAS.

Are cardiac sympathetic nerve activity and epicardial adipose tissue associated with atrial fibrillation recurrence after catheter ablation in patients without heart failure?

BACKGROUND

Cardiac sympathetic nerve activity (CSNA) and epicardial adipose tissue (EAT) are known to be major determinants in the progression of atrial fibrillation (AF).

OBJECTIVE

The aim was to investigate the relationship between the combination of CSNA and EAT, and AF recurrence (AFR) following 3 months after the index catheter ablation (CA) in patients without heart failure (HF).

METHODS AND RESULTS

Sixty-four paroxysmal AF patients without HF were studied. Cardiac metaiodobenzylguanidine (MIBG) scintigraphy was performed at baseline and 3 months post-ablation. In MIBG imaging, the MIBG washout rate (WR) was calculated. The volumes of the total EAT and periatrial EAT surrounding the left atrium were measured by computed tomography before CA, and the periatrial to total EAT volume ratio (P/T) was obtained. During the follow-up period of 11 ± 4 months, AFR was observed in 14 patients. The WR change from baseline to 3 months after CA (dWR) and P/T were significantly greater in patients with than without AFR. Greater dWR and P/T determined by ROC curve analysis were independently associated with AFR. Patients with both greater dWR (≥6.9%) and P/T (≥17.1%) had a higher risk of AFR than those with either and none of them. Periatrial EAT volume showed a significant correlation with the baseline WR.

CONCLUSIONS

The combination of dWR and P/T was associated with AFR in patients without HF. Thus, both of CSNA and EAT might be related to development of AF.

Prediction of sudden cardiac death in patients with chronic heart failure by regional washout rate in cardiac MIBG SPECT imaging

BACKGROUND

The sympathetic nervous system provides an important trigger for major arrhythmic events through regional heterogeneity of sympathetic activity, which could be evaluated by SPECT imaging as the regional MIBG washout rate (WR). There is little information available on the prognostic value of regional WR in SPECT imaging for the prediction of sudden cardiac death (SCD) in patients with chronic heart failure (CHF).

METHODS

We studied 73 CHF outpatients with LVEF < 40%. At study entry, the regional WR was measured in 17 segments on the polar map. We defined abnormal regional WR as both the regional WR range (maximum - minimum regional WR) and maximum regional WR > mean value + 2SD obtained in 15 normal controls.

RESULTS

During a mean follow-up of 7.5 ± 4.1 years, 15 of 73 patients had SCD. The abnormal regional WR and abnormal global WR on planar images were significantly and independently associated with SCD. Patients with both the abnormal regional WR and global WR had a significantly higher risk of SCD than those with none of these criteria.

CONCLUSIONS

The analysis of regional MIBG WR on SPECT imaging provides additional prognostic value to global WR on planar images for SCD prediction in CHF patients.

Sympathetic Dysautonomia in Heart Failure by 123I-MIBG: comparison between Chagasic, non-Chagasic and heart transplant patients

Background

Heart failure (HF) is a severe public health problem because of its high morbidity and mortality and elevated costs, thus requiring better understanding of its course. In its complex and multifactorial pathogenesis, sympathetic hyperactivity plays a relevant role. Considering that sympathetic dysfunction is already present in the initial phases of chronic Chagas cardiomyopathy (CCC) and frequently associated with a worse prognosis, we assumed it could be more severe in CCC than in cardiomyopathies of other etiologies (non-CCC).

Objectives

To assess the cardiac sympathetic dysfunction ¹²³I-MIBG) of HF, comparing individuals with CCC to those with non-CCC, using heart transplant (HT) patients as denervated heart parameters.

Methods

We assessed 76 patients with functional class II-VI HF, being 25 CCC (17 men), 25 non-CCC (14 men) and 26 HT (20 men), by use of cardiac ¹²³I-metaiodobenzylguanidine ¹²³I-MIBG) scintigraphy, estimating the early and late heart-to-mediastinum ratio (HMR) of ¹²³I-MIBG uptake and cardiac washout (WO%). The 5% significance level was adopted in the statistical analysis.

Results

The early and late HMR values were 1.73 ± 0.24 and 1.58 ± 0.27, respectively, in CCC, and 1.62 ± 0.21 and 1.44 ± 0.16 in non-CCC (p = NS), being, however, higher in HT patients (p < 0.001). The WO% values were 41.65 ± 21.4 (CCC), 47.37 ± 14.19% (non-CCC) and 43.29 ± 23.02 (HT), p = 0.057. The late HMR values showed a positive weak correlation with left ventricular ejection fraction (LVEF) in CCC and non-CCC (r = 0.42 and p = 0.045; and r = 0.49 and p = 0.015, respectively).

Conclusion

Sympathetic hyperactivity ¹²³I-MIBG) was evidenced in patients with class II-IV HF, LVEF < 45%, independently of the HF etiology, as compared to HT patients.

Significant correlation between renal 123I-metaiodobenzylguanidine scintigraphy and muscle sympathetic nerve activity in patients with primary hypertension

BACKGROUND

Iodine-123 metaiodobenzylguanidine (123I-MIBG) scintigraphy is used as a noninvasive imaging method for assessing cardiac sympathetic nerve activity. We tested the hypothesis that renal 123I-MIBG imaging is correlated with muscle sympathetic nerve activity (MSNA) in patients with primary hypertension.

METHODS

Thirty-one consecutive patients with primary hypertension were included. Multiunit MSNA was recorded from the peroneal nerve to evaluate direct efferent sympathetic nerve activity. Planar renal and cardiac 123I-MIBG images were acquired. Early and delayed kidney-to-mediastinum ratio (K/M), early and delayed heart-to-mediastinum ratio (H/M), and washout rates (WR) were calculated.

RESULTS

In 27 of 31 patients, blood pressure was controlled on antihypertensive medication. Mean systolic and diastolic blood pressures were 118 ± 18 and 67 ± 15 mmHg, respectively. Although early and late K/M and H/M were not significantly correlated with MSNA, both cardiac and average renal WR were significantly correlated with MSNA (r = 0.45, P = .0035 and r = 0.68, P < .001, respectively). Right and left renal WR were similarly correlated with MSNA. Renal WR was significantly higher than cardiac WR (43.2% vs 25.8%, P < .001) in these patients with hypertension.

CONCLUSIONS

Renal 123I-MIBG WR was significantly associated with multiunit MSNA. Renal 123I-MIBG imaging offers a noninvasive clinical methodology for assessing renal sympathetic nerve function.

Depletion of cardiac catecholamine stores impairs cardiac norepinephrine re-uptake by downregulation of the norepinephrine transporter

In heart failure (HF), a disturbed cardiac norepinephrine (NE) homeostasis is characterized by depleted cardiac NE stores, impairment of the cardiac NE re-uptake by the neuronal norepinephrine transporter (NET) and enhanced cardiac NE net release. Reduced cardiac NE content appears to be caused by enhanced cardiac NE net release from sympathetic neurons in HF, triggered by neurohumoral activation. However, it remains unclear whether reduced NE itself has an impact on cardiac NE re-uptake, independent of neurohumoral activation. Here, we evaluated whether depletion of cardiac NE stores alone can regulate cardiac NE re-uptake. Treatment of Wistar rats with reserpine (5 mg/kg/d) for one (1d) or five days (5d) resulted in markedly reduced cardiac NE content, comparable to NE stores in experimental HF due to pressure overload. In order to assess cardiac NE re-uptake, the specific cardiac [³H]-NE uptake via the NET in a Langendorff preparation was measured. Reserpine treatment led to decreased NE re-uptake at 1d and 5d compared to saline treatment. Expression of tyrosine hydroxylase (TH), the rate-limiting enzyme of the NE synthesis, was elevated in left stellate ganglia after reserpine. Mechanistically, measurement of NET mRNA expression in left stellate ganglia and myocardial NET density revealed a post-transcriptional downregulation of the NET by reserpine. In summary, present data demonstrate that depletion of cardiac NE stores alone is sufficient to impair cardiac NE re-uptake via downregulation of the NET, independent of systemic neurohumoral activation. Knowledge about the regulation of the cardiac NE homeostasis may offer novel therapeutic strategies in HF.

Usefulness of Cardiac MetaIodobenzylguanidine Imaging to Improve Prognostic Power of the Model for End-Stage Liver Disease Scoring System in Patients With Mild-to-Moderate Chronic Heart Failure

Liver dysfunction has a prognostic impact on the outcomes of patients with advanced heart failure (HF). The model for end-stage liver disease (MELD) score is a robust system for rating liver dysfunction, and a high score has been shown to be associated with a poor prognosis in ambulatory patients with HF. In addition, cardiac metaiodobenzylguanidine (MIBG) imaging provides prognostic information in patients with chronic HF (CHF). However, the long-term predictive value of combining the MELD score and cardiac MIBG imaging in patients with CHF has not been elucidated. To prospectively investigate whether cardiac MIBG imaging provides additional prognostic value to the MELD score in patients with mild-to-moderate CHF, we studied 109 CHF outpatients (New York Heart Association: 2.0 ± 0.6) with left ventricular ejection fraction <40%. At enrollment, an MELD score was obtained, and the heart-to-mediastinal ratio on delayed imaging and MIBG washout rate (WR) were measured using cardiac MIBG scintigraphy. During a follow-up period of 7.5 ± 4.2 years, 36 of 109 patients experienced cardiac death (CD). On multivariate Cox analysis, MELD score and WR were significantly independently associated with CD, although heart-to-mediastinal ratio showed an association with CD only on univariate Cox analysis. Patients with abnormal WR (>27%) had a significantly greater risk of CD than those with normal WR in both those with high MELD scores (≥10; hazard ratio 4.0 [1.2 to 13.6]) and with low MELD scores (<10; hazard ratio 6.4 [1.7 to 23.2]). In conclusion, cardiac MIBG imaging would provide additional prognostic information to the MELD score in patients with mild-to-moderate CHF.

Renal denervation in heart failure with preserved ejection fraction (RDT-PEF): a randomized controlled trial

AIM

Heart failure with preserved ejection fraction (HFpEF) is associated with increased sympathetic nervous system (SNS) tone. Attenuating the SNS with renal denervation (RDT) might be helpful and there are no data currently in humans with HFpEF.

METHODS AND RESULTS

In this single-centre, randomized, open-controlled study we included 25 patients with HFpEF [preserved left ventricular (LV) ejection fraction, left atrial (LA) dilatation or LV hypertrophy and raised B-type natriuretic peptide (BNP) or echocardiographic assessment of filling pressures]. Patients were randomized (2:1) to RDT with the Symplicity™ catheter or continuing medical therapy. The primary success criterion was not met in that there were no differences between groups at 12 months for Minnesota Living with Heart Failure Questionnaire score, peak oxygen uptake (VO2 ) on exercise, BNP, E/e', LA volume index or LV mass index. A greater proportion of patients improved at 3 months in the RDT group with respect to VO2 peak (56% vs. 13%, P = 0.025) and E/e' (31% vs. 13%, P = 0.04). Change in estimated glomerular filtration rate was comparable between groups. Two patients required plain balloon angioplasty during the RDT procedure to treat renal artery wall oedema.

CONCLUSION

This study was terminated early because of difficulties in recruitment and was underpowered to detect whether RD improved the endpoints of quality of life, exercise function, biomarkers, and left heart remodelling. The procedure was safe in patients with HFpEF, although two patients did require intraprocedure renal artery dilatation.

Nuclear imaging for cardiac amyloidosis

Histological analysis of endomyocardial tissue is still the gold standard for the diagnosis of cardiac amyloidosis, but has its limitations. Accordingly, there is a need for non-invasive modalities to diagnose cardiac amyloidosis. Echocardiography and ultrasound and magnetic resonance imaging can show characteristics which may not be very specific for cardiac amyloid. Nuclear medicine has gained a precise role in this context: several imaging modalities have become available for the diagnosis and prognostic stratification of cardiac amyloidosis during the last two decades. The different classes of radiopharmaceuticals have the potential to bind different constituents of the amyloidotic infiltrates, with some relevant differences among the various aetiologic types of amyloidosis and the different organs and tissues involved. This review focuses on the background of the commonly used modalities, their present clinical applications, and future clinical perspectives in imaging patients with (suspected) cardiac amyloidosis. The main focus is on conventional nuclear medicine (bone scintigraphy, cardiac sympathetic innervation) and positron emission tomography.

Effects of catheter-based renal denervation on cardiac sympathetic activity and innervation in patients with resistant hypertension

OBJECTIVES

To investigate, whether renal denervation (RDN) has a direct effect on cardiac sympathetic activity and innervation density.

BACKGROUND

RDN demonstrated its efficacy not only in reducing blood pressure (BP) in certain patients, but also in decreasing cardiac hypertrophy and arrhythmias. These pleiotropic effects occur partly independent from the observed BP reduction.

METHODS

Eleven patients with resistant hypertension (mean office systolic BP 180 ± 18 mmHg, mean antihypertensive medications 6.0 ± 1.5) underwent I-123-mIBG scintigraphy to exclude pheochromocytoma. We measured cardiac sympathetic innervation and activity before and 9 months after RDN. Cardiac sympathetic innervation was assessed by heart to mediastinum ratio (H/M) and sympathetic activity by wash out ratio (WOR). Effects on office BP, 24 h ambulatory BP monitoring, were documented.

RESULTS

Office systolic BP and mean ambulatory systolic BP were significantly reduced from 180 to 141 mmHg (p = 0.006) and from 149 to 129 mmHg (p = 0.014), respectively. Cardiac innervation remained unchanged before and after RDN (H/M 2.5 ± 0.5 versus 2.6 ± 0.4, p = 0.285). Cardiac sympathetic activity was significantly reduced by 67 % (WOR decreased from 24.1 ± 12.7 to 7.9 ± 25.3 %, p = 0.047). Both, responders and non-responders experienced a reduction of cardiac sympathetic activity.

CONCLUSION

RDN significantly reduced cardiac sympathetic activity thereby demonstrating a direct effect on the heart. These changes occurred independently from BP effects and provide a pathophysiological basis for studies, investigating the potential effect of RDN on arrhythmias and heart failure.

Cardiac 123I-MIBG Imaging for Clinical Decision Making: 22-Year Experience in Japan

Cardiac neuroimaging with (123)I-metaiodobenzylguanidine ((123)I-MIBG) has been officially used in clinical practice in Japan since 1992. The nuclear cardiology guidelines of the Japanese Circulation Society, revised in 2010, recommended cardiac (123)I-MIBG imaging for the management of heart failure (HF) patients, particularly for the assessment of HF severity and prognosis of HF patients. Consensus in North American and European countries regarding incorporation into clinical practice, however, has not been established yet. This article summarizes 22 y of clinical applications in Japan of (123)I-MIBG imaging in the field of cardiology; these applications are reflected in cardiology guidelines, including recent methodologic advances. A standardized cardiac (123)I-MIBG parameter, the heart-to-mediastinum ratio (HMR), is the basis for clinical decision making and enables common use of parameters beyond differences in institutions and studies. Several clinical studies unanimously demonstrated its potent independent roles in prognosis evaluation and risk stratification irrespective of HF etiologies. An HMR of less than 1.6-1.8 and an accelerated washout rate are recognized as high-risk indicators of pump failure death, sudden cardiac death, and fatal arrhythmias and have independent and incremental prognostic values together with known clinical variables, such as left ventricular ejection fraction and brain natriuretic peptide. Another possible use of this imaging technique is the selection of therapeutic strategy, such as pharmacologic treatment and nonpharmacologic treatment with an implantable cardioverter-defibrillator or cardiac resynchronization device; however, this possibility remains to be investigated. Recent multiple-cohort database analyses definitively demonstrated that patients who were at low risk for lethal events and who were defined by an HMR of greater than 2.0 on (123)I-MIBG studies had a good long-term prognosis. Future investigations of cardiac (123)I-MIBG imaging will contribute to better risk stratification of low-risk and high-risk populations, to the establishment of cost-effective use of this imaging technique for the management of HF patients, and to worldwide acceptance of this imaging technique in clinical cardiology practice.

Clinical Applications of Myocardial Innervation Imaging

Cardiac autonomic innervation plays an important role in regulating function. Adrenergic innervation imaging is possible with the norepinephrine analogue radiotracer iodine 123 meta-iodobenzylguanidine ((123)I-mIBG) and positron emitting tracers such carbon-11 hydroxyephedrine. (123)I-mIBG uptake is assessed globally via the heart to mediastinum ratio on planar images and regionally with tomographic imaging and has utility in various cardiac diseases. There is promise for guiding expensive invasive therapies such as implantable defibrillators, ventricular assist devices, and transplant. There are reports of utility in primary arrhythmic conditions, ischemic heart disease, and diabetes and after cardiac damaging chemotherapy.

The renal nerves in chronic heart failure: efferent and afferent mechanisms

The function of the renal nerves has been an area of scientific and medical interest for many years. The recent advent of a minimally invasive catheter-based method of renal denervation has renewed excitement in understanding the afferent and efferent actions of the renal nerves in multiple diseases. While hypertension has been the focus of much this work, less attention has been given to the role of the renal nerves in the development of chronic heart failure (CHF). Recent studies from our laboratory and those of others implicate an essential role for the renal nerves in the development and progression of CHF. Using a rabbit tachycardia model of CHF and surgical unilateral renal denervation, we provide evidence for both renal efferent and afferent mechanisms in the pathogenesis of CHF. Renal denervation prevented the decrease in renal blood flow observed in CHF while also preventing increases in Angiotensin-II receptor protein in the microvasculature of the renal cortex. Renal denervation in CHF also reduced physiological markers of autonomic dysfunction including an improvement in arterial baroreflex function, heart rate variability, and decreased resting cardiac sympathetic tone. Taken together, the renal sympathetic nerves are necessary in the pathogenesis of CHF via both efferent and afferent mechanisms. Additional investigation is warranted to fully understand the role of these nerves and their role as a therapeutic target in CHF.

Cardiac Iodine-123-Meta-Iodo-Benzylguanidine Uptake in Carotid Sinus Hypersensitivity

Background

Carotid sinus syndrome is the association of carotid sinus hypersensitivity with syncope, unexplained falls and drop attacks in generally older people. We evaluated cardiac sympathetic innervation in this disorder in individuals with carotid sinus syndrome, asymptomatic carotid sinus hypersensitivity and controls without carotid sinus hypersensitivity.

Methods

Consecutive patients diagnosed with carotid sinus syndrome at a specialist falls and syncope unit were recruited. Asymptomatic carotid sinus hypersensitivity and non-carotid sinus hypersensitivity control participants recruited from a community-dwelling cohort. Cardiac sympathetic innervation was determined using Iodine-123-metaiodobenzylguanidine (123-I-MIBG) scanning. Heart to mediastinal uptake ratio (H:M) were determined for early and late uptake on planar scintigraphy at 20 minutes and 3 hours following intravenous injection of 123-I-MIBG.

Results

Forty-two subjects: carotid sinus syndrome (n = 21), asymptomatic carotid sinus hypersensitivity (n = 12) and no carotid sinus hypersensitivity (n = 9) were included. Compared to the non- carotid sinus hypersensitivity control group, the carotid sinus syndrome group had significantly higher early H:M (estimated mean difference, B = 0.40; 95% confidence interval, CI = 0.13 to 0.67, p = 0.005) and late H:M (B = 0.32; 95%CI = 0.03 to 0.62, p = 0.032). There was, however, no significant difference in early H:M (p = 0.326) or late H:M (p = 0.351) between the asymptomatic carotid sinus hypersensitivity group and non- carotid sinus hypersensitivity controls.

Conclusions

Cardiac sympathetic neuronal activity is increased relative to age-matched controls in individuals with carotid sinus syndrome but not those with asymptomatic carotid sinus hypersensitivity. Blood pressure and heart rate measurements alone may therefore represent an over simplification in the assessment for carotid sinus syndrome and the relative increase in cardiac sympathetic innervation provides additional clues to understanding the mechanisms behind the symptomatic presentation of carotid sinus hypersensitivity.

Usefulness of cardiac meta-iodobenzylguanidine imaging to identify patients with chronic heart failure and left ventricular ejection fraction <35% at low risk for sudden cardiac death

Patients with chronic heart failure (CHF) at risk of sudden cardiac death (SCD) are often treated with implantable cardiac defibrillators (ICDs). However, current criteria for device use that is based largely on left ventricular ejection fraction (LVEF) lead to many patients receiving ICDs that never deliver therapy. It is of clinical significance to identify patients who do not require ICDs. Although cardiac I-123 meta-iodobenzylguanidine (MIBG) imaging provides prognostic information about CHF, whether it can identify patients with CHF who do not require an ICD remains unclear. We studied 81 patients with CHF and LVEF <35%, assessed by cardiac MIBG imaging at enrollment. The heart-to-mediastinal ratio (H/M) in delayed images and washout rates were divided into 6 grades from 0 to 5, according to the degree of deviation from control values. The study patients were classified into 3 groups: low (1 to 4), intermediate (5 to 7), and high (8 to 10), according to the MIBG scores defined as the sum of the H/M and washout rate scores. Sixteen patients died of SCD during a follow-up period. Patients with low MIBG score had a significantly lower risk of SCD than those with intermediate and high scores (low [n = 19], 0%; intermediate [n = 37], 19%; high [n = 25], 36%; p = 0.001). The positive predictive value of low MIBG score for identifying patients without SCD was 100%. In conclusion, the MIBG score can identify patients with CHF and LVEF <35% who have low risk of developing SCD.

Magnesium sulphate and (123)I-MIBG in pheochromocytoma: Two useful techniques for a complicated disease

Pheochromocytoma is a tumour of the chromaffin tissue. It may, through catecholamine release, have deleterious effects on myocardial structure. A 48-year-old woman with a history of hypertension and type II diabetes mellitus (ASA II) was diagnosed of pheochromocytoma-induced myocarditis, which caused severe cardiogenic shock, with an ejection fraction of 20%. Extreme blood pressure swings required aggressive therapy with vasoactive drugs (norepinephrine and dopamine) and an intra-aortic balloon pump, despite which severe haemodynamic instability persisted. Finally, the use of magnesium sulphate allowed for cardiovascular stabilization and weaning off vasoactive drugs prior to surgery. (123)I-metaiodobenzylguanidine scintigraphy helps not only to functionally confirm tumour tissue, but also to assess severity and prognosis of cardiac failure. Prognosis of pheochromocytoma-induced heart failure can be very poor. The use of these two well-known and relatively simple 'tools' for treatment and prognosis is a helpful option to keep in mind.

Radionuclide imaging of neurohormonal system of the heart

Heart failure is one of the growing causes of death especially in developed countries due to longer life expectancy. Although many pharmacological and instrumental therapeutic approaches have been introduced for prevention and treatment of heart failure, there are still limitations and challenges. Nuclear cardiology has experienced rapid growth in the last few decades, in particular the application of single photon emission computed tomography (SPECT) and positron emission tomography (PET), which allow non-invasive functional assessment of cardiac condition including neurohormonal systems involved in heart failure; its application has dramatically improved the capacity for fundamental research and clinical diagnosis. In this article, we review the current status of applying radionuclide technology in non-invasive imaging of neurohormonal system in the heart, especially focusing on the tracers that are currently available. A short discussion about disadvantages and perspectives is also included.

Aldosterone augments Na+-induced reduction of cardiac norepinephrine reuptake

Impairment of the cardiac norepinephrine (NE) reuptake by the neuronal NE transporter contributes to enhanced cardiac NE net release in congestive heart failure. Elevated plasma levels of aldosterone (AL) promote sympathetic overstimulation in failing hearts by unclear mechanisms. Our aim was to evaluate if elevated AL and/or alterations in Na(+) intake regulate cardiac NE reuptake. To test the effects of AL and Na(+) on cardiac NE reuptake, Wistar rats were fed a normal-salt (NS) diet (0.2% NaCl), a low-salt (LS) diet (0.015% NaCl), or a high-salt (HS) diet (8% NaCl). Another group of animals received AL infusion alone (0.75 μg/h) or AL infusion plus HS diet. Specific cardiac [(3)H]NE uptake via the NE transporter in a Langendorff preparation and AL plasma levels were measured at different time points between 5 and 42 days of treatment. To compare these findings from healthy animals with a disease model, Dahl salt-sensitive rats were investigated as a model of congestive heart failure with endogenously elevated AL. In summary, neither exogenous nor endogenous elevations of AL alone were sufficient to reduce cardiac NE reuptake. Only the HS diet induced a reduction of NE reuptake by 26%; additional infusion of AL augmented this effect to a further reduction of NE reuptake by 36%. In concordance, Dahl salt-sensitive rats treated with a HS diet displayed elevated AL and a marked reduction of NE reuptake. We conclude that exogenous or endogenous AL elevations alone do not reduce cardiac NE reuptake, but AL serves as an additional factor that negatively regulates cardiac NE reuptake in concert with HS intake.

Essential role of sympathetic endothelin A receptors for adverse cardiac remodeling

In preclinical studies, endothelin receptor A (ETA) antagonists (ETAi) attenuated the progression of heart failure (HF). However, clinical HF trials failed to demonstrate beneficial effects of ETAi. These conflicting data may be explained by the possibility that established HF drugs such as adrenergic receptor blockers interfered with the mechanism of ETAi action in clinical trials. Here we report that mice lacking ETA only in sympathetic neurons (SN-KO) showed less adverse structural remodeling and cardiac dysfunction in response to pathological pressure overload induced by transverse aortic constriction (TAC). In contrast, mice lacking ETA only in cardiomyocytes (CM-KO) were not protected. TAC led to a disturbed sympathetic nerve function as measured by cardiac norepinephrine (NE) tissue levels and [(124)I]-metaiodobenzylguanidine-PET, which was prevented in SN-KO. In a rat model of HF, ETAi improved cardiac and sympathetic nerve function. In cocultures of cardiomyocytes (CMs) and sympathetic neurons (SNs), endothelin-1 (ET1) led to a massive NE release and exaggerated CM hypertrophy compared with CM monocultures. ETA-deficient CMs gained a hypertrophic response through wild-type SNs, but ETA-deficient SNs failed to mediate exaggerated CM hypertrophy. Furthermore, ET1 mediated its effects indirectly via NE in CM-SN cocultures through adrenergic receptors and histone deacetylases, resulting in activation of the prohypertrophic transcription factor myocyte enhancer factor 2. In conclusion, sympathetic ETA amplifies ET1 effects on CMs through adrenergic signaling pathways. Thus, antiadrenergic therapies may blunt potentially beneficial effects of ETAi. Taken together, this may indicate that patients with β blocker intolerance or disturbed sympathetic nerve function could be evaluated for a potential benefit from ETAi.

The role of endothelin-1 in the sympathetic nervous system in the heart

Endothelin-1 (ET1) is a peptide that was initially identified as a strong inductor of vascular contraction. In the last 25 years, there have been several biological processes identified in which ET1 seems to play a critical role. In particular, genetic studies have unveiled that ET1 is important for neuronal development, growth and function. Experimental studies identified ET1 as a regulator of the interaction between sympathetic neurons and cardiac myocytes. This might be of clinical importance since patients suffering from heart failure are characterized by disrupted norepinephrine homeostasis in the heart. This review summarizes the important findings on the role of ET1 for sympathetic neurons and norepinephrine homeostasis in the heart.

Cardiac I123-MIBG correlates better than ejection fraction with symptoms severity in systolic heart failure

Background

The association of autonomic activation, left ventricular ejection fraction (LVEF) and heart failure functional class is poorly understood.

Objective

Our aim was to correlate symptom severity with cardiac sympathetic activity, through iodine-123-metaiodobenzylguanidine (¹²³I-MIBG) scintigraphy and with LVEF in systolic heart failure (HF) patients without previous beta-blocker treatment.

Methods

Thirty-one patients with systolic HF, class I to IV of the New York Heart Association (NYHA), without previous beta-blocker treatment, were enrolled and submitted to ¹²³I-MIBG scintigraphy and to radionuclide ventriculography for LVEF determination. The early and delayed heart/mediastinum (H/M) ratio and the washout rate (WR) were performed.

Results

According with symptom severity, patients were divided into group A, 13 patients in NYHA class I/II, and group B, 18 patients in NYHA class III/IV. Compared with group B patients, group A had a significantly higher LVEF (25% ± 12% in group B vs. 32% ± 7% in group A, p = 0.04). Group B early and delayed H/M ratios were lower than group A ratios (early H/M 1.49 ± 0.15 vs. 1.64 ± 0.14, p = 0.02; delayed H/M 1.39 ± 0.13 vs. 1.58 ± 0.16, p = 0.001, respectively). WR was significantly higher in group B (36% ± 17% vs. 30% ± 12%, p= 0.04). The variable that showed the best correlation with NYHA class was the delayed H/M ratio (r= -0.585; p=0.001), adjusted for age and sex.

Conclusion

This study showed that cardiac ¹²³I-MIBG correlates better than ejection fraction with symptom severity in systolic heart failure patients without previous beta-blocker treatment.

Perindopril vs Enalapril in Patients with Systolic Heart Failure: Systematic Review and Metaanalysis

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors are highly effective at improving prognosis in a variety of disease states such as hypertension, cardiovascular disease, systolic heart failure, and acute coronary syndrome. Although these medications have been used in clinical practice for decades, not all ACE inhibitors are equal, as agents within this class vary in lipophilicity, tissue-ACE binding, antioxidant properties, antiinflammatory properties, bradykinin site selectivity, and duration of action. The objective of this systematic review and metaanalysis was to evaluate the effects of perindopril vs enalapril on left ventricular function in patients with systolic heart failure.

METHODS

We conducted a systematic review and metaanalysis of trials comparing perindopril and enalapril in systolic heart failure. Relevant studies were identified through searches of MEDLINE, EMBASE, Web of Science, and Google Scholar.

RESULTS

Three trials comparing enalapril with perindopril in 116 patients with systolic heart failure were identified. Compared to enalapril, perindopril significantly improved cardiac sympathetic nerve activity: the pooled mean net change in heart to mediastinum ratio was 0.12 (95% confidence interval [CI]: 0.08, 0.16) and the pooled mean net change in washout rate was -3.51% (95% CI: -4.17, -2.85). Other variables also showed improvement. The pooled mean net change in New York Heart Association functional class was -0.44 (95% CI: -0.86, -0.03) and the change in brain natriuretic peptide was -64.1 [95% CI: -80.8, -47.4]. The change in left ventricular ejection fraction was not significantly greater with perindopril than enalapril: 1.15% (95% CI: -2.74, 5.04). However, in the 2 trials that switched patients from enalapril to perindopril, left ventricular ejection fraction at 6 months was significantly greater in the perindopril group: 2.41% (95% CI: 1.26, 3.55; P<0.0001).

CONCLUSION

In patients with systolic heart failure, perindopril significantly improves cardiac sympathetic nerve activity, brain natriuretic peptide, and New York Heart Association functional class compared to enalapril. Additionally, when patients were switched from enalapril to perindopril, left ventricular ejection fraction at 6 months was significantly greater.