Resting perfusion MPI-SPECT combined with cardiac 123I-mIBG sympathetic innervation imaging improves prediction of arrhythmic events in non-ischemic cardiomyopathy patients: sub-study from the ADMIRE-HF trial

Cardiac imaging for the prediction of sudden cardiac arrest in patients with heart failure

The identification of heart failure (HF) patients at risk for arrhythmic sudden cardiac arrest (SCA) is a major challenge in the cardiovascular field. In addition to optimal medical treatment for HF, implantable cardioverter defibrillator (ICD) is currently recommended to prevent SCA in patients with reduced left ventricular ejection fraction (LVEF). The indication for an ICD implantation, in addition to HF etiology, New York Health Association (NYHA) class and life expectancy, mainly depends on LVEF value at echocardiography. However, the actual role of LVEF in the prediction of SCA has recently been debated, while newer multimodality imaging techniques with increased prognostic accuracy have been developed. Speckle tracking imaging allows the quantification of mechanical dispersion, a marker of electrophysiological heterogeneity predisposing to malignant arrhythmias, while advanced cardiac magnetic resonance techniques such as myocardial T1-mapping and extracellular volume fraction assessment allow the evaluation of interstitial diffuse fibrosis. Nuclear imaging is helpful for the appraisal of sympathetic nervous system dysfunction, while newer computed tomography techniques assessing myocardial delayed enhancement allow the identification of focal myocardial scar. This review will focus on the most modern advances in the field of cardiovascular imaging along with its applications for the prediction of SCA in patients with HF. Modern artificial intelligence applications in cardiovascular imaging will also be discussed.

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.

Renal function and cardiac adrenergic impairment in patients affected by heart failure

Although in heart failure (HF) there is a strict correlation between heart and kidney, no data are available on the potential relationship in HF between renal dysfunction (RD) and the impaired sympathetic innervation. Aim of the present study was to assess the relationship between RD and cardiac sympathetic innervation in HF patients with reduced ejection fraction. Two hundred and sixty-three patients with mild-to-severe HF underwent iodine-123 meta-iodobenzylguanidine myocardial scintigraphy to assess sympathetic innervation, evaluating early and late heart-to-mediastinum (H/M) ratios and washout rate. In all patients, glomerular filtration rate (eGFR) by Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula was assessed. A direct association was found between EPI-eGFR and late H/M (r = .215; P < .001). Dividing the population into moderate-to-severe eGFR reduction and normal-to-mildly reduced eGFR (cutoff ≤ 60 mL·min-1·1.73 m-2), a statistically significant reduction of late H/M value was found in patients with RD compared to patients with preserved eGFR (P = .030). By multivariable linear regression analysis, eGFR resulted in the prediction of impaired late H/M in patients with RD (P = .005). Patients with RD and HF show more impaired cardiac sympathetic activity than HF patients with preserved renal function, and reduced eGFR is a predictor of reduced late H/M.

Multimodality imaging predictors of sudden cardiac death

Sudden cardiac death (SCD) is the worst clinical event occurring in the clinical context of cardiomyopathies. Current guidelines recommend using LV ejection fraction as the only imaging-derived parameter to identify patients who may benefit from ICD implantation in cardiomyopathies with reduced ejection fraction; however, a relevant proportion of high-risk population is left with unmet therapeutic goal. In case of dilated, hypertrophic, or arrhythmogenic cardiomyopathies, there is still a room for more sensitive and specific risk markers for identifying a cluster at higher risk of SCD. In this paper, we reviewed the evidence supporting the use of advanced echocardiography, CMR, and nuclear cardiology for SCD stratification in patients with the most common cardiomyopathies. The added value of these modalities may be explained on the basis of tissue characterization, especially scar detection, a central player in the pathogenesis of arrhythmias. Therefore, integration of these modalities to our everyday clinical practice may help in dealing with the gray zones where current guidelines are still ineffective for patient selection.

Summed rest score in gated myocardial perfusion imaging is a good predicator for treatment-related cardiotoxicity after anthracycline chemotherapy in patients with diffuse large B-cell lymphoma

Anthracycline chemotherapy is commonly used in the treatment of diffuse large B-cell lymphoma (DLBCL). Treatment-related cardiotoxicity (TRC) is defined as when the patient is identified to have one of the following clinical manifestations: Symptomatic heart failure, cardiac death, arrhythmia, infarction, a decrease in left ventricular ejection fraction (LVEF) of >15% from baseline or a decrease in LVEF of >10 to <50%. TRC may induce severe cardiac failure or cardiac arrhythmia as the main cause of death. The present study aimed to investigate the prognostic value of the summed rest score (SRS) in gated myocardial perfusion imaging (G-MPI) for the early detection of TRC caused by anthracycline chemotherapy in patients with DLBCL. A total of 36 DLBCL patients were enrolled in the present study, and a series of parameters were compared at baseline and after chemotherapy. According to the occurrence of TRC during the observation period, the patients were divided into two groups, and parameters associated with cardiac function were compared. The SRS in G-MPI and the corrected QT interval in the electrocardiogram were significantly different before and after chemotherapy (P=0.012 and P=0.015, respectively). By comparing parameters associated with cardiac function between the TRC group (n=22) and the no-TRC group (n=14), it was found that only SRS was significantly different (P=0.012). Multivariate logistic regression analysis showed that the SRS level was the only independent predicator for TRC (P=0.018; HR, 6.053; 95% CI, 1.364-26.869). Receiver operating characteristic curve analysis identified an optimal SRS cutoff of >1 for predicting TRC after anthracycline chemotherapy (P<0.001). Overall, the G-MPI SRS level was an early indicator for TRC surveillance in patients with DLBCL after anthracycline chemotherapy. The application of G-MPI SRS in clinical practice may contribute to early treatment and a subsequent decrease in mortality caused by such cardiovascular complications.

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.

Risk Stratification for Sudden Cardiac Death in Non-Ischaemic Dilated Cardiomyopathy

Purpose of Review

Non-ischaemic dilated cardiomyopathy (DCM) occurs in 1 in 2500 individuals in the general population and is associated with considerable morbidity and mortality. Studies involving large numbers of unselected DCM patients have led to consensus guidelines recommending implantable cardioverter-defibrillator (ICD) implantation for protection against sudden cardiac death (SCD) in those with LVEF ≤35%. The purpose of this article is to review the literature for other potential markers including serological, electrocardiographic, echocardiographic, cardiac magnetic resonance, ambulatory ECG and genetic data, to highlight other potential markers that may optimise risk stratification for SCD in this cohort and thereby allow a more personalized approach to ICD-implantation.

Recent Findings

Recent studies including the Danish study to assess the efficacy of ICDs in patients with non-ischemic systolic heart failure on mortality (DANISH) trial have questioned the benefits of ICD implantation in this group of patients with no changes in all-cause mortality. Recent pooled cohorts of patients with genetic DCM and in particular in those with Lamin A/C (LMNA) mutations have identified patients at increased risk of SCD and allowed the creation of algorithms to prognosticate SCD risk in mutation carriers. Furthermore, genetic testing has identified other DCM-causing genes including filamin C (FLNC) and RBM20 which may be associated with higher rates of ventricular arrhythmia.

Summary

To date, risk-stratification for SCD has been hampered by the utilisation of heterogenous subsets of idiopathic DCM patients and by use of static risk models where predictions are based on a single time point with a lack of consideration of disease progression. The current focus of personalised risk-stratification for SCD is shifting towards better characterisation of underlying DCM aetiology and the development of multi-parametric risk-stratification models that incorporate time-dependent disease characteristics and novel biomarkers.

A Novel Risk Stratification Score for Sudden Cardiac Death Prediction in Middle-Aged, Nonischemic Dilated Cardiomyopathy Patients: The ESTIMATED Score

BACKGROUND

We aimed to develop a risk score (LGE Based Prediction of SCD Risk in Nonischemic Dilated Cardiomyopathy [ESTIMATED]) based on late gadolinium enhancement (LGE) cardiac magnetic resonance to predict sudden cardiac death (SCD) in patients with nonischemic dilated cardiomyopathy (NIDCM) and left ventricular ejection fraction ≤ 35%.

METHODS

We recruited 395 consecutive middle-aged patients with NIDCM and performed 3-year follow-up for SCD events. The score was developed and verified in 295 primary prevention patients, and the predictive value was confirmed by comparing the SCD events between the high-risk patients stratified by the score and 100 secondary prevention patients.

RESULTS

The ESTIMATED score (constructed by the LGE extent > 14%, syncope, atrial flutter/fibrillation, nonsustained ventricular tachycardia, advanced atrioventricular block, and age ≤ 20 or > 50 years) showed good calibrations for SCD prediction in the derivation (C-statistic: 0.80, 95% confidence interval: 0.74-0.86) and validation set (C-statistic: 0.80, 95% confidence interval: 0.71-0.87). By the score, 20.3% of primary prevention patients were categorized as high risk (≥ 3 points), 28.1% as intermediate risk (2 points), and 51.6% as low risk (0-1 points) for 3-year SCD events (45.9% vs 20.1% vs 5.1%, P < 0.0001). The 3-year SCD events were also well in agreement with the score stratification in patients without implantable cardioverter-defibrillator. High-risk primary prevention patients selected by the score in the derivation and validation sets had 3-year SCD events comparable with that in secondary prevention patients (47.6% vs 40.6% vs 38.7%, P = 0.81).

CONCLUSIONS

Our study derived and validated an LGE-based (ESTIMATED) risk score providing refined SCD prediction. The score may help to identify candidates for primary prevention implantable cardioverter-defibrillator in patients with NIDCM.

Synergistic prognostic implications of left ventricular mechanical dyssynchrony and impaired cardiac sympathetic nerve activity in heart failure patients with reduced left ventricular ejection fraction

Aims

Impairment of cardiac sympathetic innervation is a potent prognostic marker in heart failure, while left ventricular mechanical dyssynchrony (LVMD) has recently been noted as a novel prognosis determinant in heart failure patients with reduced LV ejection fraction (HFrEF). This study was designed to determine the correlation between cardiac sympathetic innervation quantified by metaiodobenzylguanidine (MIBG) activity and LVMD measured by electrocardiogram-gated myocardial perfusion imaging and to evaluate their incremental prognostic values in HFrEF patients.

Methods and results

A total of 570 consecutive HFrEF patients were followed up for 19.6 months with a primary endpoint of lethal cardiac events (CE) such as sudden cardiac death, death due to pump failure and appropriate ICD shock against life-threatening ventricular tachyarrhythmias. Cardiac sympathetic function and innervation were quantified as heart-to-mediastinum ratio (HMR) and washout kinetics of cardiac MIBG activity. LVMD was assessed by a standard deviation (SD) of systolic phase angle in gated myocardial perfusion imaging. Patients with CE (n = 166, 29%) had a significantly lower HMR and a significantly greater phase SD than did non-CE patients: 1.46 ± 0.28 vs. 1.63 ± 0.29, P < 0.0001 and 39.1 ± 11.6 vs. 33.1 ± 10.1, P < 0.0001, respectively. Compared to the single use of optimal cut-offs of late HMR (1.54) and phase SD (38), their combination more precisely discriminated high-risk or low-risk patients from others with log rank values from 7.78 to 65.2 (P = 0.0053 to P ≤ 0.0001). Among significant univariate variables, multivariate Cox proportional hazards model identified NYHA functional class, estimated glomerular filtration rate (eGFR), HMR 1.54 and phase SD 60 as significant determinants of CE with hazard ratios of 3.108 (95% CI, 2.472-3.910; P < 0.0001), 0.988 (95% CI, 0.981-0.996; P = 0.0021), 0.257 (95% CI, 0.128-0.498; P < 0.0001) and 1.019 (95% CI, 1.019-1.037; P = 0.0228), respectively. By combining the four independent determinants, the prognostic powers synergistically (P < 0.0001) increased maximally to 263.8.

Conclusions

Left ventricular mechanical dyssynchrony and impairment of cardiac sympathetic innervation are synergistically related to lethal cardiac events, contributing to better stratification of lethal cardiac event-risks and probably to optimization of therapeutic strategy in patients with HFrEF.

Myocardial 123I-metaiodobenzylguanidine imaging in hypertension and left ventricular hypertrophy

Sympathetic nervous system plays a pivotal role in essential hypertension and in the development of left ventricular hypertrophy. Moreover, cardiac sympathetic dys-regulation has been demonstrated as a key con-causal factor in the genesis and progression of pathologic conditions such as congestive heart failure and ischemic heart disease to which hypertension predisposes as a risk factor. However, despite its fundamental role in cardiac pathophysiology, the evaluation of cardiac sympathetic nervous system has never gained a wide clinical application, remaining mostly a research tool. In this context, nuclear imaging techniques are the only modalities to allow the direct evaluation of cardiac sympathetic nervous integrity, giving the chance to obtain objective measures of the sympathetic tone. This review, while summarizing the general profile of currently available tests for autonomic evaluation, focuses on 123I-metaiodobenzylguanidine nuclear imaging as a preferential tool to assess cardiac sympathetic status. Specifically, the review discusses the available evidence on cardiac 123I-metaiodobenzylguanidine scintigraphy in arterial hypertension and left ventricular hypertrophy and its diagnostic and prognostic potential in congestive heart failure and ischemic heart disease.

Role of Cardiac Imaging in Evaluating Risk for Sudden Cardiac Death

Sudden cardiac death (SCD) is a major cause of death from cardiovascular disease. Our ability to predict patients at the highest risk of developing lethal ventricular arrhythmias remains limited. Despite recent studies evaluating risk stratification tools, there is no optimal strategy. Cardiac imaging provides the opportunity to assess left ventricular ejection fraction, strain, fibrosis, and sympathetic innervation, all of which are pathophysiologically related to SCD risk. These modalities may play a role in the identification of vulnerable anatomic substrates that provide the pathophysiologic basis for SCD. Further studies are required to identify optimal imaging platform for risk assessment.

Optimization of a simultaneous dual-isotope 201Tl/123I-MIBG myocardial SPECT imaging protocol with a CZT camera for trigger zone assessment after myocardial infarction for routine clinical settings: Are delayed acquisition and scatter correction necessary?

BACKGROUND

Dual-isotope 201Tl/123I-MIBG SPECT can assess trigger zones (dysfunctions in the autonomic nervous system located in areas of viable myocardium) that are substrate for ventricular arrhythmias after STEMI. This study evaluated the necessity of delayed acquisition and scatter correction for dual-isotope 201Tl/123I-MIBG SPECT studies with a CZT camera to identify trigger zones after revascularization in patients with STEMI in routine clinical settings.

METHODS

Sixty-nine patients were prospectively enrolled after revascularization to undergo 201Tl/123I-MIBG SPECT using a CZT camera (Discovery NM 530c, GE). The first acquisition was a single thallium study (before MIBG administration); the second and the third were early and late dual-isotope studies. We compared the scatter-uncorrected and scatter-corrected (TEW method) thallium studies with the results of magnetic resonance imaging or transthoracic echography (reference standard) to diagnose myocardial necrosis.

RESULTS

Summed rest scores (SRS) were significantly higher in the delayed MIBG studies than the early MIBG studies. SRS and necrosis surface were significantly higher in the delayed thallium studies with scatter correction than without scatter correction, leading to less trigger zone diagnosis for the scatter-corrected studies. Compared with the scatter-uncorrected studies, the late thallium scatter-corrected studies provided the best diagnostic values for myocardial necrosis assessment.

CONCLUSIONS

Delayed acquisitions and scatter-corrected dual-isotope 201Tl/123I-MIBG SPECT acquisitions provide an improved evaluation of trigger zones in routine clinical settings after revascularization for STEMI.

Personalizing Risk Stratification for Sudden Death in Dilated Cardiomyopathy: The Past, Present, and Future

Results from the DANISH Study (Danish Study to Assess the Efficacy of ICDs in Patients With Non-Ischemic Systolic Heat Failure on Mortality) suggest that for many patients with dilated cardiomyopathy (DCM), implantable cardioverter-defibrillators do not increase longevity. Accurate identification of patients who are more likely to die of an arrhythmia and less likely to die of other causes is required to ensure improvement in outcomes and wise use of resources. Until now, left ventricular ejection fraction has been used as a key criterion for selecting patients with DCM for an implantable cardioverter-defibrillator for primary prevention purposes. However, registry data suggest that many patients with DCM and an out-of-hospital cardiac arrest do not have a markedly reduced left ventricular ejection fraction. In addition, many patients with reduced left ventricular ejection fraction die of nonsudden causes of death. Methods to predict a higher or lower risk of sudden death include the detection of myocardial fibrosis (a substrate for ventricular arrhythmia), microvolt T-wave alternans (a marker of electrophysiological vulnerability), and genetic testing. Midwall fibrosis is identified by late gadolinium enhancement cardiovascular magnetic resonance imaging in ≈30% of patients and provides incremental value in addition to left ventricular ejection fraction for the prediction of sudden cardiac death events. Microvolt T-wave alternans represents another promising predictor, supported by large meta-analyses that have highlighted the negative predictive value of this test. However, neither of these strategies have been routinely adopted for risk stratification in clinical practice. More convincing data from randomized trials are required to inform the management of patients with these features. Understanding of the genetics of DCM and how specific mutations affect arrhythmic risk is also rapidly increasing. The finding of a mutation in lamin A/C, the cause of ≈6% of idiopathic DCM, commonly underpins more aggressive management because of the malignant nature of the associated phenotype. With the expansion of genetic sequencing, the identification of further high-risk mutations appears likely, leading to better-informed clinical decision making and providing insight into disease mechanisms. Over the next 5 to 10 years, we expect these techniques to be integrated into the existing algorithm to form a more sensitive, specific, and cost-effective approach to the selection of patients with DCM for implantable cardioverter-defibrillator implantation.

Cardiac sympathetic nervous system imaging with 123I-meta-iodobenzylguanidine: Perspectives from Japan and Europe

Cardiac sympathetic nervous system dysfunction is closely associated with risk of serious cardiac events in patients with heart failure (HF), including HF progression, pump-failure death, and sudden cardiac death by lethal ventricular arrhythmia. For cardiac sympathetic nervous system imaging, 123I-meta-iodobenzylguanidine (123I-MIBG) was approved by the Japanese Ministry of Health, Labour and Welfare in 1992 and has therefore been widely used since in clinical settings. 123I-MIBG was also later approved by the Food and Drug Administration (FDA) in the United States of America (USA) and it was expected to achieve broad acceptance. In Europe, 123I-MIBG is currently used only for clinical research. This review article is based on a joint symposium of the Japanese Society of Nuclear Cardiology (JSNC) and the American Society of Nuclear Cardiology (ASNC), which was held in the annual meeting of JSNC in July 2016. JSNC members and a member of ASNC discussed the standardization of 123I-MIBG parameters, and clinical aspects of 123I-MIBG with a view to further promoting 123I-MIBG imaging in Asia, the USA, Europe, and the rest of the world.

Life-Threatening Ventricular Arrhythmias: Current Role of Imaging in Diagnosis and Risk Assessment

Sudden cardiac arrest continues to be a major cause of death from cardiovascular disease but our ability to predict patients at the highest risk of developing lethal ventricular arrhythmias remains limited. Left ventricular ejection fraction is inversely related to the risk of sudden death but has a low sensitivity and specificity for the population at risk. Nevertheless, it continues to be the main variable considered in identifying patients most likely to benefit from implantable defibrillators to prevent sudden death. Imaging myocardial sympathetic innervation with PET and SPECT as well as imaging characteristics of myocardial infarcts using gadolinium-enhanced cardiac magnetic resonance are emerging as imaging modalities that may further refine patient selection beyond ejection fraction. This review will primarily focus on employing advanced imaging approaches to identify patients with left ventricular dysfunction that are most likely to develop lethal arrhythmias and benefit from inserting a primary prevention implantable cardiac defibrillator. While not yet tested in prospective studies, we will review risk prediction models incorporating quantitative imaging and biomarkers that have been developed that appear promising to identify those at highest risk of sudden death.

Prognostic Value of Cardiac Sympathetic Nerve Imaging Using Long-Term Follow-up Data - Ischemic vs. Non-Ischemic Heart Failure Etiology

BACKGROUND

Although there are several known prognostic determinants in heart failure (HF), individual risk profiles can vary, in particular between ischemic and non-ischemic HF background. This study investigated the difference in prognostic efficacy of cardiac (123)I-meta-iodobenzylguanidine (MIBG) imaging between the 2 etiologies.

METHODS AND RESULTS

All 1,322 patients with HF were enrolled and followed up at most after 10 years. The HF patients were divided into 2 groups: an ischemic group (n=362) and non-ischemic group (n=960), and Cox proportional hazards model was used for data analysis. During 10 years of follow-up, 296 (22.4%) of 1,322 patients died; the mortality rates were 21.8% and 22.6% for the ischemic and non-ischemic groups, respectively. The ischemic group had greater prevalence of sudden death and lethal acute myocardial infarction, and the non-ischemic group had a higher rate of pump failure death. On multivariate Cox proportional hazards analysis using categorized variables, in the ischemic group, delayed heart-to-mediastinum ratio (HMR; P<0.0001), age (P=0.0002) and LVEF (P=0.03) were the independent significant predictors of lethal events. In the non-ischemic group, delayed HMR (P<0.0001), NYHA class (P<0.0001) and age (P<0.0001) were significant determinants of lethal outcome.

CONCLUSIONS

Cardiac MIBG imaging has nearly identical prognostic value in both ischemic and non-ischemic HF, independent of cause of cardiac death.

Sympathetic nerve damage and restoration after ischemia-reperfusion injury as assessed by (11)C-hydroxyephedrine

PURPOSE

An altered state of the cardiac sympathetic nerves is an important prognostic factor in patients with coronary artery disease. The aim of this study was to investigate regional sympathetic nerve damage and restoration utilizing a rat model of myocardial transient ischemia and a catecholamine analog PET tracer, (11)C-hydroxyephedrine ((11)C-HED).

METHODS

Transient myocardial ischemia was induced by coronary occlusion for 20 min and reperfusion in male Wistar rats. Dual-tracer autoradiography was performed subacutely (7 days) and chronically (2 months) after ischemia, and in control rats without ischemia using (11)C-HED as a marker of sympathetic innervation and (201)TI for perfusion. Additional serial in vivo cardiac (11)C-HED and (18)F-FDG PET scans were performed in the subacute and chronic phases after ischemia.

RESULTS

After transient ischemia, the (11)C-HED uptake defect areas in both the subacute and chronic phases were clearly larger than the perfusion defect areas in the midventricular wall. The subacute (11)C-HED uptake defect showed a transmural pattern, whereas uptake recovered in the subepicardial portion in the chronic phase. Tyrosine hydroxylase antibody nerve staining confirmed regional denervation corresponding to areas of decreased (11)C-HED uptake. Serial in vivo PET imaging visualized reductions in the area of the (11)C-HED uptake defects in the chronic phase consistent with autoradiography and histology.

CONCLUSION

Higher susceptibility of sympathetic neurons compared to myocytes was confirmed by a larger (11)C-HED defect with a corresponding histologically identified region of denervation. Furthermore, partial reinnervation was observed in the chronic phase as shown by recovery of subepicardial (11)C-HED uptake.

Alterations of left ventricular deformation and cardiac sympathetic derangement in patients with systolic heart failure: a 3D speckle tracking echocardiography and cardiac ¹²³I-MIBG study

PURPOSE

Myocardial contractile function is under the control of cardiac sympathetic activity. Three-dimensional speckle tracking echocardiography (3D-STE) and cardiac imaging with (123)I-metaiodobenzylguanidine ((123)I-MIBG) are two sophisticated techniques for the assessment of left ventricular (LV) deformation and sympathetic innervation, respectively, which offer important prognostic information in patients with heart failure (HF). The purpose of this investigation was to explore, in patients with systolic HF, the relationship between LV deformation assessed by 3D-STE and cardiac sympathetic derangement evaluated by (123)I-MIBG imaging.

METHODS

We prospectively studied 75 patients with systolic HF. All patients underwent a 3D-STE study (longitudinal, circumferential, area and radial) and (123)I-MIBG planar and SPECT cardiac imaging.

RESULTS

3D-STE longitudinal, circumferential and area strain values were correlated with (123)I-MIBG late heart to mediastinum (H/M) ratio and late SPECT total defect score. After stratification of the patients according to ischaemic or nonischaemic HF aetiology, we observed a good correlation of all 3D-STE measurements with late H/M ratio and SPECT data in the ischaemic group, but in patients with HF of nonischaemic aetiology, no correlation was found between LV deformation and cardiac sympathetic activity. At the regional level, the strongest correlation between LV deformation and adrenergic innervation was found for the left anterior descending coronary artery distribution territory for all four 3D-STE values. In multivariate linear regression analyses, including age, gender, LV ejection fraction, NYHA class, body mass index, heart rate and HF aetiology, only 3D-STE area and radial strain values significantly predicted cardiac sympathetic derangement on (123)I-MIBG late SPECT.

CONCLUSION

This study indicated that 3D-STE measurements are correlated with (123)I-MIBG planar and SPECT data. Furthermore, 3D-STE area and radial strain values, but not LVEF, predict cardiac sympathetic derangement in human postischaemic HF.

Molecular imaging to predict ventricular arrhythmia in heart failure

Ventricular tachycardia (VT) is a major cause of sudden cardiac death (SCD) in patients with heart failure (HF). Left ventricular ejection fraction (LVEF) and heart failure class according to the New York Heart association (NYHA) are in most common use to identify patients that may benefit from implantable cardioverter defibrillator (ICD) therapy. But during 3 years of follow up only 35% of patients receive appropriate ICD action. Therefore, there is a continued need for refinement of selection criteria for ICD implantation. In this regard, molecular imaging of the autonomic nervous system, which plays a central role in HF progression and cardiac electro-mechanical regulation, can make a substantial contribution. This article reviews the currently available literature concerning the value of molecular neuronal cardiac imaging for prediction of ventricular arrhythmias in HF patients.

New insights from major prospective cohort studies with cardiac nuclear imaging

For more than two decades, radionuclide imaging has prevailed as a cornerstone in the diagnosis and treatment of patients with cardiac disease. From this experience, large cohort studies have emerged that demonstrate the prognostic value of cardiac radionuclide imaging in a variety of patient groups and conditions. Myocardial perfusion imaging has accrued the most robust evidence for accurate and independent risk stratification over traditional clinical variables. In a variety of patient populations, the presence of myocardial ischemia is a strong predictor of cardiac events on follow-up. In patients with heart failure, smaller observations have similarly established the prognostic value of viability imaging and imaging of cardiac sympathetic activity. The present review provides a summary of recent cohort studies with radionuclide imaging and a critical appraisal of their clinical implications. Its purpose is to put the available evidence into a clinical context, analyze its potential impact on patient management and identify gaps in knowledge and unanswered questions to be addressed in future randomized trials.

Role of nuclear cardiology for guiding device therapy in patients with heart failure

Heart failure is a dynamic condition with high morbidity and mortality and its prognosis should be reassessed frequently, particularly in patients for whom critical treatment decisions may depend on the results of prognostication. In patients with heart failure, nuclear cardiology techniques are useful to establish the etiology and the severity of the disease, while fewer studies have explored the potential capability of nuclear cardiology to guide cardiac resynchronization therapy (CRT) and to select patients for implantable cardioverter defibrillators (ICD). Left ventricular synchrony may be assessed by radionuclide angiography or gated single-photon emission computed tomography myocardial perfusion scintigraphy. These modalities have shown promise as predictors of CRT outcome using phase analysis. Combined assessment of myocardial viability and left ventricular dyssynchrony is feasible using positron emission tomography and could improve conventional response prediction criteria for CRT. Preliminary data also exists on integrated positron emission tomography/computed tomography approach for assessing myocardial viability, identifying the location of biventricular pacemaker leads, and obtaining left ventricular functional data, including contractile phase analysis. Finally, cardiac imaging with autonomic radiotracers may be useful in predicting CRT response and for identifying patients at risk for sudden cardiac death, therefore potentially offering a way to select patients for both CRT and ICD therapy. Prospective trials where imaging is combined with image-test driven therapy are needed to better define the role of nuclear cardiology for guiding device therapy in patients with heart failure.

The role of radionuclide imaging in heart failure

The incidence of heart failure (HF) is increasing and it remains the only area in cardiovascular disease wherein hospitalization rates and mortalities have worsened in the past 25 years. This review is provided to assess the role of radionuclide imaging in HF. The focus is on three aspects: the value of nuclear imaging to distinguish ischemic from non-ischemic etiologies; risk stratification of patients with HF with evaluation of candidates for specific treatment strategies; and the role of cardiac neuronal imaging in patients with HF. Distinguishing ischemic from non-ischemic cardiomyopathy is important because patients with ischemic cardiomyopathy can potentially have dramatic improvement with revascularization. Single photon emission computed tomography (SPECT) has excellent reported sensitivity and negative predictive value in the detection of coronary artery disease in HF patients. SPECT imaging is also useful in establishing treatment strategies in patients with HF, including those with new onset CHF. Cardiac neuronal imaging of mIBG is particularly helpful in risk stratification of patients with HF. The modality can be used to monitor the response to therapy as dysfunctional mIBG uptake may show improvement with pharmacological treatment.