123I-mIBG scintigraphy to predict risk for adverse cardiac outcomes in heart failure patients: design of two prospective multicenter international trials

Impaired Cardiac Sympathetic Activity Is Associated With Myocardial Remodeling and Established Biomarkers of Heart Failure

BACKGROUND

123Iodine-meta-iodobenzylguanidine scintigraphy is useful for assessing cardiac autonomic dysfunction and predict outcomes in heart failure (HF). The relationship of cardiac sympathetic function with myocardial remodeling and diffuse fibrosis remains largely unknown. We aimed to evaluate the cardiac sympathetic function of patients with HF and its relation with myocardial remodeling and exercise capacity.

METHODS AND RESULTS

Prospectively enrolled patients with HF (New York Heart Association class II-III) were stratified into HF with preserved left ventricular ejection fraction [LVEF] ≥45%) and reduced LVEF. Ventricular morphology/function and myocardial extracellular volume (ECV) fraction were quantified by cardiovascular magnetic resonance, global longitudinal strain by echocardiography, cardiac sympathetic function by heart-to-mediastinum ratio from 123iodine-meta-iodobenzylguanidine scintigraphy. All participants underwent cardiopulmonary exercise testing. The cohort included 33 patients with HF with preserved LVEF (LVEF, 60±10%; NT-proBNP [N-terminal pro-B-type natriuretic peptide], 248 [interquartile range, 79-574] pg/dL), 28 with HF with reduced LVEF (LVEF, 30±9%; NT-proBNP, 743 [interquartile range, 250-2054] pg/dL) and 20 controls (LVEF, 65±5%; NT-proBNP, 40 [interquartile range, 19-50] pg/dL). Delayed (4 hours) 123iodine-meta-iodobenzylguanidine heart-to-mediastinum ratio was lower in HF with preserved LVEF (1.59±0.25) and HF with reduced LVEF (1.45±0.16) versus controls (1.92±0.24; P<0.001), and correlated negatively with diffuse fibrosis assessed by ECV (R=-0.34, P<0.01). ECV in segments without LGE was increased in HF with preserved ejection fraction (0.32±0.05%) and HF with reduced left ventricular ejection fraction (0.31±0.04%) versus controls (0.28±0.04, P<0.05) and was associated with the age- and sex-adjusted maximum oxygen consumption (peak oxygen consumption); (R=-0.41, P<0.01). Preliminary analysis indicates that cardiac sympathetic function might potentially act as a mediator in the association between ECV and NT-proBNP levels.

CONCLUSIONS

Abnormally low cardiac sympathetic function in patients with HF with reduced and preserved LVEF is associated with extracellular volume expansion and decreased cardiopulmonary functional capacity.

The prognostic value of 123I-mIBG SPECT cardiac imaging in heart failure patients: a systematic review

This systematic review aimed to evaluate the prognostic value of Iodine123 Metaiodobenzylguanidine (123I-mIBG) SPECT myocardial imaging in patients with heart failure (HF) and to assess whether semi-quantitative SPECT scores can be useful for accurate risk stratification concerning arrhythmic event (AE) and sudden cardiac death (SCD) in this cohort. A systematic literature search of studies published until November 2020 regarding the application of 123I-mIBG SPECT in HF patients was performed, in Pubmed, Scopus, Medline, Central (Cochrane Library) and Web Of Science databases, including the words "MIBG", "metaiodobenzylguanidine", "heart", "spect", and "tomographic". The included studies had to correlate 123I-mIBG SPECT scores with endpoints such as overall survival and prevention of AE and SCD in HF patients. According to the sixteen studies included, the analysis showed that 123I-mIBG SPECT scores, such as summed defect score (SDS), regional wash-out (rWO), and regional myocardial tracer uptake, could have a reliable prognostic value in patients with HF. An increased SDS or rWO, as well as a reduced 123I-mIBG myocardial uptake, have proven to be effective in predicting AE- and SCD-specific risk in HF patients. Despite achieved results being promising, a more reproducible standardized method for semi-quantitative analysis and further studies with larger cohort are needed for 123I-mIBG SPECT myocardial imaging to be as reliable and, thus, accepted as the conventional 123I-mIBG planar myocardial imaging.

Analysis of Differences in Assessment of Left Ventricular Function on Echocardiography and Nuclear Perfusion Imaging

Two widely used methods for left ventricular (LV) ejection fraction (EF) determination, echocardiography (echo) and gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI), often have wide limits of agreement. Factors influencing discrepancies between core laboratory echo and MPI LVEF determinations were examined in a large series of heart failure (HF) subjects and normal controls. 879 HF and 101 control subjects had core lab analyses of echo and MPI (mean time between procedures 7-8 days). LVEF differences were analyzed using one-way analysis of variance and Bland-Altman plots. Relationships between LVEF differences and patient characteristics and outcome endpoints (mortality and arrhythmias) were explored with logistic regression, Cox proportional hazards models, and Kaplan-Meier survival analyses. There was a systematic difference between the 2 modalities; echo LVEF was higher with more severe LV dysfunction, MPI LVEF higher when systolic function was normal. LVEF results were within ±5% in only 37% of HF and 23% of control subjects. Considering discordance around the LVEF threshold 35%, there was disagreement between the 2 methods in 305 HF subjects (35%). Male gender (odds ratio (OR) = 0.200), atrial fibrillation (OR = 2.314), higher body mass index (OR = 1.051) and lower LV end-diastolic volume (OR = 0.985) were the strongest predictors of methodologic discordance. Cardiac event rates were highest if both LVEF values were ≤35% and lowest when both LVEF values were >35%. In conclusion, substantial disagreements between LVEF results by echo and MPI are common. HF patients with LVEF ≤35% by both techniques have the highest 2-year event risk.

A simplified wall-based model for regional innervation/perfusion mismatch assessed by cardiac 123I-mIBG and rest 99mTc-tetrofosmin SPECT to predict arrhythmic events in ischaemic heart failure

AIMS

Cardiac 123iodine-meta-iodobenzylguanidine (123I-mIBG) single-photon emission computed tomography (SPECT) imaging provides information on regional myocardial innervation. However, the value of the commonly used 17-segment summed defect score (SDS) as a prognostic marker is uncertain. The present study examined whether a simpler regional scoring approach for evaluation of 123I-mIBG SPECT combined with rest 99mTc-tetrofosmin SPECT myocardial perfusion imaging could improve prediction of arrhythmic events (AEs) in patients with ischaemic heart failure (HF).

METHODS AND RESULTS

Five hundred and two ischaemic HF subjects of the ADMIRE-HF study with complete cardiac 123I-mIBG and rest 99mTc-tetrofosmin SPECT studies were included. Both SPECT image sets were read together by two experienced nuclear imagers and scored by consensus. In addition to standard 17-segment scoring, the readers classified walls (i.e. anterior, lateral, inferior, septum and apex) as normal, matched defect, mismatched (innervation defect > perfusion defect), or reverse mismatched (perfusion defect > innervation defect). Cox proportional hazards ratios (HRs) were used to determine if age, body mass index, functional class, left ventricular ejection fraction (LVEF), B-type natriuretic peptide (BNP), norepinephrine, 123I-mIBG SDS, 99mTc-tetrofosmin SDS, innervation/perfusion mismatch SDS, and our simplified visual innervation/perfusion wall classification were associated with occurrence of AEs (i.e. sudden cardiac death, sustained ventricular tachycardia, resuscitated cardiac arrest, appropriate implantable cardioverter-defibrillator therapy). At 2-year median follow-up, 52 subjects (10.4%) had AEs. Subjects with 1 or 2 mismatched walls were twice as likely to have AEs compared with subjects with either 0 or 3-5 mismatched walls (16.3% vs. 8.3%, P = 0.010). Cox regression analyses showed that patients with a visual mismatch in 1-2 walls had an almost two times higher risk of AEs [HR 2.084 (1.109-3.914), P = 0.001]. None of the other innervation, perfusion and mismatch scores using standard 17 segments were associated with AEs. BNP (ng/L) was the only non-imaging parameter associated with AEs.

CONCLUSION

A visual left ventricular wall-level based scoring method identified highest AE risk in ischaemic HF subjects with intermediate levels of innervation/perfusion mismatches. This simple technique for the evaluation of SPECT studies, which are often challenging in HF subjects, seems to be superior to the 17-segment scoring method.

Cardiac 123I-MIBG normal uptake values are population-specific: Results from a cohort of controls over 60 years of age

PURPOSE

Cardiac 123I-MIBG image interpretation is affected by population differences and technical factors. We recruited older adults without cognitive decline and compared their cardiac MIBG uptake with results from the literature.

METHODS

Phantom calibration confirmed that cardiac uptake results from Japan could be applied to our center. We recruited 31 controls, 17 individuals with dementia with Lewy bodies (DLB) and 15 with Alzheimer's disease (AD). Images were acquired 20 minutes and four hours after injection using Siemens cameras with medium-energy low-penetration (MELP) collimators. Local normal heart-to-mediastinum (HMR) ratios were compared to Japanese results.

RESULTS

Siemens gamma cameras with MELP collimators should give HMRs very close to the calibrated values used in Japan. However, our cut-offs with controls were lower at 2.07 for early and 1.86 for delayed images. Applying our lower cut-off to the dementia patients may increase the specificity of cardiac MIBG imaging for DLB diagnosis in a UK population without reducing sensitivity.

CONCLUSIONS

Our local HMR cut-off values are lower than in Japan, higher than in a large US study but similar to those found in another UK center. UK centers using other cameras and collimators may need to use different cut-offs to apply our results.

Prognostic usefulness of planar 123I-MIBG scintigraphic images of myocardial sympathetic innervation in congestive heart failure: Follow-Up data from ADMIRE-HF

BACKGROUND

To evaluate whether planar 123I-MIBG myocardial scintigraphy predicts risk of death in heart failure (HF) patients up to 5 years after imaging.

METHODS AND RESULTS

Subjects from ADMIRE-HF were followed for approximately 5 years after imaging (964 subjects, median follow-up 62.7 months). Subjects were stratified according to the heart/mediastinum (H/M) ratio (< 1.60 vs ≥ 1.60) on planar 123I-MIBG scintigraphic images obtained at baseline in ADMIRE-HF. Cox proportional hazards models and Kaplan-Meier analyses were used to evaluate time to death, cardiac death, or arrhythmic events for subjects stratified by H/M ratio, baseline left ventricular ejection fraction (LVEF: < 25% and 25 to ≤ 35%), and by H/M strata within LVEF strata. All-cause mortality was 38.4% vs 20.9% and cardiac mortality was 16.8% vs 4.5%, in subjects with H/M < 1.60 vs ≥ 1.60, respectively (P < 0.05 for both comparisons). Subjects with preserved sympathetic innervation of the myocardium (H/M ≥ 1.60) were at significantly lower risk of all-cause and cardiac death, arrhythmic events, sudden cardiac death, or potentially life-threatening arrhythmias. Within LVEF strata, a trend toward a higher mortality for subjects with H/M < 1.60 was observed reaching significance for LVEF 25 to ≤ 35% only.

CONCLUSIONS

During a median follow-up of 62.7 months, patients with H/M ≥ 1.60 were at significantly lower risk of death and arrhythmic events independently of LVEF values.

Noradrenergic uptake in the liver on 123 I-mIBG imaging: Influence of heart failure and diabetes

BACKGROUND AND AIM

Imaging noradrenergic uptake in the liver with norepinephrine analog ¹²³ I-meta-iodobenzylguanidine (mIBG) was explored in normal controls and patients with heart failure (HF).

METHODS

A total of 961 HF (343 with diabetes mellitus [DM]) and 94 control subjects underwent anterior planar mIBG images including upper abdomen at 15 min (early) and 3 h 50 min (late) post-injection. Decay-corrected liver activity normalized to injected activity and body surface area (counts/pixel [cpp]/MBq/m² ) was compared in three groups: HF with DM; HF without DM; and controls. Associations with plasma norepinephrine, liver function tests, and level of cardiac innervation were explored.

RESULTS

In controls, liver mIBG activity decreased over time (early: 2.78 vs late: 2.43 cpp/MBq/m² , P < 0.0001); in HF subjects, activity increased during this interval (HF without DM: 2.85 vs 2.93 [P = 0.005]; HF with DM: 2.37 vs 2.43 [P = 0.054]). Early liver activity was lower in HF with DM subjects than in the other groups (P < 0.001); late liver activity was higher in HF without DM than in the other two groups (P < 0.01). Subjects with elevated plasma norepinephrine (> 520 pg/mL) or ≥ 1 abnormal liver function test had lower early and late liver activity. In subjects with preserved cardiac mIBG uptake, HF subjects had higher and control subjects lower liver activity than comparable subjects with decreased cardiac innervation.

CONCLUSIONS

In HF subjects, liver mIBG activity increased over time, reversing the normal washout pattern, suggesting a compensatory change in sympathetic nerve function. DM, abnormal liver function tests, and decreased cardiac innervation were associated with decreased liver mIBG uptake in HF.

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.

How do we establish cardiac sympathetic nervous system imaging with 123I-mIBG in clinical practice? Perspectives and lessons from Japan and the US

Cardiac denervation is associated with progressive left ventricular (LV) dysfunction, ventricular arrhythmias, and sudden cardiac death (SCD) in heart failure (HF). In this regard, it is important to evaluate cardiac-specific sympathetic nervous system (SNS) function. The radiotracer Iodine-123 meta-iodobenzylguanidine (123I-mIBG) can noninvasively evaluate pre-synaptic SNS function. Recent multicenter trials have shown 123I-mIBG to have strong predictive value for fatal arrhythmias and cardiac death in HF. 123I-mIBG was initially developed in the USA in the 1970s. In 1992, the Japanese Ministry of Health and Labour approved 123I-mIBG for the assessment of cardiac function. Following approval, the Japanese nuclear cardiology community developed 123I-mIBG imaging services in various medical centers. Japanese groups have been trying to establish the clinical utility of 123I-mIBG and standardize parameters for data acquisition and image analysis. The US Food and Drug Administration (FDA) has approved clinical use of 123I-mIBG for cardiac and non-cardiac imaging. However, clinical use of 123I-mIBG in the US has been very limited. The number of 123I-mIBG studies in Japan has also been limited. There are similarities and differences between the two countries. To establish the clinical utility of 123I-mIBG in both countries, it is important to characterize the situations of 123I-mIBG in each.

Transcutaneous electrical nerve stimulation attenuates cardiac sympathetic drive in heart failure: a 123MIBG myocardial scintigraphy randomized controlled trial

Cardiac sympathetic overdrive provides inotropic support to the failing heart. However, as myocardial insult evolves, this compensatory response impairs contractile function and constitutes an independent mortality predictor and a primary target in the treatment of heart failure (HF). In this prospective, randomized, double-blind, controlled crossover trial, we proposed cervicothoracic transcutaneous electrical nerve stimulation (CTENS) as a nonpharmacological therapy on cardiac sympathetic activity in patients with HF. Seventeen patients with HF were randomly assigned to an in-home CTENS (30 min twice daily, 80-Hz frequency, and 150-μs pulse duration) or a control intervention (Sham) for 14 consecutive days. Following a 60-day washout phase, patients were crossed over to the opposite intervention. The heart-to-mediastinum ratio (HMR) and washout rate (WR) (indexes of sympathetic innervation density and activity from planar ¹²³iodo-metaiodobenzylguanidine myocardial scintigraphy images, respectively), as well as blood pressure (BP) and heart rate (HR), were quantified before and after each intervention. HMR, BP, and HR did not change throughout the study. Nonetheless, CTENS reduced WR (CTENS -4 ± 10 vs. Sham +5 ± 15%, P = 0.03) when compared with Sham. When allocated in two independent groups, preserved (PCSI, HMR > 1.6, n = 10) and impaired cardiac sympathetic innervation (ICSI, HRM ≤1.6, n = 7), PCSI patients showed an important attenuation of WR (-11 ± 9 vs. Sham +8 ± 19%, P = 0.007) after CTENS. Nonetheless, neither Sham nor CTENS evoked changes in WR of the ICSI patients (P > 0.05). These findings indicate that CTENS attenuates the cardiac sympathetic overdrive in patients with HF and a preserved innervation constitutes an essential factor for this beneficial neuromodulatory impact. Clinical Trial Registration: URL: https://www.clinicaltrials.gov . Identifier: NCT03354689. NEW & NOTEWORTHY We found that short-term cervicothoracic transcutaneous electrical nerve stimulation (CTENS) attenuates cardiac sympathetic overdrive in patients with heart failure and a preserved autonomic innervation may constitute an essential factor to maximize this beneficial neuromodulatory effect. CTENS then emerges as an alternative noninvasive and nonpharmacological strategy to attenuate exaggerated cardiac sympathetic drive in patients with heart failure.

Impact of an exercise training program on cardiac neuronal function in heart failure patients on optimal medical therapy : A randomized Iodine-123 metaiodobenzylguanidine scintigraphy study

BACKGROUND

The syndrome of heart failure (HF) is characterized by left ventricular dysfunction and a compensatory chronic over activation of the sympathetic nervous system. We wanted to investigate if the beneficial effects of exercise training (ET) in HF patients on optimal medical therapy (OMT) are associated with alterations in cardiac sympathetic activity.

METHODS

Cardiac sympathetic activity was evaluated at baseline and after 12 weeks using metaiodobenzylguanidine scintigraphy in 23 patients with stable HF participating in the SmartEx trial. Patients with HF in New York Heart Association class II or III and left ventricular ejection fraction <35 % were randomized to three different ET groups.

RESULTS

We found no statistically significant changes in cardiac sympathetic activity after 12 weeks of ET. Heart to mediastinum (H/M) ratio at 15 minutes (0.00174 ± 0.0841, P = 0.922), H/M ratio at 4 hours (-0.00565 ± 0.1163, P = 0.818) and washout ratio (WR) (-1.2666 ± 16.5412, P = 0.717). A further group-wise analysis of the three ET groups did not show any difference between the groups.

CONCLUSION

A 12-week ET program did not alter the abnormal cardiac sympathetic activity in stable HF patients on modern OMT.

Current Clinical Applications and Next Steps for Cardiac Innervation Imaging

PURPOSE OF REVIEW

Autonomic innervation is crucial for regulating cardiac function. Sympathetic innervation imaging with ¹²³I-mIBG and analogous PET tracers assesses disease in ways that differ from customary methods. This review describes practical use in various clinical scenarios, discusses recent guidelines, presents new data confirming risk stratification power, describes an ongoing prospective study, and looks forward to wider use in patient management.

RECENT FINDINGS

ASNC ¹²³I-mIBG guidelines are available, expanding on European guidelines. ADMIRE-HF patient follow-up increased to 2 years in ADMIRE HFX, demonstrating independent mortality risk reclassification. ADMIRE-HF findings were substantiated in a Japanese consortium study and in the PAREPET ¹¹C-HED PET study. Exciting potential uses of adrenergic imaging are management of LVADs and VT ablation. CZT cameras provide advantages, but derived parameters differ from Anger camera values. Independent risk stratification utility of adrenergic imaging with ¹²³I-mIBG and PET tracers is continuously being confirmed. An ongoing prospective randomized study promises to establish patient management utility. There is potential for wider use and improved images with newer cameras and PET.

Assessment of 123I-mIBG and 99mTc-tetrofosmin single-photon emission computed tomographic images for the prediction of arrhythmic events in patients with ischemic heart failure: Intermediate severity innervation defects are associated with higher arrhythmic risk

RATIONALE

123I-mIBG planar image heart-to-mediastinum ratios effectively risk-stratify heart failure (HF) patients. The value of single-photon emission computed tomographic (SPECT) imaging for identifying increased risk of ventricular arrhythmias is less clear. This study sought to determine if findings from simultaneous interpretation of 123I-mIBG and 99mTc-tetrofosmin SPECT are predictive of arrhythmic events (ArEs).

METHODS

123I-mIBG SPECT images from 622 patients with ischemic HF were presented in standard displays alongside 99mTc-tetrofosmin images. Consensus interpretations using a 17-segment model produced summed scores. Cox proportional hazards analyses related findings to adjudicated ArEs over 2 years.

RESULTS

471 patients had images adequate for total 17-segment scoring. There were 48 ArEs (10.2%). Neither 123I-mIBG nor 99mTc-tetrofosmin SPECT summed scores were univariate predictors. On multivariate proportional hazards analysis, the 123I-mIBG SPECT score was independently predictive of ArEs (HR: 0.975, 95% CI 0.951-0.999, P = 0.042), but HR<1 indicated that risk decreased with increasing score. This occurred because patients with intermediately abnormal SPECT studies had a higher likelihood of ArEs compared to patients with extensive abnormalities.

CONCLUSIONS

The presumption of a monotonic increase in ArE risk with increasing summed 123I-mIBG SPECT score may not be correct as ischemic HF patients with abnormalities of intermediate extent appear at highest risk.

Persistence of 123I-mIBG Prognostic Capability in Relation to Medical Therapy in Heart Failure (from the ADMIRE-HF Trial)

¹²³I-mIBG imaging has been evaluated to assess sympathetic function and prognosis in heart failure (HF). However, the effect of combined HF medical therapies on ¹²³I-mIBG uptake and its prognostic significance has not been previously examined. This analysis examined the relation between the intensity of guideline-directed HF medical therapy and global ¹²³I-mIBG cardiac uptake in the AdreView Myocardial Imaging for Risk Evaluation in Heart Failure (ADMIRE-HF) database. A second objective was to investigate whether this guideline-based therapy, measured by total medication doses, had the expected effect on outcome, that is, that patients with higher ¹²³I-mIBG cardiac uptake and more intensive medical therapy had the fewest outcome events. Three HF cardiologists developed an HF Medication Score (HFMS) to quantify adequacy of dosages of β blockers, angiotensin-converting enzyme inhibitors, and angiotensin II receptor blockers and mineralocorticoid receptor antagonists. A Cox model was used to investigate the predictive ability of the HFMS for mortality events during median 17 months follow-up. Multiple regression and Cox models assessed the usefulness of the HFMS relative to the planar heart/mediastinum ratio (H/Mp) from ¹²³I-mIBG imaging in prediction of an event and to characterize the interaction of HFMS and H/M in predicting an event. HFMS was not a significant predictor of all-cause or cardiac death in either univariate or multivariate Cox models; H/Mp was highly significant for both event categories (p <0.0001). Mean H/Mp did not differ among HFMS ranges 0 to 3, 4 to 6, and 7 to 9. However, within each category, the mean H/Mp for subjects with events was significantly lower than that of subjects without events, with the exception of cardiac mortality in those with highest scores. In conclusion, intensity of medical therapy is not predictive of short-term mortality in HF patients. H/Mp is a good predictor for both cardiac and overall mortality regardless of medical therapy levels.

Quantitative iodine-123-metaiodobenzylguanidine (MIBG) SPECT imaging in heart failure with left ventricular systolic dysfunction: Development and validation of automated procedures in conjunction with technetium-99m tetrofosmin myocardial perfusion SPECT

BACKGROUND

The purpose of this study was to develop and validate new approaches to quantitative MIBG myocardial SPECT imaging in heart failure (HF) subjects.

METHODS AND RESULTS

Quantitative MIBG myocardial SPECT analysis methods, alone and in conjunction with 99mTc-tetrofosmin perfusion SPECT, were adapted from previously validated techniques for the analysis of SPECT and PET perfusion imaging. To account for underestimation of MIBG defect severity in subjects with global reduction in uptake, a mixed reference database based on planar heart/mediastinum (H/M) ratio categories was used. Extent and severity of voxel-based defects and number of myocardial segments with significant dysinnervation (derived score ≥2) were determined. MIBG/99mTc-tetrofosmin mismatch was quantified using regions with preserved innervation as the reference for scaling 99mTc-tetrofosmin voxel maps. Quantification techniques were tested on studies of 619 ischemic (I) and 319 non-ischemic (NI) HF subjects. Using all analytical techniques, IHF subjects had significantly greater and more severe MIBG SPECT abnormalities compared with NIHF subjects. Innervation/perfusion mismatches were also larger in IHF subjects. Findings were consistent between voxel- and myocardial-segment-based quantitation methods.

CONCLUSIONS

Multiple objective methods for quantitation of MIBG SPECT imaging studies provided internally consistent results for distinguishing the different patterns of uptake between IHF and NIHF subjects.

Predicting Risk Versus Predicting Potential Survival Benefit Using 123I-mIBG Imaging in Patients With Systolic Dysfunction Eligible for Implantable Cardiac Defibrillator Implantation: Analysis of Data From the Prospective ADMIRE-HF Study

BACKGROUND

Cardiac (123)I-metaiodobenzylguanidine ((123)I-mIBG) imaging improves prognostication in patients with left ventricular (LV) dysfunction. Whether (123)I-mIBG can identify optimal candidates for implantable cardiac defibrillator (ICD) placement is unclear. We examined whether (123)I-mIBG enhances risk assessment and identifies patients with enhanced survival with ICD in a patient cohort with reduced LV function who were candidates for ICD implantation.

METHODS AND RESULTS

We identified 777 patients (66 sites, 12 countries) without ICD at the time of enrollment in Adreview Myocardial Imaging for Risk Evaluation in Heart Failure (ADMIRE-HF) and index (123)I-mIBG study. Patients completed prescribed study protocol and follow-up. Heart-to-mediastinum (H/M) ratio was determined from (123)I-mIBG results. Survival modeling used a Cox proportional hazards mixed-effects model, including a propensity score, to adjust for nonrandomized ICD implantation after (123)I-mIBG. All-cause death occurred in 75 patients (9.6%), and 196 (25%) patients had ICD implantation on follow-up. After adjusting for multiple factors, although the H/M ratio added incremental prognostic value and enhanced reclassification, neither H/M results, BNP levels, nor left ventricular ejection fraction interacted with ICD use in the survival model, indicating that these variables did not identify patients with enhanced survival with ICD implantation. Nonetheless, H/M results did identify the number of lives saved by ICD use per 100 treated.

CONCLUSIONS

We found that although (123)I-mIBG imaging enhances the risk stratification of patients with left ventricular dysfunction who are ICD candidates, it does not identify which patients may have improved survival with ICD placement. However, (123)I-mIBG identifies the absolute benefit gained with ICD use, thus may play a role in optimizing the cost-effectiveness of this intervention.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifiers: NCT00126425 and NCT00126438.

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.

Individuals with impaired glucose tolerance demonstrate normal cardiac sympathetic innervation using I-123 mIBG scintigraphy

BACKGROUND

Impaired glucose tolerance (IGT) is associated with an increased risk of type 2 diabetes (T2DM) and cardiovascular disease. Some but not all studies have reported cardiac autonomic dysfunction in subjects with IGT and there is only one direct study of cardiac innervation in subjects with IGT. The purpose of this study was to assess global and regional cardiac sympathetic innervation and cardiac autonomic function in individuals with IGT.

METHODS AND RESULTS

We undertook (123)I-mIBG scintigraphy and cardiac autonomic function in 15 subjects with IGT and 15 age and sex-matched healthy controls. Early heart to mediastinum ratio (HMR) (1.71 ± 0.17 vs 1.67 ± 0.13, P = .49), late HMR (1.73 ± 0.18 vs 1.73 ± 0.16, P = .97) and washout rate (WR) (18.6 ± 4.2 vs 19.1 ± 7.6%, P = .84), did not differ between subjects with IGT and control subjects. More detailed regional analysis revealed reduced tracer uptake at the apex, base and inferior wall in all subjects and the anterior wall in a minority of subjects. There were no differences in total score (56.6 ± 4.0 vs 53.3 ± 8.4, P = .193), modified score (48.5 ± 3.3 vs 46.2 ± 6.0, P = .215), anterior wall score (10.2 ± 1.3 vs 10.1 ± 1.6, P = .898), inferior wall score (8.9 ± 1.9 vs 7.7 ± 2.6, P = .163), basal score (18.7 ± 1.9 vs 18.2 ± 3.3, P = .636) and tests of cardiac autonomic function between the groups.

CONCLUSION

Global and regional measures of MIBG uptake and washout as well as cardiac autonomic function did not differ between subjects with IGT and healthy controls.

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.

¹²³I-MIBG Imaging for Prediction of Mortality and Potentially Fatal Events in Heart Failure: The ADMIRE-HFX Study

ADMIRE-HF (AdreView Myocardial Imaging for Risk Evaluation in Heart Failure) established the prognostic significance of (123)I-metaiodobenzylguanidine ((123)I-MIBG) imaging in heart failure subjects (median follow-up, 17 mo) using a composite endpoint dominated by heart failure progression. The ADMIRE-HF extension (ADMIRE-HFX) extended follow-up to a median of 24 mo and used mortality as the primary endpoint. The objective of these analyses was to use multiple multivariate risk modeling techniques to determine the independent predictive ability of (123)I-MIBG imaging for mortality outcomes.

METHODS

Data from 964 New York Heart Association class II-III subjects in ADMIRE-HFX were included. All-cause mortality and a composite endpoint of death or death-equivalent events (resuscitated arrest, successful defibrillation for ventricular tachycardia or ventricular fibrillation) were analyzed with multivariate Cox proportional hazards and logistic regression techniques using demographic and clinical variables and the (123)I-MIBG heart-to-mediastinum ratio (H/M). The incremental value of H/M was also examined for the logistic regression models using receiver-operating-characteristic curve methods and for the proportional hazards models using net reclassification improvement.

RESULTS

There were 101 deaths, and 136 subjects had a composite event during follow-up. H/M was significant in all multivariate proportional hazards and logistic regression models for the 2 mortality endpoints, both models developed with only clinical variables and those including left ventricular ejection fraction and b-type natriuretic peptide (BNP). For baseline models including BNP, the addition of H/M did not significantly increase receiver-operating-characteristic curve area. However, there was significant net reclassification improvement with the addition of H/M to a proportional hazards model containing BNP and left ventricular ejection fraction.

CONCLUSION

The multivariate Cox proportional hazards and logistic regression analyses demonstrated consistent significance for H/M when added to the baseline risk models for mortality and mortality-equivalent events.

[Validation of an optimal analysis method and reproducibility to calculate the heart-to-mediastinum ratio and washout rate in the iodine-123-labeled metaiodobenzylguanidine myocardial scintigraphy]

PURPOSE

The aim of this study was to investigate an appropriate analysis method and multicenter reproducibility of heart-to-mediastinum ratio (H/M) and washout rate (WR) in iodine-123-labeled metaiodobenzylguanidine (123I-MIBG) myocardial scintigraphy with a phantom.

METHODS

We evaluated the optimal region of interest (ROI) setting method about the mediastinum and heart by varying the position and shape of the ROI. The mathematical method was changed to a combination of decay time correction (DTC) and background correction (BC). We evaluated the reproducibility of the H/M and WR between institutions.

RESULT

H/M decreased to 23.49% and WR increased to 20.68% by changing the mediastinum ROI position from upper to lower. H/M increased to 26.03% by changing the heart ROI position from base to apex. H/M decreased to 38.36% with BC, and WR was reduced up to 48.51% with DTC. Reproducibility of the H/M and WR between institutions was improved by performing optimization of the ROI setting and unification of the mathematical method.

DISCUSSION

The position of the mediastinum ROI should be set on the upper mediastinum. The position of the heart ROI should be set on the apex of the heart. WR should be calculated with DTC and BC. Our results suggest that the reproducibility of the H/M and WR between institutions was improved by performing optimization of the ROI setting and unification of the mathematical method.

Cardioprotective effect of fimasartan, a new angiotensin receptor blocker, in a porcine model of acute myocardial infarction

Cardioprotective effect of fimasartan, a new angiotensin receptor blocker (ARB), was evaluated in a porcine model of acute myocardial infarction (MI). Fifty swine were randomized to group 1 (sham, n=10), group 2 (no angiotensin-converting enzyme inhibitor [ACEI] or ARB, n=10), group 3 (perindopril 2 mg daily, n=10), group 4 (valsartan 40 mg daily, n=10), or group 5 (fimasartan 30 mg daily, n=10). Acute MI was induced by occlusion of the left anterior descending artery for 50 min. Echocardiography, single photon emission computed tomography (SPECT), and F-18 fluorodeoxyglucose cardiac positron emission tomography (PET) were performed at baseline, 1 week, and 4 weeks. Iodine-123 meta-iodobenzylguanidine (MIBG) scan was done at 6 weeks for visualization of cardiac sympathetic activity. Left ventricular function and volumes at 4 weeks were similar between the 5 groups. No difference was observed in groups 2 to 5 in SPECT perfusion defect, matched and mismatched segments between SPECT and PET at 1 week and 4 weeks. MIBG scan showed similar uptake between the 5 groups. Pathologic analysis showed similar infarct size in groups 2 to 5. Infarct size reduction was not observed with use of fimasartan as well as other ACEI and ARB in a porcine model of acute MI.

I-123 mIBG and Tc-99m myocardial SPECT imaging to predict inducibility of ventricular arrhythmia on electrophysiology testing: a retrospective analysis

OBJECTIVES

The purpose of this study is to assess mIBG uptake in scar border zone and its relation with ventricular arrhythmia (VA) inducibility on electrophysiology (EP) testing using I-123 mIBG SPECT and resting Tc-99m SPECT myocardial perfusion imaging (MPI).

METHODS

Forty-seven patients from a previous clinical trial were retrospectively analyzed. These patients underwent I-123 mIBG and resting Tc-99m tetrofosmin SPECT, and EP testing. Twenty-eight patients were positive (EP+) and 19 patients were negative (EP-) for inducibility of sustained (>30 seconds) VA on EP testing. MPI scar extent, border zone extent, and mIBG uptake in border zone were used to predict VA inducibility on EP testing, respectively.

RESULTS

There was no significant difference in scar extent between the EP+ and EP- groups. The EP+ group had significantly larger border zone and lower mIBG uptake ratio in the border zone than the EP- group. Receiver operating characteristic (ROC) curve analysis showed that the prediction accuracy for border zone extent (area under ROC = 0.75) was better than scar extent (area under ROC = 0.66). The prediction accuracy was further improved (area under ROC = 0.78), when assessing mIBG uptake in the border zone.

CONCLUSION

A new tool has been developed to measure scar and border zone and to assess mIBG uptake in scar and border zone from combined I-123 MIBG SPECT and resting Tc-99m SPECT MPI. The mIBG uptake in the border zone predicted VA inducibility on EP testing with a promising accuracy.

The utility of ADMIRE-HF risk score in predicting serious arrhythmic events in heart failure patients: incremental prognostic benefit of cardiac 123I-mIBG scintigraphy

BACKGROUND

A minority of heart failure (HF) patients who undergo implantable cardioverter defibrillator (ICD) implantation for primary prevention of sudden cardiac death (SCD) receive device therapy. Whether the addition of mIBG scintigraphy to conventional markers of arrhythmic risk can provide incremental risk stratification in HF patients has not been investigated.

METHODS

We identified 778 patients from the ADMIRE-HF study with LVEF < 35% and class II or III HF symptoms who did not have an ICD at the time of enrollment. Patients were followed up prospectively (median 5 17 months) for occurrence of arrhythmic events (ArE). Heart-to-mediastinum ratio (HMR) was determined as a measure of relative myocardial sympathetic nerve activity at baseline using 123I-mIBG. The primary endpoint was the first occurrence of ArE: a composite of SCD, appropriate ICD therapy, resuscitated cardiac arrest or sustained ventricular tachycardia. Multivariate regression was used to determine independent predictors of ArE and to derive a risk score for ArE prediction. The score was used to group patients according to their risk for ArE. Integrated discrimination improvement (IDI) was used to quantify improvement in risk assessment with addition of HMR.

RESULTS

ArE occurred in 54 patients (6.9%). ArE predictors were:HMR < 1.6 (HR 3.5, 95%CI [1.52-8], P 5 .02), LVEF < 25% (HR 2.0, 95% CI [1.28-3.05], P 5 .04) and SBP < 120 (HR 1.2,95%CI [1.03-1.39], P 5 .02). Event rates in the low-, intermediate-, and high risk groups were 2, 10 and 16%, respectively (P 5 .001). The score significantly improved risk prediction(IDI 5 45%, P 0.03).

CONCLUSION

123I-mIBG significantly provides incremental risk stratification for ArE in HF patients.

The sympathetic nervous system and heart failure

Heart failure (HF) is a syndrome characterized by upregulation of the sympathetic nervous system and abnormal responsiveness of the parasympathetic nervous system. Studies in the 1980s and 1990s demonstrated that inhibition of the renin-angiotensin-aldosterone system with angiotensin-converting enzyme inhibitors improved symptoms and mortality in HF resulting from systolic dysfunction, thus providing a framework to consider the use of β-blockers for HF therapy, contrary to the prevailing wisdom of the time. Against this backdrop, this article reviews the contemporary understanding of the sympathetic nervous system and the failing heart.

The autonomic nervous system and heart failure

The pathophysiology of heart failure (HF) is characterized by hemodynamic abnormalities that result in neurohormonal activation and autonomic imbalance with increase in sympathetic activity and withdrawal of vagal activity. Alterations in receptor activation from this autonomic imbalance may have profound effects on cardiac function and structure. Inhibition of the sympathetic drive to the heart through β-receptor blockade has become a standard component of therapy for HF with a dilated left ventricle because of its effectiveness in inhibiting the ventricular structural remodeling process and in prolonging life. Several devices for selective modulation of sympathetic and vagal activity have recently been developed in an attempt to alter the natural history of HF. The optimal counteraction of the excessive sympathetic activity is still unclear. A profound decrease in adrenergic support with excessive blockade of the sympathetic nervous system may result in adverse outcomes in clinical HF. In this review, we analyze the data supporting a contributory role of the autonomic functional alterations on the course of HF, the techniques used to assess autonomic nervous system activity, the evidence for clinical effectiveness of pharmacological and device interventions, and the potential future role of autonomic nervous system modifiers in the management of this syndrome.

Incremental utility of iodine-123 meta-iodobenzylguanidine imaging beyond established heart failure risk models

BACKGROUND

Nuclear myocardial imaging with iodine-123 meta-iodobenzylguanidine ((123)I-mIBG) is approved for risk stratification of patients with systolic heart failure (HF). Whether (123)I-mIBG imaging provides incremental prognostic utility beyond established risk models remains unclear.

METHODS AND RESULTS

In a multicenter study, 961 patients with moderate systolic HF underwent (123)I-mIBG imaging and were followed for cardiac death, progressive HF, or life-threatening arrhythmias over 2 years. We constructed 4 multivariable models, using variables from each of 4 published HF risk models, and patient-level scores were calculated both before and after adding the heart-to-mediastinum ratio (H/M) from (123)I-mIBG imaging. Incremental utility was evaluated by calculating integrated discrimination improvement (IDI), which quantifies the increase in probability of experiencing the primary end point after adding H/M to each model. The composite end point occurred in 25% of patients. After adding H/M, absolute IDI ranged from 2.1% to 3.0%, representing 33%-59% relative improvements in risk stratification. Of note, hazard ratios for H/M were remarkably similar between risk models (0.40-0.44 for predicting the composite end point, 0.10-0.18 for mortality; all P < .001).

CONCLUSIONS

Despite notable differences in predictor variables, patient populations, and analytic techniques from which each model was initially derived, adding (123)I-mIBG data to HF risk models consistently identified patients at lower risk of experiencing adverse events.

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 relationship of left ventricular mechanical dyssynchrony and cardiac sympathetic denervation to potential sudden cardiac death events in systolic heart failure

BACKGROUND

Patients with heart failure (HF) are at increased risk for left ventricular (LV) dyssynchrony which is associated with sudden cardiac death (SCD). This study examined the association of LV mechanical dyssynchrony and cardiac sympathetic denervation with potential SCD events in symptomatic patients with HF and reduced ejection fraction (HFrEF).

METHODS

Of the 917 HFrEF patients in ADMIRE-HF, 92 experienced adjudicated potential SCD events during a 17 months median follow-up. Propensity scores were used to assemble a matched cohort of 85 pairs of patients with and without potential SCD events. ADMIRE-HF subjects had rest gated SPECT Tc-99m and I-123 MIBG imaging. Perfusion images were processed using phase analysis software to derive phase standard deviation (SD), an index of mechanical dyssynchrony.

RESULTS

Of the 92 patients who experienced adjudicated potential SCD events 23 had SCD, 5 fatal myocardial infarction, 7 resuscitated cardiac arrest, 46 had appropriate ICD therapy, and 11 had sustained ventricular tachycardia. Patients who experienced potential SCD events had significantly wider phase SD than matched control patients (62.3 ± 2.4º vs 55.5 ± 2.3º, P = .03) and were more likely to have a phase SD ≥ 60º (53 % vs 35 %, P = .03). Fewer patients with potential SCD events (6 % vs 15 % of the controls, P = .08) had an MIBG heart/mediastinum uptake-ratio ≥1.6.

CONCLUSIONS

Among symptomatic HFrEF patients, LV mechanical dyssynchrony is independently associated with potential SCD events. Phase analysis may provide incremental prognostic information on top of current indicators of SCD risk in HFrEF.

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.

Adrenergic nervous system in heart failure: pathophysiology and therapy

Heart failure (HF), the leading cause of death in the western world, develops when a cardiac injury or insult impairs the ability of the heart to pump blood and maintain tissue perfusion. It is characterized by a complex interplay of several neurohormonal mechanisms that become activated in the syndrome to try and sustain cardiac output in the face of decompensating function. Perhaps the most prominent among these neurohormonal mechanisms is the adrenergic (or sympathetic) nervous system (ANS), whose activity and outflow are enormously elevated in HF. Acutely, and if the heart works properly, this activation of the ANS will promptly restore cardiac function. However, if the cardiac insult persists over time, chances are the ANS will not be able to maintain cardiac function, the heart will progress into a state of chronic decompensated HF, and the hyperactive ANS will continue to push the heart to work at a level much higher than the cardiac muscle can handle. From that point on, ANS hyperactivity becomes a major problem in HF, conferring significant toxicity to the failing heart and markedly increasing its morbidity and mortality. The present review discusses the role of the ANS in cardiac physiology and in HF pathophysiology, the mechanisms of regulation of ANS activity and how they go awry in chronic HF, methods of measuring ANS activity in HF, the molecular alterations in heart physiology that occur in HF, along with their pharmacological and therapeutic implications, and, finally, drugs and other therapeutic modalities used in HF treatment that target or affect the ANS and its effects on the failing heart.

Outcome prediction in heart failure with atrial fibrillation: relative role of left ventricular ejection fraction and neurohormonal measures

BACKGROUND

Since atrial fibrillation (AF) impacts the measurement and interpretation of left ventricular ejection fraction (LVEF), we hypothesized that the outcome in heart failure (HF) with AF and LVEF ≤ 35% would be more strongly associated with neurohormonal measures than LVEF.

METHODS AND RESULTS

Cardiac adverse events [CAE; HF progression (HFP), life-threatening arrhythmia (ARR), and cardiac death (CD)] and all-cause mortality (ACM) were recorded prospectively in 954 patients with HF and LVEF ≤ 35%: 852 in sinus rhythm (SR) and 102 in AF. Cox proportional hazard models found that the univariate hazard ratios (HR) for LVEF and the first CAE (primary outcome), HFP, ARR, CD, and ACM were significant in SR (0.933, P < .001, 0.933, P < .001, 0.929, P < .001, 0.916, P < .001, 0.945, P = .001, respectively), but not in AF (1.002, P = .95, 1.060, P = .24, 0.922, P = .15, 0.885, P = .09, 0.932, P = .25). HRs for CAEs and ACM and one or more neurohormonal measures (iodine 123 m-iodobenzylguanidine cardiac parameters, B-type natriuretic peptide, and plasma norepinephrine) were significant in SR and AF. The multivariate models for the first CAE and HFP included neurohormonal measures and LVEF in SR and neurohormonal measures in AF.

CONCLUSIONS

In HF with LVEF ≤ 35% with AF, neurohormonal measures, but not LVEF, were related to outcomes.

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

BACKGROUND

Delayed Iodine-123 meta-iodobenzylguanidine heart/mediastinum (H/M) uptake ratio predicted arrhythmic events in patients with heart failure (HF) and significant left ventricular dysfunction in ADMIRE-HF. We tested the hypothesis that resting perfusion defects on MPI-SPECT, representing scar, would further risk stratify patients beyond H/M ratio in the prediction of ventricular arrhythmic events in both ischemic (ICM) and non-ischemic cardiomyopathy (NICM) patients.

METHODS

Patients from the ADMIRE-HF database were classified as ICM and NICM and were stratified by delayed H/M ratio (<1.6/≥1.6) and by summed rest score (SRS) (≤8/>8) on MPI-SPECT. The entire cohort was also classified as high risk (H/M <1.6, SRS >8) and low risk (H/M ≥1.6, SRS ≤8). Scores were from visual interpretation of individual and derived consensus (average) reads per ASNC guidelines.

RESULTS

There were 612 (66%) ICM and 317 (34%) NICM patients. ICM patients had higher mean SRS than NICM patients (25 ± 13 vs 12 ± 10). Sixty-three arrhythmic events occurred over a median follow-up of 17 months. SRS had incremental predictive value among NICM patients with low H/M ratio (<1.6). There was no risk stratification in patients with ICM. Multivariable analysis for NICM with H/M ratio <1.6 demonstrated SRS score >8 as the only independent predictor of arrhythmic events (hazard ratio 3.3, 95% CI 1.1-9.8, P = .03). Patients classified in high-risk subgroup had statistically significant increased risk of arrhythmic events (hazard ratio 2.080, 95% CI 1.112-3.894, P = .022). There was only one event in low-risk subgroup with a trend towards lower risk of arrhythmic events (P = .07).

CONCLUSION

Resting perfusion defects provide independent risk stratification in addition to Iodine-123 meta-iodobenzylguanidine sympathetic innervation imaging in predicting arrhythmic events in patients with NICM and HF. High and potentially low-risk groups for arrhythmic events can be identified based on the severity of resting perfusion defect score and H/M ratio.