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.

Nuclear Imaging for the Diagnosis of Cardiac Amyloidosis in 2021.

Cardiac amyloidosis is caused by the deposition of misfolded protein fibrils into the extracellular space of the heart. The diagnosis of cardiac amyloidosis remains challenging because of the heterogeneous manifestations of the disease. There are many different types of amyloidosis with light-chain (AL) amyloidosis and transthyretin (ATTR) amyloidosis being the most common types of cardiac amyloidosis. Endomyocardial biopsy is considered the gold standard for diagnosing cardiac amyloidosis and differentiating amyloid subtypes, but its use is limited because of the invasive nature of the procedure, with risks for complications and the need for specialized training and centers to perform the procedure. Radionuclide cardiac imaging has recently become the most commonly performed test for the diagnosis of ATTR amyloidosis but is of limited value for the diagnosis of AL amyloidosis. Positron emission tomography has been increasingly used for the diagnosis of cardiac amyloidosis and its applications are expected to expand in the future. Imaging protocols are under refinement to achieve better quantification of the disease burden and prediction of prognosis.

Relationship between extreme obesity and mortality in patients with reduced ejection fraction.

AIMS: Although obesity is associated with increased mortality, epidemiologic studies in heart failure have reported lower mortality in obese patients compared with matched nonobese patients (the 'obesity paradox'). However, the relationship between survival and extreme (morbid) obesity (BMI ≥ 40) is poorly understood. We evaluate survival in low ejection fraction patients across a range of BMI categories, including extreme obesity. METHODS: In a retrospective review, 12 181 consecutive patients receiving nuclear stress testing at a tertiary care center were stratified based on BMI and ejection fraction. Eight-year mortality data were collected using the social security death index. RESULTS: Normal ejection fraction patients (internal control, ejection fraction ≥50%) exhibited the J-shaped association between mortality and BMI that is observed in the general population. Among patients with reduced ejection fraction (<50%), survival improved as obesity increased (P < 0.0001). Those with extreme obesity had the lowest mortality (n = 1134, P < 0.05). CONCLUSION: In this cohort of reduced Ejection fraction patients, the obesity paradox was observed in all weight categories, with the highest survival of all observed in the extremely obese BMI category. This further supports hypotheses that an obesity-related physiologic phenomenon affects mortality in reduced ejection fraction patients.

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.

Echocardiography Abnormal Findings and Laboratory Operations during the COVID-19 Pandemic at a High Volume Center in New York City.

(1) Background: This study sought to explore how the novel coronavirus (COVID-19) pandemic affected the echocardiography (TTE) laboratory operations at a high volume medical center in New York City. Changes in cardiac imaging study volume, turn-around time, and abnormal findings were analyzed and compared to a pre-pandemic period. (2) Methods: Volume of all cardiac imaging studies and TTE reports between 11 March 2020 to 5 May 2020 and the same calendar period in 2019 were retrospectively identified and compared. (3) Results: During the pandemic, our center experienced a 46.72% reduction in TTEs, 82.47% reduction in transesophageal echocardiograms, 83.16% reduction in stress echo, 70.32% reduction in nuclear tests, 46.25% reduction in calcium score, 73.91% reduction in coronary computed tomography angiography, and 87.23% reduction in cardiac magnetic resonance imaging. TTE findings were overall similar between 2020 and 2019 (all p ≥ 0.05), except for a significantly higher right ventricular systolic pressure in 2020 (39.8 ± 14.2 vs. 34.6 ± 11.2 mmHg, p = 0.012). (4) Conclusions: Despite encountering an influx of critically ill patients, our hospital center experienced a reduction in the number of cardiac imaging studies, which likely represents a change in both patient mindset and physician management approach.

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.

Radionuclide Imaging for Cardiac Sarcoidosis: Much Potential Benefit, but Still Much to Do.

Sarcoidosis, a multi-organ inflammatory condition commonly involving the heart and leading to high morbidity and mortality, is increasingly prevalent. PET imaging with 18F-FDG in conjunction with perfusion imaging is increasingly used for diagnosis, disease characterization, and to guide and follow treatment. However, various challenges remain with regard to protocols, interpretation of image findings, and how best to use test results to guide and monitor therapy. Further investigations of the testing technique, as well as better understanding of disease pathophysiology, are needed for better image utility in order to effectively improve patient outcome.

Clinical significance of incidental findings on coronary CT angiography: Insights from a randomized controlled trial.

BACKGROUND: The effect of incidental findings from coronary computed tomography angiography (CCTA) on management has not been rigorously investigated. This study uses a control group to explore this relationship. METHODS: Analysis of data from a randomized controlled trial of acute chest pain patients admitted to telemetry was performed. Patients were randomized to undergo either CCTA (n = 200) or radionuclide myocardial perfusion imaging (MPI) (n = 200). Incidental findings were determined from imaging reports. Records were reviewed to determine subsequent management and imaging during and after hospitalization. Comparisons were performed using Fischer's exact tests. RESULTS: 386 incidental findings were found among 187 CCTA studies. No extra-cardiac incidental findings were noted in the MPI arm, which served as an effective control group. There were significantly more non-coronary medical workups during admission in the CCTA group compared to the MPI group [20% (39) vs. 12% (23), P = 0.038]. CCTA patients underwent significantly more resting echocardiography during the inpatient workup compared to the MPI group [38% (75) vs. 18% (55), P = 0.042]. CCTA patients underwent significantly more non-contrast chest CT exams in the year following admission compared to MPI patients [14% (27) vs. 7% (13) P = 0.029]. CONCLUSIONS: Incidental findings on inpatient CCTAs performed for chest pain have a significant impact on treatment and imaging during and following hospital admission.

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.