Positron Emission Tomography Imaging of Regional Versus Global Myocardial Sympathetic Activity to Improve Risk Stratification in Patients With Ischemic Cardiomyopathy

Sex differences in 123I-mIBG scintigraphy imaging techniques in patients with heart failure

BACKGROUND

123I-mIBG-scintigraphy could be a useful stratifying tool for patients with heart failure (HF). The purpose of this retrospective study is to evaluate whether there are differences between men and women with HF in terms of the prediction of cardiac arrhythmic events (AE).

RESEARCH AND METHODS

A total of 306 patients, before implantable-cardioverter-defibrillator (ICD) implantation, were evaluated. They underwent 123I-mIBG-scintigraphy and an evaluation of the results was performed after 85 months of follow-up. Early and late planar and SPECT cardiac images were acquired. Heart-to-mediastinum ratio (HM) for planar images and the sum of the segmental scores (SS) for SPECT were calculated.

RESULTS

In the general population, age, early SS (ESS), late SS (LSS), and ejection fraction (EF) were statistically significant for the prediction of AE at Cox regression, while early and late HM (eHM,lHM) were not significative for the prediction of AE. Population was divided into females and males and univariate analysis was conducted separately for the two cohorts: no significant variables for prediction of AE were found in females. For males, ESS, LSS, EF, and late HM were statistically significant predictors of AE. The overall survival was similar in males and females, but the risk of AE is lower in males than in females.

CONCLUSIONS

123I-mIBG represents a more effective tool for the prediction of AE in male patients than in women.

Imaging of cardiac sympathetic dysfunction with 18F-FDOPA PET/CT in patients with heart failure: a pilot study

BACKGROUND

Routine use of cardiac sympathetic imaging in HF has been limited by the lower availability/sensitivity of radiotracers. This study was aimed to assess the feasibility of 18F-FDOPA (commonly available PET-radiotracer) in assessment of cardiac autonomic dysfunction.

METHODS

Twenty-four controls (46.5 ± 11.1 years, 16men) and 24 patients (43.5 ± 11.0 years, 18men) with diagnosed HF (Framingham-Criteria) underwent cardiac-PET/CT. Region(s) Of Interest were drawn over entire left ventricular myocardium (LV), individual walls, and mediastinum (M). Coefficient of Variation (CV) was calculated from individual wall counts.

RESULTS

HF patients had significantly lower myocardial 18F-FDOPA uptake (P < .001, independent t test) than controls [32.4% ± 9.5% global reduction; highest in apex (39.9% ± 7.0%)]. A cut-off of LV/M ≤ 1.68 could differentiate patients from controls with sensitivity and specificity of 100% and 95.8%, respectively. LV/M correlated positively with EF (Pearson coefficient = 0.460, P .031). During follow-up, 3 patients were lost to follow-up, 4 died (survival-20.5 ± 4 months), 2 worsened, and 15 remained stable/showed mild improvement. Patients who worsened/died during follow-up had higher CV than those with stable/improving symptoms [0.16 ± 0.05 vs 0.11 ± 0.05, P value .069 (independent t test); Cox regression P = .084].

CONCLUSION

Myocardial 18F-FDOPA uptake in patients with HF is significantly reduced. Higher reduction is seen in those with lower EF. CV, a maker of regional heterogeneity, is a potential prognostic marker.

Positron Emission Tomography in Heart Failure: From Pathophysiology to Clinical Application

Imaging modalities are increasingly being used to evaluate the underlying pathophysiology of heart failure. Positron emission tomography (PET) is a non-invasive imaging technique that uses radioactive tracers to visualize and measure biological processes in vivo. PET imaging of the heart uses different radiopharmaceuticals to provide information on myocardial metabolism, perfusion, inflammation, fibrosis, and sympathetic nervous system activity, which are all important contributors to the development and progression of heart failure. This narrative review provides an overview of the use of PET imaging in heart failure, highlighting the different PET tracers and modalities, and discussing fields of present and future clinical application.

Usefulness of the Vall d'Hebron Risk Score to stratify the risk of patients with ischemic cardiomyopathy

BACKGROUND

To evaluate the Vall d'Hebron-Risk-Score (VH-RS) to stratify the risk of patients with stable ischemic cardiomyopathy (ICM), and assess whether hemoglobin (Hb) and estimated glomerular filtration rate (eGFR) provide additional information to the VH-RS.

METHODS AND RESULTS

We analysed 673 consecutive patients with ICM who underwent gated SPECT. According to VH-RS, we stratified patients into 4-risk-levels: very-low-risk (VLR), low-risk (LR), moderate-risk (MR), and high-risk (HRi). We considered as MACEs: non-fatal myocardial infarction (MI), heart failure hospitalization (HF), coronary revascularization (CR), and cardiac death (CD). Also the cardiac-resynchronization-therapy (CRT), and the implantable-cardioverter-defibrillator (ICD) were investigated. During the follow-up (4.8 ± 2.7 years), 379 patients had MACEs (0.18/patient/year). There were no patients in VLR and LR. All patients were reclassified in 3-risk-levels (MRi = 48; HRi = 121; VHRi[very high risk] = 504). Most patients with MACEs were in VHRi level (test-for-trend: MACEs ≥ 1 without CRT/ICD, P < .001; combined non-fatal MI, CD and CR, P < .001; MACEs ≥ 1 with CRT/ICD, P < .001). The Hb and eGFR values do not properly improve the risk stratification obtained by the VH-RS (global-NRI[net-reclassification-improvement] was: (MACEs ≥ 1 without CRT/ICD: - 10.6%; non-fatal MI, CD and CR: - 9.08%; and MACEs ≥ 1 with CRT/ICD: - 8.85%).

CONCLUSION

VH-RS is effective in evaluating risk of patients with stable ICM. In our population, adding Hb and eGFR variables do not improve the performance of the VH-RS.

Emerging PET Tracers in Cardiac Molecular Imaging

¹⁸F-fluorodeoxyglucose (FDG) and ¹⁸F-sodium fluoride (NaF) represent emerging PET tracers used to assess atherosclerosis-related inflammation and molecular calcification, respectively. By localizing to sites with high glucose utilization, FDG has been used to assess myocardial viability for decades, and its role in evaluating cardiac sarcoidosis has come to represent a major application. In addition to determining late-stage changes such as loss of perfusion or viability, by targeting mechanisms present in atherosclerosis, PET-based techniques have the ability to characterize atherogenesis in the early stages to guide intervention. Although it was once thought that FDG would be a reliable indicator of ongoing plaque formation, micro-calcification as portrayed by NaF-PET/CT appears to be a superior method of monitoring disease progression. PET imaging with NaF has the additional advantage of being able to determine abnormal uptake due to coronary artery disease, which is obscured by physiologic myocardial activity on FDG-PET/CT. In this review, we discuss the evolving roles of FDG, NaF, and other PET tracers in cardiac molecular imaging.

Regional Distribution of Fluorine-18-Flubrobenguane and Carbon-11-Hydroxyephedrine for Cardiac PET Imaging of Sympathetic Innervation

OBJECTIVES

The aim of this study was to investigate the regional distribution of novel ¹⁸F-labeled positron emission tomographic (PET) tracer flubrobenguane (FBBG) (whose longer half-life could enable more widespread use) to assess myocardial presynaptic sympathetic nerve function in humans in comparison to [¹¹C]meta-hydroxyephedrine (HED).

BACKGROUND

The sympathetic nervous system (SNS) is vitally linked to cardiovascular regulation and disease. SNS imaging has shown prognostic value. HED is the most commonly used PET tracer for evaluation of sympathetic function in humans, but widespread clinical use is limited because of the short half-life of ¹¹C.

METHODS

A total of 25 participants (n = 6 healthy; n = 14 ischemic cardiomyopathy, left ventricular [LV] ejection fraction [EF] = 34 ± 5%; and n = 5 nonischemic cardiomyopathy, EF = 33 ± 3%) underwent 2 separate PET imaging visits 8.7 ± 7.6 days apart. On 1 visit, participants underwent dynamic HED PET imaging. On a different visit, participants underwent dynamic FBBG PET imaging. The order of testing was random. HED and FBBG global innervation (retention index [RI] and distribution volume [DV]) and regional denervation (% nonuniformity) were quantified to assess regional presynaptic sympathetic innervations.

RESULTS

FBBG RI (r² = 0.72; ICC = 0.79; p < 0.0001), DV (r² = 0.62; ICC = 0.78; p < 0.0001), and regional denervation (r² = 0.97; ICC = 0.98; p < 0.0001) correlated highly with HED. Average LV RI values were highly similar between HED (7.3 ± 2.4%/min) and FBBG (7.0 ± 1.7%/min; p = 0.33). Post-hoc analysis did not reveal any between-tracer differences on a regional level (17-segment), suggesting equivalent regional distributions in both patients with and without ischemic cardiomyopathy.

CONCLUSIONS

FBBG and HED yield equivalent global and regional distributions in both patients with and without ischemic cardiomyopathy. ¹⁸F-labeled PET tracers, such as FBBG, are critical for widespread distribution necessary for multicenter clinical trials and to maximize patient impact.