Factors relevant to atrial 18F-fluorodeoxyglucose uptake in atrial fibrillation

18F-FDG PET-CT in patients with prosthetic heart valves: variations in imaging findings: A review of the literature

Imaging is a cornerstone of the diagnosis of prosthetic valve endocarditis. An abnormal 18F-FDG PET-CT was added as a major diagnostic criterion in the 2015 European Society of Cardiology guidelines for the management of endocarditis. However, interpretation of uptake around prosthetic heart valves (PHVs) can be difficult, because physiological factors and confounders may result in false-positive or false-negative results. This review provides a comprehensive overview of 'normal' uptake by reviewing the literature on uptake surrounding non-infected PHVs. We will elaborate on qualitative and quantitative measures of uptake. Then, differences in uptake between different valve types, implant positions and the natural course of uptake over time following PHV implantation will be discussed. Finally, factors possibly hampering assessment or mimicking infection are reviewed. We aim to support clinical implementation of 18F-FDG PET-CT in suspected prosthetic valve endocarditis and to provide practical guidance to the differentiation between physiological, postoperative and pathological uptake around PHVs.

The predictive value of changes in 18F-FDG PET/CT cardiac uptake patterns and metabolic parameters for anthracycline based chemotherapy induced cardiac toxicity in lymphoma patients

OBJECTIVE

This study aims to examine alterations in positron emission tomography with 2-deoxy-2-[fluorine-18]fluoro-D-glucose integrated with computed tomography (18F-FDG PET/CT) heart uptake patterns and metabolic factors before and after anthracycline-based chemotherapy in lymphoma patients, and to investigate the added benefit of oncological 18F-FDG PET/CT in chemotherapy-induced heart damage.

MATERIALS AND METHODS

Between July 2017 and December 2022, lymphoma patients diagnosed at the Second Affiliated Hospital of Dalian Medical University who underwent 6 cycles of anthracycline-based chemotherapy and had baseline and 6-cycle oncological 18F-FDG PET/CT scans were included. A total of 366 patients with complete data sets were enrolled. Relevant parameters including blood tests, lipid profile, cardiac biomarkers, lactate dehydrogenase (LDH), erythrocyte sedimentation rate (ESR), albumin (ALB), β2-microglobulin (β2-MG), and cardiac ultrasound findings were collected. Patients were monitored from the initiation of chemotherapy until January 2024, and the occurrence of cancer therapy-related cardiovascular toxicity (CTR-CVT) was documented. Changes in PET/CT heart uptake patterns pre- and post-treatment, along with the presence or absence of CTR-CVT, were used to analyze alterations in left ventricular and epicardial adipose tissue metabolic parameters, as well as changes in echocardiographic parameters. Logistic regression analysis was employed to identify risk factors for CTR-CVT.

RESULTS

Among lymphoma patients who received 6 cycles of anthracycline-based chemotherapy, compared to their initial state, there was a notable decrease in white blood cell count (WBC), neutrophil-to-lymphocyte ratio (NLR), erythrocyte sedimentation rate (ESR), and β2-microglobulin (β2-MG) levels post-treatment. Conversely, albumin (ALB) levels and blood lipid levels significantly rose after treatment. Post-treatment, the maximum standardized uptake value (SUVmax) and mean standardized uptake value (SUVmean) of the left ventricle significantly increased, and the percentage of patients exhibiting no uptake pattern in the left ventricle significantly decreased, while those with diffuse uptake pattern notably increased. Moreover, the count of patients with abnormal cardiac uptake significantly rose post-treatment. Analyzing changes in uptake patterns, the group displaying abnormal changes exhibited an increase in left atrial diameter and a decrease in left ventricular ejection fraction compared to the group with normal changes. The SUVmax of the epicardial adipose tissue was notably higher in the abnormal change group compared to the normal change group. Based on the presence or absence of CTR-CVT, the CTR-CVT group showcased higher left atrial diameter and left ventricular end-systolic diameter, and lower left ventricular ejection fraction compared to the non-CTR-CVT group. Additionally, the SUVmax and SUVmean of the epicardial adipose tissue were higher in the CTR-CVT group than in the non-CTR-CVT group. Left atrial end-systolic diameter, left ventricular ejection fraction, SUVmax of the epicardial adipose tissue, and change in uptake pattern were identified as risk factors for CTR-CVT.

CONCLUSION

In lymphoma patients treated with anthracycline-based chemotherapy, alterations in 18F-FDG PET/CT cardiac uptake patterns and metabolic parameters observed during the follow-up period before and after treatment, as well as changes in epicardial adipose tissue metabolic parameters post-treatment, could serve as predictors for the occurrence of CTR-CVT.

Atrial FDG Uptake: Etiologies, Clinical Significance, and Implications

PURPOSE OF REVIEW

This review aims to explore the clinical significance of atrial fluorodeoxyglucose (FDG) uptake observed in positron emission tomography (PET) scans, focusing on its association with atrial fibrillation (AF), cardiac sarcoidosis, and myocarditis. We discuss the implications of atrial uptake for patient management and prognosis.

RECENT FINDINGS

Recent studies have demonstrated that atrial FDG uptake is frequently present in patients with AF, particularly those with persistent AF, and is linked to increased risks of stroke and poorer outcomes after ablation. In cardiac sarcoidosis, atrial uptake correlates with inflammation and an elevated risk of AF. Additionally, non-granulomatous myocarditis has been associated with localized atrial FDG uptake, necessitating careful differentiation from other causes. : Atrial FDG uptake reflects underlying pathological processes such as inflammation, which can significantly impact patient management and outcomes across various cardiovascular diseases. Recognizing these findings can facilitate early intervention, improve prognosis, and support the development of clear guidelines for clinical practice, emphasizing the need for continued research in this area.

Tissue-resident memory T cells in epicardial adipose tissue comprise transcriptionally distinct subsets that are modulated in atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia and carries an increased risk of stroke and heart failure. Here we investigated how the immune infiltrate of human epicardial adipose tissue (EAT), which directly overlies the myocardium, contributes to AF. Flow cytometry analysis revealed an enrichment of tissue-resident memory T (TRM) cells in patients with AF. Cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) and single-cell T cell receptor (TCR) sequencing identified two transcriptionally distinct CD8+ TRM cells that are modulated in AF. Spatial transcriptomic analysis of EAT and atrial tissue identified the border region between the tissues to be a region of intense inflammatory and fibrotic activity, and the addition of TRM populations to atrial cardiomyocytes demonstrated their ability to differentially alter calcium flux as well as activate inflammatory and apoptotic signaling pathways. This study identified EAT as a reservoir of TRM cells that can directly modulate vulnerability to cardiac arrhythmia.

The relationship between right atrial wall inflammation and poor prognosis of atrial fibrillation based on 18F-FDG positron emission tomography/computed tomography

Background

Atrial fibrillation (AF) has been identified to increase stroke risk, even after oral anticoagulants (OACs), and the recurrence rate is high after radiofrequency catheter ablation (RFCA). Inflammation is an essential factor in the occurrence and persistence of AF. 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) is an established molecular imaging modality to detect local inflammation. We aimed to investigate the relationship between atrial inflammatory activity and poor prognosis of AF based on 18F-FDG PET/CT.

Methods

A total of 204 AF patients including 75 with paroxysmal AF (ParAF) and 129 with persistent AF (PerAF) who underwent PET/CT before treatment were enrolled in this prospective cohort study. Clinical data, electrocardiograph (ECG), echocardiography, and cardiac 18F-FDG uptake were collected. Follow-up information was obtained from patient clinical case notes or telephone reviews, with the starting point being the time of PET/CT scan. The follow-up deadline was either the date of AF recurrence after RFCA, new-onset stroke, or May 2023. Cox proportional hazards regression models were used to identify predictors of poor prognosis and hazard ratios (HRs) with 95% confidence intervals (CIs) was calculated.

Results

Median follow-up time was 29 months [interquartile range (IQR), 22-36 months]. Poor prognosis occurred in 52 patients (25.5%), including 34 new-onset stroke patients and 18 recrudescence after RFCA. The poor prognosis group had higher congestive heart failure, hypertension, age ≥75 years (doubled), diabetes mellitus, prior stroke or transient ischemic attack (TIA) or thromboembolism (doubled), vascular disease, age 65-74 years, sex category (female) (CHA2DS2-VASc) score [3.0 (IQR, 1.0-3.75) vs. 2.0 (IQR, 1.0-3.0), P=0.01], right atrial (RA) wall maximum standardized uptake value (SUVmax) (4.13±1.82 vs. 3.74±1.58, P=0.04), higher percentage of PerAF [39 (75.0%) vs. 90 (59.2%), P=0.04], left atrial (LA) enlargement [45 (86.5%) vs. 104 (68.4%), P=0.01], and RA wall positive FDG uptake [40 (76.9%) vs. 79 (52.0%), P=0.002] compared with the non-poor prognosis group. Univariate and multivariate Cox proportional hazard regression analysis concluded that only CHA2DS2-VASc score (HR, 1.29; 95% CI: 1.06-1.57; P=0.01) and RA wall positive FDG uptake (HR, 2.68; 95% CI: 1.10-6.50; P=0.03) were significantly associated with poor prognosis.

Conclusions

RA wall FDG positive uptake based on PET/CT is tightly related to AF recurrence after RFCA or new-onset stroke after antiarrhythmic and anticoagulation treatment.

Right atrial wall inflammation detected by 18F-FDG PET/CT may be significantly associated with persistent atrial fibrillation: a prospective case-control study

AIM

Atrial fibrillation (AF) is a progressive disease from paroxysmal to persistent, and persistent AF (PerAF) had worse prognosis. AF has potential link with inflammation, but it is not clear whether PerAF or paroxysmal AF (ParAF) is more closely related to inflammation. On the basis of inhibiting myocardial physiological uptake, 18F-fluorodeoxyglucosepositron emission tomography/computed tomography (18F-FDG PET/CT) is an established imaging modality to detect cardiac inflammation. We aimed to decipher the association between AF and atrial inflammatory activity by 18F-FDG PET/CT.

METHODS

Thirty-five PerAF patients were compared to age and sex matched ParAF group with baseline 18F-FDG PET/CT scans prior to radiofrequency catheter ablation (RFCA) in the prospective case-control study. High-fat and low-carbohydrate diet and prolonged fast (HFLC+Fast) was applied to all AF patients before PET/CT. Then 22 AF patients with positive right atrial (RA) wall FDG uptake (HFLC+Fast) were randomly selected and underwent HFLC+Fast+heparin the next day. The CHA2DS2-VASc score was calculated to evaluate the risk of stroke. Clinical data, ECG, echocardiography, and atrial 18F-FDG uptake were compared.

RESULTS

PerAF patients had significantly higher probability of RA wall positive FDG uptake and higher SUVmax than ParAF group [91.4% VS. 28.6%, P < 0.001; SUVmax: 4.10(3.20-4.90) VS. 2.60(2.40-3.10), P < 0.001]. Multivariate logistic regression analyses demonstrated that RA wall SUVmax was the independent influencing factor of PerAF (OR = 1.80, 95%CI 1.02-3.18, P = 0.04). In 22 AF patients with RA wall positive FDG uptake (HFLC+Fast), the "HFLC+Fast+Heparin" method did not significantly change RA wall FDG uptake evaluated by either quantitative analysis or visual analysis. High CHA2DS2-VASc score group had higher RA wall 18F-FDG uptake [3.35 (2.70, 4.50) vs, 2.8 (2.4, 3.1) P = 0.01].

CONCLUSIONS

RA wall FDG positive uptake was present mainly in PerAF. A higher RA wall 18F-FDG uptake was an independent influencing factor of PerAF. RA wall FDG uptake based on 18F-FDG PET/CT may indicate pathological inflammation.

TRIAL REGISTRATION

http://www.chictr.org.cn , ChiCTR2000038288.

Imaging and biophysical modelling of thrombogenic mechanisms in atrial fibrillation and stroke

Atrial fibrillation (AF) underlies almost one third of all ischaemic strokes, with the left atrial appendage (LAA) identified as the primary thromboembolic source. Current stroke risk stratification approaches, such as the CHA₂DS₂-VASc score, rely mostly on clinical comorbidities, rather than thrombogenic mechanisms such as blood stasis, hypercoagulability and endothelial dysfunction-known as Virchow's triad. While detection of AF-related thrombi is possible using established cardiac imaging techniques, such as transoesophageal echocardiography, there is a growing need to reliably assess AF-patient thrombogenicity prior to thrombus formation. Over the past decade, cardiac imaging and image-based biophysical modelling have emerged as powerful tools for reproducing the mechanisms of thrombogenesis. Clinical imaging modalities such as cardiac computed tomography, magnetic resonance and echocardiographic techniques can measure blood flow velocities and identify LA fibrosis (an indicator of endothelial dysfunction), but imaging remains limited in its ability to assess blood coagulation dynamics. In-silico cardiac modelling tools-such as computational fluid dynamics for blood flow, reaction-diffusion-convection equations to mimic the coagulation cascade, and surrogate flow metrics associated with endothelial damage-have grown in prevalence and advanced mechanistic understanding of thrombogenesis. However, neither technique alone can fully elucidate thrombogenicity in AF. In future, combining cardiac imaging with in-silico modelling and integrating machine learning approaches for rapid results directly from imaging data will require development under a rigorous framework of verification and clinical validation, but may pave the way towards enhanced personalised stroke risk stratification in the growing population of AF patients. This Review will focus on the significant progress in these fields.

Association of atrial 18F-fluorodeoxyglucose uptake and prior ischemic stroke in non-atrial fibrillation patients

BACKGROUND

Atrial cardiomyopathy has gained increasing attention in the field of ischemic stroke due to its prothrombotic substrate. Timely identification of high-risk individuals without atrial fibrillation (AF) is essential in secondary prevention. We sought to explore the feasibility of atrial 18F-fluorodeoxyglucose (FDG) imaging in detecting diseased atrial substrate and in identifying ischemic stroke in a non-AF population.

METHODS

1444 non-AF inpatients were initially identified. Among them, 196 patients had enhanced atrial FDG uptake, while 392 patients without atrial activity were selected as controls. Atrial activity, the history of ischemic stroke, and atrial cardiomyopathy were analyzed.

RESULTS

Patients with atrial cardiomyopathy had a higher prevalence of enhanced atrial activity (47.1% vs 26.0%, P < .001), and patients with increased atrial activity had a higher prevalence of a prior history of ischemic stroke (12.2% vs 3.3%, P < .001). Multivariate regression analysis demonstrated that atrial activity was independently related to ischemic stroke after adjustment for risk factors (OR 4.02, 95% CI 1.97-8.19, P < .001) and atrial cardiomyopathy (OR 3.63, 95% CI 1.51-8.74, P = .004).

CONCLUSIONS

This study identified an association between atrial FDG activity and a history of ischemic stroke and atrial cardiomyopathy in non-AF individuals. Further longitudinal study is warranted to demonstrate their causal relationship.

Visualizing diastolic failure: Non-invasive imaging-biomarkers in patients with heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction is an increasing challenge for modern day medicine and has been drawing more attention recently. Invasive right heart catheterization represents the mainstay for the diagnosis of diastolic dysfunction, however due to its attributable risk of an invasive procedure, other non-invasive clinical pathways are trying to approach this pathology in clinical practice. Diastolic failure is complex, and imaging is based on various parameters. In addition to transthoracic echocardiography, numerous novel imaging approaches, such as cardiac magnetic resonance imaging, computed tomography, positron emission (computed) tomography or single photon emission computed tomography techniques are being used to supplement deeper insights into causal pathology and might open targets for dedicated therapy options. This article provides insights into these sophisticated imaging techniques, their incremental value for the diagnosis of this poorly understood disease and recent promising results for an enhanced prognostication of outcome and therapy monitoring.

Right Atrial Fluorodeoxyglucose Uptake Is a Risk Factor for Stroke and Improves Prediction of Stroke Above the CHA2DS2-VASc Score in Patients With Atrial Fibrillation

Background

Atrial fibrillation (AF) is a common arrhythmia, and its most severe and dreaded complication is stroke. The CHA2DS2-VASc score is currently recommended for stroke risk assessment in AF. We aimed to explore the relationship between atrial FDG uptake and stroke and whether atrial FDG uptake could provide incremental value above the CHA2DS2-VAS score to predict stroke in AF by 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT).

Materials and Methods

From September 2017 to December 2020, we retrospectively enrolled 230 patients (115 with AF and 115 without AF as the non-AF group, matched for the date of PET/CT examination and the basic characteristics of the patient) who underwent 18F-FDG PET/CT due to tumor screening or preoperative staging after prolonged fasting and followed up for at least 12 months from the date of PET/CT examination; the endpoint event is the occurrence of stroke. We visually and quantitatively analyzed 18F-FDG uptake in the right and left atria (RA/LA), right and left atrial appendage (RAA/LAA), right and left ventricle (RV/LV), and collected clinical features. In addition, according to the endpoint event (stroke), the enrolled population was divided into the stroke group and non-stroke group, and relevant clinical features and atrial FDG uptake indicators of the two groups were analyzed. Univariate and multivariate Cox regression analyzes were used to analyze the risk factors of stroke events. The Kaplan–Meier survival curve of atrial FDG uptake was drawn, and the log-rank method was used to compare the differences in the survival curves of the two groups. Receiver operating characteristic (ROC) curves were used to examine the discriminatory power of atrial FDG uptake in predicting stroke and determine whether the addition of atrial FDG uptake improves predictive value beyond the CHA2DS2-VASc score for stroke.

Results

In the AF group, more than half of patients had RA FDG uptake and one-fifth had LA FDG uptake, while one patient had RA FDG uptake and two patients had LA FDG uptake in the non-AF group. In quantitative analysis, the maximum standardized uptake value (SUVmax) of the RA and LA in the AF group was significantly higher than that of the non-AF group (all P &lt; 0.001). We followed up the patients for 28 ± 10 months, and finally, 31 patients had stroke. In the stroke group, atrial fibrillation, RA SUVmax, RAA SUVmax, LAA SUVmax, age ≥ 75 years, and left atrial dilation were significantly higher than those of the non-stroke group (all P &lt; 0.05). Multivariate Cox regression analysis showed that high RA SUVmax (RA SUVmax ≥ 2.62) was an independent risk factor for stroke (HR = 4.264, 95% CI 1.368–13.293, P = 0.012). By using the log-rank test, patients with high RA SUVmax had a significantly higher incidence of stroke compared with patients with low RA SUVmax (P &lt; 0.001). Addition of high RA SUVmax to the CHA2DS2-VASc score could predict stroke more effectively, with a larger AUC 0.790 (P &lt; 0.001).

Conclusion

This study found a significant correlation between atrial FDG uptake and AF, especially in RA. Meanwhile, RA FDG uptake is an independent risk factor for stroke, and patients with high RA SUVmax have a significantly higher risk of stroke. Moreover, RA FDG uptake improves prediction of stroke above the CHA2DS2-VASc score in patients with AF.

Association of Serum Biomarkers and Cardiac Inflammation in Patients With Atrial Fibrillation: Identification by Positron Emission Tomography

Background: Peripheral biomarkers may be affected by various factors, their reliability in reflecting local cardiac inflammatory status in patients with atrial fibrillation (AF) needs further exploration. This prospective study was aimed to investigate the relationship between circulating biomarkers and local cardiac inflammation measured by epicardial adipose tissue (EAT) activity via¹⁸F-fluorodeoxyglucose (FDG) imaging in AF patients.

Methods: From 2017 to 2018, 83 AF patients [43 persistent AF (PsAF) and 40 paroxysmal AF (PAF)] referred for radiofrequency catheter ablation (RFCA) were recruited. Pre- and post-RFCA blood samples were collected to measure IL-6, IL-8, IL-10, IL-18, TNF-α, Hsp27, Hsp60, Hsp70, PDGF-BB, MMP-2, MMP-9, MPO, TGF-β1, Gal-3, and sST2. Pre-RFCA FDG images were obtained to assess EAT activity. Sixty-seven patients (35 PAF and 32 PsAF) received RFCA were regularly followed for 27 (24, 29) months.

Results: Higher hsCRP and IL-6 and lower TGF-β1 were demonstrated in PsAF patients compared with PAF patients. Multivariate logistic regression analysis demonstrated that Gal-3 (OR: 1.221, 95% CI: 1.024–1.456, P = 0.026) and MPO (OR: 1.002, 95% CI: 1.001–1.003, P = 0.027) were independently correlated with EAT activity. The percentage decrease of Hsp60 linearly correlated with that of EAT activity post-RFCA (Spearman r_s = 0.455, P = 0.019). Seventeen patients (10 PsAF and 7 PAF) had AF recurrence, but none of the selected biomarkers were predictive of post-RFCA recurrence.

Conclusion: Our findings demonstrated that in patients with AF, Gal-3 correlated with local cardiac inflammation, and Hsp60 was associated with the alleviation of cardiac inflammation after RFCA.

Review of cardiovascular imaging in the Journal of Nuclear Cardiology 2020: positron emission tomography, computed tomography, and magnetic resonance

Although the year 2020 was different from other years in many respects, the Journal of Nuclear Cardiology published excellent articles pertaining to imaging in patients with cardiovascular disease due to the dedication of the investigators in our field all over the world. In this review, we will summarize a selection of these articles to provide a concise review of the main advancements that have recently occurred in the field and provide the reader with an opportunity to review a wide selection of articles. We will focus on publications dealing with positron emission tomography, computed tomography, and magnetic resonance and hope that you will find this review helpful.

Series of myocardial FDG uptake requiring considerations of myocardial abnormalities in FDG-PET/CT

Distinct from cardiac PET performed with preparation to control physiological FDG uptake in the myocardium, standard FDG-PET/CT performed with 4-6 h of fasting will show variation in myocardial FDG uptake. For this reason, important signs of myocardial and pericardial abnormality revealed by myocardial FDG uptake tend to be overlooked. However, recognition of possible underlying disease will support further patient management to avoid complications due to the disease. This review demonstrates the mechanism of FDG uptake in the myocardium, discusses the factors affecting uptake, and provides notable image findings that may suggest underlying disease.

18F-fluorodeoxyglucose positron emission tomography/computed tomography imaging in atrial fibrillation: a pilot prospective study

AIMS

This prospective study explored relevant factors and clinical significance of atrial 18F-fluorodeoxyglucose (FDG) uptake in patients with atrial fibrillation (AF).

METHODS AND RESULTS

One hundred AF patients underwent baseline FDG imaging prior to radiofrequency catheter ablation (RFCA). Of those, 30 subjects underwent additional FDG imaging at 3 months post-RFCA. Voltage mapping of the left atrium was analysed as a voltage score. Patients who received RFCA were followed for 26 months (17-31 months) to assess recurrence. At baseline FDG imaging, 74% of patients with persistent AF (PsAF) and 24% of patients with paroxysmal AF showed increased atrial FDG uptake. The prevalence was higher in the right atrium (49%) than in the left atrium (15%, P < 0.001) or left atrial appendage (21%, P < 0.001). Multivariate analysis demonstrated that PsAF and elevated B-type natriuretic peptide (BNP) were related to enhanced right atrial (RA) activity, and increased epicardial adipose tissue (EAT) activity was predictive of left atrial (LA) activity. LA activity was inversely associated with voltage score, while increased FDG uptake in the right atrium was predictive of successful AF termination by RFCA. Atrial FDG activities decreased significantly post-RFCA, but none of the FDG parameters were predictive of AF recurrence.

CONCLUSIONS

Enhanced RA activity was associated with elevated BNP level, whereas LA activity was related to the increased activity of EAT and inversely correlated with LA fibrosis. Increased RA activity was predictive of successful AF termination by RFCA in PsAF patients.

18F-fluorodeoxyglucose positron emission tomography for the detection of inflammatory lesions of the arterial vessel walls in Wistar rats

The present study aimed to evaluate the use of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) for detection of high-fat and high-salt diet-induced inflammatory lesions of the arterial vessel walls in Wistar rats. A total of 20 healthy, 8-week-old, male Wistar rats were randomly assigned to the high-fat diet group and the normal diet group. After 16 and 24 weeks of feeding, Wistar rats in the normal diet group and the high-fat diet group (five rats in each group) were injected with ¹⁸F-FDG through the tail vein at a dose of 1 mCi/kg after fasting for 12 h. After 1 h, the rats were anesthetized with 2% isoflurane, followed by micro-PET imaging with a 10-min image capture duration and immunohistochemical staining. The standardized uptake values (SUVs) of ¹⁸F-FDG were significantly higher in the iliac artery in the high-fat diet group compared with those in the normal diet group at 16 weeks (1.53±0.08 vs. 1.04±0.03; P<0.05) and at 24 weeks (1.96±0.17 vs. 1.12±0.07; P<0.05). The SUVs of ¹⁸F-FDG were also significantly greater in the abdominal aorta in the high-fat diet group compared with those in the normal diet group at 16 weeks (1.35±0.08 vs. 1.02±0.02; P<0.05) and at 24 weeks (1.54±0.09 vs. 1.04±0.02; P<0.05). In addition, the SUVs of ¹⁸F-FDG in the iliac artery and abdominal aorta were significantly higher at 24 weeks compared with those at 16 weeks in the high-fat diet group (P<0.05). As determined by immunohistochemistry, the percentage of CD68-positive cells in the total number of cells per unit area in each group was 3.20±1.80% in the 24-week normal diet group, 4.70±2.02% in the 16-week high-fat diet group and 6.94±2.02% in the 24-week high-fat diet group; the percentage of CD68-positive cells in the high-fat diet group at 24 weeks was significantly higher than that in the high-fat diet group at 16 weeks and in the normal diet group at 24 weeks (P<0.05). In conclusion, ¹⁸F-FDG PET is a noninvasive imaging tool that can continuously monitor inflammatory lesions of the arterial vessel walls in Wistar rats. Further improvement of the Wistar rat atherosclerosis model may provide data to support the early assessment of and intervention in atherosclerosis.

Visualization of intensive atrial inflammation and fibrosis after cryoballoon ablation: PET/MRI and LGE-MRI analysis

BACKGROUND

Atrial inflammation plays an important role in initiating atrial fibrosis, which could perpetuate atrial fibrillation (AF). However, the method of visualization of atrial inflammation has not been established. We sought to investigate whether the intensive atrial inflammation caused by cryoballoon ablation (CBA) could be detected by positron emission tomography/ magnetic resonance imaging (PET/MRI) and whether the atrial inflammation could be associated with consequent fibrosis.

METHODS

A total of 10 paroxysmal atrial fibrillation patients after CBA were enrolled. To detect and quantify intensive atrial inflammation, PET/MRI was performed to assess regional 18F-fluorodeoxyglucose (18F-FDG) uptake one day after the CBA, and the standardized uptake values (SUV) max were compared between the pulmonary vein (PV) antrum where CBA could be applied and the healthy left atrial (LA) wall where CBA could not be applied. Furthermore, the atrial inflammation one day after the procedure and atrial fibrosis areas one month after the procedure were three-dimensionally quantified by PET/MRI and late-gadolinium enhancement magnetic resonance imaging (LGE-MRI), respectively.

RESULTS

The mean SUV max at the PV antrum was significantly higher than that on the healthy LA wall (2.12 ± 0.35 vs 1.73 ± 0.30, P = .00021). The volume of the atrial inflammation strongly correlated with that of the atrial fibrosis (r = .94 [.76-.99], P = .00006).

CONCLUSIONS

The atrial inflammation after CBA could be detected by PET/MRI. CBA-induced atrial inflammation was strongly associated with consequent lesion maturation.

Visualization of Inflammation After Cryoballoon Ablation in Atrial Fibrillation Patients - Protocol for Proof-of-Concept Feasibility Trial

Background: Atrial fibrosis and inflammation play important roles in perpetuating and initiating atrial fibrillation (AF). Although the fibrotic area can be visualized as a delayed enhancement area on late gadolinium enhancement magnetic resonance imaging (LGE-MRI), atrial inflammation has not yet been visualized on any imaging modality. We describe the protocol for a feasibility study to visualize atrial inflammation on positron emission tomography/MRI (PET/MRI).

Methods and Results: This is a single-arm, prospective, open-label proof-of concept trial, involving AF patients after cryoballoon ablation (CBA). A total of 30 paroxysmal AF patients will be enrolled and undergo simultaneous PET/MRI for the assessment of regional ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake 1 day after the CBA. Furthermore, LGE-MRI will be performed before CBA, and at 1 and 4 weeks after assessing the regional LGE area. The main outcome measures will be (1) the feasibility of imaging inflammation in the left atrium on PET/MRI; and (2) the safety of the intervention.

Conclusions: There are few data on the visualization of atrial inflammation using PET/MRI. Establishing the visualization methodology will contribute to elucidating the fundamental histopathologic findings of the progress to fibrosis, and to the planning and execution of a larger definitive trial to test the usefulness of PET/MRI.