PET/CT-identified atrial hypermetabolism is an index of atrial inflammation in patients with atrial fibrillation.

BACKGROUND: Although atrial inflammation has been implicated in the pathophysiology of atrial fibrillation (AF), the identification of atrial inflammation remains challenging. We aimed to establish a positron emission tomography/computed tomography (PET/CT) protocol with 18Fluor-labeled fluorodeoxyglucose (18F-FDG) for the detection of atrial hypermetabolism as surrogate for inflammation in AF. METHODS: We included n = 75 AF and n = 75 non-AF patients undergoing three common PET/CT protocols (n = 25 per group) optimized for the detection of (a) inflammation and (b) malignancy in predefined fasting protocols, and (c) cardiac viability allowing for maximized glucose uptake. 18F-FDG-uptake was analyzed in predefined loci. RESULTS: Differences of visual atrial uptake in AF vs non-AF patients were observed in fasting (inflammation [13/25 vs 0/25] and malignancy [10/25 vs 0/25]) protocols while viability protocols showed non-specific uptake in both the groups. In the inflammation protocol, AF patients showed higher uptake in the right atrium [(SUVmax: 2.5 ± .7 vs 2.0 ± .7, P = .01), atrial appendage (SUVmax: 2.4 ± .7 vs 2.0 ± .6, P = .03), and epicardial adipose tissue (SUVmax: 1.4 ± .5 vs 1.1 ± .4, P = .04)]. Malignancy and viability protocols failed to differentiate between AF and non-AF. CONCLUSION: Glucose uptake suppression protocols appear suitable in detecting differential atrial 18F-FDG uptake between AF and non-AF patients. Imaging-based assessment of inflammation might help to stratify AF patients offering individualized therapeutic approaches.

Role of catheter location on local impedance measurements and clinical outcome with the new direct sense technology in cardiac ablation procedures.

Background: A novel catheter technology (direct sense, DS) enables periprocedural local impedance (LI) measurement for estimation of tissue contact during radiofrequency ablation (RFA) for real-time assessment of lesion generation. This measure reflects specific local myocardial conduction properties in contrast to the established global impedance (GI) using a neutral body electrode. Our study aimed to assess representative LI values for the cardiac chambers, to evaluate LI drop in response to RF delivery and to compare those values to established GI measures in patients undergoing RFA procedures. Methods and Results: Seventy-three patients undergoing RFA with the DS technology were included. Within the cardiac chambers, baseline LI was significantly different, with the highest values in the left atrium (LA 107.5 ± 14.3 Ω; RV 104.6 Ω ± 12.9 Ω; LV 100.7 Ω ± 11.7 Ω, and RA 100.5 Ω ± 13.4 Ω). Baseline LI was positively correlated to the corresponding LI drop during RF delivery (R2 = 0.26, p = 0.01) representing a promising surrogate of lesion generation. The observed mean LI drop (15.6 ± 9.5 Ω) was threefold higher as GI drop (4.9 ± 7.4 Ω), p < 0.01. We evaluated the clinical outcome in a subgroup of patients undergoing DS-guided pulmonary vein isolation, which was comparable regarding arrhythmia recurrence to a conventional ablation cohort (57 % vs 50 %, p = 0.2). Conclusion: We provide detailed information on LI measures in electrophysiological procedures with significant differences within the cardiac chambers highlighting that RFA-related LI drop can serve as a promising surrogate for real-time assessment of lesion generation. Guiding the electrophysiologist in RFA procedures, this additional information promises to improve safety profile and success rates in the interventional treatment of arrhythmias.

Cardiac fibroblast activation detected by Ga-68 FAPI PET imaging as a potential novel biomarker of cardiac injury/remodeling.

BACKGROUND: Fibroblast activation protein (FAP) as a specific marker of activated fibroblasts can be visualized by positron emission tomography (PET) using Ga-68-FAP inhibitors (FAPI). Gallium-68-labeled FAPI is increasingly used in the staging of various cancers. In addition, the first cases of theranostic approaches have been reported. In this work, we describe the phenomenon of myocardial FAPI uptake in patients who received a Ga-68 FAPI PET for tumor staging. METHOD AND RESULTS: Ga-68 FAPI PET examinations for cancer staging were retrospectively analyzed with respect to cardiac tracer uptake. Standardized uptake values (SUV) were correlated to clinical covariates in a univariate regression model. From 09/2018 to 11/2019 N = 32 patients underwent FAPI PET at our institution. Six out of 32 patients (18.8%) demonstrated increased localized myocardial tracer accumulation, with remote FAPI uptake being significantly higher in patients with vs without localized focal myocardial uptake (SUVmax 2.2 ± .6 vs 1.5 ± .4, P < .05 and SUVmean 1.6 ± .4 vs 1.2 ± .3, P < .05, respectively). Univariate regression demonstrated a significant correlation of coronary artery disease (CAD), age and left ventricular ejection fraction (LVEF) with remote SUVmean uptake, the latter with a very strong correlation with remote uptake (R2 = .74, P < .01). CONCLUSION: Our study indicates an association of CAD, age, and LVEF with FAPI uptake. Further studies are warranted to assess if fibroblast activation can be reliably measured and may be used for risk stratification regarding early detection or progression of CAD and left ventricular remodeling.

ANTECEDENTES: Proteína de activación de fibroblastos (FAP) como marcador específico de fibroblastos maduros activados se puede visualizar mediante tomografía por emisión de positrones (PET) usando inhibidores de Ga-68-FAP (FAPI). El FAPI marcado con galio 68 se usa cada vez más en la estatificación de varios tipos de cáncer.Además, se han reportado los primeros casos de abordajes teranósticos. En este trabajo describimos el fenómeno de la captación de FAPI miocárdica en pacientes que recibieron Ga-68 FAPI PET para estatificación tumoral. MéTODO Y RESULTADOS: Los exámenes de PET Ga-68 FAPI para estadificación de cáncer se analizaron retrospectivamente con respecto a la captación del marcador cardíaco. Los valores de absorción estandarizados (SUV) se correlacionaron con covariables clínicas en un modelo de regresión univariante. Del 09/2018 al 11/2019 con una n = 32 pacientes fueron sometidos a PET FAPI en nuestra institución. Seis de 32 pacientes (18.8%) demostraron un aumento de acumulación del marcador localizado en el miocardio, con la captación remota de FAPI siendo significativamente mayor en pacientes con aumento de la captación vs sin captación focalizada de miocardio (SUVmax 2.2 ± 0.6 vs. 1.5 ± 0.4, p <0.05 y SUV mean 1.6 ± 0.4 vs. 1.2 ± 0.3, p <0.05, respectivamente). La regresión univariante demostró una correlación significativa de la enfermedad de la arteria coronaria (CAD), la edad y la fracción de eyección ventricular izquierda (FEVI) con absorción SUV remota, esta última con una muy fuerte correlación con la captación remota (R² = 0.74, p <0.01). CONCLUSIóN: Nuestro estudio indica una asociación de CAD, edad y FEVI con la captación de FAPI. Se necesitan más estudios para evaluar si la activación de fibroblastos se puede medir de manera confiable y se puede usar para la estratificación de riesgo con respecto a la detección temprana o la progresión de la CAD y la remodelación ventricular izquierda.

CONTEXTE: La protéine d'activation des fibroblastes (FAP) activés et matures peut être visualisée par tomographie à émission de positons (TEP) à l'aide d'inhibiteurs de l'activation des fibroblastes (FAPI). FAPI marqué au gallium 68 est de plus en plus utilisé dans la stratification de divers cancers. De plus, les premiers exemples d'approches théranostiques ont été rapportés. Dans ce travail nous décrivons la captation myocardique de FAPI chez les patients qui bénéficié d'une TEP au Ga-68 FAPI pour stratification tumorale. MéTHODE ET RéSULTATS: Les examens TEP Ga-68 FAPI pour la stratification oncologique ont été analysés rétrospectivement pour l'absorption du traceur au niveau cardiaque. Les valeurs d'absorption normalisées (SUV) font été corrélées aux variables cliniques selon un modèle de régression univarié. A partir de septembre 2018 jusqu'en novembre 2019, 32 patients ont bénéficié d'une TEP FAPI dans notre établissement. Six de nos 32 patients (18,8%) ont démontré une augmentation focale de captation du tracer au niveau myocardique. Les foyers systémiques se sont révélés significativement plus élevé chez les patients avec foyers myocardiques localisés (SUV max 2,2 ± 0,6 vs 1,5 ± 0,4, p <0,05 et SUV mean 1,6 ± 0,4 vs 1,2 ± 0,3, p <0,05, respectivement). Nous avons observé une corrélation significative entre la maladie coronarienne, l'âge, la fraction d'éjection du ventricule gauche et la présence de foyer myocardiques FAPI (R² = 0,74, p <0,01) CONCLUSION: Notre étude indique une association entre la maladie cardiovasculaire coronarienne, l'âge et la FEVG et la captation myocardique de FAPI. Des études additionnelles sont nécessaires pour déterminer si l'activation des fibroblastes peut être mesurée de manière fiable et utilisée pour la détection et la progression de la maladie coronarienne et le remodelage du ventricule gauche.