Morpho-metabolic post-surgical patterns of non-infected prosthetic heart valves by [18F]FDG PET/CTA: “normality” is a possible diagnosis

Abstract

Aims To define characteristic PET/CTA patterns of FDG uptake and anatomic changes following prosthetic heart valves (PVs) implantation over time, to help not to misdiagnose post-operative inflammation and avoid false-positive cases. Methods and results Prospective evaluation of 37 post-operative patients without suspected infection that underwent serial cardiac PET/CTA examinations at 1, 6, and 12 months after surgery, in which metabolic features (FDG uptake distribution pattern and intensity) and anatomic changes were evaluated. Standardized uptake values (SUVs) were obtained and a new measure, the valve uptake index (VUI), (SUVmax–SUVmean)/SUVmax, was tested to homogenize SUV results. In total, 111 PET/CTA scans were performed in 37 patients (19 aortic and 18 mitral valves). FDG uptake was visually detectable in 79.3% of patients and showed a diffuse, homogeneous distribution pattern in 93%. Quantitative analysis yielded a mean maximum standardized uptake value (SUVmax) of 4.46 ± 1.50 and VUI of 0.35 ± 0.10. There were no significant differences in FDG distribution or uptake values between 1, 6, or 12 months. No abnormal anatomic changes or endocarditis lesions were detected in any patient during follow-up. Conclusions FDG uptake, often seen in recently implanted PVs, shows a characteristic pattern of post-operative inflammation and, in the absence of associated anatomic lesions, could be considered a normal finding. These features remain stable for at least 1 year after surgery, so questioning the recommended 3-month safety period. A new measure, the VUI, can be useful for evaluating the FDG distribution pattern.

Revisiting the relevance of the 3-month safety period in the evaluation of prosthetic valve endocarditis with FDG-PET/CT

“…Importantly, there were no significant differences in SUV max , SUV ratio (PHV SUV max divided by mean SUV of the blood pool), or pattern of FDG uptake between the three time points. These results are concordant with those recently reported by Roque et al, 13 who performed serial FDG-PET/ CT scans in patients with PHV and without clinical suspicion of PVE at 1, 6, and 12 months post implantation. Interestingly, both studies report very similar SUV max around aortic PHV at their earliest imaging timepoint (mean SUV max of 4,1 in both studies).…”

Multimodality Imaging in the Diagnostic Work-Up of Endocarditis and Cardiac Implantable Electronic Device (CIED) Infection

“…Even in the case of negative PET results (that includes also a whole-body evaluation for embolism detection), a thorough interpretation of the echocardiography and CCTA scan is essential. Indeed, in the absence of infection, PV generally shows mild, diffuse, and homogeneous uptake that usually remains stable for at least one year after surgery, most likely resulting from persistent host reaction against the biomaterial coating the sewing ring of PV and chronic tension or friction exerted on these anchor points [51][52][53]. Such ( 18 F)FDG uptake seems to be slightly greater in mechanical versus biological prostheses.…”

Molecular Imaging of Cardiovascular Device Infection: Targeting the Bacteria or the Host–Pathogen Immune Response?

“…Thus, 18 F-FDG PET/CT has been recommended by the European Society for Cardiology for the diagnosis of cardiac device-related and prosthetic valve endocarditis (7). Although 18 F-FDG is criticized for its nonspecific accumulation in inflammation sites (56,57), differentiation between infection and inflammation can be reasonably achieved by recognizing the 18 F-FDG uptake pattern: 18 F-FDG uptake in an infection site is generally heterogeneous, with focal increased activity, whereas the distribution of 18 F-FDG in an inflammatory area is more homogeneous and mild (58,59). In addition, clinical information such as about the device material (metal or bioprosthesis) and surgical technique (use of adhesion glue or anticalcification material) is also useful for the differentiation.…”