Surgical Treatment of Primary Cardiac Paragangliomas: A Single-Center Experience

Background: Cardiac paragangliomas are rare neuroendocrine tumors that will cause significant morbidity if left undiagnosed. Because of the paucity of cohort data, their rapid diagnosis and appropriate management still pose unique challenges to cardiac surgeons. We aimed to investigate the clinical features and surgical management of primary cardiac paragangliomas in our single center. Methods: From May 2014 to October 2020, patients diagnosed with primary cardiac paragangliomas retrospectively were reviewed. Demographic data, clinical presentation, preoperative imaging methods, surgical resection, perioperative management, histological analysis, and outcomes were recorded. Postoperative follow up also was reviewed. Results: With multiple imaging methods, including echocardiography, computed tomography, positron-emission tomographic-computed tomography, and biochemical tests, there were five cases of primary cardiac paraganglioma verified by postoperative immunohistochemical staining, two of which were hormonally active. There were no metastatic cardiac paragangliomas, according to positron-emission tomographic-computed tomography, and all patients accepted surgical treatment. Preoperative adrenoceptor blockade was given to hormonally active patients, accordingly. Complete resection of the tumor was accomplished under cardiopulmonary bypass in each case. Tumor distribution included two masses on the roof of the left atrium, two masses in the right atrioventricular groove, and one between the ascending aorta and main pulmonary artery. Immunohistochemical staining for chromogranin, neuron-specific enolase, synaptophysin, and S-100 were positive, which were typical of cardiac paraganglioma. There were no operative deaths. All the patients had an uneventful recovery except one patient who underwent low cardiac output syndrome. During follow up (mean 4.2 years, range 0.6-7.0 years), all patients were well with New York Heart Association class I or II. Only one patient developed thyroid carcinoma three years after surgery but with no paraganglioma recurrence during periodic computed tomography, and this patient recovered well after thyroidectomy. Conclusion: Although cardiac paragangliomas are rare and may present surgical challenges for clinicians, surgical resection remains the choice of treatment with favorable outcomes through a multidisciplinary heart team. Moreover, lifelong surveillance still is recommended to detect possible recurrence or associated nonchromaffin tumors in time.

Effect of metformin on 18F-fluorodeoxyglucose uptake and positron emission tomographic imaging

Metformin is widely used to treat diabetes, but induces changes in glucose uptake in both normal organs and tumors. Here, we review the effects of metformin on the uptake of 18F-fluorodeoxyglucose (18F-FDG) in tissues and tumors, and its influence on 18F-FDG positron emission tomographic imaging (18F-FDG PET), as well as the mechanisms involved. This is an important issue, because metformin has diverse effects on tissue uptake of 18F-FDG, and this can affect the quality and interpretation of PET images. Metformin increases glucose uptake in the gastrointestinal tract, cerebral white matter, and the kidney, while regions of the cerebrum associated with memory show decreased glucose uptake, and the myocardium shows no change. Hepatocellular carcinoma and breast cancer show increased glucose uptake after metformin administration, while thyroid cancer shows decreased uptake, and colon and pancreatic cancers show no change. A high-energy diet increases 18F-FDG uptake, but this effect is blocked by metformin. Withdrawal of metformin 48 h before PET image acquisition is widely recommended. However, based on our review of the literature, we propose that the differentiation of metformin discontinuation could be reasonable. But future clinical trials are still needed to support our viewpoint.

Positron Emission Tomographic imaging of tumor cell death using Zirconium-89-labeled APOMAB® following cisplatin chemotherapy in lung and ovarian cancer xenograft models

The authors have requested that this preprint be withdrawn due to erroneous posting.