Nuclear Imaging in Infective Endocarditis

PET/CT Imaging of Infectious Diseases: Overview of Novel Radiopharmaceuticals

Infectious diseases represent one of the most common causes of hospital admission worldwide. The diagnostic work-up requires a complex clinical approach, including laboratory data, CT and MRI, other imaging tools, and microbiologic cultures. PET/CT with 18F-FDG can support the clinical diagnosis, allowing visualization of increased glucose metabolism in activated macrophages and monocytes; this tracer presents limits in differentiating between aseptic inflammation and infection. Novel PET radiopharmaceuticals have been developed to overcome these limits; 11C/18F-labeled bacterial agents, several 68Ga-labeled molecules, and white blood cells labeled with 18F-FDG are emerging PET tracers under study, showing interesting preliminary results. The best choice among these tracers can be unclear. This overview aims to discuss the most common diagnostic applications of 18F-FDG PET/CT in infectious diseases and, as a counterpoint, to describe and debate the advantages and peculiarities of the latest PET radiopharmaceuticals in the field of infectious diseases, which will probably improve the diagnosis and prognostic stratification of patients with active infectious diseases.

Manifestations of Prosthetic Valve Endocarditis: Lessons From Multimodality Imaging and Pathological Correlation

Heart valve replacement has steadily increased over the past decades due to improved surgical mortality, an aging population, and the increasing use of transcatheter valve technology. With these developments, prosthetic valve complications, including prosthetic valve endocarditis, are increasingly encountered. In this review, we aim to characterize the manifestations of prosthetic valve endocarditis using representative case studies from our institution to highlight the advances and contributions of modern multimodality imaging techniques.

Novel Diagnostic Methods for Infective Endocarditis

Infective endocarditis (IE) remains a dangerous disease and continues to have a high mortality rate. Unfortunately, despite continuous improvements in diagnostic methods, in many cases, blood cultures remain negative, and the pathogen causing endocarditis is unknown. This makes targeted therapy and the selection of appropriate antibiotics impossible. Therefore, we present what methods can be used to identify the pathogen in infective endocarditis. These are mainly molecular methods, including PCR and MGS, as well as imaging methods using radiotracers, which offer more possibilities for diagnosing IE. However, they are still not widely used in the diagnosis of IE. The article summarizes in which cases we should choose them and what we are most hopeful about in further research into the diagnosis of IE. In addition, registered clinical trials that are currently underway for the diagnosis of IE are also presented.

Contemporary applications of multimodality imaging in infective endocarditis

INTRODUCTION

Infective endocarditis (IE) is an increasingly important condition with significant morbidity and mortality. With advancements in cardiovascular interventions including prosthetic valve implantation and utilization of intracardiac devices, the prevalence of IE is rising in the modern era. Early detection and management of this condition are critical.

AREAS COVERED

This review presents a contemporary review of the applications of multi-modality imaging in IE, taking a comparative approach of the various imaging modalities.

EXPERT OPINION

Transthoracic and transesophageal echocardiography are essential imaging modalities in establishing the diagnosis of IE, as well as evaluating for complications of IE. Other imaging modalities such as cardiac computed tomography and nuclear imaging play an important role as adjuvant imaging modalities for the evaluation of IE, particularly in prosthetic valve IE and cardiovascular implantable device associated IE. It is crucial to understand the strengths, weaknesses, and clinical application of each imaging modality, to improve the diagnosis, management, and outcomes of patients with IE.

Multimodality Imaging Diagnosis in Infective Endocarditis

Imaging is an important tool in the diagnosis and management of infective endocarditis (IE). Echocardiography is an essential examination, especially in native valve endocarditis (NVE), but its diagnostic accuracy is reduced in prosthetic valve endocarditis (PVE). The diagnostic ability is superior for transoesophageal echocardiography (TEE), but a negative test cannot exclude PVE. Both transthoracic echocardiography (TTE) and TEE can provide normal or inconclusive findings in up to 30% of cases, especially in patients with prosthetic devices. New advanced non-invasive imaging tests are increasingly used in the diagnosis of IE. Nuclear medicine imaging techniques have demonstrated their superiority over TEE for the diagnosis of PVE and cardiac implantable electronic device infective endocarditis (CIED-IE). Cardiac computed tomography angiography imaging is useful in PVE cases with inconclusive TTE and TEE investigations and for the evaluation of paravalvular complications. In the present review, imaging tools are described with their values and limitations for improving diagnosis in NVE, PVE and CIED-IE. Current knowledge about multimodality imaging approaches in IE and imaging methods to assess the local and distant complications of IE is also reviewed. Furthermore, a potential diagnostic work-up for different clinical scenarios is described. However, further studies are essential for refining diagnostic and management approaches in infective endocarditis, addressing limitations and optimizing advanced imaging techniques across different clinical scenarios.

Apoptosis as a Potential Target to Arrest and Survival of Hydatid Cyst

Background

Hydatidosis is a serious and life-threatening disease that may lead to the death of the host if diagnosed and treated improperly. Apoptosis has been investigated as a mechanism of host innate immunity in suppressing parasites and also the survival of cysts in the human body. The present study investigates the process and role of apoptosis caused by a host cell or parasite in hydatid cysts.

Materials and Methods

Survey cytotoxic effect and apoptotic mortality of hydatid-treated lymphocytes were investigated. Also, to determine the mechanism of apoptosis in host and parasite, the mean gene expressions of Bcl-2, Bax, Caspase 3 in hydatid-treated lymphocytes, and Fas-L gene in the laminated-germinal layer of fertile and infertile hydatid cysts were evaluated.

Results

The viability of fertile and infertile hydatid fluid-treated lymphocytes was significantly different compared with the control group. Flow cytometry also showed apoptotic cells. Bax mean gene expression was significantly different between fertile and infertile treated lymphocytes. However, there was no significant difference in the mean expression of Caspase 3, and Bcl-2 genes in these two groups. Although the expression of the Fas-L gene in infertile cysts was higher than in fertile cysts, the result was not significant.

Conclusion

It seems that hydatid cyst fluid may induce apoptosis in lymphocytes so that, hydatid cysts can escape from the immune system and stay alive. On the other hand, the results represent the possible immune path of host apoptosis against the parasite as one of the important routes in infertility of hydatid cysts.

Contemporary Review of Multi-Modality Cardiac Imaging Evaluation of Infective Endocarditis

Infective endocarditis (IE) remains to be a heterogeneous disease with high morbidity and mortality rates, which can affect native valves, prosthetic valves, and intra-cardiac devices, in addition to causing systemic complications. The combination of clinical, laboratory, and cardiac imaging evaluation is critical for early diagnosis and risk stratification of IE. This can facilitate timely medical and surgical management to improve patient outcomes. Key imaging findings for IE include vegetations, valve perforation, prosthetic valve dehiscence, pseudoaneurysms, abscesses, and fistulae. Transthoracic echocardiography continues to be the first-line imaging modality of choice, while transesophageal echocardiography subsequently provides an improved structural assessment and characterization of lesions to facilitate management decision in IE. Recent advances in other imaging modalities, especially cardiac computed tomography and 18F-fluorodeox-yglucose positron emission tomography, and to a lesser extent cardiac magnetic resonance imaging and other nuclear imaging techniques, have demonstrated important roles in providing complementary IE diagnostic and prognostic information. This review aims to discuss the individual and integrated utilities of contemporary multi-modality cardiac imaging for the assessment and treatment guidance of IE.

Advances in Molecular Imaging in Infective Endocarditis

Infective endocarditis (IE) is a growing epidemiological challenge. Appropriate diagnosis remains difficult due to heterogenous etiopathogenesis and clinical presentation. The disease may be followed by increased mortality and numerous diverse complications. Developing molecular imaging modalities may provide additional insights into ongoing infection and support an accurate diagnosis. We present the current evidence for the diagnostic performance and indications for utilization in current guidelines of the hybrid modalities: single photon emission tomography with technetium99m-hexamethylpropyleneamine oxime-labeled autologous leukocytes (^99mTc-HMPAO-SPECT/CT) along with positron emission tomography with fluorodeoxyglucose (¹⁸F-FDG PET/CT). The role of molecular imaging in IE diagnostic work-up has been constantly growing due to technical improvements and the increasing evidence supporting its added diagnostic and prognostic value. The various underlying molecular processes of ^99mTc-HMPAO-SPECT/CT as well as ¹⁸F-FDG PET/CT translate to different imaging properties, which should be considered in clinical practice. Both techniques provide additional diagnostic value in the assessment of patients at risk of IE. Nuclear imaging should be considered in the IE diagnostic algorithm, not only for the insights gained into ongoing infection at a molecular level, but also for the determination of the optimal clinical therapeutic strategies.

[Global and national trends in the evolution of infective endocarditis]

For the recent 20 years, substantial changes have occurred in all aspects of infectious endocarditis (IE), the evolution of risk factors, modernization of diagnostic methods, therapeutic and preventive approaches. The global trends are characterized by increased IE morbidity among people older than 65 who use intravenous psychoactive drugs. The epidemiological trend is represented by reduced roles of chronic rheumatic heart disease and congenital heart defects, increased proportion of IE associated with medical care, valve replacement, installation of intracardiac devices, and increased contribution of Staphylococcus spp. and Enterococcus spp. to the IE etiology. Additional visualization methods (fluorodeoxyglucose positron emission tomography with 18F-fludesoxyglucose (18F-FDG PET-CT), labeled white blood cell single-photon emission computed tomography (SPECT), and modernization of the etiological diagnostic algorithm for determining the true pathogen (immunochemistry, polymerase chain reaction, sequencing) also become increasingly important. The COVID-19 pandemic has also adversely contributed to the IE epidemiology. New prospects of treatment have emerged, such as bacteriophages, lysins, oral antibacterial therapy, minimally invasive surgical strategies (percutaneous mechanical aspiration), endovascular mechanical embolectomy. The physicians' compliance with clinical guidelines (CG) is low, which contributes to the high rate of adverse outcomes of IE, while simple adherence to the CG together with more frequent use of surgical treatment doubles survival. Systematic adherence to CG, timely prevention and implementation of the Endocarditis Team into practice play the decisive role in a favorable prognosis of dynamically changing IE. This article presents the authors' own data that confirm the evolutionary trends of current IE.

Neuroprotective and anti-neuroinflammatory activity of frankincense in bile duct ligaion-induced hepatic encephalopathy

Objectives

Hepatic encephalopathy induces cognitive disturbances. Patients show neuroinflammation due to accumulation of toxic substances. Frankincense has neuroprotective and anti-inflammatory properties. Accordingly, we intended to evaluate the impact of frankincense on memory performance, inflammation, and the amount of hippocampal neurons in bile duct-ligated rats.

Materials and Methods

The bile duct was ligated in three groups of adult male Wistar rats (BDL groups). In two of these groups, frankincense was administered (100 or 200 mg/kg; by gavage) starting from one week before surgery to 28 days after surgery. The third BDL group received saline. In the sham group, the bile duct was not ligated and the animals received saline. Twenty-eight days after surgery, spatial memory was evaluated by the Morris water maze test. Five rats from each group were sacrificed to measure the expression of the hippocampal tumor necrosis factor-alpha (TNF-α). Three rats from each group were perfused to determine the amount of hippocampal neurons.

Results

Bile duct ligation impaired memory acquisition, while frankincense amended it. Bile duct ligation significantly increased the expression of TNF-α. Frankincense reduced TNF-α in BDL rats, significantly. The number of neurons in the hippocampal CA₁ and CA₃ areas was significantly lower in the BDL group and in the group that received frankincense (100 mg/kg) equated to the sham group. Frankincense (200 mg/kg) augmented the amount of neurons in the CA₁ area, slightly and in the CA₃ area, significantly.

Conclusion

The results indicate the anti-inflammatory and neuroprotective effects of frankincense in bile duct ligation-induced hepatic encephalopathy.

Utilizing clinical pharmacology in the drug repurposing arena: a look into COVID-19

INTRODUCTION

Drug repurposing represented an important contribution in the management of COVID-19, becoming the first line of defense to mitigate the effects of the new coronavirus. In a brief time, drug repurposing (DR) provided potentially effective and already available drugs for COVID-19, while specific therapies against SARS-CoV-2 and/or vaccines were developing. Identifying repurposed drugs requires a multidisciplinary approach, where clinical pharmacology represents the missing piece of the puzzle.

AREAS COVERED

Nowadays, clinical pharmacology is recognized as a discipline at the core of translational science, whose activities lead to the identification of the right drug for the right patient. In the context of the COVID-19 pandemic, its role in drug development and therapy choice has been decisive and itself repositioned. In this review, we tried to highlight the important role of clinical pharmacology in the identification and evaluation of possible repurposed drugs for COVID-19.

EXPERT OPINION

We believe that clinical pharmacology had an important role in identifying patient-oriented therapy during the COVID-19 pandemic. In this context, DR was just one of the challenges for clinical pharmacology, which proved that this discipline is ready to respond to future threats.