Imaging of programmed cell death in arrhythmogenic right ventricle cardiomyopathy/dysplasia

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a myocardial disease that predominantly affects the right ventricle (RV). Its hallmark feature is fibrofatty replacement of the RV myocardium. Apoptosis in ARVC/D has been proposed as an important process that mediates the slow, ongoing loss of heart muscle cells which is followed by ventricular dysfunction. We aimed to establish whether cardiac apoptosis can be assessed noninvasively in patients with ARVC/D. Six patients fulfilling the ARVC/D criteria were studied. Regional myocardial apoptosis was assessed with (99m)Tc-annexin V scintigraphy. Overall, the RV wall showed a higher (99m)Tc-annexin V signal than the left ventricular wall (p = 0.049) and the interventricular septum (p = 0.026). However, significantly increased uptake of (99m)Tc-annexin V in the RV was present in only three of the six ARVC/D patients (p = 0.001, compared to (99m)Tc-annexin V uptake in the RV wall of the other three patients). Our results are suggestive of a chamber-specific apoptotic process. Although the role of apoptosis in ARVC/D is unsolved, the ability to assess apoptosis noninvasively may aid in the diagnostic course. In addition, the ability to detect apoptosis in vivo with (99m)Tc-annexin V scintigraphy might allow individual monitoring of disease progression and response to diverse treatments aimed at counteracting ARVC/D progressio

Phosphatidylserine targeting for diagnosis and treatment of human diseases

Cells are able to execute apoptosis by activating series of specific biochemical reactions. One of the most prominent characteristics of cell death is the externalization of phosphatidylserine (PS), which in healthy cells resides predominantly in the inner leaflet of the plasma membrane. These features have made PS-externalization a well-explored phenomenon to image cell death for diagnostic purposes. In addition, it was demonstrated that under certain conditions viable cells express PS at their surface such as endothelial cells of tumor blood vessels, stressed tumor cells and hypoxic cardiomyocytes. Hence, PS has become a potential target for therapeutic strategies aiming at Targeted Drug Delivery. In this review we highlight the biomarker PS and various PS-binding compounds that have been employed to target PS for diagnostic purposes. We emphasize the 35 kD human protein annexin A5, that has been developed as a Molecular Imaging agent to measure cell death in vitro, and non-invasively in vivo in animal models and in patients with cardiovascular diseases and cancer. Recently focus has shifted from diagnostic towards therapeutic applications employing annexin A5 in strategies to deliver drugs to cells that express PS at their surface

High-resolution imaging of human atherosclerotic carotid plaques with micro18F-FDG PET scanning exploring plaque vulnerability

FDG-PET can be used to identify vulnerable plaques in atherosclerotic disease. Clinical FDG-PET camera systems are restricted in terms of resolution for the visualization of detailed inflammation patterns in smaller vascular structures. The aim of the study is to evaluate the possible added value of a high-resolution microPET system in excised carotid plaques using FDG. In this study, 17 patients with planned carotid endarterectomy were included. Excised plaques were incubated in FDG and subsequently imaged with microPET. Macrophage presence in plaques was evaluated semi-quantitatively by immunohistochemistry. Plaque calcification was assessed additionally with CT and correlated to FDG uptake. Finally, FDG uptake and macrophage infiltration were compared with patient symptomatology. Heterogeneous distributions and variable intensities of FDG uptake were found within the plaques. A positive correlation between the distribution of macrophages and the FDG uptake (r = 0.68, P <.01) was found. A negative correlation was found between areas of calcifications and FDG uptake (r = -0.84, P <.001). Ratio FDG(max) values as well as degree of CD68 accumulation were significantly higher in CVA patients compared with TIA or amaurosis fugax patients (P <.05) and CVA patients compared with asymptomatic patients (P <.05). This ex vivo study demonstrates that excised carotid plaques can be visualized in detail using FDG microPET. Enhancement of clinical PET/CT resolution for similar imaging results in patients is needed

Carotid Plaque Imaging with SPECT/CT and PET/CT

A major contributor to the occurrence of ischemic stroke is the existence of carotid atherosclerosis. A vulnerable carotid atherosclerotic plaque may rupture or erode, thus causing a thrombotic event. Currently, clinical decision-making with regard to carotid endarterectomy or stenting is still primarily based on the extent of luminal stenosis, estimated with CT angiography and/or (duplex) ultrasonography. However, there is growing evidence that the anatomic impact of stenosis alone has limited value in predicting the exact consequences of plaque vulnerability. Various molecular processes have, independently of degree of stenosis, shown to be importantly associated with the plaque's capability to cause thrombotic events. These molecular processes can be visualized with nuclear medicine techniques allowing the identification of vulnerable patients by non-invasive in vivo SPECT(/CT) and PET(/CT) imaging. This chapter provides an overview of SPECT(/CT) and PET(/CT) imaging with specific radiotracers that have been evaluated for the detection of plaques together with a future perspective in this field of imaging.</p

2-deoxy-2[F-18]fluoro-D-mannose positron emission tomography imaging in atherosclerosis

Progressive inflammation in atherosclerotic plaques is associated with increasing risk of plaque rupture. Molecular imaging of activated macrophages with 2-deoxy-2[F-18]fluoro-D-glucose ([F-18]FDG) has been proposed for identification of patients at higher risk for acute vascular events. Because mannose is an isomer of glucose that is taken up by macrophages through glucose transporters and because mannose receptors are expressed on a subset of the macrophage population in high-risk plaques, we applied F-18-labeled mannose (2-deoxy-2[F-18]fluoro-D-mannose, [F-18]FDM) for targeting of plaque inflammation. Here, we describe comparable uptake of [F-18]FDM and [F-18]FDG in atherosclerotic lesions in a rabbit model; [F-18]FDM uptake was proportional to the plaque macrophage population. Our FDM competition studies in cultured cells with 2-deoxy-2-[C-14]carbon-D-glucose ([C-14]2DG) support at least 35% higher [F-18]FDM uptake by macrophages in cell experiments. We also demonstrate that FDM restricts binding of anti mannose receptor antibody to macrophages by approximately 35% and that mannose receptor targeting may provide an additional avenue for imaging of plaque inflammation