Regadenoson and seizures: a real clinical concern

The role of the adenosine system in epilepsy and its comorbidities

Epilepsy is one of the most serious and common chronic neurological conditions, characterised by recurrent hypersynchronous electrical activity in the brain that lead to seizures. Despite over 50 million people being affected worldwide, only ~70% of people with epilepsy have their seizures successfully controlled with current pharmacotherapy, and many experience significant psychiatric and physical comorbidities. Adenosine, a ubiquitous purine metabolite, is a potent endogenous anti-epileptic substance that can abolish seizure activity via the adenosine A1 G protein-coupled receptor. Activation of A1 receptors decreases seizure activity in animal models, including models of drug-resistant epilepsy. Recent advances have increased our understanding of epilepsy comorbidities, highlighting the potential for adenosine receptors to modulate epilepsy-associated comorbidities, including cardiovascular dysfunction, sleep and cognition. This review provides an accessible resource of the current advances in understanding the adenosine system as a therapeutic target for epilepsy and epilepsy-associated comorbidities. LINKED ARTICLES: This article is part of a themed issue Therapeutic Targeting of G Protein-Coupled Receptors: hot topics from the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists 2021 Virtual Annual Scientific Meeting. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.14/issuetoc.

PET/CT Myocardial Perfusion Imaging Acquisition and Processing: Ten Tips and Tricks to Help You Succeed

PURPOSE OF REVIEW

Positron emission tomography (PET) is a leading non-invasive modality for the diagnosis of coronary artery disease due to its diagnostic accuracy and high image quality. With the latest advances in PET systems, clinicians are able to assess for myocardial ischemia and myocardial blood flow while exposing patients to extremely low radiation doses. This review will focus on the basics of acquisition and processing of hybrid PET/CT systems from appropriate patient selection to common artifacts and pitfalls.

RECENT FINDINGS

The continued development of hybrid PET/CT technology is producing scanners with exquisite sensitivity capable of generating high-quality images while exposing patients to low radiation doses. List mode acquisition is an essential component in all modern PET/CT scanners allowing simultaneous dynamic and ECG-gated imaging without lengthening scan duration. Various PET radiotracers are currently being developed but rubidium-82 and 13N-ammonia remain the most commonly used perfusion radiotracers. The development of mini 13N-ammonia cyclotrons is a promising tool that should increase access to this radiotracer. Misregistration, attenuation from extra-cardiac activity, and patient motion are the most common causes of artifacts during perfusion imaging. Techniques to automatically realign images and correct respiratory or patient motion artifacts continue to evolve. Despite the continuous evolution of PET imaging techniques, basic knowledge of scan parameters, acquisition techniques, and post processing tools remains essential to ensure high-quality images are produced and artifacts are recognized and corrected. Future research should focus on optimizing scanners to allow for shorter scan protocols and lower radiation exposure as well as continue developing techniques to minimize and correct for motion and misregistration artifacts.

Safety of vasodilator stress myocardial perfusion imaging in patients with elevated cardiac biomarkers

BACKGROUND

While adenosine and dipyridamole as myocardial perfusion imaging (MPI) stress agents have literature supporting their safety in the setting of myocardial infarction (MI), regadenoson does not. Studying a high risk cohort of patients with elevated cardiac biomarkers may shed light on potential safety issues of these agents which might also affect lower risk cohorts.

METHODS

All patients who had undergone a clinically indicated stress MPI study at two academic centers from 1/1/2010 through 12/31/2012 with elevated troponin ≤7 days prior to testing were included. The primary endpoint was a composite of death, non-fatal MI, congestive heart failure (CHF), stroke, ventricular arrhythmias, atrial fibrillation/flutter, or atrioventricular block requiring intervention within 24 h of testing.

RESULTS

Of the 703 stress MPI studies that met inclusion criteria, 360 (51.2%), 199 (28.3%), 74 (10.5%), 9 (1.3%), and 61 (8.7%) underwent regadenoson, dipyridamole, adenosine, dobutamine, and exercise stress, respectively. The primary endpoint occurred in 11 (1.6%) patients with an incidence of 1.4% (n = 5), 1.0% (n = 2), 1.4% (n = 1), 11.1% (n = 1), and 3.3% (n = 2) following regadenoson, dipyridamole, adenosine, dobutamine, and exercise stress, respectively (P = 0.137). The adverse events included non-fatal MI in 7 (1.0%) patients, death in 1 (0.1%) patient, CHF in 1 (0.1%) patient, ventricular arrhythmia in 1 (0.1%) patient, and atrial arrhythmia in 1 (0.1%) patient.

CONCLUSION

In the setting of elevated troponin, serious complications associated with either exercise or vasodilator stress testing appear to be relatively rare with no increased risk attributable to a particular vasodilator agent.

EANM procedural guidelines for radionuclide myocardial perfusion imaging with SPECT and SPECT/CT: 2015 revision

Since the publication of the European Association of Nuclear Medicine (EANM) procedural guidelines for radionuclide myocardial perfusion imaging (MPI) in 2005, many small and some larger steps of progress have been made, improving MPI procedures. In this paper, the major changes from the updated 2015 procedural guidelines are highlighted, focusing on the important changes related to new instrumentation with improved image information and the possibility to reduce radiation exposure, which is further discussed in relation to the recent developments of new International Commission on Radiological Protection (ICRP) models. Introduction of the selective coronary vasodilator regadenoson and the use of coronary CT-contrast agents for hybrid imaging with SPECT/CT angiography are other important areas for nuclear cardiology that were not included in the previous guidelines. A large number of minor changes have been described in more detail in the fully revised version available at the EANM home page: http://eanm.org/publications/guidelines/2015_07_EANM_FINAL_myocardial_perfusion_guideline.pdf.

Review of cardiovascular imaging in The Journal of Nuclear Cardiology in 2014: Part 2 of 2: Myocardial perfusion imaging

In this new feature of The Journal of Nuclear Cardiology we will summarize key articles that were published in the Journal in the previous year. In the first article of this 2-part series we concentrated on publications dealing with cardiac positron emission tomography, computed tomography, and neuronal imaging. This review will focus on myocardial perfusion imaging summarizing advances in the field including in diagnosis, prognosis, appropriateness, and safety of testing.