Synergic PDE3 and PDE4 control intracellular cAMP and cardiac excitation-contraction coupling in a porcine model

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Interventricular Differences in β‐Adrenergic Responses in the Canine Heart: Role of Phosphodiesterases

Background RV and LV have different embryologic, structural, metabolic, and electrophysiologic characteristics, but whether interventricular differences exist in β‐adrenergic (β‐AR) responsiveness is unknown. In this study, we examine whether β‐AR response and signaling differ in right (RV) versus left (LV) ventricles. Methods and Results Sarcomere shortening, Ca2+ transients, ICa,L and IKs currents were recorded in isolated dog LV and RV midmyocytes. Intracellular [cAMP] and PKA activity were measured by live cell imaging using FRET‐based sensors. Isoproterenol increased sarcomere shortening ≈10‐fold and Ca2+‐transient amplitude ≈2‐fold in LV midmyocytes (LVMs) versus ≈25‐fold and ≈3‐fold in RVMs. FRET imaging using targeted Epac2camps sensors revealed no change in subsarcolemmal [cAMP], but a 2‐fold higher β‐AR stimulation of cytoplasmic [cAMP] in RVMs versus LVMs. Accordingly, β‐AR regulation of ICa,L and IKs were similar between LVMs and RVMs, whereas cytoplasmic PKA activity was increased in RVMs. Both PDE3 and PDE4 contributed to the β‐AR regulation of cytoplasmic [cAMP], and the difference between LVMs and RVMs was abolished by PDE3 inhibition and attenuated by PDE4 inhibition. Finally LV and RV intracavitary pressures were recorded in anesthetized beagle dogs. A bolus injection of isoproterenol increased RV dP/dtmax≈5‐fold versus 3‐fold in LV. Conclusion Canine RV and LV differ in their β‐AR response due to intrinsic differences in myocyte β‐AR downstream signaling. Enhanced β‐AR responsiveness of the RV results from higher cAMP elevation in the cytoplasm, due to a decreased degradation by PDE3 and PDE4 in the RV compared to the LV

Intracardiac electrophysiology to characterize susceptibility to ventricular arrhythmias in murine models

Introduction: Sudden cardiac death (SCD) and ventricular fibrillation are rare but severe complications of many cardiovascular diseases and represent a major health issue worldwide. Although the primary causes are often acute or chronic coronary diseases, genetic conditions, such as inherited channelopathies or non-ischemic cardiomyopathies are leading causes of SCD among the young. However, relevant experimental models to study the underlying mechanisms of arrhythmias and develop new therapies are still needed. The number of genetically engineered mouse models with cardiac phenotype is growing, making electrophysiological studies in mice essential tools to study arrhythmogenicity and arrhythmia mechanisms and to test novel treatments. Recently, intracardiac catheterization via the jugular vein was described to induce and record ventricular arrhythmias in living anesthetized mice. Several strategies have been reported, developed in healthy wild-type animals and based on aggressive right ventricular stimulation.Methods: Here, we report a protocol based on programmed electrical stimulation (PES) performed in clinical practice in patients with cardiac rhythm disorders, adapted to two transgenic mice models of arrhythmia - Brugada syndrome and cardiolaminopathy.Results: We show that this progressive protocol, based on a limited number of right ventricular extrastimuli, enables to reveal different rhythmic phenotypes between control and diseased mice. In this study, we provide detailed information on PES in mice, including catheter positioning, stimulation protocols, intracardiac and surface ECG interpretation and we reveal a higher susceptibility of two mouse lines to experience triggered ventricular arrhythmias, when compared to control mice.Discussion: Overall, this technique allows to characterize arrhythmias and provides results in phenotyping 2 arrhythmogenic-disease murine models

Impact of early complications on outcomes in patients with implantable cardioverter-defibrillator for primary prevention

International audienceBackground - The lifesaving benefit of implantable cardioverter-defibrillators (ICDs) has been demonstrated. Their use has increased considerably in the past decade, but related complications have become a major concern. Objective - The purpose of this study was to assess the incidence and effect on outcomes of early (≤30 days) complications after ICD implantation for primary prevention in a large French population. Methods - We analyzed data from 5539 patients from the multicenter French DAI-PP (Défibrillateur Automatique Implantable-Prévention Primaire) registry (2002-2012) who had coronary artery disease or dilated cardiomyopathy and were implanted with an ICD for primary prevention. Results - Overall, early complications occurred in 707 patients (13.5%), mainly related to lead dislodgment or hematoma (57%). Independent factors associated with occurrence of early complications were severe renal impairment (odds ratio [OR] 1.66, 95% confidence interval [CI] 1.17-2.37, P = .02), age ≥75 years (OR 1.01, 95% CI 1.00-1.02, P = .03), cardiac resynchronization therapy (OR 1.58, 95% CI 1.16-2.17, P = .01), and anticoagulant therapy (OR 1.28, 95% CI 1.02-1.61, P = .03). During a mean ± SD follow-up of 3.1 ± 2.3 years, 824 (15.8%) patients experienced ≥1 late complication (>30 days), and 782 (14.9%) patients died. After adjustment, early complications remained associated with occurrence of late complications (OR 2.15, 95% CI 1.73-2.66, P < .0001) and mortality (OR 1.70, 95% CI 1.34-2.17, P = .003). Conclusion - Early complications are common after ICD implantation for primary prevention, occurring in 1 in 7 patients, and are associated with an increased risk of late complications and overall mortality. Further studies are needed to investigate the underlying mechanisms of such associations

Permanent Pacemaker Implantation After Tricuspid Valve Surgery

Tricuspid valve (TV) surgery carries a high risk of atrioventricular block. In this report, we illustrate several options for managing conduction disorders after TV surgery. The choice of cardiac implantable devices must take account of several parameters such as surgical procedure, patient’s rhythm and history, and etiology of TV disease. (Level of Difficulty: Intermediate.

Can Nuclear Imaging Techniques Predict Patient Outcome and Guide Medical Management in Hereditary Transthyretin Cardiac Amyloidosis?

International audiencePurpose of Review Nuclear imaging recently gained a key role in the diagnosis and prognostic assessment of transthyretin (TTR)-related cardiac amyloidosis. This review aims at summarizing the state-of-the art regarding the implementation of nuclear imaging in the management of hereditary mutated TTR-cardiac amyloidosis (mTTR-CA). Recent Findings Although cardiac uptake of bone tracers is acknowledged as a specific marker of TTR amyloid cardiac burden, recent studies validated the implementation of bone scan in the flow chart for non-invasive diagnosis and follow-up of CA in multicenter trials. Simultaneously, cardiac denervation evidenced by MIBG scintigraphy proved to be a strong and independent prognostic marker of poor outcome in mTTR-CA. Summary By its unique ability to assess both amyloid burden and cardiac denervation, nuclear imaging may prove useful as part of multimodality imaging tools to trigger treatment initiation and monitoring in patients with mTTR-CA

Cardiac denervation evidenced by MIBG occurs earlier than amyloid deposits detection by Diphosphonates scintigraphy in patients with aTTR-FAP

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Cardiac denervation evidenced by MIBG occurs earlier than amyloid deposits detection by Diphosphonates scintigraphy in patients with aTTR-FAP

International audienc

The value of basic research insights into atrial fibrillation mechanisms as a guide to therapeutic innovation: a critical analysis

Atrial fibrillation (AF) is an extremely common clinical problem associated with increased morbidity and mortality. Current antiarrhythmic options include pharmacological, ablation, and surgical therapies, and have significantly improved clinical outcomes. However, their efficacy remains suboptimal, and their use is limited by a variety of potentially serious adverse effects. There is a clear need for improved therapeutic options. Several decades of research have substantially expanded our understanding of the basic mechanisms of AF. Ectopic firing and re-entrant activity have been identified as the predominant mechanisms for arrhythmia initiation and maintenance. However, it has become clear that the clinical factors predisposing to AF and the cellular and molecular mechanisms involved are extremely complex. Moreover, all AF-promoting and maintaining mechanisms are dynamically regulated and subject to remodelling caused by both AF and cardiovascular disease. Accordingly, the initial presentation and clinical progression of AF patients are enormously heterogeneous. An understanding of arrhythmia mechanisms is widely assumed to be the basis of therapeutic innovation, but while this assumption seems self-evident, we are not aware of any papers that have critically examined the practical contributions of basic research into AF mechanisms to arrhythmia management. Here, we review recent insights into the basic mechanisms of AF, critically analyse the role of basic research insights in the development of presently used anti-AF therapeutic options and assess the potential value of contemporary experimental discoveries for future therapeutic innovation. Finally, we highlight some of the important challenges to the translation of basic science findings to clinical application