Prediction of stroke risk based on left atrial appendage morphology: from pareidolia to artificial intelligence

<jats:title>Abstract</jats:title><jats:p>The global carbon-climate system is a complex dynamical system with multiple feedbacks among components, and to steer this system away from dangerous climate change, it may not be enough to prescribe action according to long-term scenarios of fossil fuel emissions. We introduce here concepts from control theory, a branch of applied mathematics that is effective at steering complex dynamical systems to desired states, and distinguish between open- and closed-loop control. We attempt (1) to show that current scientific work on carbon-climate feedbacks and climate policy more closely resembles the conceptual model of open- than closed-loop control, (2) to introduce a mathematical generalization of the carbon-climate system as a compartmental dynamical system that can facilitate the formal treatment of the closed-loop control problem, and (3) to formulate carbon-climate control as a congestion control problem, discussing important concepts such as observability and controllability. We also show that most previous discussions on climate change mitigation and policy development have relied on an implicit assumption of open-loop control that does not consider frequent corrections due to deviations of goals from observations. Using a reduced complexity model, we illustrate that the problem of managing the global carbon cycle can be abstracted as a network congestion problem, accounting for nonlinear behavior and feedback from a global carbon monitoring system. As opposed to <jats:italic>scenarios</jats:italic>, the goal of closed-loop control is to develop <jats:italic>rules</jats:italic> for continuously steering the global carbon-climate system away from dangerous climate change.</jats:p&gt

Exercise and the heart: unmasking Mr Hyde

As physicians, we often face patients with cardiovascular risk factors or different kinds of heart disease. We prescribe statins, ACE inhibitors or β-blockers, but also (should) encourage our patients to engage in regular physical activity to reduce cardiovascular disease burden...

Exercise, sex and atrial fibrillation: arrhythmogenesis beyond Y-chromosome?

Although prevailing research trends favour large clinical trials and registries, meticulous observation during daily clinical practice remains a valuable source for hypothesis generation in medical research. Clinical experience has allowed the identification of several risk factors in the cardiovascular field...

Diagnosis, pathophysiology, and management of exercise-induced arrhythmias

The cardiovascular benefits of physical activity are indisputable. Nevertheless, growing evidence suggests that both atrial fibrillation and right ventricular arrhythmia can be caused by intense exercise in some individuals. Exercise-induced atrial fibrillation is most commonly diagnosed in middle-aged, otherwise healthy men who have been engaged in endurance training for >10 years, and is mediated by atrial dilatation, parasympathetic enhancement, and possibly atrial fibrosis. Cardiac ablation is evolving as a first-line tool for athletes with exercise-induced arrhythmia who are eager to remain active. The relationship between physical activity and right ventricular arrhythmia is complex and involves genetic and physical factors that, in a few athletes, eventually lead to right ventricular dilatation, followed by subsequent myocardial fibrosis and lethal ventricular arrhythmias. Sinus bradycardia and atrioventricular conduction blocks are common in athletes, most of whom remain asymptomatic, although incomplete reversibility has been shown after exercise cessation. In this Review, we summarize the evidence supporting the existence of exercise-induced arrhythmias and discuss the specific considerations for the clinical management of these patients

Undetected displacement of a subcutaneous implantable cardioverter-defibrillator lead

Background: In recent years, subcutaneous implantable cardioverter-defibrillator (S-ICD) implants have progressively increased and have been shown to be safe and highly successful, affording low reintervention rates regardless of the technique used. Case summary: We present a case of S-ICD implantation in a patient diagnosed with idiopathic ventricular fibrillation. In the first follow-up consultation the patient showed appropriate detection parameters in the three configurations. However, chest X-ray revealed lead displacement with a tip migration from the manubrium area of the sternum to the xiphoid process. Discussion: This case highlights the importance of performing at least one chest X-ray during the first weeks after S-ICD implantation, allowing the detection of a problem such as lead displacement, which can lead to undersensing of ventricular arrhythmias or S-ICD oversensing

Atrial fibrillation progression: How sick is the atrium?

After many years of lack of interest in the atrium by clinical cardiologists, the evidence of increased morbidity and mortality in patients with atrial fibrillation (AF) relocated the atrium to a central position in cardiology more than 2 decades ago.1 First came the studies showing improved outcome with the use of anticoagulants; later, the ever-lasting controversy on rate vs rhythm control; and at present, new imaging techniques and new therapeutic tools to better define atrial remodeling and improve therapy..

Ablation Lesion Assessment with MRI

Late gadolinium enhancement (LGE) MRI is capable of detecting not only native cardiac fibrosis, but also ablation-induced scarring. Thus, it offers the unique opportunity to assess ablation lesions non-invasively. In the atrium, LGE-MRI has been shown to accurately detect and localise gaps in ablation lines. With a negative predictive value close to 100% it can reliably rule out pulmonary vein reconnection non-invasively and thus may avoid unnecessary invasive repeat procedures where a pulmonary vein isolation only approach is pursued. Even LGE-MRI-guided repeat pulmonary vein isolation has been demonstrated to be feasible as a standalone approach. LGE-MRI-based lesion assessment may also be of value to evaluate the efficacy of ventricular ablation. In this respect the elimination of LGE-MRI-detected arrhythmogenic substrate may serve as a potential endpoint, but validation in clinical studies is lacking. Despite holding great promise, the widespread use of LGE-MRI is still limited by the absence of standardised protocols for image acquisition and post-processing. In particular, reproducibility across different centres is impeded by inconsistent thresholds and internal references to define fibrosis. Thus, uniform methodological and analytical standards are warranted to foster a broader implementation in clinical practice

Novel Computational Analysis of Left Atrial Anatomy Improves Prediction of Atrial Fibrillation Recurrence after Ablation

The left atrium (LA) can change in size and shape due to atrial fibrillation (AF)-induced remodeling. These alterations can be linked to poorer outcomes of AF ablation. In this study, we propose a novel comprehensive computational analysis of LA anatomy to identify what features of LA shape can optimally predict post-ablation AF recurrence. To this end, we construct smooth 3D geometrical models from the segmentation of the LA blood pool captured in pre-procedural MR images. We first apply this methodology to characterize the LA anatomy of 144 AF patients and build a statistical shape model that includes the most salient variations in shape across this cohort. We then perform a discriminant analysis to optimally distinguish between recurrent and non-recurrent patients. From this analysis, we propose a new shape metric called vertical asymmetry, which measures the imbalance of size along the anterior to posterior direction between the superior and inferior left atrial hemispheres. Vertical asymmetry was found, in combination with LA sphericity, to be the best predictor of post-ablation recurrence at both 12 and 24 months (area under the ROC curve: 0.71 and 0.68, respectively) outperforming other shape markers and any of their combinations. We also found that model-derived shape metrics, such as the anterior-posterior radius, were better predictors than equivalent metrics taken directly from MRI or echocardiography, suggesting that the proposed approach leads to a reduction of the impact of data artifacts and noise. This novel methodology contributes to an improved characterization of LA organ remodeling and the reported findings have the potential to improve patient selection and risk stratification for catheter ablations in AF

Mechanisms of atrial fibrillation in athletes: what we know and what we do not know.

Exercise is an emerging cause of atrial fibrillation (AF) in young individuals without coexisting cardiovascular risk factors. The causes of exercise-induced atrial fibrillation remain largely unknown, and conclusions are jeopardised by apparently conflicting data. Some components of the athlete's heart are known to be arrhythmogenic in other settings. Bradycardia, atrial dilatation and, possibly, atrial premature beats are therefore biologically plausible contributors to exercise-induced AF. Challenging findings in an animal model suggest that exercise might also prompt the development of atrial fibrosis, possibly due to cumulative minor structural damage after each exercise bout. However, there is very limited, indirect data supporting this hypothesis in athletes. Age, sex, the presence of comorbidities and cardiovascular risk factors, and genetic individual variability might serve to flag those athletes who are at the higher risk of exercise-induced AF. In this review, we will critically address current knowledge on the mechanisms of exercise-induced AF