Observable Atrial and Ventricular Fibrillation Episode Durations Are Conformant With a Power Law Based on System Size and Spatial Synchronization.

BACKGROUND: Atrial fibrillation (AF) and ventricular fibrillation (VF) episodes exhibit varying durations, with some spontaneously ending quickly while others persist. A quantitative framework to explain episode durations remains elusive. We hypothesized that observable self-terminating AF and VF episode lengths, whereby durations are known, would conform with a power law based on the ratio of system size and correlation length ([Formula: see text]. METHODS: Using data from computer simulations (2-dimensional sheet and 3-dimensional left-atrial), human ischemic VF recordings (256-electrode sock, n=12 patients), and human AF recordings (64-electrode basket-catheter, n=9 patients; 16-electrode high definition-grid catheter, n=42 patients), conformance with a power law was assessed using the Akaike information criterion, Bayesian information criterion, coefficient of determination (R2, significance=P<0.05) and maximum likelihood estimation. We analyzed fibrillatory episode durations and [Formula: see text], computed by taking the ratio between system size ([Formula: see text], chamber/simulation size) and correlation length (xi, estimated from pairwise correlation coefficients over electrode/node distance). RESULTS: In all computer models, the relationship between episode durations and [Formula: see text] was conformant with a power law (Aliev-Panfilov R2: 0.90, P<0.001; Courtemanche R2: 0.91, P<0.001; Luo-Rudy R2: 0.61, P<0.001). Observable clinical AF/VF durations were also conformant with a power law relationship (VF R2: 0.86, P<0.001; AF basket R2: 0.91, P<0.001; AF grid R2: 0.92, P<0.001). [Formula: see text] also differentiated between self-terminating and sustained episodes of AF and VF (P<0.001; all systems), as well as paroxysmal versus persistent AF (P<0.001). In comparison, other electrogram metrics showed no statistically significant differences (dominant frequency, Shannon Entropy, mean voltage, peak-peak voltage; P>0.05). CONCLUSIONS: Observable fibrillation episode durations are conformant with a power law based on system size and correlation length.

Role of interatrial conduction in atrial fibrillation: Mechanistic insights from renewal theory-based fibrillatory dynamic analysis.

Background: Interatrial conduction has been postulated to play an important role in atrial fibrillation (AF). The pathways involved in interatrial conduction during AF remain incompletely defined. Objective: We recently showed physiological assessment of fibrillatory dynamics could be performed using renewal theory, which determines rates of phase singularity formation (λf) and destruction (λd). Using the renewal approach, we aimed to understand the role of the interatrial septum and other electrically coupled regions during AF. Method: RENEWAL-AF is a prospective multicenter observational study recruiting AF ablation patients (ACTRN 12619001172190). We studied unipolar electrograms obtained from 16 biatrial locations prior to ablation using a 16-electrode Advisor HD Grid catheter. Renewal rate constants λf and λd were calculated, and the relationships between these rate constants in regions of interatrial connectivity were examined. Results: Forty-one AF patients (28.5% female) were recruited. A positive linear correlation was observed between λf and λd (1) across the interatrial septum (λf r2 = 0.5, P < .001, λd r2 = 0.45, P < .001), (2) in regions connected by the Bachmann bundle (right atrial appendage-left atrial appendage λf r2 = 0.29, P = .001; λd r2 = 0.2, P = .008), and (3) across the inferior interatrial routes (cavotricuspid isthmus-left atrial septum λf r2 = 0.67, P < .001; λd r2 = 0.55, P < .001). Persistent AF status and left atrial volume were found to be important effect modifiers of the degree of interatrial renewal rate statistical correlation. Conclusion: Our findings support the role of interseptal statistically determined electrical disrelation in sustaining AF. Additionally, renewal theory identified preferential conduction through specific interatrial pathways during fibrillation. These findings may be of importance in identifying clinically significant targets for ablation in AF patients.

Lead-Specific Features Predisposing to the Development of Tricuspid Regurgitation After Endocardial Lead Implantation.

BACKGROUND: Endocardial lead in the right ventricle is recognized as a cause for tricuspid regurgitation (TR), but the mechanism remains elusive. We sought to evaluate lead-specific features on the development of TR after endocardial lead implantation. METHODS: This was a prospective single-center study. The patients underwent 2-dimensional echocardiograms before endocardial lead implantation and at follow-up visits at 4 to 6 weeks, 6 months, and 12 months. We assessed the position of the endocardial lead at the tricuspid annulus by 3-dimensional echocardiography, the tricuspid leaflet interference by the endocardial lead by both 2- and 3-dimensional echocardiography, and the degree of lead slack radiologically. Patient characteristics and lead-related factors were evaluated in the prediction of new or worse TR by univariable and multivariable analyses. RESULTS: New or increased TR was detected in 38 of 128 patients at the 12-month follow-up. The postero-septal commissure was the most common lead position, and tricuspid leaflet interference detected in 21 patients was associated with a noncommissural lead position. The implantation of an implantable cardioverter defibrillator lead was not associated with new TR compared with the implantation of a pacemaker lead. Tricuspid leaflet interference (P < 0.0001), but not lead position or lead slack, was the only lead-specific factor associated with the development of TR. CONCLUSION: After right ventricle endocardial lead implantation, leaflet interference determined by echocardiography, but not the nature of the lead, the lead position at the tricuspid annulus, and the radiological lead slack, predicted TR development at 1 year postimplantation.

CONTEXTE: Il est établi que la présence d'une sonde endocavitaire dans le ventricule droit est une cause de régurgitation tricuspide (RT), mais le mécanisme en cause n'est pas encore bien compris. Nous avons tenté d'évaluer la corrélation entre certaines caractéristiques des sondes et l'apparition d'une RT secondaire à l'implantation d'une sonde endocavitaire. MÉTHODOLOGIE: Il s'agit d'une étude prospective menée dans un seul centre. Une échocardiographie bidimensionnelle a été réalisée avant la mise en place d'une sonde endocavitaire, ainsi qu'aux visites de suivi menées 4 à 6 semaines, 6 mois et 12 mois après l'intervention. Nous avons évalué la position de la sonde endocavitaire par rapport à l'anneau tricuspidien par échocardiographie tridimensionnelle, l'interférence de la sonde avec la valve tricuspide par échocardiographie bidimensionnelle et tridimensionnelle, et le degré de liberté de mouvement de la sonde par radiographie. Les caractéristiques des patients et les facteurs liés à la sonde ont été pris en compte dans la prédiction du risque de RT nouvelle ou d'aggravation d'une RT existante au moyen d'analyses univariées et multivariées. RÉSULTATS: Une RT nouvelle ou aggravée a été détectée au suivi à 12 mois chez 38 des 128 patients. Dans la plupart des cas, la sonde se trouvait à la commissure postéroseptale; chez 21 patients, une interférence avec la valve tricuspide a été détectée alors que la sonde ne se trouvait pas à la commissure. La mise en place d'une sonde de défibrillateur implantable n'a pas été associée à l'apparition d'une RT, comparativement à l'implantation d'une sonde de stimulateur cardiaque. L'interférence avec la valve tricuspide (p < 0,0001) était le seul facteur lié à la sonde associé à l'apparition d'une RT; aucun lien n'a été établi avec la position et le degré de liberté de mouvement de la sonde. CONCLUSION: Après la mise en place d'une sonde endocavitaire dans le ventricule droit, l'interférence avec la valve tricuspide établie par échocardiographie permettait de prédire l'apparition d'une RT dans l'année suivant la mise en place de la sonde sans égard au type de sonde, à sa position par rapport à l'anneau tricuspidien ou à la liberté de mouvement détectée par radiographie.

Atrial arrhythmias in the young: early onset atrial arrhythmias preceding a diagnosis of a primary muscular dystrophy.

AIMS: The aetiology of atrial arrhythmias in the otherwise healthy and young is usually unrecognized. We hypothesized that rare cases of atrial arrhythmias in the young may represent the initial manifestation of a muscular dystrophy syndrome. METHODS AND RESULTS: We describe the clinical characteristics, disease progression, results of electrophysiological study, and genetic findings in four patients (age <40 years) presenting with idiopathic atrial arrhythmias who subsequently received a diagnosis of a muscular dystrophy syndrome. The mean age at presentation with atrial arrhythmias was 29.5 years (range, 21-37 years), and the mean delay to diagnosis of muscular dystrophy was 3.6 years (range, 0.5-6 years). Two patients received a subsequent diagnosis of myotonic dystrophy type 1 and 2 a diagnosis of Emery-Dreifuss muscular dystrophy. Disease-causing genetic defects were identified in all four patients. One patient underwent catheter ablation of atrial flutter, experiencing improvement in arrhythmia symptoms. Two patients required device therapy, each receiving cardiac resynchronization therapy-defibrillator implantation for progressive left ventricular dysfunction. CONCLUSION: Early onset atrial arrhythmias may be the first clinical manifestation of a muscular dystrophy syndrome. Appropriate clinical assessment and surveillance may uncover this primary cause and provide an opportunity for timely genetic counselling and family screening.

Interrupted aorta diagnosed in a 51-year-old woman.

A 51-year-old lady presented with increasing heart failure symptoms and palpitations. She had recently been diagnosed with a congenital ventricular septal defect, bicuspid aortic valve, and Eisenmenger's syndrome. There was clinical evidence of right heart failure and differential clubbing and cyanosis affecting the feet but not hands. A cardiac magnetic resonance imaging demonstrated interruption of the aortic arch beyond the left subclavian artery, with the descending aorta perfused entirely through a large patent ductus arteriosus.

Clinical use of telemonitoring in chronic heart failure: keeping up with the times or misuse of time?

Close follow-up of patients with severe heart failure, especially after hospital discharge, has been shown to impact the mortality and readmission rates in this patient population. Monitoring of the patients' physiological status is important for predicting a potential heart failure decompensation. Earlier studies on structured telephone support and telemonitoring suggested a clear benefit on mortality and heart failure admissions, though recent large randomized controlled trials have been neutral. This review looks into the possible reasons for discrepancies in the outcomes. Remote monitoring of implantable cardiac devices is becoming increasingly utilized in a proportion of patients for device follow-up, and recent technology advances have suggested utility of certain device algorithms in detecting heart failure decompensations. Implantable hemodynamic monitors also show promise in this sphere, though have limited evidence at this stage, and further development in the technology is likely before they become part of routine practice.