PULSED-FIELD ABLATION: COMPUTATIONAL MODELLING OF ELECTRIC FIELDS FOR LESION DEPTH ANALYSIS

Background

Pulsed-field ablation (PFA) is an emerging and promising nonthermal technology for cardiac ablation. The effective applied voltage to achieve adequate irreversible myocardial injury is not well studied. The pulsed-field strength remains independent of tissue contact; therefore, PFA is assumed to be an ablation technology, not mandating the need for tissue contact.

Objective

Determine the effect of applied voltage and distance to surface on depth of myocardial injury using PFA.

Methods

A computational model was developed and validated based on extracted data from in vivo studies to examine the effect of different applied voltages and the impact of distance between the catheter and endocardial surface on the depth of irreversible myocardial injury using PFA.

Results

The depth of lesions created by PFA are dose-dependent, and there is a direct correlation between applied PFA voltages and depth of irreversible myocardial injury. The minimum applied voltage of PFA required to create a lesion deeper than 1 mm is 300 volts. The catheter-tissue contact plays a pivotal role in determining lesion depth. With optimal catheter contact in the absence of trabeculation, the minimal applied energy required to achieve a 3-mm-deep lesion is 700 volts. A minor increase in the catheter-tissue distance of 1–2 mm doubles the minimum required applied voltage, increasing it to 1500 volts.

Conclusion

PFA is an important new technology that is proposed to be more efficacious and safer than currently used thermal ablation. Here we demonstrate the impact of dose dependence and the need for maintaining tissue contact during ablation.

Endomysial fibrosis, rather than overall connective tissue content, is the main determinant of conduction disturbances in human atrial fibrillation

Aims

Although in persistent atrial fibrillation (AF) a complex AF substrate characterized by a high incidence of conduction block has been reported, relatively little is known about AF complexity in paroxysmal AF (pAF). Also, the relative contribution of various aspects of structural alterations to conduction disturbances is not clear. In particular, the contribution of endomysial fibrosis to conduction disturbances during progression of AF has not been studied yet.

Methods and results

During cardiac surgery, epicardial high-density mapping was performed in patients with acutely induced (aAF, n = 11), pAF (n = 12), and longstanding persistent AF (persAF, n = 9) on the right atrial (RA) wall, the posterior left atrial wall (pLA) and the LA appendage (LAA). In RA appendages, overall and endomysial (myocyte-to-myocyte distances) fibrosis and connexin 43 (Cx43) distribution were quantified. Unipolar AF electrogram analysis showed a more complex pattern with a larger number of narrower waves, more breakthroughs and a higher fractionation index (FI) in persAF compared with aAF and pAF, with no differences between aAF and pAF. The FI was consistently higher at the pLA compared with the RA. Structurally, Cx43 lateralization increased with AF progression (aAF = 7.5 ± 8.9%, pAF = 24.7 ± 11.1%, persAF = 35.1 ± 11.4%, P < 0.001). Endomysial but not overall fibrosis correlated with AF complexity (r = 0.57, P = 0.001; r = 0.23, P = 0.20; respectively).

Conclusions

Atrial fibrillation complexity is highly variable in patients with pAF, but not significantly higher than in patients with acutely induced AF, while in patients with persistent AF complexity is higher. Among the structural alterations studied, endomysial fibrosis, but not overall fibrosis, is the strongest determinant of AF complexity.

Alcohol intake and bradyarrhythmia risk: a cohort study of 407 948 individuals

AIMS 

There is a paucity of epidemiological evidence on alcohol and the risk of bradyarrhythmias. We thus characterized associations of total and beverage-specific alcohol consumption with incident bradyarrhythmias using data from the UK Biobank.

METHODS AND RESULTS 

Alcohol consumption reported at baseline was calculated as UK standard drinks (8 g alcohol)/week. Bradyarrhythmia events were defined as sinus node dysfunction (SND), high-level atrioventricular block (AVB), and permanent pacemaker implantations. Outcomes were assessed through hospitalization and death records, and dose-response associations were characterized using Cox regression models with correction for regression dilution bias. We studied 407 948 middle-aged individuals (52.4% female). Over a median follow-up time of 11.5 years, a total of 8 344 incident bradyarrhythmia events occurred. Increasing total alcohol consumption was not associated with an increased risk of bradyarrhythmias. Beer and cider intake were associated with increased bradyarrhythmia risk up to 12 drinks/week; however, no significant associations were observed with red wine, white wine, or spirit intake. When bradyarrhythmia outcomes were analysed separately, a negative curvilinear was observed for total alcohol consumption and risk of SND, but no clear association with AVB was observed.

CONCLUSION 

In this predominantly White British cohort, increasing total alcohol consumption was not associated with an increased risk of bradyarrhythmias. Associations appeared to vary according to the type of alcoholic beverage and between different types of bradyarrhythmias. Further epidemiological and experimental studies are required to clarify these findings.

Autonomic Afferent Dysregulation in Atrial Fibrillation

OBJECTIVES

This study sought to evaluate the role of cardiac afferent reflexes in atrial fibrillation (AF).

BACKGROUND

Efferent autonomic tone is not associated with atrial remodeling and AF persistence. However, the role of cardiac afferents is unknown.

METHODS

Individuals with nonpermanent AF (n = 48) were prospectively studied (23 in the in-AF group and 25 in sinus rhythm [SR]) with 12 matched control subjects. We performed: 1) low-level lower body negative pressure (LBNP), which decreases cardiac volume, offloading predominantly cardiac afferent (volume-sensitive) low-pressure baroreceptors; 2) Valsalva reflex (predominantly arterial high-pressure baroreceptors); and 3) isometric handgrip reflex (both baroreceptors). We measured beat-to-beat mean arterial pressure (MAP) and heart rate (HR). LBNP elicits reflex vasoconstriction, estimated using venous occlusion plethysmography-derived forearm blood flow (∝1/vascular resistance), maintaining MAP. To assess reversibility, we repeated LBNP (same day) after 1-hour low-level tragus stimulation (in n = 5 in the in-AF group and n = 10 in the in-SR group) and >6 weeks post-cardioversion (n = 7).

RESULTS

The 3 groups were well matched for age (59 ± 12 years, 83% male), body mass index, and risk factors (P = NS). The in-AF group had higher left atrial volume (P < 0.001) and resting HR (P = 0.01) but similar MAP (P = 0.7). The normal LBNP vasoconstriction (-49 ± 5%) maintaining MAP (control subjects) was attenuated in the in-SR group (-12 ± 9%; P = 0.005) and dysfunctional in the in-AF group (+11 ± 6%; P < 0.001), in which MAP decreased and HR was unchanged. Valsalva was normal throughout. Handgrip MAP response was lowest in the in-AF group (P = 0.01). Interestingly, low-level tragus stimulation and cardioversion improved LBNP vasoconstriction (-48 ± 15%; P = 0.04; and -32 ± 9%; P = 0.02, respectively).

CONCLUSIONS

Cardiac afferent (volume-sensitive) reflexes are abnormal in AF patients during SR and dysfunctional during AF. This could contribute to AF progression, thus explaining "AF begets AF." (Characterisation of Autonomic function in Atrial Fibrillation [AF-AF Study]; ACTRN12619000186156).

Computerized tomography image correlation of His bundle/deep septal pacing location and outcomes: an analysis from the Canberra HIs bundle/deep septal Pacing Study (CHIPS)

Background

Localisation of the conduction system under fluoroscopy is not easy and the ideal location of the pacing leads in physiological pacing is still being debated.

Objective

The primary aim was to assess the lead locations using cardiac CT scan. Secondary aims were clinical outcomes including success and safety of the procedure and lead performance.

Methods

Of the 100 consecutive patients who received physiological pacing, 34 patients underwent follow-up cardiac CT scan. The four different types of pacing were identified as His bundle (HBP), para-Hisian, left bundle branch (LBBP), and deep septal pacing.

Results

Most patients had successful HBP via the right atrium (RA) (87.5%) as compared to the right ventricle (RV) (12.5%). Lower thresholds were observed when leads were placed within 2 mm of the junction of the membranous and muscular ventricular septum. Unlike HBP, LBBP was possible at a wide region of the septum and selective capture of individual fascicles was feasible. LBBP showed deeper penetration of leads into the septum, as compared to deep septal pacing (70% vs. 45%). Approximately, 80% of patients did not have an intra-ventricular portion of the membranous septum.

Conclusions

The anterior part of the atrio-ventricular (AV) septum at the junction between the membranous and muscular septum via RA appeared to be the best target to successfully pace His bundle. LBBP was possible at a wide region of the septum and selective capture of individual fascicle was feasible. Adequate depth of penetration of lead was very important to capture the left bundle.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10840-022-01133-z.

Predictive role of atrial fibrillation in cognitive decline: a systematic review and meta-analysis of 2.8 million individuals

Aims

To systematic review and meta-analyse the association and mechanistic links between atrial fibrillation (AF) and cognitive impairment.

Methods and results

PubMed, EMBASE, and Cochrane Library were searched up to 27 March 2021 and yielded 4534 citations. After exclusions, 61 were analysed; 15 and 6 studies reported on the association of AF and cognitive impairment in the general population and post-stroke cohorts, respectively. Thirty-six studies reported on the neuro-pathological changes in patients with AF; of those, 13 reported on silent cerebral infarction (SCI) and 11 reported on cerebral microbleeds (CMB). Atrial fibrillation was associated with 39% increased risk of cognitive impairment in the general population [n = 15: 2 822 974 patients; hazard ratio = 1.39; 95% confidence interval (CI) 1.25–1.53, I² = 90.3%; follow-up 3.8–25 years]. In the post-stroke cohort, AF was associated with a 2.70-fold increased risk of cognitive impairment [adjusted odds ratio (OR) 2.70; 95% CI 1.66–3.74, I² = 0.0%; follow-up 0.25–3.78 years]. Atrial fibrillation was associated with cerebral small vessel disease, such as white matter hyperintensities and CMB (n = 8: 3698 patients; OR = 1.38; 95% CI 1.11–1.73, I² = 0.0%), SCI (n = 13: 6188 patients; OR = 2.11; 95% CI 1.58–2.64, I² = 0%), and decreased cerebral perfusion and cerebral volume even in the absence of clinical stroke.

Conclusion

Atrial fibrillation is associated with increased risk of cognitive impairment. The association with cerebral small vessel disease and cerebral atrophy secondary to cardioembolism and cerebral hypoperfusion may suggest a plausible link in the absence of clinical stroke. PROSPERO CRD42018109185.

Atrial fibrillation incidence, prevalence, predictors, and adverse outcomes in acute coronary syndromes: A pooled analysis of data from 8 million patients

OBJECTIVE

To summarize data on the prevalence/incidence, risk factors and prognosis of atrial fibrillation (AF) in patients with acute coronary syndromes (ACS).

METHODS

MEDLINE, Embase, and Web of Science were searched to identify all published studies providing relevant data through August 23, 2020. Random-effects meta-analysis method was used to pool estimates.

RESULTS

We included 109 studies reporting data from a pooled population of 8 239 364 patients. The prevalence rates were 5.8% for pre-existing AF, 7.3% for newly diagnosed AF, and 11.3% for prevalent (total) AF, in patients with ACS. Predictors of newly diagnosed AF included age (per year increase) (adjusted odds ratio [aOR]: 1.05), C-reactive protein (aOR: 1.49), left atrial (LA) diameter (aOR: 1.08), LA dilatation (aOR: 2.32), left ventricular ejection fraction <40% (aOR: 1.82), hypertension (aOR: 1.87), and Killip ˃ 1 (aOR: 1.85), p < .01 in all analyzes. Newly diagnosed AF was associated with an increased risk of acute heart failure (adjusted hazard ratio [aHR]: 3.20), acute kidney injury (aHR: 3.09), re-infarction (aHR: 1.96), stroke (aHR: 2.15), major bleeding (aHR: 2.93), and mortality (aHR: 1.80) in the short term; and with an increased risk of heart failure (aHR: 2.21), stroke (aHR: 1.75), mortality (aHR: 1.67), CV mortality (aHR: 2.09), sudden cardiac death (aHR: 1.53), and a composite of major adverse cardiovascular events (aHR: 1.54) in the long term (beyond 1 month), p < .05 in all analyzes.

CONCLUSION

One in nine patients with ACS has AF, with a high proportion of newly diagnosed AF. AF, in particular newly diagnosed AF, is associated with poor short-term and long-term outcomes in patients with ACS.

Heart failure with preserved ejection fraction: An alternative paradigm to explain the clinical implications of atrial fibrillation

Atrial fibrillation (AF) is associated with exercise intolerance, stroke, and all-cause mortality. However, whether this can be solely attributable to the arrhythmia itself or alternative mechanisms remains controversial. Heart failure with preserved ejection (HFpEF) commonly coexists with AF and may contribute to the poor outcomes associated with AF. Indeed, several invasive hemodynamic studies have confirmed that patients with AF are at increased risk of underlying HFpEF and that the presence of HFpEF may have important prognostic implications in these patients.

Mechanistically, AF and HFpEF are closely linked. Both conditions are driven by the presence of common cardiovascular risk factors and are associated with left atrial (LA) myopathy, characterized by mechanical and electrical dysfunction. Progressive worsening of this left atrial (LA) myopathy is associated with both increased AF burden and worsening HFpEF. In addition, there is growing evidence to suggest that worsening LA myopathy is associated with poorer outcomes in both conditions and that reversal of the LA myopathy could improve outcomes. In this review article, we will present the epidemiologic and mechanistic evidence underlying the common coexistence of AF and HFpEF, discuss the importance of a progressive LA myopathy in the pathogenesis of both conditions, and review the evidence from important invasive hemodynamic studies. Finally, we will review the prognostic implications of HFpEF in patients with AF and discuss the relative merits of AF burden reduction vs HFpEF reduction in improving outcomes of patients with AF and HFpEF.

Cardiac Implantable Electronic Devices: Reoperations and the Competing Risk of Death

BACKGROUND

The use of cardiac implantable electronic devices (CIED), which includes pacemakers, implantable cardioverter-defibrillators (ICD), cardiac resynchronisation therapy pacemakers (CRT-P) and cardiac resynchronisation therapy defibrillators (CRT-D) has increased over the past 20 years, but there is a lack of real world evidence on the longevity of these devices in the older population which is essential to inform health care delivery and support clinical decisions.

METHODS AND RESULTS

We conducted a retrospective cohort study using data from the Australian Government Department of Veterans' Affairs database. The cohort consisted of people who had a CIED procedure between 2005 and 2015. The cumulative risk of generator replacement/reoperations was estimated accounting for the competing risk of death. A total of 16,662 patients were included. In pacemaker recipients with an average age of 85 years, the 5-year risk of reoperation ranged from 2.8% in single chamber, 3.6% in dual chamber to 7.6% in CRT-P recipients, while the 5-year risk of dying with the index pacemaker in situ was 63% in single chamber, 46% in dual chamber and 56% in CRT-P recipients. In defibrillator recipients with an average age of 80 years, the 5-year risk of reoperation ranged from 11% in single chamber, 13% in dual chamber to 24% in CRT-D recipients, while the 5-year risk of dying with the index defibrillator in situ was 46% in single chamber, 40% in dual chamber and 41% in CRT-D recipients.

CONCLUSION

In this cohort of older patients the 5-year risk of generator reoperation was low in pacemaker recipients whereas up to one in four CRT-D recipients would have a reoperation within 5 years.

Prevalence and Assessment of Sleep-Disordered Breathing in Patients With Atrial Fibrillation: A Systematic Review and Meta-analysis

BACKGROUND

In this study, we sought to estimate the prevalence of concomitant sleep-disordered breathing (SDB) in patients with atrial fibrillation (AF) and to systematically evaluate how SDB is assessed in this population.

METHODS

We searched Medline, Embase and Cinahl databases through August 2020 for studies reporting on SDB in a minimum 100 patients with AF. For quantitative analysis, studies were required to have systematically assessed for SDB in consecutive AF patients. Pooled prevalence estimates were calculated with the use of the random effects model. Weighted mean differences and odds ratios were calculated when possible to assess the strength of association between baseline characteristics and SDB.

RESULTS

The search yielded 2758 records, of which 33 studies (n = 23,894 patients) met the inclusion criteria for qualitative synthesis and 13 studies (n = 2660 patients) met the meta-analysis criteria. The pooled SDB prevalence based on an SDB diagnosis cutoff of apnea-hypopnea index (AHI) ≥ 5/h was 78% (95% confidence interval [CI] 70%-86%; P < 0.001). For moderate-to-severe SDB (AHI ≥ 15/h), the pooled SDB prevalence was 40% (95% CI 32%-48%; P < 0.001). High degrees of heterogeneity were observed (I² = 96% and 94%, respectively; P < 0.001). Sleep testing with the use of poly(somno)graphy or oximetry was the most common assessment tool used (in 22 studies, 66%) but inconsistent diagnostic thresholds were used.

CONCLUSIONS

SDB is highly prevalent in patients with AF. Wide variation exists in the diagnostic tools and thresholds used to detect concomitant SDB in AF. Prospective systematic testing for SDB in unselected cohorts of AF patients may be required to define the true prevalence of SDB in this population.

Quality indicators for the care and outcomes of adults with atrial fibrillation

AIMS

To develop quality indicators (QIs) that may be used to evaluate the quality of care and outcomes for adults with atrial fibrillation (AF).

METHODS AND RESULTS

We followed the ESC methodology for QI development. This methodology involved (i) the identification of the domains of AF care for the diagnosis and management of AF (by a group of experts including members of the ESC Clinical Practice Guidelines Task Force for AF); (ii) the construction of candidate QIs (including a systematic review of the literature); and (iii) the selection of the final set of QIs (using a modified Delphi method). Six domains of care for the diagnosis and management of AF were identified: (i) Patient assessment (baseline and follow-up), (ii) Anticoagulation therapy, (iii) Rate control strategy, (iv) Rhythm control strategy, (v) Risk factor management, and (vi) Outcomes measures, including patient-reported outcome measures (PROMs). In total, 17 main and 17 secondary QIs, which covered all six domains of care for the diagnosis and management of AF, were selected. The outcome domain included measures on the consequences and treatment of AF, as well as PROMs.

CONCLUSION

This document defines six domains of AF care (patient assessment, anticoagulation, rate control, rhythm control, risk factor management, and outcomes), and provides 17 main and 17 secondary QIs for the diagnosis and management of AF. It is anticipated that implementation of these QIs will improve the quality of AF care.

Rationale and design of the IRON-AF study: a double-blind, randomised, placebo-controlled study to assess the effect of intravenous ferric carboxymaltose in patients with atrial fibrillation and iron deficiency

INTRODUCTION

Atrial fibrillation (AF) is associated with significantly impaired quality-of-life. Iron deficiency (ID) is prevalent in patients with AF. Correction of ID in other patient populations with intravenous iron supplementation has been shown to be a safe, convenient and effective way of improving exercise tolerance, fatigue and quality-of-life. The IRON-AF (Effect of Iron Repletion in Atrial Fibrillation) study is designed to assess the effect of iron repletion with intravenous ferric carboxymaltose in patients with AF and ID.

METHODS AND ANALYSIS

The IRON-AF study is a double-blind, randomised controlled trial that will recruit at least 84 patients with AF and ID. Patients will be randomised to receive infusions of either ferric carboxymaltose or placebo, given in repletion and then maintenance doses. The study will have follow-up visits at weeks 4, 8 and 12. The primary endpoint is change in peak oxygen uptake from baseline to week 12, as measured by cardiopulmonary exercise testing (CPET) on a cycle ergometer. Secondary endpoints include changes in quality-of-life and AF disease burden scores, blood parameters, other CPET parameters, transthoracic echocardiogram parameters, 6-minute walk test distance, 7-day Holter/Event monitor burden of AF, health resource utilisation and mortality.

ETHICS AND DISSEMINATION

The study protocol has been approved by the Central Adelaide Local Health Network Human Research Ethics Committee, Australia. The results of this study will be disseminated through publications in peer-reviewed journals and conference presentations.

TRIAL REGISTRATION NUMBER

Australian New Zealand Clinical Trials Registry (ACTRN12620000285954).