Quality of Warfarin Anticoagulation in Indigenous and Non-Indigenous Australians With Atrial Fibrillation

BACKGROUND

Studies have shown that suboptimal anticoagulation quality, as measured by time in therapeutic range (TTR), affects a significant percentage of patients with atrial fibrillation (AF). However, TTR has not been previously characterised in Indigenous Australians who experience a greater burden of AF and stroke.

METHOD

Indigenous and non-Indigenous Australians with AF on warfarin anticoagulation therapy were identified from a large tertiary referral centre between 1999 and 2012. Time in therapeutic range was calculated as a proportion of daily international normalised ratio (INR) values between 2 and 3 for non-valvular AF and 2.5 to 3.5 for valvular AF. INR values between tests were imputed using the Rosendaal technique. Linear regression models were employed to characterise predictors of TTR.

RESULTS

Five hundred and twelve (512) patients with AF on warfarin were included (88 Indigenous and 424 non-Indigenous). Despite younger age (51±13 vs 71±12 years, p<0.001), Indigenous Australians had greater valvular heart disease, diabetes, and alcohol excess compared to non-Indigenous Australians (p<0.05 for all). Time in therapeutic range was significantly lower in Indigenous compared to non-Indigenous Australians (40±29 vs 50±31%, p=0.006). Univariate predictors of poorer TTR included Indigenous ethnicity, younger age, diuretic use, and comorbidities, such as valvular heart disease, heart failure and chronic obstructive pulmonary disease (p<0.05 for all). Valvular heart disease remained a significant predictor of poorer TTR in multivariate analyses (p=0.004).

CONCLUSION

Indigenous Australians experience particularly poor warfarin anticoagulation quality. Our data also suggest that many non-Indigenous Australians spend suboptimal time in therapeutic range. These findings reinforce the importance of monitoring warfarin anticoagulation quality to minimise stroke risk.

Association between physical activity and risk of incident arrhythmias in 402 406 individuals: evidence from the UK Biobank cohort

Aims

Physical activity reduces cardiovascular disease burden and mortality, although its relationship with cardiac arrhythmias is less certain. The aim of this study was to assess the association between self-reported physical activity and atrial fibrillation (AF), ventricular arrhythmias and bradyarrhythmias, across the UK Biobank cohort.

Methods and results

We included 402 406 individuals (52.5% female), aged 40–69 years, with over 2.8 million person-years of follow-up who underwent self-reported physical activity assessment computed in metabolic equivalent-minutes per week (MET-min/wk) at baseline, detailed physical assessment and medical history evaluation. Arrhythmia episodes were diagnosed through hospital admissions and death reports. Incident AF risk was lower amongst physically active participants, with a more pronounced reduction amongst female participants [hazard ratio (HR) for 1500 vs. 0 MET-min/wk: 0.85, 95% confidence interval (CI) 0.74–0.98] than males (HR for 1500 vs. 0 MET-min/wk: 0.90, 95% CI 0.82–1.0). Similarly, we observed a significantly lower risk of ventricular arrhythmias amongst physically active participants (HR for 1500 MET-min/wk 0.78, 95% CI 0.64–0.96) that remained relatively stable over a broad range of physical activity levels between 0 and 2500 MET-min/wk. A lower AF risk amongst female participants who engaged in moderate levels of vigorous physical activity was observed (up to 2500 MET-min/wk). Vigorous physical activity was also associated with reduced ventricular arrhythmia risk. Total or vigorous physical activity was not associated with bradyarrhythmias.

Conclusion

The risk of AF and ventricular arrhythmias is lower amongst physically active individuals. These findings provide observational support that physical activity is associated with reduced risk of atrial and ventricular arrhythmias.

Epicardial and subcutaneous adipose tissue in Indigenous and non-Indigenous individuals: Implications for cardiometabolic diseases

BACKGROUND

Obesity is prevalent in Indigenous populations who exhibit significant differences in body fat composition. While excess regional adiposity can be partially inferred from clinical measurements, noninvasive imaging allows for direct quantification of specific fat depots. Epicardial fat is a visceral adipose tissue that has been strongly associated with cardiometabolic disease in other populations. However, this ectopic fat depot has yet to be characterized in Indigenous populations.

METHODS

We studied 100 individuals matched for ethnicity (Indigenous Australian and Caucasian descent), age, gender, and body mass index. Epicardial and subcutaneous adipose tissue volumes was quantified with computed tomography. Associations of ethnicity and adiposity measures were assessed using linear regression.

RESULTS

Indigenous individuals had significantly greater epicardial fat volumes compared to non-Indigenous individuals (95.8±37.5 vs 54.1±27.6cm³, p<0.001). In contrast, subcutaneous fat volumes were comparable in Indigenous compared to non-Indigenous individuals (22.1±15.1 vs 20.3±13.5cm³, p=0.54). Sequential adjustment for age, gender, comorbidities, biochemical parameters, and medication use did not attenuate the association between Indigenous ethnicity and greater epicardial fat volume in multivariable models (B=43.0, p<0.001). Furthermore, this association did not materially change with the inclusion of various adiposity measures, such as body mass index, subcutaneous adipose tissue, or weight.

CONCLUSIONS

Indigenous individuals have significantly greater epicardial fat, but similar subcutaneous fat volumes, compared to non-Indigenous individuals. This finding extends previous observations on body fat composition differences in these individuals, and supports the possibility that epicardial fat and other visceral adipose depots may be contributing to the greater burden of cardiovascular disease in Indigenous populations.

Clinical safety of ProMRI implantable cardioverter-defibrillator systems during head and lower lumbar magnetic resonance imaging at 1.5 Tesla

Magnetic resonance imaging (MRI) has long been contraindicated in patients with implanted pacemakers, defibrillators, and cardiac resynchronisation therapy (CRT) devices due to the risk of adverse effects through electromagnetic interference. Since many recipients of these devices will have a lifetime indication for an MRI scan, the implantable systems should be developed as ‘MRI-conditional’ (be safe for the MRI environment under predefined conditions). We evaluated the clinical safety of several Biotronik ProMRI (‘MRI-conditional’) defibrillator and CRT systems during head and lower lumbar MRI scans at 1.5 Tesla. The study enrolled 194 patients at 22 sites in Australia, Canada, and Europe. At ≥9 weeks after device implantation, predefined, non-diagnostic, specific absorption rate (SAR)-intensive head and lower lumbar MRI scans (total ≈30 minutes per patient) were performed in 146 patients that fulfilled pre-procedure criteria. Three primary endpoints were evaluated: freedom from serious adverse device effects (SADEs) related to MRI and defibrillator/CRT (leading to death, hospitalisation, life-threatening condition, or potentially requiring implanted system revision or replacement), pacing threshold increase, and sensing amplitude decrease, all at the 1-month post-MRI clinical visit. No MRI-related SADE occurred. Lead values remained stable, measured in clinic and monitored daily by the manufacturer home monitoring technology.

P5657Fibrosis detected by late-gadolinium enhancement cardiac MRI is associated with atrial fibrillation and poorer ablation outcome: A meta-analysis

Background

Fibrosis is a hallmark of atrial fibrillation (AF) substrate. Recent data suggests that fibrosis detected by late-gadolinium enhancement (LGE) cardiac MRI (CMR) can predict AF. However, this relationship is not well described.

Objective

To delineate the association of cardiac fibrosis detected by LGE CMR with AF prevalence, AF recurrence after catheter ablation.

Methods

PubMed, Embase, Web of Science and Ovid MEDLINE were searched through November 2018, using the keywords: LGE AND Fibrosis AND CMR AND AF. Inclusion criteria: 1. LGE CMR of left atrial (LA LGE), ventricular wall (LV LGE) or right ventricular wall (RV LGE); 2. Studies reporting AF or recurrent arrhythmia after ablation; 3. Patient ≥18 years; and 4. ≥50 participants. Included studies were pooled in a random effects meta-analysis and reported as: mean difference (MD); unadjusted risk ratios (RR); adjusted hazard ratios (HR); and 95% confidence intervals (95% CI).

Results

After exclusions, we identified 9 studies (2,307 patients [65.9% males, 34.1% females]) conducted between 2003 and 2015 for LGE and AF. Fibrosis was present in 666 (35.1%) and detected by LV LGE in 7 (78%) and RV LGE in 2 (22%). The presence of AF was higher in patients positive for ventricular LGE than those negative, trending towards significance (RR: 1.51, 95% CI: 0.94–2.45, p=0.09). Pooled LV fibrosis associated with AF progression (RR [NPAF vs. PAF]: 2.2, 95% CI: 1.22–3.94, p=0.009). We identified 8 studies (2,041 patients [65.8% males, 34.2% females]) conducted between 2006 and 2016 reporting LGE and AF recurrence after catheter ablation, with fibrosis detected in 644 (31.6%) by LA LGE in 8 (88.9%, biased towards one centre). After 17.8±14.2 follow-up years, atrial fibrosis was significantly greater in recurrent AF than controls (MD: 4.97%, 95% CI: 1.23–8.7, p<0.01), and predicted 16% increased risk of AF recurrence (RR: 1.16, 95% CI: 1.07–1.26, p<0.05).

Conclusion

Myocardial fibrosis detected by LGE associates with prevalence and progress of AF and is predictive of AF recurrence post ablation. This further supports the proarrhythmic role of fibrosis and selection of patients for ablation therapy based on LGE.

P1234Weight fluctuation demonstrates residual atrial arrhythmogenic substrate despite final weight loss in a chronic sheep model: implications for epicardial fat and fibrofatty infiltrates

Background

Obesity-mediated epicardial adipose tissue (EAT) expansion drives fat cell infiltration which forms the unique substrate for atrial fibrillation (AF). The LEGACY study showed the benefits of weight loss but an attenuated response with weight fluctuation. How fluxes in weight impacts the atrial substrate in not known.

Objective

To investigate EAT and the atrial substrates due to weight fluctuation, with comparison to stable obesity.

Methods

We studied 24 sheep in 3 equal groups over 80 weeks: 1. Obesity induced by high calorie diet fed ad libitum; 2. Weight fluctuation induced by 20-week cycle of weight gain/loss (20:20:20:20); and 3. Lean controls fed quality hay to maintain baseline weight. All sheep underwent: daily weight measurement; haemodynamic and imaging assessments (cardiac MRI; dual-energy X-ray absorptiometry; and matrix assisted laser desorption infrared lipid imaging); electrophysiological studies and electroanatomic mapping; histological and structural analysis. Evaluations included: atrial voltage, conduction velocity, and refractoriness (7 sites, 2 cycle lengths), electrogram fractionation, EAT volume, fibro-fatty infiltration, myolysis of myocytes, and spatial distribution of intra-atrial lipids.

Results

The Table shows the group differences. Compared to reference controls, obesity demonstrated: Increased atrial volume and pressure, abnormal atrial electrical properties, expanded EAT and ensuing fibro-fatty infiltrations, and myolysis of myocytes. Despite comparable weight and EAT with controls, weight fluctuation resulted in extensive and severe fibro-fatty infiltrations, and twofold greater myolysis that persisted. Moreover, characteristic profiles and abundance of lipid species in the atrial myocardium were noted on further evaluation. More importantly, EAT and fibro-fatty infiltrates strongly correlated with increased atrial volume and pressure; with only fibro-fatty infiltrates correlating with fractionated electrograms (r=0.71, p<0.001) and conduction slowing (r=−0.59, p=0.006). Similarly, atrial myolysis exhibited significant correlations with atrial enlargement and haemodynamics, and electrical substrates (p<0.05 for all).

Conclusions

Obesity induces fibro-fatty replacement of atrial myocytes and deterioration of contractile units, which may drive impaired electrical remodeling. Despite final weight loss, weight fluctuation demonstrates residual electro-structural, fibro-fatty and contractile substrates.

P6294NLRP3 inflammasome is activated in the atrium of an ovine model of sustained obesity

Introduction

Obesity and enhanced inflammatory response are two independent risk factors involved in the pathogenesis of atrial fibrillation (AF). Components of the NLRP3 inflammasome have been found to be expressed in cardiomyocytes and cardiac fibroblasts and that increased inflammasome activation contributes to the pathogenesis of AF. The NLRP3 inflammasome is a multi-protein signaling complex that is activated in two steps: 1st) a priming event that includes a NFκB-activating stimuli which increases the expression of pro-inflammatory cytokines, and 2nd) a triggering event that includes the assembly of the inflammasome complex and activation of caspase-1 which promotes the production of pro-inflammatory cytokines like interleukin 1 beta (IL-1b).

Purpose

We used a sheep model of sustained obesity to characterize the association between atrial myocardial fat infiltration, atrial activation of the NLRP3 inflammasome and the development of an atrial arrhythmogenic substrate for AF.

Methods

Eight sheep were fed ad libitum calorie-dense diet over 40 weeks to gain weight and were maintained in this state of sustained obesity for another 40 weeks. Eight lean, weight-controlled and aged-matched sheep served as control. Atrial fat infiltration was determined by oil-red staining and NLRP3 inflammasome activation was assessed by immunoblot in atrial whole-tissue lysate. Atrial effective refractory periods (aERPs) were evaluated (twice diastolic threshold, cycle length (CL) of 400 ms, S1S2 -protocol).

Results

Sustained obesity was associated with increased atrial fat infiltration (lean: 0.8±0.3% vs. obese: 2.3±1.2%, p=0.1) and shorter aERP (lean: 169±22ms vs. obese: 138±26ms, p=0.03). Protein levels of caspase-1 and mature IL-1β were significantly enhanced (p=0.04 and p=0.01, respectively). Further shortening of aERP correlated with increasing atrial protein levels of caspase-1 (r=0.59, p=0.02). In contrast, levels of TNFα and NFκB were not significantly changed in atria of sheep with sustained obesity.

Conclusions

Sustained obesity is associated with increased expression of NLRP3 inflammasome-related proteins and the development of an arrhythmogenic substrate for AF. Our study suggest that the increased activity is due to increased triggering, rather than increased gene transcription. Whether NLRP3 inflammasome activation represents a modifiable target to prevent AF in obesity warrants further study.

PREVEntion and regReSsive Effect of weight-loss and risk factor modification on Atrial Fibrillation: the REVERSE-AF study

Aims

Atrial fibrillation (AF) is a progressive disease. Obesity is associated with progression of AF. This study evaluates the impact of weight and risk factor management (RFM) on progression of the AF.

Methods and results

As described in the Long-Term Effect of Goal-Directed Weight Management in an Atrial Fibrillation Cohort: A Long-Term Follow-Up (LEGACY) Study, of 1415 consecutive AF patients, 825 had body mass index ≥ 27 kg/m2 and were offered weight and RFM. After exclusion, 355 were included for analysis. Weight loss was categorized as: Group 1 (<3%), Group 2 (3-9%), and Group 3 (≥10%). Change in AF type was determined by clinical review and 7-day Holter yearly. Atrial fibrillation type was categorized as per the Heart Rhythm Society consensus. There were no differences in baseline characteristic or follow-up duration between groups (P = NS). In Group 1, 41% progressed from paroxysmal to persistent and 26% from persistent to paroxysmal or no AF. In Group 2, 32% progressed from paroxysmal to persistent and 49% reversed from persistent to paroxysmal or no AF. In Group 3, 3% progressed to persistent and 88% reversed from persistent to paroxysmal or no AF (P < 0.001). Increased weight loss was significantly associated with greater AF freedom: 45 (39%) in Group 1, 69 (67%) in Group 2, and 116 (86%) in Group 3 (P ≤ 0.001).

Conclusion

Obesity is associated with progression of the AF disease. This study demonstrates the dynamic relationship between weight/risk factors and AF. Weight-loss management and RFM reverses the type and natural progression of AF.

No time to weight: obesity through life and AF risk

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Nightly sleep apnea severity in patients with atrial fibrillation: Potential applications of long-term sleep apnea monitoring

In patients with atrial fibrillation (AF), the prevalence of moderate-to-severe sleep-disordered breathing (SDB) ranges between 21% and 72% and observational studies have demonstrated that SDB reduces the efficacy of rhythm control strategies, while treatment with continuous positive airway pressure lowers the rate of AF recurrence. Currently, the number of apneas and hypopneas per hour (apnea-hypopnea-index, AHI) determined during a single overnight sleep study is clinically used to assess the severity of SDB. However, recent studies suggest that SDB-severity in an individual patient is not stable over time but exhibits a considerable night-to-night variability which cannot be detected by only one overnight sleep assessment. Nightly SDB-severity assessment rather than the single-night diagnosis by one overnight sleep study may better reflect the exposure to SDB-related factors and yield a superior metric to determine SDB-severity in the management of AF. In this review we discuss mechanisms of night-to-night SDB variability, arrhythmogenic consequences of night-to-night SDB variability, strategies for longitudinal assessment of nightly SDB-severity and clinical implications for screening and management of SDB in AF patients.

Feasibility, Safety, and Efficacy of Posterior Wall Isolation During Atrial Fibrillation Ablation

Background:

The posterior left atrium is an arrhythmogenic substrate that contributes to the initiation and maintenance of atrial fibrillation (AF); however, the feasibility, safety, and efficacy of posterior wall isolation (PWI) as an AF ablation strategy has not been widely reported.

Methods:

We undertook a systematic review and meta-analysis of studies performing PWI to assess (1) acute procedural success including the ability to achieve PWI and the number of procedure-related complications, (2) Long-term, clinical success including rates of arrhythmia recurrence and posterior wall reconnection, and (3) The efficacy of PWI compared with pulmonary vein isolation on preventing arrhythmia recurrence. MEDLINE, EMBASE, and Web of Science databases were searched in May 2018 to retrieve relevant studies. Results were pooled using a random effects model.

Results:

Seventeen studies (13 box isolation, 3 single ring isolation, and 1 debulking ablation) comprising 1643 patients (31.3% paroxysmal AF, left atrial diameter 41±3.1 mm) were included in the final analysis. In studies focusing specifically on PWI, the acute procedural success rate for achieving PWI was 94.1% (95% CI, 87.2%–99.3%). Single-procedure 12-month freedom from atrial arrhythmia was 65.3% (95% CI, 57.7%–73.9%) overall and 61.9% (54.2%–70.8%) for persistent AF. Randomized control trials comparing PWI to pulmonary vein isolation (3 studies, 444 patients) yielded conflicting results and could not confirm an incremental benefit to PWI. Fifteen major complications (0.1%), including 2 atrio-esophageal fistulas, were reported.

Conclusions:

PWI as an end point of AF ablation can be achieved in a large proportion of cases with good rates of 12-month freedom from atrial arrhythmia. Although the procedure-related complication rate is low, it did not eliminate the risk of atrio-esophageal fistula.

Registration:

URL: http://www.crd.york.ac.uk/prospero . PROSPERO registration number: CRD42018107212.

Increasing trends in hospitalisations due to atrial fibrillation in Australia from 1993 to 2013

OBJECTIVE

The aim of this study is to characterise hospitalisations due to atrial fibrillation (AF) compared with two other common cardiovascular conditions, myocardial infarction (MI) and heart failure (HF), in addition to the associated economic burden of these hospitalisations and contribution of AF-related procedures.

METHODS

The primary outcome measure was the rate of increase of AF, MI and HF hospitalisations from 1993 to 2013. The rate of increase of AF-related procedures including cardioversion and ablation were also collected, in addition to direct costs associated with hospitalisations for each of these three conditions.

RESULTS

AF hospitalisations increased 295% over the 21-year period to a total of 61 424 in 2013. In comparison, MI and HF hospitalisations increased by only 73% and 39%, respectively, over the same period. Considering population changes, there was an annual increase in AF hospitalisations of 5.2% (incidence rate ratio [IRR] 1.052; 95% CI 1.046 to 1.059; p<0.001). In contrast, there was a 2.2% increase per annum for MI (IRR 1.022; 95% CI 1.017 to 1.027; p<0.001) and negligible annual change for HF hospitalisations (IRR 1.000; 95% CI 0.997 to 1.002; p=0.78). Cardioversion and AF ablation increased by 10% and 26% annually, respectively. AF hospitalisation costs rose by 479% over the 21-year period, an increase that was more than double that of MI and HF.

CONCLUSIONS

The burden of AF hospitalisations continues to rise unabated. AF has now surpassed both MI and HF hospitalisations and represents a growing cost burden. New models of healthcare delivery are required to stem this growing healthcare burden.