Atrial fibrillation: current knowledge and future directions in epidemiology and genomics

[Myocardial Infarction in the Group of Patients With Atrial Fibrillation]

Prevalence of patients with myocardial infarction (MI) and atrial fibrillation (AF) has been growing every year. These patients represent a highest risk group and, thus, require special attention of clinicians. The article foсused on mechanisms of the AF and MI interaction, special aspects of prediction depending on the type of AF and MI, and the issue of antithrombotic therapy in this patient category. A group of AF-associated, embologenic MIs was isolated, and diagnostic criteria and therapeutic regimens were provided.

Left atrial mechanical remodelling assessed as the velocity of left atrium appendage wall motion during atrial fibrillation is associated with maintenance of sinus rhythm after electrical cardioversion in patients with persistent atrial fibrillation

The velocity of left atrium appendage (LAA) wall motion during atrial fibrillation (AF) is a potential marker of mechanical remodelling. In this study, we investigated whether the velocity of LAA wall motion during AF predicted the success of electrical cardioversion and long-term sinus rhythm maintenance. Standard echocardiographic data were obtained by transthoracic echocardiography, and LAA wall motion velocities were measured by transoesophageal echocardiography. With logistic regression and receiver operating characteristic curve analyses, we related echocardiographic and clinical data to cardioversion outcomes and sinus rhythm maintenance at 12 months. Of 121 patients prospectively included in the study, electrical cardioversion restored sinus rhythm in 97 (81.2%), and 51 (42%) patients maintained sinus rhythm at 12 months. Patients in whom cardioversion restored sinus rhythm had higher LAA wall motion velocities than did the patients with failed cardioversions (p <0.001). Compared to patients with AF at 12 months, patients who maintained sinus rhythm had lower maximum and end-diastolic left atrial volumes (p ≤ 0.01), lower E/e’ ratios (p = 0.005), higher s’ values (p = 0.013), and higher LAA motion velocities (p < 0.001). On multivariate logistic regression, only LAA wall motion velocity and E/e’ ratios remained significant predictors of sinus rhythm maintenance at 12 months (p ≤ 0.04). LAA wall motion velocity was also a significant predictor of sinus rhythm maintenance when corrected for clinical variables (p = 0.039). Conclusion: LAA wall motion velocity, as a marker of mechanical remodelling, can predict short-term and long-term sinus rhythm maintenance after electrical cardioversion in AF.

Cost-effectiveness of Dabigatran Compared With Rivaroxaban for Prevention of Stroke and Systemic Embolism in Patients With Atrial Fibrillation in China

PURPOSE

In China, dabigatran and rivaroxaban are the only approved non-vitamin K antagonist oral anticoagulants for the treatment of atrial fibrillation (AF). The goal of this article was to assess the cost-effectiveness of dabigatran versus rivaroxaban for the prevention of stroke and systemic embolism in Chinese patients with AF from the perspective of the Chinese health care system.

METHODS

A Markov model was constructed to estimate the cost-effectiveness of dabigatran versus rivaroxaban. Clinical events were modeled for a lifetime horizon, based on clinical efficacy data from indirect treatment comparisons. The weighted average of the most recent prices of these 2 drugs was used as the drug acquisition cost. Other costs, including follow-up costs and event costs, were collected by using a survey from a panel of local experts. Utility inputs (health state utilities, clinical event disutilities, and event history utility) were obtained from published literature. Sensitivity analyses that included scenario analyses and a probabilistic sensitivity analysis were conducted to examine the robustness of the economic model.

FINDINGS

Over a lifetime, patients treated with dabigatran experienced fewer ischemic strokes (2.14 dabigatran vs 2.61 rivaroxaban) and fewer intracranial hemorrhage (0.48 vs 0.94) per 100 patient-years. In the base case analysis, dabigatran had an incremental cost of ¥28,128 but with higher life years (10.38 vs 10.14) and quality-adjusted life years (QALYs) (7.95 vs 7.70). The resulting incremental cost-effectiveness ratio of ¥112,910 per QALY gained and net monetary benefit of ¥12,214 versus rivaroxaban showed that dabigatran was a cost-effective alternative to rivaroxaban. Extensive sensitivity analyses indicated that the results were robust over a wide range of inputs. The probabilistic sensitivity analysis indicated that dabigatran was cost-effective in 84.2% of the 10,000 Monte Carlo simulations compared with rivaroxaban.

IMPLICATIONS

Dabigatran reduced the occurrence of clinical events and increased QALYs compared with rivaroxaban. The use of dabigatran for the prevention of stroke and systemic embolism is a cost-effective option compared with rivaroxaban among patients with AF in China.

Atrial Fibrillation, Brain Volumes, and Subclinical Cerebrovascular Disease (from the Atherosclerosis Risk in Communities Neurocognitive Study [ARIC-NCS])

The aim of the present study was to investigate the association between atrial fibrillation (AF) and total and regional brain volumes among participants in the community-based Atherosclerosis Risk in Communities Neurocognitive study (ARIC-NCS). A total of 1,930 participants (130 with AF) with a mean age of 76.3 ± 5.2, who underwent 3T brain MRI scans in 2011 to 2013 were included. Prevalent AF was ascertained from study ECGs and hospital discharge codes. Brain volumes were measured using FreeSurfer image analysis software. Markers of subclinical cerebrovascular disease included lobar microhemorrhages, subcortical microhemorrhages, cortical infarcts, subcortical infarcts, lacunar infarcts, and volume of white matter hyperintensities. Linear regression models were used to assess the associations between AF status and brain volumes. In adjusted analyses, AF was not associated with markers of subclinical cerebrovascular disease. However, AF was associated with smaller regional brain volumes (including temporal, occipital, and parietal lobes; deep gray matter; Alzheimer disease signature region; and hippocampus [all p <0.05]) after controlling for demographics, cardiovascular risk factors, prevalent cardiovascular disease, and markers of subclinical cerebrovascular disease. Subgroup analysis revealed a significant interaction between AF and total brain volume with respect to age (p = 0.02), with associations between AF and smaller brain volumes being stronger for older individuals. In conclusion, AF was associated with smaller brain volumes, and the association was stronger among older individuals. This finding may be related to the longer exposure period of the older population to AF or the possibility that older people are more susceptible to the effects of AF on brain volume.

Noninvasive biomarker-based risk stratification for development of new onset atrial fibrillation after coronary artery bypass surgery

BACKGROUND

Postoperative atrial fibrillation (PoAF) is a common complication after cardiac surgery. A pre-existing atrial substrate appears to be important in postoperative development of dysrhythmia, but its preoperative estimation is challenging. We tested the hypothesis that a combination of clinical predictors, noninvasive surrogate markers for atrial fibrosis defining abnormal left atrial (LA) mechanics, and biomarkers of collagen turnover is superior to clinical predictors alone in identifying patients at-risk for PoAF.

METHODS

In patients without prior AF undergoing coronary artery bypass grafting, concentrations of biomarkers reflecting collagen synthesis and degradation, extracellular matrix, and regulatory microRNA-29s were determined in serum from preoperative blood samples and correlated to atrial fibrosis extent, alteration in atrial deformation properties determined by 3D speckle-tracking echocardiography, and AF development.

RESULTS

Of 90 patients without prior AF, 34 who developed PoAF were older than non-PoAF patients (72.04 ± 10.7 y; P = 0.043) with no significant difference in baseline comorbidities, LA size, or ventricular function. Global (P = 0.007) and regional longitudinal LA strain and ejection fraction (P = 0.01) were reduced in PoAF vs. non-PoAF patients. Preoperative amino-terminal-procollagen-III-peptide (PIIINP) (103.1 ± 39.7 vs. 35.1 ± 19.3; P = 0.041) and carboxy-terminal-procollagen-I-peptide levels were elevated in PoAF vs. non-PoAF patients with a reduction in miR-29 levels and correlated with atrial fibrosis extent. Combining age as the only significant clinical predictor with PIIINP and miR-29a provided a model that identified PoAF patients with higher predictive accuracy.

CONCLUSIONS

In patients without a previous history of AF, using age and biomarkers of collagen synthesis and regulation, a noninvasive tool was developed to identify those at risk for new-onset PoAF.

Temporal trends in prevalence and outcomes of atrial fibrillation in patients undergoing percutaneous coronary intervention

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia in patients undergoing percutaneous coronary intervention (PCI).

HYPOTHESIS

Large administrative data may provide further insight into temporal trends in the prevalence and burden of AF in patients who underwent PCI.

METHODS

Using the National Inpatient Sample database in the U.S., AF patients ≥18 years who underwent PCI between 2005 and 2014 and were identified by the International Classification of Diseases, ninth revision, Clinical Modification, were examined. In-hospital mortality, morbidity, resource use, and medical costs were evaluated in crude and propensity-matched analyses.

RESULTS

Among an estimated 6 272 232 hospitalizations, of patients undergoing PCI, AF prevalence was 9.9% and steadily increased from 8.6% to 12.0% between 2005 and 2014 (P < .001); there was also a greater proportion of comorbidities. There was a marked increase in AF prevalence among those aged ≥65 years and those undergoing elective PCIs. AF was independently associated with higher in-hospital mortality and higher rates of transient ischaemic attack/stroke, bleeding complications, and non-home discharge. Excessive in-hospital mortality, stroke rate, gastrointestinal bleeding, blood transfusion, length of stay, and costs among AF hospitalizations were consistently observed throughout the study period.

CONCLUSION

AF becomes more prevalent in patients undergoing PCI, possibly due to a higher comorbidity, particularly in elderly patients with non-acute indications. Less favorable trends in mortality, bleeding, and stroke among AF patients who underwent PCI were consistent over time. Continuous efforts are needed to improve outcomes and manage strategies for AF patients undergoing PCI.

Evaluation of Risk Prediction Models of Atrial Fibrillation (from the Multi-Ethnic Study of Atherosclerosis [MESA])

Atrial fibrillation (AF) is prevalent and strongly associated with higher cardiovascular disease (CVD) risk. Machine learning is increasingly used to identify novel predictors of CVD risk, but prediction improvements beyond established risk scores are uncertain. We evaluated improvements in predicting 5-year AF risk when adding novel candidate variables identified by machine learning to the CHARGE-AF Enriched score, which includes age, race/ethnicity, height, weight, systolic and diastolic blood pressure, current smoking, use of antihypertensive medication, diabetes, and NT-proBNP. We included 3,534 participants (mean age, 61.3 years; 52.0% female) with complete data from the prospective Multi-Ethnic Study of Atherosclerosis. Incident AF was defined based on study electrocardiograms and hospital discharge diagnosis ICD-9 codes, supplemented by Medicare claims. Prediction performance was evaluated using Cox regression and a parsimonious model was selected using LASSO. Within 5 years of baseline, 124 participants had incident AF. Compared with the CHARGE-AF Enriched model (c-statistic, 0.804), variables identified by machine learning, including biomarkers, cardiac magnetic resonance imaging variables, electrocardiogram variables, and subclinical CVD variables, did not significantly improve prediction. A 23-item score derived by machine learning achieved a c-statistic of 0.806, whereas a parsimonious model including the clinical risk factors age, weight, current smoking, NT-proBNP, coronary artery calcium score, and cardiac troponin-T achieved a c-statistic of 0.802. This analysis confirms that the CHARGE-AF Enriched model and a parsimonious 6-item model performed similarly to a more extensive model derived by machine learning. In conclusion, these simple models remain the gold standard for risk prediction of AF, although addition of the coronary artery calcium score should be considered.

MicroRNA-133 suppresses ZFHX3-dependent atrial remodelling and arrhythmia

AIM

Atrial fibrillation (AF) is an important cause of morbidity and mortality in the modern world. Loss-of-function mutation in the zinc finger homeobox 3 gene (ZFHX3) is associated with increased risk of AF. MicroRNAs (miRNAs) participate in arrhythmogenesis, and thus miRNA modulators may be applicable as therapeutic modalities for AF. However, the altered miRNA profiles after ZFHX3 knockdown (KD) remain unclear. This study aimed to analyse the changes of miRNA expression in loss-of-function of ZFHX3 and the effect of miRNA modulation on atrial arrhythmias in this model.

METHODS

We performed small RNA deep sequencing on ZFHX3-KD and control HL-1 mouse atrial myocytes. The effect of miRNAs on ZFHX3-dependent atrial arrhythmia was evaluated through in vitro and in vivo assays in mice.

RESULTS

Among the differentially expressed miRNAs, 11 were down-regulated and 6 were up-regulated after ZFHX3 KD. Quantitative real-time PCR analysis confirmed that after ZFHX3 KD, miR-133a and miR-133b were significantly down-regulated, whereas miR-184 was the most significantly up-regulated. DIANA-miRPath analysis suggested that miR-133a/b down-regulation increases the targeted signalling of miR-133 (ie, adrenergic, Wnt/calcium and fibroblast growth factor receptor 1 signalling), which could contribute to pathological remodelling of cardiomyocytes. These results were confirmed through Western blotting. After transfection of miR-133a/b mimics in ZFHX3-KD cells, miR-133a/b levels increased, accompanied by the inhibition of their target signalling. Treatment with miR-133a/b mimics diminished ZFHX3 KD-induced atrial ectopy in mice.

CONCLUSION

ZFHX3-KD promotes distinct miRNA expressional changes in atrial myocytes. MiR-133a/b mimics may reverse signalling of ZFHX3 KD-mediated cardiac remodelling and atrial arrhythmia.

Atrial Fibrillation and Deterioration in Cognitive Function

The link between atrial fibrillation and cognitive decline and dementia has gained interest of the medical community lately. More research is being conducted to prevent and or delay this morbidity as no curative therapy is available for cognitive decline and dementia. The exact mechanism of causation is unclear. Multiple pathophysiological mechanisms have been implicated. Lately, treatment for atrial fibrillation including anticoagulation and catheter ablation therapies have shown to decrease the risk of deterioration of cognitive function. In this review we summarize epidemiologic studies linking the association, potential mechanisms, and impact of various modalities of therapy of atrial fibrillation on cognitive function outcomes.

Association of Race/Ethnicity With Oral Anticoagulant Use in Patients With Atrial Fibrillation: Findings From the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation II

Importance

Black and Hispanic patients are less likely than white patients to use oral anticoagulants for atrial fibrillation. Little is known about racial/ethnic differences in use of direct-acting oral anticoagulants (DOACs) for atrial fibrillation.

Objective

To assess racial/ethnic differences in the use of oral anticoagulants, particularly DOACs, in patients with atrial fibrillation.

Design, Setting, and Participants

This cohort study used data from the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation II, a prospective, US-based registry of outpatients with nontransient atrial fibrillation 21 years and older who were followed up from February 2013 to July 2016. Data were analyzed from February 2017 to February 2018.

Exposures

Self-reported race/ethnicity as white, black, or Hispanic.

Main Outcomes and Measures

The primary outcome was use of any oral anticoagulant, particularly DOACs. Secondary outcomes included the quality of anticoagulation received and oral anticoagulant discontinuation at 1 year.

Results

Of 12 417 patients, 11 100 were white individuals (88.6%), 646 were black individuals (5.2%), and 671 were Hispanic individuals (5.4%) with atrial fibrillation. After adjusting for clinical features, black individuals were less likely to receive any oral anticoagulant than white individuals (adjusted odds ratio [aOR], 0.75 [95% CI, 0.56, 0.99]) and less likely to receive DOACs if an anticoagulant was prescribed (aOR, 0.63 [95% CI, 0.49-0.83]). After further controlling for socioeconomic factors, oral anticoagulant use was no longer significantly different in black individuals (aOR, 0.78 [95% CI, 0.59-1.04]); among patients using oral anticoagulants, DOAC use remained significantly lower in black individuals (aOR, 0.73 [95% CI, 0.55-0.95]). There was no significant difference between white and Hispanic groups in use of oral anticoagulants. Among patients receiving warfarin, the median time in therapeutic range was lower in black individuals (57.1% [IQR, 39.9%-72.5%]) and Hispanic individuals (51.7% [interquartile range {IQR}, 39.1%-66.7%]) than white individuals (67.1% [IQR, 51.8%-80.6%]; P < .001). Black and Hispanic individuals treated with DOACs were more likely to receive inappropriate dosing than white individuals (black patients, 61 of 394 [15.5%]; Hispanic patients, 74 of 409 [18.1%]; white patients, 1003 of 7988 [12.6%]; P = .01). One-year persistence on oral anticoagulants was the same across groups.

Conclusions and Relevance

After controlling for clinical and socioeconomic factors, black individuals were less likely than white individuals to receive DOACs for atrial fibrillation, with no difference between white and Hispanic groups. When atrial fibrillation was treated, the quality of anticoagulant use was lower in black and Hispanic individuals. Identifying modifiable causes of these disparities could improve the quality of care in atrial fibrillation.

Pitx2c inhibition increases atrial fibroblast activity: Implications in atrial arrhythmogenesis

BACKGROUND

A Pitx2c deficiency increases the risk of atrial fibrillation (AF). Atrial structural remodelling with fibrosis blocks electrical conduction and leads to arrhythmogenesis. A Pitx2c deficiency enhances profibrotic transforming growth factor (TGF)-β expression and calcium dysregulation, suggesting that Pitx2c may play a role in atrial fibrosis. The purposes of this study were to evaluate whether a Pitx2c deficiency modulates cardiac fibroblast activity and study the underlying mechanisms.

MATERIALS AND METHODS

A migration assay, proliferation analysis, Western blot analysis and calcium fluorescence imaging were conducted in Pitx2c-knockdown human atrial fibroblasts (HAFs) using short hairpin (sh)RNA or small interfering (si)RNA.

RESULTS

Compared to control HAFs, Pitx2c-knockdown HAFs had a greater migration but a similar proliferative ability. Pitx2c-knockdown HAFs had a higher calcium influx with enhanced phosphorylation of calmodulin kinase II (CaMKII), α-smooth muscle actin and matrix metalloproteinase-2. In the presence of a CaMKII inhibitor (KN-93, 0.5 μmol/L), control and Pitx2c-knockdown HAFs exhibited similar migratory abilities.

CONCLUSION

These findings suggest that downregulation of Pitx2c may regulate atrial fibrosis through modulating calcium homeostasis, which may contribute to its role in anti-atrial fibrosis, and Pitx2c downregulation may change the atrial electrophysiology and AF occurrence through modulating fibroblast activity.

Prevalence and Characteristics of Subclinical Atrial Fibrillation in a Community-Dwelling Elderly Population: The ARIC Study

BACKGROUND

The prevalence of subclinical atrial fibrillation (AF) in the elderly general population is unclear. We sought to define the prevalence of subclinical AF in a community-based elderly population and to characterize subclinical AF and the incremental diagnostic yield of 4 versus 2 weeks of continuous ECG monitoring.

METHODS

We conducted a cross-sectional analysis within the community-based multicenter observational ARIC study (Atherosclerosis Risk in Communities) using visit 6 (2016-2017) data. The 2616 ARIC study participants who wore a leadless, ambulatory ECG monitor (Zio XT Patch) for up to 2 weeks were aged 79±5 years, 42% men, and 26% black. In a subset, 386 participants without clinically recognized AF wore the monitor twice, each time for up to 2 weeks. We characterized the prevalence of subclinical AF (ie, AF detected on the Zio XT Patch without clinically recognized AF) over 2 weeks of monitoring and the diagnostic yield of 4 versus 2 weeks of monitoring.

RESULTS

The prevalence of subclinical AF was 2.5%; the prevalence of subclinical AF was 3.3% among white men, 2.5% among white women, 2.1% among black men, and 1.6% among black women. Subclinical AF was mostly intermittent (75%). Among those with intermittent subclinical AF, 91% had AF burden ≤10% during the monitoring period. In a subset of 386 participants without clinical AF, 78% more subclinical AF was detected by 4 weeks versus 2 weeks of ECG monitoring.

CONCLUSIONS

In our study, the prevalence of subclinical AF was lower than previously reported and monitoring beyond 2 weeks provided substantial incremental diagnostic yield. Future studies should focus on individuals with higher risk to increase diagnostic yield and consider continuous monitoring duration longer than 2 weeks.

Echocardiographic assessment of left atrial morphology and function to predict maintenance of sinus rhythm after electrical cardioversion in patients with non-valvular persistent atrial fibrillation and normal function or mild dysfunction of left ventricle

BACKGROUND

The aim of this study was to assess whether echocardiographic measurements of left atrial (LA) morphology and function could predict sinus rhythm maintenance after electrical cardioversion among patients with atrial fibrillation (AF) and normal function or mild dysfunction of the left ventricle (LV).

METHODS

One hundred seventeen patients with persistent AF who underwent successful electrical cardioversion were prospectively enrolled. Echocardiography was performed one day subsequent to successful cardioversion. Patients were followed up clinically and electrocardiographically at 1, 6, and 12 months. At 12 months, 61 (52%) patients had maintained sinus rhythm (SR).

RESULTS

Compared to patients who maintained SR, those with AF recurrence had larger LAs, worse LA systolic function, and increased LV filling pressure. On multivariate stepwise logistic regression, E/A ratios (odds ratio [OR] 0.550, 95% confidence interval [CI] 0.341-0.886; p = 0.014) and E/e' ratios (OR 0.871, 95% CI 0.771-0.985; p = 0.027) were significant predictors of AF recurrence. On receiver operator characteristic curve analysis of AF recurrence at 12 months, the area under curve for both E/A and E/e' ratios were 0.726. With an E/A cutoff of 2.2, the sensitivity for predicting AF recur-rence at 12 months was 72%, and specificity was 73%. With an E/e' cutoff of 9.17, the sensitivity for predicting AF recurrence at 12 months was 72%, and specificity was 74%.

CONCLUSIONS

Left ventricular filling pressure assessed with E/A and E/e' ratios predict AF recurrence after electrical cardioversions among patients with AF and normal function of LV.

The imminent epidemic of atrial fibrillation and its concomitant diseases - Myocardial infarction and heart failure - A cause for concern

Atrial fibrillation (AF) is increasingly common in the general population. It often coincides with myocardial infarction (MI) and heart failure (HF) which are also diseases in older adults. All three conditions share common cardiovascular risk factors. While hypertension and obesity are central risk factors for all three diseases, smoking and diabetes appear to have less impact on AF. To date, age is the single most important risk factor for AF in the general population. Further, epidemiological studies suggest a strong association of AF to MI and HF. The underlying pathophysiological mechanisms are complex and not fully understood. Both MI and HF can trigger development of AF, mainly by promoting structural and electrical atrial remodeling. On the other hand, AF facilitates HF and MI development via multiple mechanisms, resulting in a vicious circle of cardiac impairment and adverse cardiovascular prognosis. Consequently, to prevent and treat the coincidence of AF and HF or MI a strict optimization of cardiovascular risk factors is required.

Heat shock protein inducer GGA*-59 reverses contractile and structural remodeling via restoration of the microtubule network in experimental Atrial Fibrillation

BACKGROUND

Atrial Fibrillation (AF) is the most common progressive tachyarrhythmia. AF progression is driven by abnormalities in electrical impulse formation and contractile function due to structural remodeling of cardiac tissue. Previous reports indicate that structural remodeling is rooted in derailment of protein homeostasis (proteostasis). Heat shock proteins (HSPs) play a critical role in facilitating proteostasis. Hence, the HSP-inducing compound geranylgeranylacetone (GGA) and its derivatives protect against proteostasis derailment in experimental models for AF. Whether these compounds also accelerate reversibility from structural remodeling in tachypaced cardiomyocytes is unknown.

OBJECTIVE

To investigate whether the potent HSP inducer GGA*-59 restores structural remodeling and contractile dysfunction in tachypaced cardiomyocytes and explore the underlying mechanisms.

MATERIALS AND RESULTS

HL-1 cardiomyocytes post-treated with GGA*-59 or recombinant HSPB1 (rcHSPB1) revealed increased levels of HSPB1 expression and accelerated recovery from tachypacing (TP)-induced calcium transient (CaT) loss compared to non-treated cardiomyocytes. In addition, protein levels of the microtubule protein (acetylated) α-tubulin, and contractile proteins cardiac troponin I (cTnI) and troponin T (cTnT) were reduced after TP and significantly recovered by GGA*-59 or rcHSPB1 post-treatment. The mRNA levels of α-tubulin encoding genes, but not cardiac troponin genes, were reduced upon TP and during recovery, but significantly enhanced by GGA*-59 and rcHSPB1 post-treatment. In addition, TP increased calpain activity, which remained increased during recovery and GGA*-59 post-treatment. However, HDAC6 activity, which deacetylates α-tubulin resulting in microtubule disruption, was significantly increased after TP and during recovery, but normalized to control levels by GGA*-59 or rcHSPB1 post-treatment in HL-1 cardiomyocytes.

CONCLUSIONS

Our results imply that the HSP inducer GGA*-59 and recombinant HSPB1 accelerate recovery from TP-induced structural remodeling and contractile dysfunction in HL-1 cardiomyocytes. GGA*-59 increases HSPB1 levels, represses HDAC6 activity and restores contractile protein and microtubule levels after TP, indicating that HSP-induction is an interesting target to accelerate recovery from AF-induced remodeling.

Loss of Protein Phosphatase 1 Regulatory Subunit PPP1R3A Promotes Atrial Fibrillation

BACKGROUND

Abnormal calcium (Ca²⁺) release from the sarcoplasmic reticulum (SR) contributes to the pathogenesis of atrial fibrillation (AF). Increased phosphorylation of 2 proteins essential for normal SR-Ca²⁺ cycling, the type-2 ryanodine receptor (RyR2) and phospholamban (PLN), enhances the susceptibility to AF, but the underlying mechanisms remain unclear. Protein phosphatase 1 (PP1) limits steady-state phosphorylation of both RyR2 and PLN. Proteomic analysis uncovered a novel PP1-regulatory subunit (PPP1R3A [PP1 regulatory subunit type 3A]) in the RyR2 macromolecular channel complex that has been previously shown to mediate PP1 targeting to PLN. We tested the hypothesis that reduced PPP1R3A levels contribute to AF pathogenesis by reducing PP1 binding to both RyR2 and PLN.

METHODS

Immunoprecipitation, mass spectrometry, and complexome profiling were performed from the atrial tissue of patients with AF and from cardiac lysates of wild-type and Pln-knockout mice. Ppp1r3a-knockout mice were generated by CRISPR-mediated deletion of exons 2 to 3. Ppp1r3a-knockout mice and wild-type littermates were subjected to in vivo programmed electrical stimulation to determine AF susceptibility. Isolated atrial cardiomyocytes were used for Stimulated Emission Depletion superresolution microscopy and confocal Ca²⁺ imaging.

RESULTS

Proteomics identified the PP1-regulatory subunit PPP1R3A as a novel RyR2-binding partner, and coimmunoprecipitation confirmed PPP1R3A binding to RyR2 and PLN. Complexome profiling and Stimulated Emission Depletion imaging revealed that PLN is present in the PPP1R3A-RyR2 interaction, suggesting the existence of a previously unknown SR nanodomain composed of both RyR2 and PLN/sarco/endoplasmic reticulum calcium ATPase-2a macromolecular complexes. This novel RyR2/PLN/sarco/endoplasmic reticulum calcium ATPase-2a complex was also identified in human atria. Genetic ablation of Ppp1r3a in mice impaired binding of PP1 to both RyR2 and PLN. Reduced PP1 targeting was associated with increased phosphorylation of RyR2 and PLN, aberrant SR-Ca²⁺ release in atrial cardiomyocytes, and enhanced susceptibility to pacing-induced AF. Finally, PPP1R3A was progressively downregulated in the atria of patients with paroxysmal and persistent (chronic) AF.

CONCLUSIONS

PPP1R3A is a novel PP1-regulatory subunit within the RyR2 channel complex. Reduced PPP1R3A levels impair PP1 targeting and increase phosphorylation of both RyR2 and PLN. PPP1R3A deficiency promotes abnormal SR-Ca²⁺ release and increases AF susceptibility in mice. Given that PPP1R3A is downregulated in patients with AF, this regulatory subunit may represent a new target for AF therapeutic strategies.

Association of a Family History of Atrial Fibrillation With Incidence and Outcomes of Atrial Fibrillation: A Population-Based Family Cohort Study

Importance

The heritability of atrial fibrillation (AF), the contribution of genetic and environmental factors, and the association of a family history of AF with prognosis are unclear.

Objectives

To measure genetic and environmental factors in the familial aggregation of AF and to estimate the association of a family history of AF with major adverse cardiovascular events (MACE).

Design, Setting, and Participants

In this Taiwanese nationwide population-based study among more than 23 million people, a custom data set was obtained using the data of all patients having a diagnosis of AF recorded between January 1996 and December 2013 in the Taiwan National Health Insurance Research Database. The study population comprised all 23 422 955 individuals registered with the database in 2013, of whom 177 770 had a diagnosis of AF and were included in the heritability estimation. From the latter, a subgroup of patients having newly diagnosed AF with a first-degree relative affected by AF between 2000 and 2010 were selected and matched 1:4 to controls without a family history for estimating MACE-free survival. The dates of analysis were January 2010 to December 2013.

Main Outcomes and Measures

The prevalence and relative risk of AF in relatives of patients with AF, as well as the relative contributions of heritability and shared and nonshared environmental factors to AF susceptibility. Also measured was MACE-free survival after AF was diagnosed.

Results

In total, 1510 patients (204 [13.5%] female; mean [SD] age, 57.9 [9.2] years) had newly diagnosed AF with a first-degree relative affected by AF. Individuals with a first-degree relative affected by AF had a relative risk of 1.92 (95% CI, 1.84-1.99) for AF. The accountability for the phenotypic variance of AF was 19.9% for genetic factors (heritability), 3.5% for shared environmental factors, and 76.6% for nonshared environmental factors. After matching for age, sex, hypertension, type 2 diabetes, previous stroke, and anticoagulation, incident AF patients with vs without an affected first-degree relative had similar MACE-free survival.

Conclusions and Relevance

Genetic and environmental factors were associated with AF, with nonshared environmental factors accounting for three-fourths of the phenotypic variance in Taiwan. Patients having AF with a first-degree relative affected by AF did not have more MACE. Therefore, family history may not be particularly informative in the diagnosis or management of AF.

Quantitative proteomics of changes in succinylated proteins expression profiling in left appendages tissue from valvular heart disease patients with atrial fibrillation

BACKGROUND

Previous studies have suggested that proteomic modifications are closely associated with cardiovascular diseases. The aim of this study was to identify potential mechanisms by profiling the changes in succinylated protein expression in left appendage tissues from patients with valvular heart disease and atrial fibrillation (AF).

METHODS

Using dimethyl labeling for relative and absolute quantification-coupled high-performance liquid chromatography-tandem mass spectrometry, we analyzed the proteomics profiles and succinylation events in 18 left atrial appendage tissue samples from patients who underwent cardiac valvular surgery, including nine patients with permanent AF and nine patients with sinus rhythm (SR).

RESULTS

In total, after setting the quantification ratio > 1.3 and < 1:1.3 representing the up- and downregulated cutoff values, respectively, 132 proteins were classified as targets of upregulation and 117 proteins as targets of downregulation. Within these proteins, 246 sites exhibited upregulated succinylation and 45 sites exhibited downregulated succinylation. Protein-protein interaction networks showed that the proteins exhibiting lysine succinylation and AF status were highly enriched in energy metabolism, extracellular matrix-related, and cellular structure-related proteins. These results were confirmed by western blot.

CONCLUSIONS

The differences in succinylation level of energy metabolism-related proteins indicates the possible involvement of these proteins in AF of valvular heart disease patients, and provide insight for further analysis of their biological functions.

Homocysteine and Incident Atrial Fibrillation: The Atherosclerosis Risk in Communities Study and the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Although many studies have investigated the association of blood homocysteine with major cardiovascular diseases such as coronary heart disease and stroke, research on its association with atrial fibrillation (AF) is scarce.

METHODS

We analysed data from Atherosclerosis Risk in Communities (ARIC) Study (n=492, age 45-64 years) and Multi-Ethnic Study of Atherosclerosis (MESA) (n=6,641, age 45-84 years).

RESULTS

During the 10,106 and 67,613 person-years of follow-up, we identified 85 and 351 AF events in ARIC and MESA, respectively. An age-, sex-, and race-adjusted model showed dose-response relations between plasma homocysteine concentrations and AF incidence in both ARIC and MESA. Further adjustments for other AF risk factors did not change the associations. In the fully adjusted model, a meta-analysis of both studies showed a significant association between homocysteine and AF [hazard ratio (95% confidence interval) per 1 unit increment in log2(homocysteine), 1.27 (1.01-1.61)]. Individuals with higher levels of all three B vitamins (vitamin B6 and B12, and folate) had a lower risk of AF, but those associations were not statistically significant. In the full ARIC cohort [n=12,686 (2079 AF events)], there was no association between the C677T methylenetetrahydrofolate reductase (MTHFR) mutation and AF.

CONCLUSIONS

In the prospective population-based ARIC and MESA cohorts, elevated homocysteine was modestly associated with an increased risk of incident AF, but the C677T MTHFR mutation was not associated with AF risk, suggesting that homocysteine may be a novel risk marker for AF rather than a causal risk factor.

Transient outward K+ current can strongly modulate action potential duration and initiate alternans in the human atrium

Efforts to identify the mechanisms for the initiation and maintenance of human atrial fibrillation (AF) often focus on changes in specific elements of the atrial "substrate," i.e., its electrophysiological properties and/or structural components. We used experimentally validated mathematical models of the human atrial myocyte action potential (AP), both at baseline in sinus rhythm (SR) and in the setting of chronic AF, to identify significant contributions of the Ca2+-independent transient outward K+ current ( Ito) to electrophysiological instability and arrhythmia initiation. First, we explored whether changes in the recovery or restitution of the AP duration (APD) and/or its dynamic stability (alternans) can be modulated by Ito. Recent reports have identified disease-dependent spatial differences in expression levels of the specific K+ channel α-subunits that underlie Ito in the left atrium. Therefore, we studied the functional consequences of this by deletion of 50% of native Ito (Kv4.3) and its replacement with Kv1.4. Interestingly, significant changes in the short-term stability of the human atrial AP waveform were revealed. Specifically, this K+ channel isoform switch produced discontinuities in the initial slope of the APD restitution curve and appearance of APD alternans. This pattern of in silico results resembles some of the changes observed in high-resolution clinical electrophysiological recordings. Important insights into mechanisms for these changes emerged from known biophysical properties (reactivation kinetics) of Kv1.4 versus those of Kv4.3. These results suggest new approaches for pharmacological management of AF, based on molecular properties of specific K+ isoforms and their changed expression during progressive disease. NEW & NOTEWORTHY Clinical studies identify oscillations (alternans) in action potential (AP) duration as a predictor for atrial fibrillation (AF). The abbreviated AP in AF also involves changes in K+ currents and early repolarization of the AP. Our simulations illustrate how substitution of Kv1.4 for the native current, Kv4.3, alters the AP waveform and enhances alternans. Knowledge of this "isoform switch" and related dynamics in the AF substrate may guide new approaches for detection and management of AF.

Comparisons of efficacy, safety, and recurrence risk factors of paroxysmal and persistent atrial fibrillation catheter ablation using robotic magnetic navigation system

Background

No data exist on comparisons of efficacy, safety, and recurrence risk factors of paroxysmal and persistent atrial fibrillation (AF) ablation using robotic magnetic navigation system (MNS), respectively.

Methods

About 151 AF patients were prospectively enrolled and divided into paroxysmal AF group (n = 102) and persistent AF group (n = 49). Circumferential pulmonary vein antrum isolation (CPVI) was performed in all patients. Linear ablation at the left atrial roof and mitral isthmus was performed in patients with persistent AF in addition to CPVI. The procedural time, X‐ray exposure time, acute and long‐term success rates of CPVI, and procedure‐related complications were analyzed. The AF recurrence rates in the two groups were compared during 1 year, and Cox regression was used to analyze the recurrence risk factors.

Results

The acute success rates of CPVI in the two groups were 98.04% and 97.96%, respectively. There were no significant differences in the procedural time, X‐ray exposure time, and ablation time between the two groups (P > 0.05). No serious complications appeared in either group. The AF ablation success rates were 70.6% and 57.1% for the paroxysmal and persistent groups respectively at 12‐month follow‐up (P = 0.102). AF duration and coronary heart disease prior to ablation were associated with the higher AF recurrence in patients with persistent AF.

Conclusion

Ablation using MNS is effective and safe both in patients with paroxysmal and persistent AF. AF duration and coronary heart disease prior to ablation are two independent risk factors of AF recurrence in patients with persistent AF postoperatively.

Upstream therapeutic strategies of valsartan and fluvastatin on hypertensive patients with non-permanent atrial fibrillation

AIM

To investigate the upstream therapeutic effects of fluvastatin and valsartan on hypertensive patients with non-permanent atrial fibrillation (AF).

METHODS

A total of 189 patients who were admitted to outpatient and inpatient department from eight medical centers in China, diagnosed as hypertension with non-permanent AF, were divided into four groups randomly: the CCBs group (group A, n = 45); CCB + fluvastatin group (group B, n = 48); valsartan group (group C, n = 46); valsartan + fluvastatin group (group D, n = 50). The four groups were followed up for 24 months. The blood routine, biochemical examination, echocardiography, high sensitive C-reactive protein (hs-CRP), N-terminal pro-brain natriuretic peptide (NT-proBNP), the maintenance rate of sinus rhythm, and the recurrence of paroxysmal AF or persistent AF incidence were observed in these groups before and after 24 months' treatment.

RESULTS

After 24 months of follow-up, there were 178 cases of patients who have completed the study. (a) There was no significant difference in blood routine, liver, and renal function in each group (P > 0.05). (b) The blood lipids level in groups B and D was significantly reduced after treatment (P < 0.01). There was no significant difference of hs-CRP level in group A (P > 0.05). The left ventricular remodeling was significantly alleviated in group C and group D (P < 0.05). The NT-ProBNP level was significantly decreased in group D (P < 0.05). (c) The sinus rhythm maintenance rate of group B, group C, and group D was higher than group A (77.78%, 70.45%, 79.17% vs 43.90%), the occurrence of persistent AF was significantly lower than group A (11.11%, 14.29%, 8.33% vs 31.71%; P < 0.05).

CONCLUSIONS

CCB plus fluvastatin and valsartan can reduce the recurrence rate of non-permanent AF and to delay the progression from non-permanent AF to permanent AF in patients with hypertension. The combined application of valsartan and fluvastatin is more effective than valsartan or CCB alone in the upstream therapies of AF.

Racial Differences in Atrial Fibrillation-Related Cardiovascular Disease and Mortality: The Atherosclerosis Risk in Communities (ARIC) Study

IMPORTANCE

The adverse outcomes associated with atrial fibrillation (AF) have been studied in predominantly white cohorts. Racial differences in outcomes associated with AF merit continued investigation.

OBJECTIVE

To evaluate the race-specific associations of AF with stroke, heart failure, coronary heart disease (CHD), and all-cause mortality in a community-based cohort.

DESIGN, SETTING, AND PARTICIPANTS

The Atherosclerosis Risk in Communities (ARIC) Study is a prospective, observational cohort. From 1987 through 1989, the ARIC Study enrolled 15 792 men and women and conducted 4 follow-up examinations (2011-2013) with active surveillance for vital status and hospitalizations. Race was determined by self-report and categorized as white, black, or other.

MAIN OUTCOMES AND MEASURES

Atrial fibrillation (adjudicated using electrocardiograms, hospital discharge codes, and death certificates), stroke, heart failure, CHD, and mortality.

RESULTS

After exclusions, 15 080 participants (mean [SD] age, 54.2 [5.8] years; 8290 women [55.5%]; 3831 black individuals [25.4%]) were included in this analysis. During a mean (SD) follow-up of 20.6 (6.2) years, there were 2348 cases of incident AF. The incident rates of AF per 1000 person-years were 8.1 (95% CI, 7.7-8.5) in white individuals and 5.8 (95% CI, 5.2-6.3) in black individuals. The rates of stroke, heart failure, CHD, and mortality were higher in black individuals with AF than white individuals with AF. The association of AF with these outcomes, estimated with rate differences (rate of the end point in those with AF minus the rate in those without AF per 1000 person-years), also differed by race. The rate difference for stroke in individuals with AF was 10.2 (95% CI, 6.6-13.9) in white individuals and 21.4 (95% CI, 10.2-32.6) in black individuals. For heart failure and CHD, the rate differences were 1.5- to 2.0-fold higher in black individuals than white individuals. White individuals with AF had a rate difference of 55.9 (95% CI, 48.1-63.7) for mortality compared with black individuals, who had a rate difference of 106.0 (95% CI, 86.0-125.9).

CONCLUSIONS AND RELEVANCE

In the prospective ARIC Study, the outcome of AF on the rates of stroke, heart failure, CHD, and mortality was considerably larger in black individuals than white individuals. These results indicate the vulnerability and increased risk in black individuals with AF. Continued investigation of racial differences in AF and its related adverse outcomes are essential to identify and mitigate racial disparities in the treatment of AF.

Chronic obstructive pulmonary disease and the development of atrial fibrillation

BACKGROUND

Chronic obstructive pulmonary disease (COPD) has been associated with atrial fibrillation (AF). More insight into the epidemiology and underlying mechanisms is required to optimize management.

METHODS

The Rotterdam Study is a large, population-based cohort study with long-term follow-up. Time dependent Cox proportional hazard models were constructed to study the effect of COPD on incident AF, adjusted for age, sex and pack years of cigarette smoking, and additionally stratified according to exacerbation frequency, left atrial size and baseline systemic inflammatory levels.

RESULTS

1369 of 10,943 subjects had COPD, of whom 804 developed AF. The AF incidence rate was 14 per 1000 person years in COPD and 8 per 1000 person years in subjects without COPD. The adjusted hazard ratio (HR) for COPD subjects to develop AF as compared to subjects without COPD was 1.28 (95%CI [1.04, 1.57]). COPD subjects with frequent exacerbations had a twofold increased AF risk (HR 1.99 [1.42, 2.79]) and COPD subjects with a left atrial size ≥40 mm also had an elevated AF risk (HR 1.77 [1.07, 2.94]). COPD subjects with baseline systemic inflammatory levels above the median had significantly increased AF risks (hsCRP≥1.83 mg/L: HR 1.51 [1.13, 2.03] and IL6 ≥ 1.91 ng/L: HR 2.49 [1.18, 5.28]), whereas COPD subjects below the median had in both analyses no significantly increased AF risk.

CONCLUSIONS

COPD subjects had a 28% increased AF risk, which further increased with frequent exacerbations and an enlarged left atrium. The risk was driven by COPD subjects having elevated systemic inflammatory levels.

Radiofrequency Ablation versus Cryoablation in the Treatment of Paroxysmal Atrial Fibrillation: A Meta-Analysis

Background

Pulmonary vein isolation is commonly performed using radiofrequency energy with cryoablation gaining acceptance. We performed a meta-analysis of randomized controlled trials which compared radiofrequency versus cryoablation for patients with atrial fibrillation.

Methods

A systematic search strategy identified both published and unpublished articles from inception to November 10, 2016, in multiple databases. The primary outcomes for this meta-analysis were long-term freedom from atrial fibrillation at 12-month follow-up and overall postoperative complication rates. For all included studies, the methodological quality was assessed through the Cochrane Collaboration's tool for risk of bias.

Results

A total of 247 articles were identified with eight being included in this review as they satisfied the prespecified inclusion criteria. Overall, there was no significant difference in freedom from atrial fibrillation at ≥12-month follow-up between those receiving cryoballoon and radiofrequency ablation, respectively (OR = 0.98, CI = 0.67–1.43, I² = 56%, p=0.90). Additionally, the secondary outcomes of duration of ablation, fluoroscopy time, and ablation time failed to reach significance. Cryoballoon ablation had significantly greater odds of postoperative phrenic nerve injury at 12-month follow-up.

Conclusions

Our meta-analysis suggests that cryoballoon ablation provides comparable benefits with regard to freedom from atrial fibrillation at medium-term follow-up, fluoroscopy time, ablation time, operative duration, and overall complication rate in comparison to radiofrequency ablation.

Handheld Ultrasound as a Novel Predictive Tool in Atrial Fibrillation: Prediction of Outcomes Following Electrical Cardioversion

Background

Atrial fibrillation (AF) recurrence after successful direct current cardioversion (CV) is common, and clinical predictors may be useful. We evaluated the risk of early AF recurrence according to inferior vena cava (IVC) measurements by handheld ultrasound (HHU) at the time of CV.

Objective

Assess HHU and objectively obtained measurements acquired at the point of care as potential clinical predictors of future clinical outcomes in patients with AF undergoing CV.

Methods

Maximum IVC diameter (IVCd) and collapsibility with inspiration were measured by the Vscan HHU (General Electric Healthcare Division) in 128 patients immediately before and after successful CV for AF. Patients were followed by chart review for recurrence of AF.

Results

Mean IVCd was 2.16 cm in AF pre-CV and 2.01 cm in sinus rhythm post-CV (P<.001). AF recurred within 30 days of CV in 34 of 128 patients (26.6%). Among patients with IVCd <2.1 cm pre-CV and decrease in IVCd post-CV, AF recurrence was 12.1%, compared to 31.6% in patients not meeting these parameters (odds ratio [OR] 0.299, P=.04). This association persisted after adjustment for age, ejection fraction <50%, left atrial enlargement, and amiodarone use (adjusted OR 0.185, P=.01). Among patients with IVCd post-CV <1.7 cm, AF recurrence was 13.5%, compared to 31.9% in patients not meeting this parameter (OR 0.185, P=.01). IVC parameters did not predict AF recurrence at 180 or 365 days.

Conclusions

The presence of a normal IVCd pre-CV that becomes smaller post-CV and the presence of a small IVCd post-CV were each independently associated with reduced likelihood of early, but not late, AF recurrence. HHU assessment of IVCd at the time of CV may be useful to identify patients at low risk of early recurrence of AF after CV.

Coronary CT angiography in patients with atrial fibrillation: Standard-dose and low-dose imaging with a high-resolution whole-heart CT scanner

OBJECTIVE

To compare image quality, observer confidence, radiation exposure in the standard-dose (SD-CCTA) and low-dose (LD-CCTA) protocols of coronary CT angiography (CCTA) in patients with atrial fibrillation (AF).

MATERIAL AND METHODS

CCTA was performed in 303 patients using a CT scanner with 16-cm coverage (111 scans during sinus rhythm (SR); 192 during AF). LD-CCTA was used in 218 patients; SD-CCTA in 85 patients suspected of having coronary artery disease (CAD). Image quality and observer confidence were evaluated on 5-point scales. Radiation doses were recorded.

RESULTS

Image quality was superior in the SD-CCTA compared to the LD-CCTA (SR 1.45±0.40; AF 1.72±0.46; vs. SR 1.83±0.48; AF 1.92±0.50; p < 0.001). Observers were more confident with SD-CCTA than with LD-CCTA (SR 1.38±0.33; AF 1.61±0.43; vs. SR 1.70±0.45; AF 1.82±0.50; p < 0.001). Radiation doses in AF were significantly higher than in the SR (LD-CCTA, 1.68±0.71 mSv; SD-CCTA, 3.72±1.95 mSv; vs. LD-CCTA, 1.3 ±0.52 mSv; SD-CCTA, 2.67±1.47 mSv; p < 0.001).

CONCLUSION

Using a low-dose protocol in AF, radiation exposure can be decreased by 50 % at the expense of 20 % impaired image quality. A low-dose CCTA protocol can be considered in young patients, whereas the standard-dose protocol is recommended for older patients and those suspected of having CAD.

KEY POINTS

• Whole-heart CT allows visualization of the coronary arteries in atrial fibrillation. • Low-dose CT decreases radiation exposure by 50%, image quality by 20%. • Standard-dose CT seems advantageous when concomitant coronary artery disease is suspected.

Racial Differences in Hospital Death for Atrial Fibrillation: The National Inpatient Sample 2001-2012

BACKGROUND

Understanding racial differences in outcomes for atrial fibrillation (AF) may guide interventions to diminish health inequities.

METHODS AND RESULTS

In a retrospective, cross-sectional study of adults hospitalized with a principal diagnosis of AF using the 2001-2012 National Inpatient Sample, we assessed racial differences for in-hospital. We accounted for case-mix and clustering by race within hospitals to estimate odds ratios (OR) for death associated with individual patient race and hospital racial composition. We identified 676,567 hospitalizations (mean age 71.8 years, 53.6% women) with principal diagnosis of AF (84.2% White, 7.1% Black, 5.0% Hispanic). Black (vs. White) race was associated with 1.63-fold (95% CI, 1.50-1.78) risk of death. Other races had similar risk of death as Whites. Risk of death for Blacks (vs. Whites) declined over time [2001: OR 1.78(95% CI 1.31-2.43); 2012: OR 1.23(95% CI 0.92-1.64)]. Racial differences in deaths within hospitals narrowed, while hospitals with larger proportions of Blacks had persistently worse outcomes than hospitals with fewer Blacks (OR 1.08 per 10% increase in Blacks in 2001 and 2012).

CONCLUSION

Black patients with a principal diagnosis of AF were more likely to suffer in-hospital death than Whites. Our findings suggest racial disparities based upon individual patients' race improved over time, but outcomes were persistently worse at hospitals with higher proportions of Black patients, regardless of patients' races.

Eplerenone Reduces Atrial Fibrillation Burden Without Preventing Atrial Electrical Remodeling

BACKGROUND

The aldosterone inhibitor eplerenone (EPL) has been shown to reduce the incidence of atrial fibrillation (AF) in patients with systolic heart failure, but the mechanism is unknown.

OBJECTIVES

This study hypothesized that by reducing atrial dilation and fibrosis in the absence of heart failure, EPL also reduces AF burden and prevents AF perpetuation.

METHODS

The authors conducted a randomized controlled study in 34 sheep that were atrially tachypaced (13 ± 1 week). They compared daily oral EPL (n = 19) versus sugar pill (SP) treatment (n = 15) from the start of tachypacing. The endpoint was a continuous 7-day stretch of persistent AF (n = 29) or completion of 23 weeks tachypacing (n = 5).

RESULTS

EPL significantly reduced the rate of left atrial dilation increase during AF progression. Atria from EPL-treated sheep had less smooth muscle actin protein, collagen-III expression, interstitial atrial fibrosis, and cell hypertrophy than SP-treated sheep atria did. However, EPL did not modify the AF-induced increase in the rate of dominant frequency and ion channel densities seen under SP treatment, but rather prolonged the time to persistent AF in 26% of animals. It also reduced the degree of fibrillatory conduction, AF inducibility, and AF burden.

CONCLUSIONS

In the sheep model, EPL mitigates fibrosis and atrial dilation, modifies AF inducibility and AF complexity, and prolongs the transition to persistent AF in 26% of animals, but it does not prevent AF-induced electrical remodeling or AF persistence. The results highlight structural remodeling as a central upstream target to reduce AF burden, and the need to prevent electrical remodeling to avert AF perpetuation.

The Atrial Fibrillation Health Literacy Information Technology System: Pilot Assessment

Background

Atrial fibrillation (AF) is a highly prevalent heart rhythm condition that has significant associated morbidity and requires chronic treatment. Mobile health (mHealth) technologies have the potential to enhance multiple aspects of AF care, including education, monitoring of symptoms, and encouraging and tracking medication adherence. We have previously implemented and tested relational agents to improve outcomes in chronic disease and sought to develop a smartphone-based relational agent for improving patient-centered outcomes in AF.

Objective

The objective of this study was to pilot a smartphone-based relational agent as preparation for a randomized clinical trial, the Atrial Fibrillation Health Literacy Information Technology Trial (AF-LITT).

Methods

We developed the relational agent for use by a smartphone consistent with our prior approaches. We programmed the relational agent as a computer-animated agent to simulate a face-to-face conversation and to serve as a health counselor or coach specific to AF. Relational agent’s dialogue content, informed by a review of literature, focused on patient-centered domains and qualitative interviews with patients with AF, encompassed AF education, common symptoms, adherence challenges, and patient activation. We established that the content was accessible to individuals with limited health or computer literacy. Relational agent content coordinated with use of the smartphone AliveCor Kardia heart rate and rhythm monitor. Participants (N=31) were recruited as a convenience cohort from ambulatory clinical sites and instructed to use the relational agent and Kardia for 30 days. We collected demographic, social, and clinical characteristics and conducted baseline and 30-day assessments of health-related quality of life (HRQoL) with the Atrial Fibrillation Effect on Quality of life (AFEQT) measure; self-reported medication adherence with the Morisky 8-item Medication Adherence Scale (MMAS-8); and patient activation with the Patient Activation Measure (PAM).

Results

Participants (mean age 68 [SD 11]; 39% [12/31] women) used the relational agent for an average 17.8 (SD 10.0) days. The mean number of independent log-ins was 19.6 (SD 10.7), with a median of 20 times over 30 days. The mean number of Kardia uses was 26.5 (SD 5.9), and participants using Kardia were in AF for 14.3 (SD 11.0) days. AFEQT scores improved significantly from 64.5 (SD 22.9) at baseline to 76.3 (SD 19.4) units at 30 days (P<.01). We observed marginal but statistically significant improvement in self-reported medication adherence (baseline: 7.3 [SD 0.9], 30 days: 7.7 [SD 0.5]; P=.01). Assessments of acceptability identified that most of the participants found the relational agent useful, informative, and trustworthy.

Conclusions

We piloted a 30-day smartphone-based intervention that combined a relational agent with dedicated content for AF alongside Kardia heart rate and rhythm monitoring. Pilot participants had favorable improvements in HRQoL and self-reported medication adherence, as well as positive responses to the intervention. These data will guide a larger, enhanced randomized trial implementing the smartphone relational agent and the Kardia monitor system.

The Association between Galectin-3 and hs-CRP and the Clinical Outcome after Non-ST-Elevation Myocardial Infarction with Preexisting Atrial Fibrillation

Increased galectin-3 plasma concentration has been linked to an unfavorable outcome in patients with heart failure or atrial fibrillation (AF). There are no published data about the prognostic utility of galectin-3 and high-sensitivity C-reactive protein (hs-CRP) for long-term clinical outcome in the Non-ST elevation acute myocardial infarction (NSTEMI) patients with preexisting AF. Thirty-two patients with the first acute NSTEMI and preexisting AF and 22 patients without preexisting AF, were prospectively followed for fifteen months. Patients with AF had significantly higher galectin-3 plasma levels (p < 0.05) and hs-CRP concentration (p < 0.01), compared with patients without AF. Galectin-3 plasma concentration was not a significant covariate of the composite outcomes (p = 0.913). Patients with high hs-CRP (above 4.55 mg/L) showed 2.5 times increased risk (p < 0.05) of the composite outcome occurrence (p < 0.05). Besides, three-vessel coronary artery disease, creatinine serum level, and creatinine clearance were significant covariates (p < 0.05; p < 0.05; p < 0.01) of the composite outcome, respectively. Creatinine clearance, solely, has been shown to be an independent predictor of unfavorable prognosis after a 15-month follow-up. Galectin-3 and hs-CRP plasma levels were elevated in NSTEMI patients with AF, but with differential predictive value for an unfavorable clinical outcome. Only hs-CRP was associated with increased risk of composite outcome occurrence.

Catheter Ablation as First-Line Therapy for Atrial Fibrillation: Ready for Prime-Time?

Current guidelines include atrial fibrillation (AF) catheter ablation as part of the management strategy in patients that have failed at least one oral antiarrhythmic drug treatment course. However, growing evidence derived from both randomized and non-randomized studies demonstrate lower rates of AF recurrence and AF burden in patients with paroxysmal AF that are naïve to antiarrhythmic drug treatment. Furthermore, progression from paroxysmal AF to persistent AF appears to be delayed by early catheter ablation of AF. The current review addresses the question of the best timing for ablation in patients with paroxysmal AF and provides the rationale for offering AF ablation as first-line therapy based on the most updated evidence available.

Leukocyte TRP channel gene expressions in patients with non-valvular atrial fibrillation

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice and is a major cause of morbidity and mortality. The upregulation of TRP channels is believed to mediate the progression of electrical remodelling and the arrhythmogenesis of the diseased heart. However, there is limited data about the contribution of the TRP channels to development of AF. The aim of this study was to investigate leukocyte TRP channels gene expressions in non-valvular atrial fibrillation (NVAF) patients. The study included 47 NVAF patients and 47 sex and age matched controls. mRNA was extracted from blood samples, and real-time polymerase chain reaction was performed for gene expressions by using a dynamic array system. Low levels of TRP channel expressions in the controls were markedly potentiated in NVAF group. We observed marked increases in MCOLN1 (TRPML1), MCOLN2 (TRPML2), MCOLN3 (TRPML3), TRPA1, TRPM1, TRPM2, TRPM3, TRPM4, TRPM5, TRPM6, TRPM7, TRPM8, TRPC1, TRPC2, TRPC3, TRPC4, TRPC5, TRPC6, TRPC7, TRPV1, TRPV2, TRPV3, TRPV4, TRPV5, TRPV6, and PKD2 (TRPP2) gene expressions in NVAF patients (P < 0.05). However, there was no change in PKD1 (TRPP1) gene expression. This is the first study to provide evidence that elevated gene expressions of TRP channels are associated with the pathogenesis of NVAF.

Incidence and risk factors of atrial fibrillation in Asian COPD patients

Objective

To investigate the incidence and risk factors of atrial fibrillation (AF) in Asian chronic obstructive pulmonary disease (COPD) patients.

Patients and methods

We selected a study population older than 40 years with a COPD diagnosis and who had used at least one inhaled bronchodilator medication between 1998 and 2012. The date of the index COPD diagnosis was defined as the index date. We excluded patients with a history of AF, significant mitral valve disease, disorders of the thyroid gland, or ischemic heart disease before the index date. We followed all patients from the index date to the day of AF occurrence, the day of death, or the date of December 31, 2013. The baseline of comorbidities was identified before the index date. Comorbidities included hypertension, diabetes mellitus, end-stage renal disease, congenital heart failure, stroke, peripheral arterial occlusive disease, and malignancy.

Results

We included 6,208 COPD patients and 12,409 patients without COPD. The incidence of AF was higher in COPD patients than in those without COPD. The adjusted hazard ratio (HR) for AF among those with COPD was 2.23 with a 95% confidence interval (CI) of 1.98–2.51 compared to those without COPD. After multiple analyses, patients with hypertension (HR 1.43 [95% CI =1.26–1.62]) or heart failure (HR 2.36 [95% CI =1.81–3.08]) were found to have a significantly higher incidence of AF than those without these conditions.

Conclusion

It is important for physicians to monitor, prevent, and provide early intervention for AF in COPD patients with hypertension or heart failure.

Antiarrhythmic drug therapy among patients presenting to emergency department with symptomatic atrial fibrillation - a prospective nationwide cohort

BACKGROUND

Atrial fibrillation (AF) is a common arrhythmia that causes numerous visits to emergency departments (ED). The aim of the FinFib2 study was to evaluate whether treatment of patients with AF in ED is consistent with the contemporary European Society of Cardiology (ESC) management guidelines. Here we report the results of antiarrhythmic drug therapy (AAD) in ED.

METHODS

All patients within the two-week study period whose primary reason for the ED visit was symptomatic AF were included into this prospective multicentre study. Comprehensive data on factors contributing to the treatment of AF were collected, including a data of previous use of ADDs, and changes made for them during a visit in ED.

RESULTS

The study population consisted of 1013 consecutive patients (mean age 70 ± 13 years, 47.6% female). The mean European Heart Rhythm Association (EHRA) symptom score was 2.2 ± 0.8. Rhythm control strategy was opt for 498 (63.8%) and 140 (64.5%) patients with previously and newly diagnosed AF, respectively. In patients with previously diagnosed AF the most frequently used AAD was a beta blocker (80.9%). Prior use of class I (11.4%) and III (9.1%) AADs as well as start or adjustment of their dosage (7.4%) were uncommon. Most of the patients with newly diagnosed AF were prescribed a beta blocker (71.0%) or a calcium channel antagonist (24.0%), and only two of them received class I or class III AADs.

CONCLUSIONS

Our data demonstrated that in patients presenting to the ED with recurrent symptomatic AF and aimed for rhythm control strategy, the use of class I and class III AADs was rare despite ESC guideline recommendations. It is possible that early adaptation of a more aggressive rhythm control strategy might improve a quality of life for symptomatic patients and alleviate the ED burden associated with AF. Beta blockers were used by majority of patients as rate control therapy both in rate and rhythm control groups.

TRIAL REGISTRATION

NCT01990105 . Registered 15 November 2013.

Angiotensin-converting enzyme-2 overexpression improves atrial electrical remodeling through TRPM7 signaling pathway

Atrial electrical remodeling is an important factor in the development and persistence of atrial fibrillation. The aim of this study was to examine the effects of atrial angiotensin-converting enzyme-2 overexpression on atrial electrical remodeling and to elucidate the molecular mechanisms underlying these effects. Twenty-eight male and female dogs were randomly divided into the following 4 groups: a sham-operation group, a control group, an adenovirus-enhanced green fluorescent protein (Ad-EGFP) gene group and an Ad-ACE2 gene group. All dogs in the Ad-EGFP and Ad-ACE2 groups were rhythmized at 450 bpm for 14 days. Two weeks later, all the dogs underwent thoracotomy and epicardial gene painting. On day 21 after gene transfer, all the animals were subjected to electrophysiological and molecular studies. AF induction rates and durations were significantly increased in the control and Ad-EGFP groups compared to the sham-operated and Ad-ACE2 groups. Transient receptor potential melastatin 7 (TRPM7) expression levels in the Ad-EGFP and control groups were significantly higher than those in the sham-operated and Ad-ACE2 groups.

Basal [Mg²⁺]_i was significantly decreased in siRNA transfected cells compared with control and non-silencing siRNA-transfected cells. Our results suggest that ACE2 overexpression suppresses atrial electrical remodeling and improves atrial function through the TRPM7 signaling pathway.

Lichen extracts regulate the expression of BMP7 via miR-194-5p targeting to decrease the risk atrial fibrillation

BACKGROUND

Atrial fibrillation (AF), the most common cardiac supraventricular arrhythmia, affects more than 5 million people worldwide. Increasing evidence has demonstrated that genetic factors play an important role in the pathogenesis of AF, and multiple genes responsible for AF have been identified. A better understanding of the genetic mechanism underlying AF would be expected to lead to more accurate risk stratification of AF and optimal clinical treatment strategies.

METHODS

Immunofluorescence staining was performed to find the components which would have effects on the H9c2 cells development. The changes of BMP7 and miR-194-5p expressions were detected before and after Human Cardiac Myocytes (HCM) were treated with Lichen extraction. In order to confirm whether Lichen could increase the expression of BMP7 through inhibiting the expression of miR-194-5p, the mRNA levels of BMP7 and miR-194-5p were determined in HCM before and after the treatment of Lichen on the conditions that miR-194-5p was over-expressed or not.

RESULTS

After 48 hours' treatment with 20 µg/mL Lichen extracts, the Collagen I expression level significantly decreased. The expressions of several genes in H9c2 cells could were changed after the treatment of Lichen extracts and some mRNA of them could also be targeted by miR-194-5p including BMP7. Lichen could depress the expression of miR-194-5p in HCM no matter miR-194-5p was overexpressed or not and correspondingly, the expression of BMP7 could be increased in both conditions.

CONCLUSIONS

It is indicated that Lichen extracts could regulate the expression of atrial fibrillation-associated genes via miR-194-5a targeting.

Deep sequencing of atrial fibrillation patients with mitral valve regurgitation shows no evidence of mosaicism but reveals novel rare germline variants

BACKGROUND

Atrial fibrillation (AF) is the most common cardiac arrhythmia. Valvular heart disease is a strong predictor, yet the underlying molecular mechanisms are unknown.

OBJECTIVE

The purpose of this study was to investigate the prevalence of somatic variants in AF candidate genes in an AF patient population undergoing surgery for mitral valve regurgitation (MVR) to determine whether these patients are genetically predisposed to AF.

METHODS

DNA was extracted from blood and left atrial tissue from 44 AF patients with MVR. Using next-generation sequencing, we investigated 110 genes using the HaloPlex Target Enrichment System. MuTect software was used for identification of somatic point variants. We functionally characterized selected variants using electrophysiologic techniques.

RESULTS

No somatic variants were identified in the cardiac tissue. Thirty-three patients (75%) had a rare germline variation in ≥1 candidate genes. Fourteen variants were novel. Fifteen variants were predicted damaging or likely damaging in ≥6 in silico predictions. We identified rare variants in genes never directly associated with AF: KCNE4, SCN4B, NEURL1, and CAND2. Interestingly, 7 patients (16%) had variants in genes involved in cellular potassium handling. The variants KCNQ1 (p.G272S) and KCNH2 (p.A913V) resulted in gain of function due to faster activation (KCNQ1) and slowed deactivation kinetics (KCNQ1, KCNH2).

CONCLUSION

We did not find any somatic variants in patients with AF and MVR. Surprisingly, we found that our cohort of non-lone AF patients might, like lone AF patients, be predisposed to AF by rare germline variants. Our findings emphasize the extent of still unknown factors in the pathogenesis of AF.

Upregulation of sestrins protect atriums against oxidative damage and fibrosis in human and experimental atrial fibrillation

Atrial Fibrillation (AF) is common in the elderly and Sestrins (Sesns) have been suggested to prevent age-related pathologies. The aim of this study was to investigate the effects of Sesns in AF. Clinical data were collected and a small sample of atrial appendage and atrium was obtained from patients undergoing valve repairment. The expression of Sesn1, Sesn2, and Sesn3 was significantly higher in patients with permanent atrial fibrillation (PmAF) than that in sinus rhythm (SR), and further greater in the left atrium than the right in PmAF patients. Superoxide anion and malondialdehyde were enhanced and positively correlated to the protein expression of Sesn1/2/3. Reactive oxygen species (ROS) production and Ca²⁺ overload were significantly decreased and cell survival was enhanced by overexpression of Sesns 1/2/3 in cultured HL-1 cells. Conversely, knockdown of Sesn1/2/3 resulted in significantly increased ROS and Ca²⁺ overload. In addition, the overexpression of Sesn1/2 significantly reduced the proliferation of fibroblasts, as well as decreased the protein expression of collagen and fibronectin1 in angiotensin II-stimulated cardiac fibroblasts. Our study demonstrated for the first time that Sesns expression is significantly up-regulated in AF, which therefore may protect hearts against oxidative damage and atrial fibrosis.

Clinical, biomarker, and genetic predictors of specific types of atrial fibrillation in a community-based cohort: data of the PREVEND study

Aims

Atrial fibrillation (AF) may present variously in time, and AF may progress from self-terminating to non-self-terminating AF, and is associated with impaired prognosis. However, predictors of AF types are largely unexplored. We investigate the clinical, biomarker, and genetic predictors of development of specific types of AF in a community-based cohort.

Methods

We included 8042 individuals (319 with incident AF) of the PREVEND study. Types of AF were compared, and multivariate multinomial regression analysis determined associations with specific types of AF.

Results

Mean age was 48.5 ± 12.4 years and 50% were men. The types of incident AF were ascertained based on electrocardiograms; 103(32%) were classified as AF without 2-year recurrence, 158(50%) as self-terminating AF, and 58(18%) as non-self-terminating AF. With multivariate multinomial logistic regression analysis, advancing age (P< 0.001 for all three types) was associated with all AF types, male sex was associated with AF without 2-year recurrence and self-terminating AF (P= 0.031 and P= 0.008, respectively). Increasing body mass index and MR-proANP were associated with both self-terminating (P= 0.009 and P< 0.001) and non-self-terminating AF (P= 0.003 and P< 0.001). The only predictor associated with solely self-terminating AF is prescribed anti-hypertensive treatment (P= 0.019). The following predictors were associated with non-self-terminating AF; lower heart rate (P= 0.018), lipid-lowering treatment prescribed (P= 0.009), and eGFR <60 mL/min/1.73 m2 (P= 0.006). Three known AF-genetic variants (rs6666258, rs6817105, and rs10821415) were associated with self-terminating AF.

Conclusions

We found clinical, biomarker and genetic predictors of specific types of incident AF in a community-based cohort. The genetic background seems to play a more important role than modifiable risk factors in self-terminating AF.

Clinical utility and functional analysis of variants in atrial fibrillation-associated locus 4q25

BACKGROUND

Chromosome 4q25 has been repeatedly identified as atrial fibrillation (AF)-sensitive locus in multiple genome-wide association studies (GWAS) and is considered to hold some clues to AF pathogenesis. We aimed to investigate the clinical utilities in Japanese and to unveil the function of the 4q25 locus in affecting transcription of adjacent genes.

METHODS

We conducted AF GWAS in Japanese population (1382 AF cases and 1478 controls) and the replication panel (1666 AF cases and 1229 controls) with detailed clinical information which showed the acceleration of AF onset. Stepwise investigations with linkage disequilibrium analysis, histone code patterns, and reporter assay in the 4q25 locus were performed.

RESULTS

The AF GWAS confirmed a significant association of rs4611994 and rs1906617 in chromosome 4q25 with AF. In the clinical analysis, AF onset of the individuals with risk allele accelerated 2.5 years compared with those with protective allele (p=0.00012). Next, in the functional analysis, three single nucleotide polymorphisms (SNPs) in the variant group selected by linkage disequilibrium analysis were identified as candidates for the cis-regulatory element toward adjacent genes in chromatin immunoprecipitation assay. Among them, rs4611994 and rs72900144 regions showed higher effects on the transcriptional activity of luciferase gene in the risk alleles than those in the protective alleles (p<0.0001, p<0.005, respectively).

CONCLUSIONS

AF GWAS in Japanese confirmed the association with 4q25 locus and indicated that its SNP affected the acceleration of AF onset. The candidate regions of the causative SNPs, rs4611994 and rs72900144, could alter the adjacent gene expression level.

Atrial Fibrillation and Hypertension: Mechanistic, Epidemiologic, and Treatment Parallels

Atrial fibrillation (AF) is an increasingly prevalent condition and the most common sustained arrhythmia encountered in ambulatory and hospital practice. Several clinical risk factors for AF include age, sex, valvular heart disease, obesity, sleep apnea, heart failure, and hypertension (HTN). Of all the risk factors, HTN is the most commonly encountered condition in patients with incident AF. Hypertension is associated with a 1.8-fold increase in the risk of developing new-onset AF and a 1.5-fold increase in the risk of progression to permanent AF. Hypertension predisposes to cardiac structural changes that influence the development of AF such as atrial remodeling. The renin angiotensin aldosterone system has been demonstrated to be a common mechanistic link in the pathogenesis of HTN and AF. Importantly, HTN is one of the few modifiable AF risk factors, and guideline-directed management of HTN may reduce the incidence of AF.

Atrial electrocardiography in obesity and hypertension: Clinical insights from the Polish-Norwegian Study (PONS)

OBJECTIVE

Obesity and hypertension often coexist and represent risk factors for atrial fibrillation. This study hypothesized that their single and joint effects on atrial remodeling would be reflected in the PR interval and P-wave durations on electrocardiogram (ECG).

METHODS

This cross-sectional analysis of a community-based study included 11,308 men and women age 45-64. Atrial indices were obtained from digital standard 12-lead resting ECG. Analyses were adjusted for traditional cardiovascular risk factors.

RESULTS

Both ECG indices displayed a progressive increase across anthropometric indices. Each 5-unit increment in body mass index (BMI) increased P-wave duration by 1.9 ms (95% CI 1.5-2.2) and PR interval by 2.4 ms (95% CI 1.9-3.0), with similar trends for central obesity, even among those without obesity by BMI. Both ECG indices displayed graded increases across levels of blood pressure control, including prehypertension. A joint effect of overweight and hypertension on both ECG indices was detected. P-wave duration or PR interval among people with obesity was not additionally increased by hypertension.

CONCLUSIONS

P-wave indices increase in general and central obesity. Hypertension exerts an incremental effect in people with overweight but not in people with obesity. The study furthered the understanding of atrial remodeling in the setting of major atrial fibrillation risk factors.