Left atrial structure and function in atrial fibrillation: ENGAGE AF-TIMI 48

Intercalated Disk Extracellular Nanodomain Expansion in Patients With Atrial Fibrillation

Aims: Atrial fibrillation (AF) is the most common sustained arrhythmia. Previous evidence in animal models suggests that the gap junction (GJ) adjacent nanodomain – perinexus – is a site capable of independent intercellular communication via ephaptic transmission. Perinexal expansion is associated with slowed conduction and increased ventricular arrhythmias in animal models, but has not been studied in human tissue. The purpose of this study was to characterize the perinexus in humans and determine if perinexal expansion associates with AF.

Methods: Atrial appendages from 39 patients (pts) undergoing cardiac surgery were fixed for immunofluorescence and transmission electron microscopy (TEM). Intercalated disk distribution of the cardiac sodium channel Nav1.5, its β1 subunit, and connexin43 (C×43) was determined by confocal immunofluorescence. Perinexal width (Wp) from TEM was manually segmented by two blinded observers using ImageJ software.

Results: Nav1.5, β1, and C×43 are co-adjacent within intercalated disks of human atria, consistent with perinexal protein distributions in ventricular tissue of other species. TEM revealed that the GJ adjacent intermembrane separation in an individual perinexus does not change at distances greater than 30 nm from the GJ edge. Importantly, Wp is significantly wider in patients with a history of AF than in patients with no history of AF by approximately 3 nm, and Wp correlates with age (R = 0.7, p < 0.05).

Conclusion: Human atrial myocytes have voltage-gated sodium channels in a dynamic intercellular cleft adjacent to GJs that is consistent with previous descriptions of the perinexus. Further, perinexal width is greater in patients with AF undergoing cardiac surgery than in those without.

Right atrial structure and function in patients with hypertension and with chronic heart failure

BACKGROUND

Prior studies have shown that both heart failure (HF) and atrial fibrillation (AF) are factors that impact left atrial function and structure. However, right atrial (RA) function measured as RA emptying fraction (RAEF) on echocardiography has not been analyzed systematically in a chronic HF population. The aim of this study was to assess RA volume index (RAVI) and RAEF in patients with chronic HF and patients with hypertension (HTN) and to relate these findings to other cardiopulmonary ultrasound parameters and 12-month outcomes.

METHODS AND RESULTS

In this prospective observational study, we identified 119 patients with chronic HF (64 patients without a history of AF [HF without AF], 55 with AF [HF with AF]), and 127 patients with HTN but without important cardiac disease who underwent routine outpatient transthoracic echocardiography. We found that RAEF was impaired in patients with HF without AF compared to patients with HTN (35% ±2 vs 50% ±1, P < .001), whereas RAVI did not differ between these two groups. Lower RAEF was associated with larger RAVI and higher estimated RA pressures but not with a higher degree of pulmonary congestion by lung ultrasound. Both lower RAEF and higher RAVI were associated with an increased risk of 12-month HF hospitalizations or all-cause death (age, sex, and AF adjusted HR: 4.07, 95% CI: 1.69-9.79; P = .002, vs 2.74, 95% CI: 1.15-6.54, P = .023).

CONCLUSIONS

In an outpatient HF cohort, both lower RAEF and increased RAVI were associated with other markers of impaired cardiac function and 12-month adverse events.

Direct oral anticoagulants versus warfarin for preventing stroke and systemic embolic events among atrial fibrillation patients with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is an independent risk factor for atrial fibrillation (AF), which is more prevalent among CKD patients than the general population. AF causes stroke or systemic embolism, leading to increased mortality. The conventional antithrombotic prophylaxis agent warfarin is often prescribed for the prevention of stroke, but risk of bleeding necessitates regular therapeutic monitoring. Recently developed direct oral anticoagulants (DOAC) are expected to be useful as alternatives to warfarin.

OBJECTIVES

To assess the efficacy and safety of DOAC including apixaban, dabigatran, edoxaban, and rivaroxaban versus warfarin among AF patients with CKD.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Specialised Register (up to 1 August 2017) through contact with the Information Specialist using search terms relevant to this review. Studies in the Specialised Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) which directly compared the efficacy and safety of direct oral anticoagulants (direct thrombin inhibitors or factor Xa inhibitors) with dose-adjusted warfarin for preventing stroke and systemic embolic events in non-valvular AF patients with CKD, defined as creatinine clearance (CrCl) or eGFR between 15 and 60 mL/min (CKD stage G3 and G4).

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, assessed quality, and extracted data. We calculated the risk ratio (RR) and 95% confidence intervals (95% CI) for the association between anticoagulant therapy and all strokes and systemic embolic events as the primary efficacy outcome and major bleeding events as the primary safety outcome. Confidence in the evidence was assessing using GRADE.

MAIN RESULTS

Our review included 12,545 AF participants with CKD from five studies. All participants were randomised to either DOAC (apixaban, dabigatran, edoxaban, and rivaroxaban) or dose-adjusted warfarin. Four studies used a central, interactive, automated response system for allocation concealment while the other did not specify concealment methods. Four studies were blinded while the other was partially open-label. However, given that all studies involved blinded evaluation of outcome events, we considered the risk of bias to be low. We were unable to create funnel plots due to the small number of studies, thwarting assessment of publication bias. Study duration ranged from 1.8 to 2.8 years. The large majority of participants included in this study were CKD stage G3 (12,155), and a small number were stage G4 (390). Of 12,545 participants from five studies, a total of 321 cases (2.56%) of the primary efficacy outcome occurred per year. Further, of 12,521 participants from five studies, a total of 617 cases (4.93%) of the primary safety outcome occurred per year. DOAC appeared to probably reduce the incidence of stroke and systemic embolism events (5 studies, 12,545 participants: RR 0.81, 95% CI 0.65 to 1.00; moderate certainty evidence) and to slightly reduce the incidence of major bleeding events (5 studies, 12,521 participants: RR 0.79, 95% CI 0.59 to 1.04; low certainty evidence) in comparison with warfarin.

AUTHORS' CONCLUSIONS

Our findings indicate that DOAC are as likely as warfarin to prevent all strokes and systemic embolic events without increasing risk of major bleeding events among AF patients with kidney impairment. These findings should encourage physicians to prescribe DOAC in AF patients with CKD without fear of bleeding. The major limitation is that the results of this study chiefly reflect CKD stage G3. Application of the results to CKD stage G4 patients requires additional investigation. Furthermore, we could not assess CKD stage G5 patients. Future reviews should assess participants at more advanced CKD stages. Additionally, we could not conduct detailed analyses of subgroups and sensitivity analyses due to lack of data.

Evaluating the morphology of the left atrial appendage by a transesophageal echocardiographic 3-dimensional printed model

The novel 3-dimensional printing (3DP) technique has shown its ability to assist personalized cardiac intervention therapy. This study aimed to determine the feasibility of 3D-printed left atrial appendage (LAA) models based on 3D transesophageal echocardiography (3D TEE) data and their application value in treating LAA occlusions.Eighteen patients with transcatheter LAA occlusion, and preprocedure 3D TEE and cardiac computed tomography were enrolled. 3D TEE volumetric data of the LAA were acquired and postprocessed for 3DP. Two types of 3D models of the LAA (ie, hard chamber model and flexible wall model) were printed by a 3D printer. The morphological classification and lobe identification of the LAA were assessed by the 3D chamber model, and LAA dimensions were measured via the 3D wall model. Additionally, a simulation operative rehearsal was performed on the 3D models in cases of challenging LAA morphology for the purpose of understanding the interactions between the device and the model.Three-dimensional TEE volumetric data of the LAA were successfully reprocessed and printed as 3D LAA chamber models and 3D LAA wall models in all patients. The consistency of the morphological classifications of the LAA based on 3D models and cardiac computed tomography was 0.92 (P < .01). The differences between the LAA ostium dimensions and depth measured using the 3D models were not significant from those measured on 3D TEE (P > .05). A simulation occlusion was successfully performed on the 3D model of the 2 challenging cases and compared with the real procedure.The echocardiographic 3DP technique is feasible and accurate in reflecting the spatial morphology of the LAA, which may be promising for the personalized planning of transcatheter LAA occlusion.

Clinical and Echocardiographic Correlates of Left Atrial Function Index: The Framingham Offspring Study

BACKGROUND

Left atrial (LA) remodeling is a predictor of cardiovascular disease (CVD). We performed measurement of the LA function index (LAFI), a composite measure of LA structure and function, in a community-based cohort and here report the distribution and cross-sectional correlates of LAFI.

METHODS

In 1,719 Framingham Offspring Study participants (54% women, mean age 66 ± 9 years), we derived LAFI from the LA emptying fraction, left ventricular (LV) outflow tract velocity time integral, and indexed maximal LA volume. We used multivariable linear regression to assess the clinical and echocardiographic correlates of LAFI adjusting for age, sex, anthropometric measurements, and CVD risk factors.

RESULTS

The average LAFI was 35.2 ± 12.1. Overall, LAFI declined with advancing age (β = -0.27, P < .001). LAFI was significantly higher (37.5 ± 11.6) in a subgroup of participants free of CVD and CVD risk factors compared with those with either of these conditions (34.5 ± 12.2). In multivariable models, LAFI was inversely related to antihypertensive use (β = -1.26, P = .038), prevalent atrial fibrillation (β = -4.46, P = .001), heart failure (β = -5.86, P = .008), and coronary artery disease (β = -2.01, P = .046). In models adjusting for echocardiographic variables, LAFI was directly related to LV ejection fraction (β = 14.84, P < .001) and inversely related to LV volume (β = -7.03, P < .001).

CONCLUSIONS

LAFI was inversely associated with antihypertensive use and prevalent CVD and was related to established echocardiographic traits of LV remodeling. Our results offer normative ranges for LAFI in a white community-based sample and suggest that LAFI represents a marker of pathological atrial remodeling.

Different Implications of Heart Failure, Ischemic Stroke, and Mortality Between Nonvalvular Atrial Fibrillation and Atrial Flutter-a View From a National Cohort Study

BACKGROUND

Atrial flutter (AFL) has been identified to be equivalent to atrial fibrillation (AF) in terms of preventing ischemic stroke, although differences exist in atrial rate, substrate, and electrophysiological mechanisms. This study aimed to investigate differences in clinical outcomes between nonvalvular AF and AFL.

METHODS AND RESULTS

AF and AFL patients without any prescribed anticoagulation were enrolled from a 13-year national cohort database. Under series exclusion criteria, ischemic stroke, heart failure hospitalization, and all-cause mortality were compared between the groups in real-world conditions and after propensity score matching. We identified 175 420 patients in the AF cohort and 6239 patients in the AFL cohort, and the prevalence of most comorbidities and frequency of medications were significantly higher in the AF group than the AFL group. In the real-world setting the AF patients had higher incidence rates of ischemic stroke, heart failure hospitalization, and all-cause mortality than the AFL patients (all P<0.001). After propensity score matching, the incidence rate of ischemic stroke in the AF cohort was 1.63-fold higher than in the AFL cohort (P<0.001), the incidence rate of heart failure hospitalization in the AF cohort was 1.70-fold higher than in the AFL cohort (P<0.001), and the incidence rate of all-cause mortality in the AF cohort was 1.08-fold higher than in the AFL cohort (P=0.002).

CONCLUSIONS

There were differences between AF and AFL in comorbidities and prognosis with regard to ischemic stroke, heart failure hospitalization, and all-cause mortality.

Multimodality Cardiac Imaging for the Assessment of Left Atrial Function and the Association With Atrial Arrhythmias

Several cardiac imaging modalities are able to visualize the left atrium (LA) and, therefore, allow for quantification of both structural and functional properties of this cardiac chamber. In echocardiography, only the maximal LA volume is included in the assessment of diastolic function at the current moment. Numerous studies, however, have shown that functional measures may be superior to the maximal LA volume in several aspects and to possess clinical value even in the absence of structural abnormalities. Such functional measures could prove particularly useful in the setting of predicting atrial fibrillation, which will be a point of focus in this review. Pivotal cardiac magnetic resonance imaging studies have revealed high correlation between LA fibrosis and risk of atrial fibrillation recurrence after catheter ablation, and subsequent multimodality imaging studies have uncovered an inverse relationship between LA reservoir function and degree of LA fibrosis. This has sparked an increased interest into the application of advanced imaging modalities, including both speckle tracking echocardiography and tissue tracking by cardiac magnetic resonance imaging. Even though increasing evidence has supported the use of functional measures and proven its superiority to the maximal LA volume, they have still not been adopted in clinical guidelines. The reason for this discrepancy may rely on the fact that there is little to no agreement on how to technically perform deformation analysis of the LA. Such technical considerations, limitations, and alternate imaging prospects will be addressed in this review.

Cardiac Magnetic Resonance-Measured Left Atrial Volume and Function and Incident Atrial Fibrillation: Results From MESA (Multi-Ethnic Study of Atherosclerosis)

BACKGROUND

Early detection of structural changes in left atrium (LA) before atrial fibrillation (AF) development could be helpful in identification of those at higher risk for AF. Using cardiac magnetic resonance imaging, we examined the association of LA volume and function, and incident AF in a multiethnic population free of clinical cardiovascular diseases.

METHODS AND RESULTS

In a case-cohort study embedded in MESA (Multi-Ethnic Study of Atherosclerosis), baseline LA size and function assessed by cardiac magnetic resonance feature-tracking were compared between 197 participants with incident AF and 322 participants randomly selected from the whole MESA cohort. Participants were followed up for 8 years. Incident AF cases had a larger LA volume and decreased passive, active, and total LA emptying fractions and peak global LA longitudinal strain (peak LA strain) at baseline. In multivariable analysis, elevated LA maximum volume index (hazard ratio, 1.38 per SD; 95% confidence interval, 1.01-1.89) and decreased peak LA strain (hazard ratio, 0.68 per SD; 95% confidence interval, 0.48-0.96), and passive and total LA emptying fractions (hazard ratio for passive LA emptying fractions, 0.55 per SD; 95% confidence interval, 0.40-0.75 and hazard ratio for active LA emptying fractions, 0.70 per SD; 95% confidence interval, 0.52-0.95), but not active LA emptying fraction, were associated with incident AF.

CONCLUSIONS

Elevated LA volumes and decreased passive and total LA emptying fractions were independently associated with incident AF in an asymptomatic multiethnic population. Including LA functional variables along with other risk factors of AF may help to better risk stratify individuals at risk of AF development.

Transient left atrial dysfunction is a feature of Takotsubo syndrome

BACKGROUND

Takotsubo syndrome (TTS) is characterized by a transient left and/or right ventricular dysfunction as a consequence of a distinctive pattern of regional wall motion abnormalities. However, a systematic evaluation of the left atrial (LA) function in patients with TTS is lacking. The aim of the present study was therefore to comprehensively assess LA performance indexes and function in patients with TTS.

METHODS

We compared LA function assessed by volumetric indexes derived from fractional volume changes in cardiovascular magnetic resonance (CMR) between 125 TTS patients and 125 patients with anterior ST-segment elevation myocardial infarction (STEMI). Furthermore, recovery of LA performance was evaluated in a subgroup of 20 TTS patients with follow-up CMR data.

RESULTS

Patients with TTS demonstrated a significantly lower total LA emptying fraction (EF) [44% (interquartile range (IQR) 34-53%) versus 51% (IQR 42-56%); p < 0.01], passive LA-EF [21% (IQR 14-30%) versus 24% (IQR 20-29%); p = 0.03] and active LA-EF [29% (IQR 20-38%) versus 35% (28-42%); p < 0.01] compared to patients with anterior STEMI. Among the 20 TTS patients with serial CMR data, the total LA-EF significantly improved from 42% (IQR 29-48%) at the acute stage to 51% (IQR 46-59%) at follow-up (p < 0.01). Similarly, active LA-EF (p < 0.01) and passive LA-EF (p = 0.02) improved significantly as well.

CONCLUSION

Compared to anterior STEMI, TTS patients demonstrated a significantly decreased LA function during the acute/subacute phase of the disease. However, impairment of LA performance seems to be transient in TTS with recovery during follow-up.

Functional Remodeling of Both Atria is Associated with Occurrence of Stroke in Patients with Paroxysmal and Persistent Atrial Fibrillation

BACKGROUND

It is critical to recognize high risk patients who are prone to develop stroke in the management of atrial fibrillation (AF). The purpose of this study was to identify the determinants of AF related stroke by assessing the anatomical and functional remodeling of cardiac chambers.

METHODS

We compared the cardiac structure and function of 28 consecutive patients with paroxysmal and persistent AF-related stroke with 69 patients with AF and 21 controls without stroke using contrast-enhanced 64-slice multi-detector computed tomography during sinus rhythm.

RESULTS

The volume of left atrium (LA), LA appendage (LAA) and right atrium (RA) were significantly increased across the groups with sinus rhythm (SR), AF and AF-related stroke (p < 0.001 for each, respectively). The emptying fraction and booster-pump function of LA, LAA and RA were decreased across the groups (p < 0.001 for each). In addition, the left ventricular mass index was increased in AF related stroke (p = 0.003). Using multivariate analysis, increased age (p = 0.003), reduced booster-pump function of LA (p = 0.01), LAA (p < 0.001) and RA (p < 0.001) were shown to be independently associated with the occurrence of stroke.

CONCLUSIONS

The dilatation and contractile dysfunction of both atria are related to the development of stroke in patients with paroxysmal and persistent AF. Our results suggested that the use of substrate-based assessment may help improve risk stratification of stroke in patients with AF.

Contemporary Assessment of Left Ventricular Diastolic Function in Older Adults: The Atherosclerosis Risk in Communities Study

BACKGROUND

Although age-associated changes in left ventricular diastolic function are well recognized, limited data exist characterizing measures of diastolic function in older adults, including both reference ranges reflecting the older adult population and prognostically relevant values for incident heart failure (HF), as well as their associations with circulating biomarkers of HF risk.

METHODS

Among 5801 elderly participants in the ARIC study (Atherosclerosis Risk in Communities; age range, 67-90 years; mean age, 76±5 years; 42% male; 21% black), we determined the continuous association of diastolic measures (tissue Doppler imaging [TDI] e', E/e', and left atrial size) with concomitant N-terminal pro-brain natriuretic peptide and subsequent HF hospitalization or death. We also determined sex-specific 10th and 90th percentile limits for these measures using quantile regression in 401 participants free of prevalent cardiovascular disease and risk factors.

RESULTS

Each measure of diastolic function was robustly associated with N-terminal pro-brain natriuretic peptide and incident HF or death. ARIC-based reference limits for TDI e' (4.6 and 5.2 cm/s for septal and lateral TDI e', respectively) were substantially lower than guideline cut points (7 and 10 cm/s, respectively), whereas E/e' and left atrial size demonstrated good agreement with guideline cut points. TDI e' was nonlinearly associated with incident HF or death, with inflection points for risk supportive of ARIC-based limits. ARIC-based limits for diastolic function improved risk discrimination over guideline-based cut points based on the integrated discrimination improvement (P<0.001) and continuous net reclassification improvement (P<0.001), reclassifying 42% of the study population as having normal diastolic function. We replicate these findings in the Copenhagen City Heart Study. With these limits, 46% had normal diastolic function and were at low risk of HF hospitalization or death (1%/y over a mean 1.7-year follow-up), 49% had 1 or 2 abnormal measures and were at intermediate risk (2.4%/y), and all 3 diastolic measures were abnormal in 5% who were at high risk (7.5%/y).

CONCLUSIONS

Our findings suggest that left ventricular longitudinal relaxation velocity declines as a part of healthy aging and is largely prognostically benign. The use of age-based normative values when considering an elderly population improves the risk discrimination of diastolic measures for incident HF or death.

Association of chronic kidney disease with impaired left atrial reservoir function: A community-based cohort study

Background Chronic kidney disease (CKD) is an independent risk factor for atrial fibrillation, although the pathophysiological mechanisms remain unclear. This study investigated the relationship between CKD and left atrial (LA) volume and function in a sample of the general population without overt cardiac disease. Design and methods We examined 358 participants from the Cardiovascular Abnormalities and Brain Lesions study. The LA minimum volume index (LAVI_min), LA maximum volume index (LAVI_max), and LA emptying fraction (LAEF) were assessed by real-time three-dimensional echocardiography. Based on their estimated glomerular filtration rate (eGFR), the participants were divided into a CKD group (eGFR <60 ml/min/1.73 m²) and a non-CKD group (eGFR ≥60 ml/min/1.73 m²). Results Of the 358 participants, 69 (19%) were classified as having CKD and 289 (81%) as non-CKD. Participants with CKD were older, had a greater prevalence of hypertension and use of antihypertensive drugs, a larger left ventricular (LV) mass index, and a higher prevalence of diastolic dysfunction than those without CKD (all p < 0.05). There was no significant difference in LAVI_max between the CKD and non-CKD groups (23.4 ± 7.1 vs. 22.8 ± 5.8 ml/m², p = 0.47), whereas significant differences were observed for LAVI_min (13.6 ± 5.5 vs. 12.0 ± 4.6 ml/m², p = 0.01) and LAEF (42.7 ± 11.4 vs. 47.8 ± 11.5%, p = 0.001). Multivariate regression analysis revealed that the eGFR was significantly associated with LAEF independent of age, LV mass index, and diastolic dysfunction (all p < 0.05). Conclusions Participants with CKD in an unselected community-based cohort had significantly impaired LA reservoir function. Assessment of LA function may add important information in the prognostic assessment of patients with CKD even in the absence of overt cardiac disease.

Determinants of Left Atrial Volume in Patients with Atrial Fibrillation

Introduction

Left atrial (LA) enlargement is an important risk factor for incident stroke and a key determinant for the success of rhythm control strategies in patients with atrial fibrillation (AF). However, factors associated with LA volume in AF patients remain poorly understood.

Methods

Patients with paroxysmal or persistent AF were enrolled in this study. Real time 3-D echocardiography was performed in all participants and analyzed offline in a standardized manner. We performed stepwise backward linear regression analyses using a broad set of clinical parameters to determine independent correlates for 3-D LA volume.

Results

We included 210 patients (70.9% male, mean age 61±11years). Paroxysmal and persistent AF were present in 95 (45%) and 115 (55%) patients, respectively. Overall, 115 (55%) had hypertension, 11 (5%) had diabetes, and 18 (9%) had ischemic heart disease. Mean indexed LA volume was 36±12ml/m². In multivariable models, significant associations were found for female sex (β coefficient -10.51 (95% confidence interval (CI) -17.85;-3.16), p = 0.0053), undergoing cardioversion (β 11.95 (CI 5.15; 18.74), p = 0.0006), diabetes (β 14.23 (CI 2.36; 26.10), p = 0.019), body surface area (BSA) (β 34.21 (CI 19.30; 49.12), p<0.0001), glomerular filtration rate (β -0.21 (CI -0.36; -0.06), p = 0.0064) and plasma levels of NT-pro brain natriuretic peptide (NT-proBNP) (β 6.79 (CI 4.05; 9.52), p<0.0001), but not age (p = 0.59) or hypertension (p = 0.42). Our final model explained 52% of the LA volume variability.

Conclusions

In patients with AF, the most important correlates with LA volume are sex, BSA, diabetes, renal function and NT-proBNP, but not age or hypertension. These results may help to refine rhythm control strategies in AF patients.

Left atrial enlargement is an independent predictor of stroke and systemic embolism in patients with non-valvular atrial fibrillation

Controversy exists regarding whether left atrial enlargement (LAE) is a predictor of stroke/systemic embolism (SE) in atrial fibrillation (AF) patients. The Fushimi AF Registry, a community-based prospective survey, enrolled all AF patients in Fushmi-ku, Japan, from March 2011. Follow-up data and baseline echocardiographic data were available for 2,713 patients by August 2015. We compared backgrounds and incidence of events over a median follow-up of 976.5 days between patients with LAE (left atrial diameter > 45 mm; LAE group) and those without in the Fushimi AF Registry. The LAE group accounted for 39% (n = 1,049) of cohort. The LAE group was older and had longer AF duration, with more prevalent non-paroxysmal AF, higher CHADS₂/CHA₂DS₂-VASc score, and oral anticoagulant (OAC) use. A higher risk of stroke/SE during follow-up in the LAE group was found (entire cohort; hazard ratio (HR): 1.92, 95% confidence interval (CI): 1.40–2.64; p < 0.01; without OAC; HR: 1.97, 95% CI: 1.18–3.25; p < 0.01; with OAC; HR: 1.83, 95% CI: 1.21–2.82; p < 0.01). LAE was independently associated with increased risk of stroke/SE (HR: 1.74, 95% CI: 1.25–2.42; p < 0.01) after adjustment by the components of CHA₂DS₂-VASc score and OAC use. In conclusion, LAE was an independent predictor of stroke/SE in large community cohort of AF patients.

Restoration of Mitral Inflow Velocity Until Blanking Period Is Associated With Successful Ablation for Persistent Atrial Fibrillation

Radiofrequency catheter ablation (RFCA) is a useful therapeutic option for atrial fibrillation (AF), although outcomes are less effective for persistent AF. The aim of this study was to elucidate the echocardiographic parameters associated with successful RFCA in patients with persistent AF.A total of 159 patients (mean age, 60.8 ± 9.6 years, 125 males [78.6%]) who underwent RFCA for persistent AF from April 2009 to May 2014 were included, retrospectively. Transthoracic echocardiography was performed at baseline, 3 months, 6 months, and 1 year following RFCA. The subjects were divided into 2 groups, a recurrence group and a non-recurrence group. One hundred eleven of the 159 patients (69.8%) remained free from recurrent atrial tachyarrhythmia during follow-up (mean, 20.6 ± 17.4 months). Peak A wave velocity (38.1 ± 14.1 in the recurrence group; 48.0 ± 20.7 in the non-recurrence group, P = 0.01), peak E wave velocity (76.4 ± 19.1 versus 68.8 ± 19.5, P = 0.03), deceleration time (196.3 ± 54.4 versus 219.9 ± 64.1, P = 0.04), and left atrial (LA) diameter (44.5 ± 7.3 versus 41.0 ± 5.6, P = 0.01) at 3 months after ablation were significantly different between the two groups. Among echocardiographic parameters, peak A wave velocity (OR 0.96, 95% confidence interval [CI] 0.92-0.99) and LA diameter (OR 1.13, 95% CI 1.011.25) were associated with AF recurrence.After RFCA for persistent AF, LA anatomical and functional changes occurred during a 3-month blanking period. Restoration of peak A wave velocity and LA size are associated with successful ablation.

Advanced Left Atrial Remodeling and Appendage Contractile Dysfunction in Women Than in Men Among the Patients With Atrial Fibrillation: Potential Mechanism for Stroke

Background

The risk of stroke imposed by atrial fibrillation (AF) is significantly greater in women than men; however, the mechanism remains elusive. We hypothesized that left atrial (LA) remodeling and poor contractile function of LA appendage (LAA) would be more predominant in women than men among AF patients.

Methods and Results

A total of 579 AF patients (216 women vs age‐, AF type–, and incidences of heart failure, hypertension, diabetes mellitus, stroke or transient ischemic attack, and vascular disease–matched 363 men, 61.3±10.2 years old, 70.1% paroxysmal AF) who underwent AF catheter ablation were included. Sex differences in LA volume index (LAVI) and LAA emptying flow velocity (FV) were analyzed in risk factor 0, 1, and ≥2 groups, according to their CHA₂DS₂‐VASc scores beyond sex category. LAA‐FV was more significantly reduced in women with risk factor ≥2 than in men of the same risk group (P=0.022). Women showed greater LAVI than their male counterparts in the risk factor ≥2 group (P<0.001). The majority of female patients with a history of stroke had a large LAVI and low LAA‐FV (P<0.001); however, no such distribution was observed in men (P=0.596). LA volume index (odds ratio [OR], 1.038; 95% CI, 1.003–1.075, P=0.035) or LAA‐FV (OR, 0.976; 95% CI, 0.952–0.999; P=0.047) was significantly associated with a history of stroke in women.

Conclusions

More‐extensive LA remodeling and deterioration in LAA function were noted in women than in men with high calculated risk of stroke in AF.

The role of myocardial wall thickness in atrial arrhythmogenesis

Changes in the structure and electrical behaviour of the left atrium are known to occur with conditions that predispose to atrial fibrillation (AF) and in response to prolonged periods of AF. We review the evidence that changes in myocardial thickness in the left atrium are an important part of this pathological remodelling process. Autopsy studies have demonstrated changes in the thickness of the atrial wall between patients with different clinical histories. Comparison of the reported tissue dimensions from pathological studies provides an indication of normal ranges for atrial wall thickness. Imaging studies, most commonly done using cardiac computed tomography, have demonstrated that these changes may be identified non-invasively. Experimental evidence using isolated tissue preparations, animal models of AF, and computer simulations proves that the three-dimensional tissue structure will be an important determinant of the electrical behaviour of atrial tissue. Accurately identifying the thickness of the atrial may have an important role in the non-invasive assessment of atrial structure. In combination with atrial tissue characterization, a comprehensive assessment of the atrial dimensions may allow prediction of atrial electrophysiological behaviour and in the future, guide radiofrequency delivery in regions based on their tissue thickness.

The Prognostic Significance of Cardiac Structure and Function in Atrial Fibrillation: The ENGAGE AF-TIMI 48 Echocardiographic Substudy

BACKGROUND

Atrial fibrillation (AF) is associated with increased risk for thromboembolism and death; however, the relationships between cardiac structure and function and adverse outcomes among individuals with AF are incompletely understood.

METHODS

The Effective Anticoagulation with Factor Xa Next Generation in AF-Thrombolysis in Myocardial Infarction 48 study tested the once-daily oral factor Xa inhibitor edoxaban in comparison with warfarin for the prevention of stroke (ischemic or hemorrhagic) or systemic embolism in 21,105 subjects with nonvalvular AF and increased risk for thromboembolic events (CHADS2 score ≥ 2). In a prospective substudy of 971 subjects who underwent transthoracic echocardiography at baseline, Cox proportional hazards models were used to evaluate associations between cardiac structure and function and the risks for death and thromboembolism (ischemic stroke, transient ischemic attack, or systemic embolism).

RESULTS

Over a median follow-up period of 2.5 years, 89 deaths (9.2%) and 48 incident thromboembolic events (4.9%) occurred in 971 subjects. In models adjusted for CHADS2 score, aspirin use, and randomized treatment, larger left ventricular (LV) end-diastolic volume index (hazard ratio per 1 SD [12.9 mL/m(2)], 1.49; 95% CI, 1.16-1.91) and higher LV filling pressures measured by E/e' ratio (hazard ratio per 1 SD [4.6], 1.32; 95% CI, 1.08-1.61) were independently associated with increased risks for death. E/e' ratio > 13 significantly improved the prediction of death beyond clinical factors alone. No features of cardiac structure and function were independently associated with thromboembolism in this population. Findings were similar when adjusted for CHA2DS2-VASc score in place of CHADS2 score.

CONCLUSIONS

In a contemporary population of patients with AF at increased risk for thromboembolic events, larger LV size and higher filling pressures were significantly associated with increased risk for death, but neither left atrial nor LV measures were associated with thromboembolic risk. LV size and filling pressures may help identify patients with AF at increased risk for death.

Atrial fibrillation: mechanisms, therapeutics, and future directions

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia, affecting 1% to 2% of the general population. It is characterized by rapid and disorganized atrial activation leading to impaired atrial function, which can be diagnosed on an EKG by lack of a P-wave and irregular QRS complexes. AF is associated with increased morbidity and mortality and is a risk factor for embolic stroke and worsening heart failure. Current research on AF support and explore the hypothesis that initiation and maintenance of AF require pathophysiological remodeling of the atria, either specifically as in lone AF or secondary to other heart disease as in heart failure-associated AF. Remodeling in AF can be grouped into three categories that include: (i) electrical remodeling, which includes modulation of L-type Ca(2+) current, various K(+) currents and gap junction function; (ii) structural remodeling, which includes changes in tissues properties, size, and ultrastructure; and (iii) autonomic remodeling, including altered sympathovagal activity and hyperinnervation. Electrical, structural, and autonomic remodeling all contribute to creating an AF-prone substrate which is able to produce AF-associated electrical phenomena including a rapidly firing focus, complex multiple reentrant circuit or rotors. Although various remodeling events occur in AF, current AF therapies focus on ventricular rate and rhythm control strategies using pharmacotherapy and surgical interventions. Recent progress in the field has started to focus on the underlying substrate that drives and maintains AF (termed upstream therapies); however, much work is needed in this area. Here, we review current knowledge of AF mechanisms, therapies, and new areas of investigation.

Edoxaban for reducing the risk of stroke and systemic embolism in patients with non-valvular atrial fibrillation

INTRODUCTION

Oral anticoagulation is central to the management of patients with atrial fibrillation (AF) and at least one additional stroke risk factor. For decades, the vitamin K antagonists (e.g. warfarin) remained the only oral anticoagulant available for stroke prevention in AF. The non-vitamin K oral anticoagulants (NOACs) are now available, and these drugs include the direct thrombin inhibitors and factor Xa inhibitors. The latter class includes edoxaban, which has recently been approved for stroke prevention in AF by the United States Food and Drug Administration and the European Medicine Agency. In line with other NOACs, edoxaban avoids the many limitations of warfarin associated with variability of anticoagulation effect and multiple food and drug interactions.

AREAS COVERED

In this review, the currently available evidence on edoxaban in patients with non-valvular AF is discussed. The pharmacology, efficacy and safety, and current aspects of use of edoxaban in patients with non-valvular AF for stroke and thromboembolism prevention are reviewed.

EXPERT OPINION

Phase III trials on edoxaban for stroke prevention in non-valvular AF confirms non-inferiority of edoxaban compared to well-managed warfarin both in terms of efficacy and safety. Currently ongoing and future trials as well as real-world data are warranted to confirm its effectiveness and safety for chronic anticoagulation and improve evidence in other areas which are lacking evidence where NOAC use remains controversial.

Quantification of atrial dynamics using cardiovascular magnetic resonance: inter-study reproducibility

BACKGROUND

Cardiovascular magnetic resonance (CMR) offers quantification of phasic atrial functions based on volumetric assessment and more recently, on CMR feature tracking (CMR-FT) quantitative strain and strain rate (SR) deformation imaging. Inter-study reproducibility is a key requirement for longitudinal studies but has not been defined for CMR-based quantification of left atrial (LA) and right atrial (RA) dynamics.

METHODS

Long-axis 2- and 4-chamber cine images were acquired at 9:00 (Exam A), 9:30 (Exam B) and 14:00 (Exam C) in 16 healthy volunteers. LA and RA reservoir, conduit and contractile booster pump functions were quantified by volumetric indexes as derived from fractional volume changes and by strain and SR as derived from CMR-FT. Exam A and B were compared to assess the inter-study reproducibility. Morning and afternoon scans were compared to address possible diurnal variation of atrial function.

RESULTS

Inter-study reproducibility was within acceptable limits for all LA and RA volumetric, strain and SR parameters. Inter-study reproducibility was better for volumetric indexes and strain than for SR parameters and better for LA than for RA dynamics. For the LA, reservoir function showed the best reproducibility (intraclass correlation coefficient (ICC) 0.94-0.97, coefficient of variation (CoV) 4.5-8.2%), followed by conduit (ICC 0.78-0.97, CoV 8.2-18.5%) and booster pump function (ICC 0.71-0.95, CoV 18.3-22.7). Similarly, for the RA, reproducibility was best for reservoir function (ICC 0.76-0.96, CoV 7.5-24.0%) followed by conduit (ICC 0.67-0.91, CoV 13.9-35.9) and booster pump function (ICC 0.73-0.90, CoV 19.4-32.3). Atrial dynamics were not measurably affected by diurnal variation between morning and afternoon scans.

CONCLUSIONS

Inter-study reproducibility for CMR-based derivation of LA and RA functions is acceptable using either volumetric, strain or SR parameters with LA function showing higher reproducibility than RA function assessment. Amongst the different functional components, reservoir function is most reproducibly assessed by either technique followed by conduit and booster pump function, which needs to be considered in future longitudinal research studies.

Association of left atrial function and left atrial enhancement in patients with atrial fibrillation: cardiac magnetic resonance study

BACKGROUND

Atrial fibrillation (AF) is associated with left atrial (LA) structural and functional changes. Cardiac magnetic resonance late gadolinium enhancement (LGE) and feature-tracking are capable of noninvasive quantification of LA fibrosis and myocardial motion, respectively. We sought to examine the association of phasic LA function with LA enhancement in patients with AF.

METHODS AND RESULTS

LA structure and function was measured in 90 patients with AF (age 61±10 years; 76% men) referred for ablation and 14 healthy volunteers. Peak global longitudinal LA strain, LA systolic strain rate, and early and late diastolic strain rates were measured using cine-cardiac magnetic resonance images acquired during sinus rhythm. The degree of LGE was quantified. Compared with patients with paroxysmal AF (60% of cohort), those with persistent AF had larger maximum LA volume index (56±17 versus 49±13 mL/m(2); P=0.036), and increased LGE (27.1±11.7% versus 36.8±14.8%; P<0.001). Aside from LA active emptying fraction, all LA parameters (passive emptying fraction, peak global longitudinal LA strain, systolic strain rate, early diastolic strain rate, and late diastolic strain rate) were lower in patients with persistent AF (P<0.05 for all). Healthy volunteers had less LGE and higher LA functional parameters compared with patients with AF (P<0.05 for all). In multivariable analysis, increased LGE was associated with lower LA passive emptying fraction, peak global longitudinal LA strain, systolic strain rate, early diastolic strain rate, and late diastolic strain rate (P<0.05 for all).

CONCLUSIONS

Increased LA enhancement is associated with decreased LA reservoir, conduit, and booster pump functions. Phasic measurement of LA function using feature-tracking cardiac magnetic resonance may add important information about the physiological importance of LA fibrosis.

Atrial fibrillation recurrence predictors after conversion to sinus rhythm

Purpose: We aimed to identify predictors of atrial fibrillation recurrence after conversion to sinus rhythm. Material/Methods: We included 100 patients with a history of documented atrial fibrillation in the last 12 months that were assessed by transthoracic echocardiography, 12-lead electrocardiogram and signal averaged electrocardiogram of the P wave. Follow-up was 7.3 ± 2.2 months. Results: Atrial fibrillation recurrence was documented in 27 patients. It was more frequent in patients with longer duration of previous atrial fibrillation episode, with increased left atrium size and left ventricular mass, and it was correlated with the filtered P wave duration and Integral of the P wave. Conclusions: Signal averaged ECG of the P wave, left atrium size and left ventricular mass determined by echocardiography could be helpful in predicting the risk of atrial fibrillation recurrence after conversion.

Heart failure and atrial fibrillation: from basic science to clinical practice

Heart failure (HF) and atrial fibrillation (AF) are two growing epidemics associated with significant morbidity and mortality. They often coexist due to common risk factors and shared pathophysiological mechanisms. Patients presenting with both HF and AF have a worse prognosis and present a particular therapeutic challenge to clinicians. This review aims to appraise the common pathophysiological background, as well as the prognostic and therapeutic implications of coexistent HF and AF.

Risk of ischaemic stroke according to pattern of atrial fibrillation: analysis of 6563 aspirin-treated patients in ACTIVE-A and AVERROES

AIMS

The pattern of atrial fibrillation (AF) occurrence-paroxysmal, persistent, or permanent-is associated with progressive stages of atrial dysfunction and structural changes and may therefore be associated with progressively higher stroke risk. However, previous studies have not consistently shown AF pattern to predict stroke but have been hampered by methodological shortcomings of low power, variable event ascertainment, and variable anticoagulant use.

METHODS AND RESULTS

We analysed the rates of stroke and systemic embolism in 6563 aspirin-treated patients with AF from the ACTIVE-A/AVERROES databases. There was thorough searching for events and adjudication. Multivariable analyses were performed with the adjustment for known risk factors for stroke. Mean age of patients with paroxysmal, persistent, and permanent AF was 69.0 ± 9.9, 68.6 ± 10.2, and 71.9 ± 9.8 years (P < 0.001). The CHA2DS2-VASc score was similar in patients with paroxysmal and persistent AF (3.1 ± 1.4), but was higher in patients with permanent AF (3.6 ± 1.5, P < 0.001). Yearly ischaemic stroke rates were 2.1, 3.0, and 4.2% for paroxysmal, persistent, and permanent AF, respectively, with adjusted hazard ratio of 1.83 (P < 0.001) for permanent vs. paroxysmal and 1.44 (P = 0.02) for persistent vs. paroxysmal. Multivariable analysis identified age ≥ 75 year, sex, history of stroke or TIA, and AF pattern as independent predictors of stroke, with AF pattern being the second strongest predictor after prior stroke or TIA.

CONCLUSION

In a large population of non-anticoagulated AF patients, pattern of AF was a strong independent predictor of stroke risk and may be helpful to assess the risk/benefit for anticoagulant therapy, especially in lower risk patients.

Relation of left atrial dysfunction to ischemic stroke in patients with coronary heart disease (from the heart and soul study)

This study sought to determine whether left atrial (LA) dysfunction independently predicts ischemic stroke. Atrial fibrillation (AF) impairs LA function and is associated with ischemic stroke. However, ischemic stroke frequently occurs in patients without known AF. The direct relation between LA function and risk of ischemic stroke is unknown. We performed transthoracic echocardiography at rest in 983 subjects with stable coronary heart disease. To quantify LA dysfunction, we used the left atrial function index (LAFI), a validated formula incorporating LA volumes at end-atrial systole and diastole. Cox proportional hazards models were used to evaluate the association between LAFI and ischemic stroke or transient ischemic attack (TIA). Over a mean follow-up of 7.1 years, 58 study participants (5.9%) experienced an ischemic stroke or TIA. In patients without known baseline AF or warfarin therapy (n = 893), participants in the lowest quintile of LAFI had >3 times the risk of ischemic stroke or TIA (hazard ratio 3.3, 95% confidence interval 1.1 to 9.7, p = 0.03) compared with those in the highest quintile. For each standard deviation (18.8 U) decrease in LAFI, the hazard of ischemic stroke or TIA increased by 50% (hazard ratio 1.5, 95% confidence interval 1.0 to 2.1, p = 0.04). Among measured echocardiographic indexes of LA function, including LA volume, LAFI was the strongest predictor of ischemic stroke or TIA. In conclusion, LA dysfunction is an independent risk factor for stroke or TIA, even in patients without baseline AF.