***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background — Atrial fibrillation ( AF ) is common among patients with heart failure and preserved ejection fraction ( HFpEF ) , but its clinical profile and impact on exercise capacity remain unclear . RELAX ( Phosphodiesterase-5 Inhibition to Improve Clinical Status and Exercise Capacity in HFpEF ) was a multicenter r and omized trial testing the impact of sildenafil on peak VO2 in stable out patients with chronic HFpEF . We sought to compare clinical features and exercise capacity among patients with HFpEF who were in sinus rhythm ( SR ) or AF . Methods and Results — RELAX enrolled 216 patients with HFpEF , of whom 79 ( 37 % ) were in AF , 124 ( 57 % ) in SR , and 13 in other rhythms . Participants underwent baseline cardiopulmonary exercise testing , echocardiogram , biomarker assessment , and rhythm status assessment before r and omization . Patients with AF were older than those in SR but had similar symptom severity , comorbidities , and renal function . & bgr;-blocker use and chronotropic indices were also similar . Despite comparable left ventricular size and mass , AF was associated with worse systolic ( lower EF , stroke volume , and cardiac index ) and diastolic ( shorter deceleration time and larger left atria ) function compared with SR . Pulmonary artery systolic pressure was higher in AF . Patients with AF had higher N-terminal pro-B-type natriuretic peptide , aldosterone , endothelin-1 , troponin I , and C-telopeptide for type I collagen levels , suggesting more severe neurohumoral activation , myocyte necrosis , and fibrosis . Peak VO2 was lower in AF , even after adjustment for age , sex , and chronotropic response , and VE/VCO2 was higher . Conclusions — AF identifies an HFpEF cohort with more advanced disease and significantly reduced exercise capacity . These data suggest that evaluation of the impact of different rate or rhythm control strategies on exercise tolerance in patients with HFpEF and AF is warranted . Clinical Trial Registration — URL : http://www . clinical trials.gov . Unique identifier : NCT00763867 Background — Isolated atrial fibrillation ( AF ) is associated with mild enlargement of the left atrium ( LA ) and left ventricular ( LV ) diastolic dysfunction . The impact of ablation of isolated AF on left chamber size and function is unclear , and whether diastolic dysfunction is the cause or the consequence of AF remains unknown . The objective of this prospect i ve study was to evaluate the impact of sinus rhythm restoration by catheter ablation on LV diastolic dysfunction , LA morphology , and mechanical function . Methods and Results — Forty-eight patients with isolated AF were studied by serial echocardiographic studies at baseline and at 1- , 3- , 6- , 9- , and 12-month intervals after radiofrequency ablation .  LA dimensions and mechanical function and LV systolic and diastolic functions were evaluated at each time interval . Diastolic function was assessed with conventional Doppler parameters and new indexes such as tissue Doppler imaging , mitral flow propagation velocity , and combined criteria . LV diastolic dysfunction was present in paroxysmal and chronic AF patients with a reduction of tissue Doppler imaging lateral early diastolic peak velocity in 37 % ( P<0.001 ) and 48 % ( P<0.01 ) , respectively , compared with healthy control subjects . At the end of the follow-up , LA area decreased significantly by 18 % ( P<0.001 ) in paroxysmal and 23 % ( P<0.05 ) in chronic AF patients . Diastolic function improved significantly with an increase in lateral early diastolic peak velocity of 29 % ( P<0.001 ) in paroxysmal AF and 46 % ( P<0.05 ) in chronic AF patients . A significant increase in LV ejection fraction was also noted for both groups : 7.7 % and 18.8 % , respectively . Conclusions — This study demonstrates reverse morphological remodeling of the LA and improvement of LV diastolic and systolic functions after restoration of sinus rhythm by ablation for isolated AF . Because patients with isolated AF have none of the traditional causes of LV diastolic dysfunction , our findings suggest that AF may be partly the cause rather than the consequence of diastolic dysfunction 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 r and omly 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 OBJECTIVES The aim of this study was to investigate the utility of a comprehensive imaging protocol including echocardiography and cardiac magnetic resonance in the diagnosis and differentiation of hypertensive heart disease and heart failure with preserved ejection fraction ( HFpEF ) . BACKGROUND Hypertension is present in up to 90 % of patients with HFpEF and is a major etiological component . Despite current recommendations and diagnostic criteria for HFpEF , no noninvasive imaging technique has as yet shown the ability to identify any structural differences between patients with hypertensive heart disease and HFpEF . METHODS We conducted a prospect i ve cross-sectional study of 112 well-characterized patients ( 62 with HFpEF , 22 with hypertension , and 28 healthy control subjects ) . All patients underwent cardiopulmonary exercise and biomarker testing and an imaging protocol including echocardiography with speckle-tracking analysis and cardiac magnetic resonance including T1 mapping pre- and post-contrast . RESULTS Echocardiographic global longitudinal strain ( GLS ) and extracellular volume ( ECV ) measured by cardiac magnetic resonance were the only variables able to independently stratify among the 3 groups of patients . ECV was the best technique for differentiation between hypertensive heart disease and HFpEF ( ECV area under the curve : 0.88 ; GLS area under the curve : 0.78 ; p < 0.001 for both ) . Using ECV , an optimal cutoff of 31.2 % gave 100 % sensitivity and 75 % specificity . ECV was significantly higher and GLS was significantly reduced in subjects with reduced exercise capacity ( lower peak oxygen consumption and higher minute ventilation-carbon dioxide production ) ( p < 0.001 for both ECV and GLS ) . CONCLUSIONS Both GLS and ECV are able to independently discriminate between hypertensive heart disease and HFpEF and identify patients with prognostically significant functional limitation . ECV is the best diagnostic discriminatory marker of HFpEF and could be used as a surrogate endpoint for therapeutic studies BACKGROUND S Paroxysmal atrial fibrillation ( AF ) frequently , but not always , progresses to persistent/permanent AF . The aim of this study was to evaluate the echocardiographic predictors of AF progression in patients with paroxysmal AF . METHODS A multicenter , prospect i ve , observational study was conducted that included 313 patients with paroxysmal AF who underwent two-dimensional speckle-tracking echocardiography .  The diameter , volume , and mechanical function of the left atrium , including global strain ( ε ) and ε rate , were measured . RESULTS Progression to persistent or permanent AF occurred in 52 patients ( 16.6 % ) during a median follow-up period of 26 months . Echocardiographic measure of left atrial ( LA ) diameter , volume , and function ( E velocity , E/A and E/e ' ratio , LA expansion index , active emptying fraction , global longitudinal ε and ε rate ) were associated with AF progression . LA ε ≤ 30.9 % was the strongest predictor of AF progression , which was associated with a more than fourfold hazard increase for AF progression ( hazard ratio , 4.224 ; P = .001 ) . LA diameter > 39 mm and maximal LA volume index > 34.2 mL/m(2 ) were associated with about a twofold hazard increase for AF progression ( hazard ratios , 1.994 and 2.649 ; P = .016 and P = .001 , respectively ) . When adjusted for a model combining maximal LA volume index , E velocity , LA expansion index , and active emptying fraction , LA ε ≤ 30.9 % maintained a more than threefold hazard increase for AF progression ( adjusted hazard ratio , 3.970 ; P = .003 ) . CONCLUSIONS Echocardiographic measures of LA diameter , volume , and mechanical function , including LA ε , were associated with AF progression . LA ε was the strongest independent predictor of AF progression and is expected to serve as a valuable predictor of AF progression Background — Atrial fibrillation ( AF ) is associated with diffuse left atrial fibrosis and a reduction in endocardial voltage . These changes are indicators of AF severity and appear to be predictors of treatment outcome . In this study , we report the utility of delayed-enhancement magnetic resonance imaging ( DE-MRI ) in detecting abnormal atrial tissue before radiofrequency ablation and in predicting procedural outcome . Methods and Results — Eighty-one patients presenting for pulmonary vein antrum isolation for treatment of AF underwent  3-dimensional DE-MRI of the left atrium before the ablation .  Six healthy volunteers also were scanned . DE-MRI images were manually segmented to isolate the left atrium , and custom software was implemented to quantify the spatial extent of delayed enhancement , which was then compared with the regions of low voltage from electroanatomic maps from the pulmonary vein antrum isolation procedure . Patients were assessed for AF recurrence at least 6 months after pulmonary vein antrum isolation , with an average follow-up of 9.6±3.7 months ( range , 6 to 19 months ) . On the basis of the extent of preablation enhancement , 43 patients were classified as having minimal enhancement ( average enhancement , 8.0±4.2 % ) , 30 as having moderate enhancement ( 21.3±5.8 % ) , and 8 as having extensive enhancement ( 50.1±15.4 % ) . The rate of AF recurrence was 6 patients ( 14.0 % ) with minimal enhancement , 13 ( 43.3 % ) with moderate enhancement , and 6 ( 75 % ) with extensive enhancement ( P<0.001 ) . Conclusions — DE-MRI provides a noninvasive means of assessing left atrial myocardial tissue in patients suffering from AF and might provide insight into the progress of the disease . Preablation DE-MRI holds promise for predicting responders to AF ablation and may provide a metric of overall disease progression BACKGROUND Left atrial ( LA ) enlargement facilitates induction and /or maintenance of atrial fibrillation ( AF ) . However , little is known about risk factors for AF with normal LA size . METHODS We prospect ively followed 34713 initially healthy women for incident AF . Information on echocardiographic LA size at first AF diagnosis was abstract ed from medical charts during AF confirmation . LA enlargement was defined as LA diameter > 40 mm . Using a competing risk approach , we constructed Cox proportional-hazards models to calculate hazard ratios ( HR ) and 95 % confidence intervals ( CI ) of risk factors for incident AF with and without LA enlargement , respectively . RESULTS Among 796 women with incident AF and available LA size , 328 ( 41 % ) had LA enlargement . In multivariable competing risk models , the relationship between age and incident AF was stronger in those with ( HR 1.12 , 95 % CI 1.10 - 1.14 ) versus without ( HR 1.08 , 95 % CI 1.06 - 1.09 ) LA enlargement ( p for difference < 0.0001 ) . Body weight was associated with AF only in the presence of LA enlargement ( HR per 10 kg 1.34 , 95 % CI 1.26 - 1.43 ; versus 1.07 , 95 % CI 0.998 - 1.14 , p for difference<0.0001 ) . Hypertension and height were significantly associated with 
    Output:
    
An integrated evaluation should be also applied to patients with a high arrhythmic risk , in whom eccentric LA remodelling and higher LA stiffness are associated with a greater AF risk .
Evaluation of LA size , volume , function and structure are m and atory in the management of patients with HT , HFpEF and AF .
A multi-modality approach could provide additional information , identifying subjects with more severe LA remodelling .