Levels of PAI-1 and outcome after electrical cardioversion for atrial fibrillation

Altered fibrin clot properties and fibrinolysis in patients with atrial fibrillation: practical implications

Compelling evidence indicates that a hypercoagulable state occurs in patients with atrial fibrillation (AF) including those in sinus rhythm following paroxysmal and persistent AF. Activation of blood coagulation in AF reflects heightened thrombin generation with the subsequent increased formation of fibrin as evidenced by elevated soluble fibrin monomers and D-dimer. Formation of denser fibrin meshworks, relatively resistant to plasmin-mediated lysis has been demonstrated in patients with AF. The presence of stroke risk factors in AF, such as diabetes, heart failure, hypertension, previous myocardial infarction, or stroke, advanced age have been shown to be linked to the prothrombotic clot characteristics, including reduced clot permeability and lysability. Importantly, biomarkers, including cardiac troponins and N-terminal pro-brain natriuretic peptide, are associated with thrombin generation and fibrin-related markers in AF patients. Recently, increased fibrin clot density (low clot permeability measured in plasma-based assays) and impaired fibrinolysis measured off anticoagulation have been demonstrated to predict ischaemic cerebrovascular events in patients with AF receiving vitamin K antagonists and those on rivaroxaban. The current review summarizes evidence for a role of altered fibrin clot properties and hypofibrinolysis in AF and their prognostic value in terms of adverse events.

Atrial fibrillation: the role of hypoxia-inducible factor-1-regulated cytokines

Atrial fibrillation (AF) is a common arrhythmia that has major morbidity and mortality. Hypoxia plays an important role in AF initiation and maintenance. Hypoxia-inducible factor (HIF), the master regulator of oxygen homeostasis in cells, plays a fundamental role in the regulation of multiple chemokines and cytokines that are involved in different physiological and pathophysiological pathways. HIF is also involved in the pathophysiology of AF induction and propagation mostly through structural remodeling such as fibrosis; however, some of the cytokines discussed have even been implicated in electrical remodeling of the atria. In this article, we highlight the association between HIF and some of its related cytokines with AF. Additionally, we provide an overview of the potential diagnostic benefits of using the mentioned cytokines as AF biomarkers. Research discussed in this review suggests that the expression of these cytokines may correlate with patients who are at an increased risk of developing AF. Furthermore, cytokines that are elevated in patients with AF can assist clinicians in the diagnosis of suspect paroxysmal AF patients. Interestingly, some of the cytokines have been elevated specifically when AF is associated with a hypercoagulable state, suggesting that they could be helpful in the clinician's and patient's decision to begin anticoagulation. Finally, more recent research has demonstrated the promise of targeting these cytokines for the treatment of AF. While still in its early stages, tools such as neutralizing antibodies have proved to be efficacious in targeting the HIF pathway and treating or preventing AF.

The prothrombotic state in atrial fibrillation: pathophysiological and management implications

Atrial fibrillation (AF) is the commonest sustained cardiac arrhythmia and is associated with significant morbidity and mortality. There is plenty of evidence available to support the presence of a prothrombotic or hypercoagulable state in AF, but the contributory factors are multifactorial and cannot simply be explained by blood stasis. Abnormal changes in atrial wall (anatomical and structural, as ‘vessel wall abnormalities’), the presence of spontaneous echo contrast to signify abnormal changes in flow and stasis (‘flow abnormalities’), and abnormal changes in coagulation, platelet, and other pathophysiologic pathways (‘abnormalities of blood constituents’) are well documented in AF. The presence of these components therefore fulfils Virchow’s triad for thrombogenesis. In this review, we present an overview of the established and professed pathophysiological mechanisms for thrombogenesis in AF and its management implications.

High-Sensitivity Troponin I and Rhythm Outcome after Electrical Cardioversion for Persistent Atrial Fibrillation

OBJECTIVES

We hypothesised that high-sensitivity troponin I (hs-TnI) might predict long-term rhythm outcome after cardioversion for persistent atrial fibrillation (AF), and that maintenance of sinus rhythm and/or treatment with the angiotensin II type 1 receptor blocker candesartan would reduce hs-TnI levels.

METHODS

In a double-blind, placebo-controlled study, 171 patients referred for electrical cardioversion for AF were randomised to receive candesartan or placebo for 3-6 weeks before cardioversion and for 6 months after electrical cardioversion. Blood samples for analysis of hs-TnI (Abbott Diagnostics) were available in 129 patients at baseline and in 60 successfully cardioverted patients at study end.

RESULTS

Hs-TnI was detectable in all subjects, with a median value of 5.3 ng/l (25th percentile 3.7, 75th percentile 7.2). hs-TnI at baseline was not predictive of rhythm outcome 6 months after electrical cardioversion for persistent AF. Treatment with candesartan did not influence the levels of hs-TnI. hs-TnI was unchanged from baseline to study end in patients who maintained sinus rhythm [4.9 (3.7, 7.0) and 5.0 (4.0, 6.4) ng/l, respectively; p = 0.699).

CONCLUSIONS

hs-TnI did not predict AF recurrence after cardioversion. hs-TnI levels were unchanged in patients maintaining sinus rhythm for 6 months after electrical cardioversion. hs-TnI levels were not influenced by treatment with candesartan.

Impact of atrial fibrillation on levels of high-sensitivity troponin I in a 75-year-old population

PURPOSE

Atrial fibrillation (AF) has been associated with elevated levels of cardiac troponins; however, it is not clear if this association is independent of underlying cardiovascular disease. The aim of this study was to investigate the impact of AF on cardiac troponin I levels in a 75-year-old cohort from the general population, using a recently introduced, highly sensitive assay.

METHODS

All 75-year-old citizens in Asker and Baerum counties were invited to participate in a prevalence study of AF. High-sensitive troponin I (hs-TnI) levels were measured (Abbott Diagnostics) in serum samples collected from 62 subjects with AF and a gender-matched control group of 126 subjects in sinus rhythm.

RESULTS

Hs-TnI was detectable in all subjects (median 7.3 ng/L [range 3.0-88.7]). Patients with AF had higher levels than subjects in sinus rhythm (8.3 ng/L [3.7-88.7] vs. 6.8 ng/L [3.0-77.5]; p = 0.011). Male gender (p = 0.002), hypertension (p = 0.001), coronary heart disease (p < 0.001), heart failure (p < 0.001), prior stroke or transient ischemic attack (p = 0.013) and serum creatinine (p < 0.001) were all associated with higher levels of hs-TnI in univariate analysis. Heart failure and coronary heart disease remained significantly associated with hs-TnI in multivariate analysis, whereas the relation between AF and hs-TnI was no longer statistically significant.

CONCLUSION

All subjects had detectable levels of hs-TnI. AF patients had higher hs-TnI levels than subjects in sinus rhythm; however, this difference was not statistically significant after adjustment for heart failure and coronary heart disease.

Angiotensin II blockade, YKL-40 and maintenance of sinus rhythm after electrical cardioversion for atrial fibrillation

High levels of the novel inflammatory marker YKL-40 have been demonstrated in inflammatory environments and in remodeling of the extracellular matrix. Both are key components in atrial wall remodeling in atrial fibrillation (AF). We studied the relation between rhythm outcome after electrical cardioversion (ECV) for persistent AF and serum levels of YKL-40. A secondary point of interest was a potential effect of the angiotensin receptor blocker candesartan on YKL-40 levels. In the Candesartan in the Prevention of Relapsing Atrial Fibrillation (CAPRAF) study, 171 patients with persistent AF were randomized to receive candesartan 8mg once daily or placebo for 3-6 weeks before ECV and candesartan 16mg once daily or placebo for 6 months after ECV. Serum levels of YKL-40 were measured in fasting blood samples collected at baseline and at end of the study. Mean age was 64±11 years, and 39 (22.8%) were women. Sinus rhythm was maintained for 6 months after ECV in 41 (23.9%). Baseline levels of YKL-40 were significantly correlated to age (Spearmans rho; rs=0.442; p<0.001), CHA2DS2-VASc(1) score (rs=0.256; p<0.001) and left atrial diameter (rs=0.185; p=0.017). By use of Kaplan-Meier quartile analysis of baseline YKL-40 levels, no relation between YKL-40 levels and risk of AF recurrence was found. End of study YKL-40 levels were unchanged from baseline, both in patients with AF recurrence and those maintaining sinus rhythm for 6 months. Treatment with candesartan had no influence on serum YKL-40 levels.

Importance of physical fitness on predictive effect of body mass index and weight gain on incident atrial fibrillation in healthy middle-age men

The incidence of both atrial fibrillation (AF) and obesity is increasing in the community, and lifestyle intervention is recommended. We aimed to test whether the predictive effect of body mass index (BMI) and weight change from age 25 years to midlife on incident AF were influenced by physical fitness. In 1972 to 1975, 2,014 healthy middle-age men conducted a bicycle exercise electrocardiographic test as a part of a cardiovascular survey program, defining physical fitness as work performed divided by body weight. During 35 years of follow-up, 270 men developed AF, documented by scrutiny of the health files in all Norwegian hospitals. Risk estimation was analyzed using Cox proportional hazard models and tested for age-adjusted physical fitness above and below the median. The mean BMI of 24.6 kg/m(2) defined a lean baseline cohort. The men with a baseline BMI of ≥28 kg/m(2) (11%) compared to a BMI <28 kg/m(2) had a 1.68-fold risk of AF (95% confidence interval 1.14 to 2.40) and men reporting weight gain of ≥10 kg (24%) compared to weight loss (11%) of 1.66-fold (95% confidence interval 1.00 to 2.89), respectively. The dichotomy into men with age-adjusted physical fitness above and below the median, demonstrated statistically significant risk associations only for men with low fitness. The overall risk of AF was reduced by 23% in the fit men. In conclusion, within our lean baseline cohort of healthy middle-age men, a BMI of ≥28 kg/m(2) and weight gain of ≥10 kg from age 25 to midlife were long-term predictors of incident AF in men with physical fitness below the population median. The fit men had an overall slightly reduced risk of AF.

Mechanisms of thrombogenesis in atrial fibrillation: Virchow's triad revisited

Atrial fibrillation is the most common sustained cardiac arrhythmia, which is associated with a high risk of stroke and thromboembolism. Increasing evidence suggests that the thrombogenic tendency in atrial fibrillation is related to several underlying pathophysiological mechanisms. Abnormal changes in flow are evident by stasis in the left atrium, and seen as spontaneous echocontrast. Abnormal changes in vessel walls-essentially, anatomical and structural defects-include progressive atrial dilatation, endocardial denudation, and oedematous or fibroelastic infiltration of the extracellular matrix. Additionally, abnormal changes in blood constituents are well described, and include haemostatic and platelet activation, as well as inflammation and growth factor changes. These changes result in the fulfilment of Virchow's triad for thrombogenesis, and accord with a prothrombotic or hypercoagulable state in this arrhythmia. In this Review, we present an overview of the established and purported mechanisms for thrombogenesis in atrial fibrillation.