Relationship of interleukin-6 and C-reactive protein to the prothrombotic state in chronic atrial fibrillation.

OBJECTIVES: We sought to test the hypothesis that there is a relationship between inflammation and the prothrombotic state in atrial fibrillation (AF). BACKGROUND: Atrial fibrillation is associated with a prothrombotic or hypercoagulable state, which may contribute to an increased risk of stroke and thromboembolism. Inflammation may be involved in the pathogenesis of AF, but the role of inflammation in the pathophysiology of the prothrombotic state of AF has not been studied in detail, despite evidence of a link between inflammation and arterial atherothrombotic disorders. METHODS: We measured plasma indexes of inflammation (C-reactive protein [CRP] and interleukin-6 [IL-6]) and the prothrombotic state, including markers of platelet activation (soluble P-selectin), endothelial damage/dysfunction (von Willebrand factor), the coagulation cascade (tissue factor [TF], fibrinogen), and indexes of blood rheology (plasma viscosity, plasma fibrinogen, and hematocrit) in 106 patients with chronic AF and 41 healthy control subjects included in a cross-sectional analysis. RESULTS: Compared with controls, AF patients had higher levels of IL-6 (p = 0.034), CRP (p = 0.003), TF (p = 0.019), and plasma viscosity (p = 0.045). Plasma IL-6 levels were higher among AF patients at "high" risk of stroke (p = 0.003). After adjusting for potential confounding clinical variables (e.g., vascular disease), AF remained significantly associated with a raised logarithmic transformation (log) of TF (p = 0.04), but the relationships between AF and log IL-6, log CRP, and plasma viscosity became nonsignificant. Among AF patients, log TF (p < 0.001) and high stroke risk (p = 0.003) were independent associates of log IL-6 (adjusted r(2) = 0.443), whereas log fibrinogen (p < 0.001) and plasma viscosity (p = 0.04) were independent associates of log CRP (adjusted r(2) = 0.259). CONCLUSIONS: Increased plasma IL-6, CRP, and plasma viscosity support the case for the existence of an inflammatory state among "typical" populations with chronic AF. These indexes of inflammation are related to indexes of the prothrombotic state and may be related to the clinical variables of the patients (underlying vascular disease and co-morbidities), rather than simply to the presence of AF itself.

Prognostic significance of raised plasma levels of interleukin-6 and C-reactive protein in atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is a risk factor for stroke and death. Inflammation has been associated with AF, but the prognostic significance of inflammatory mediators, such as interleukin-6 (IL-6) and C-reactive protein (CRP), among patients with AF is unknown. We hypothesized that increased plasma levels of IL-6 and CRP, as indexes of an inflammatory state, would be associated with an increased risk of stroke and death among patients with AF. METHODS: We undertook a pilot study to determine dates of stroke or death occurring among 77 AF cases, with stored plasma samples having initially been obtained during attendance at our specialist AF clinic between 1993 and 1995. Plasma IL-6 and CRP were measured by ELISA and a high-sensitivity latex particle turbidimetric assay, respectively. RESULTS: Patients were followed up for a median duration of 2305 days (interquartile range, 1692 to 2592) [equivalent to 6.3 (4.6 to 7.1) years]. During this period, there were 8 (10%) strokes, 22 (29%) deaths, and 28 (36%) patients who had stroke or death. Prior stroke and high (above median) IL-6 levels were independent predictors of stroke. Age was the only independent predictor of death. High (above median) IL-6 levels remained a significant predictor of stroke or death, even after adjustment for age (hazard ratio, 2.91; 95% CI, 1.20 to 6.51; P =.007), and was the only independent predictor of stroke or death. Trends toward increased risk with high plasma CRP did not reach statistical significance (P =.06 for stroke or death). CONCLUSIONS: In this pilot study, high plasma IL-6 levels were an independent predictor of stroke and the composite end point of stroke or death, suggesting that inflammation in AF may predict a poor prognosis.

Predictive value of indexes of inflammation and hypercoagulability on success of cardioversion of persistent atrial fibrillation.

The aim of the present study was to investigate whether success or failure of direct-current cardioversion in patients with persistent atrial fibrillation may be related to indexes of inflammation (as indicated by C-reactive protein and interleukin-6, platelet activation [soluble P-selectin levels], endothelial damage/dysfunction [von Willebrand factor], coagulation cascade [tissue factor and fibrinogen], and rheology [plasma viscosity and hematocrit]). We found that C-reactive protein levels are a predictor of initial cardioversion success, although they failed to predict long-term outcome. Although inflammation may be associated with "permanence" of atrial fibrillation, indexes of platelet activation, endothelial damage/dysfunction, or coagulation showed no relation to the immediate and long-term (2-month) cardioversion outcome.

Relation of interleukin-6, C-reactive protein, and the prothrombotic state to transesophageal echocardiographic findings in atrial fibrillation.

Atrial fibrillation (AF) is a major cause of morbidity and mortality from stroke due to thromboembolism from the fibrillating left atrium, including its appendage. We hypothesized that indexes of inflammation (as indicated by C-reactive protein and interleukin-6) and indexes of the prothrombotic state in AF that represent platelet activation (soluble P-selectin levels), endothelial damage or dysfunction (von Willebrand factor), coagulation (tissue factor and fibrinogen), and hemorrheology (plasma viscosity and hematocrit) would be related to the presence of thromboembolic predictors on transesophageal echocardiography in patients with long-term AF. To test this hypothesis, we recruited 37 patients with long-term AF who were receiving warfarin therapy with an international normalized ratio of > or =2.0 for > or =3 weeks before transesophageal echocardiography. Twenty-two patients had dense spontaneous echo contrast (SEC) visible in the left atrium or left atrial appendage, 10 had complex atheromatous plaque in the descending aorta, 11 had peak left atrial appendage velocities < or =0.2 m/s, and 3 had thrombus visible in the left atrial appendage. Twenty-eight patients had > or =1 transesophageal echocardiographic (TEE) risk factor for thromboembolism. Plasma levels of C-reactive protein (p = 0.03) and soluble P-selectin (p = 0.04) and hematocrit (p = 0.004) were higher among patients with AF with dense SEC than among those without. No significant associations were found for other TEE risk factors. Hematocrit was the only variable significantly associated with the presence of > or =1 TEE risk factor among patients with AF (p = 0.007) and the only independent associate of dense SEC after multivariate analysis (relative risk 1.4, 95% confidence interval 1.1 to 1.6) per 1% increase in hematocrit (p = 0.003, r(2) = 0.22). Although hematocrit was the only independent associate of dense SEC and > or =1 TEE risk factor, significant associations between dense SEC and the 2 indexes, C-reactive protein and soluble P-selectin, may indicate that mechanisms other than stasis are present with dense SEC. These observations support an "inflammatory hypothesis" in the pathogenesis of SEC that may have implications for thrombogenesis in AF.