Fibrinopeptide A (FPA) levels in atrial fibrillation and the effects of heparin administration

Left atrial appendage occlusion: rationale, evidence, devices, and patient selection

Atrial fibrillation (AF) is a worldwide epidemic associated with significant morbidity and mortality, often due to disabling or fatal thromboembolic stroke. Oral anticoagulation is highly effective at preventing ischaemic stroke and improving all-cause survival in patients with non-valvular AF. Despite the efficacy of oral anticoagulation, many patients are not treated due to either absolute or perceived contraindications to therapy, including bleeding. Left atrial appendage (LAA) closure has emerged as a mechanical alternative to pharmacologic stroke prevention. Initial and mid-term clinical trial data suggest that LAA closure is safe, with less intracranial bleeding, and a net clinical benefit that appears to be non-inferior to oral anticoagulation. However, concern remains over the possible increased risk of ischaemic stroke in long-term follow-up. Careful patient selection for LAA closure is paramount. Patients with prior intracranial bleeding or recurrent serious bleeding who are not eligible for long-term oral anticoagulation are typical candidates for LAA closure; however, other populations may benefit as well, such as patients with end-stage renal disease. Clinical investigation and randomized trials are needed to clarify the best methods of LAA occlusion, optimal pharmacologic strategies in the short-term after LAA closure, and to identify patient populations who will derive the most benefit from LAA occlusion. In this article, we review the rationale for LAA closure, the currently available devices and their evidence base, patient selection, challenges in management, and future directions for LAA closure science.

Indication, Patient Selection, and Referral Pathways for Left Atrial Appendage Closure

Left atrial appendage closure (LAAC) has emerged as a viable option for stroke prevention, especially in those intolerant of or not suitable for long-term oral anticoagulation therapy. This article describes the clinical characteristics, indications, and a proposed referral system for potential LAAC patients. Patient selection remains a challenge because of the paradox between the available randomized data on this intervention and the actual patient population who may gain maximum benefit. Further investigations comparing different LAAC devices with each other and with novel oral anticoagulants are needed. Also, the optimal antithrombotic regimen post-procedure has yet to be determined.

Anticoagulation in atrial fibrillation

Atrial fibrillation increases the risk of stroke, which is a leading cause of death and disability worldwide. The use of oral anticoagulation in patients with atrial fibrillation at moderate or high risk of stroke, estimated by established criteria, improves outcomes. However, to ensure that the benefits exceed the risks of bleeding, appropriate patient selection is essential. Vitamin K antagonism has been the mainstay of treatment; however, newer drugs with novel mechanisms are also available. These novel oral anticoagulants (direct thrombin inhibitors and factor Xa inhibitors) obviate many of warfarin's shortcomings, and they have demonstrated safety and efficacy in large randomized trials of patients with non-valvular atrial fibrillation. However, the management of patients taking warfarin or novel agents remains a clinical challenge. There are several important considerations when selecting anticoagulant therapy for patients with atrial fibrillation. This review will discuss the rationale for anticoagulation in patients with atrial fibrillation; risk stratification for treatment; available agents; the appropriate implementation of these agents; and additional, specific clinical considerations for treatment.

Contemporary management of atrial fibrillation: update on anticoagulation and invasive management strategies

Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice. Its increasing prevalence, particularly among the elderly, renders it one of the most serious current medical epidemics. Several management questions confront the clinician treating a patient with AF: Should the condition be treated? Is the patient at risk of death or serious morbidity as a result of this diagnosis? If treatment is necessary, is rate control or rhythm control superior? Which patients need anticoagulation therapy, and for how long? This review of articles obtained by a search of the PubMed and MEDLINE databases presents the available evidence that can guide the clinician in answering these questions. After discussing the merits of available therapy, including medications aimed at controlling rate, rhythm, or both, we focus on the present status of ablative therapy for AF. Catheter ablation, particularly targeting the pulmonary veins, is being increasingly performed, although the precise indications for this approach and its effectiveness and safety are being actively investigated. We briefly discuss other invasive options that are less frequently used, such as pacemakers, defibrillators, left atrial appendage closure devices, and the surgical maze procedure.

Acute anticoagulation adjustment in patients with atrial fibrillation at risk for stroke: approaches, strategies, risks and benefits

The acute management of anticoagulation in patients with atrial fibrillation to prevent stroke and other thromboembolic complications includes the use of individualized strategies tailored to the patient and based on the situation (cardioversion, surgeries, dental procedures, cardiac interventions, other invasive procedures and initiation of, or adjustment to, warfarin dosing). The vast range of choices can cause confusion and few randomized controlled clinical trials in this area provide adequate guidance. Chronic anticoagulation management is more straightforward since clinical evidence is ample, randomized clinical trial data provides cogent informaiton and guidelines have been established. Acute management of anticoagulation in patients with atrial fibrillation to prevent thromboembolic complications is often unrecognized but is emerging as a crucial, but challenging, and increasingly complex aspect of the care of patients with atrial fibrillation. This review addresses issues regarding such patients who may be at risk for stroke and require acute adjustments of anticoagulation (in light of, or in lieu of, chronic anticoagulation). Several promising new strategies are considered in light of established medical care. This analysis provides practical recommendations based on available data and presents results from recent investigations that may provide insight into future strategies.

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.

Factor V Leiden mutation and its relation to left atrial thrombus in chronic nonrheumatic atrial fibrillation

The genetic defect of coagulation factor V, known as factor V Leiden, produces a resistance to degradation by activated protein C and increased venous thrombosis. However, the role of factor V Leiden in the formation of left atrial thrombus with nonrheumatic atrial fibrillation has not been studied. We investigated whether factor V Leiden is a risk factor for left atrial thrombus in patients with nonrheumatic atrial fibrillation. We analyzed clinical, echocardiographic, and biochemical data in 105 consecutive patients with nonrheumatic atrial fibrillation. These patients were divided into two groups: group A (n = 37) with left atrial thrombus and group B (n = 68) without left atrial thrombus. The study also included 42 control subjects. Left atrial thrombus was investigated by using both transthoracic echocardiography and transesophageal echocardiography. Blood samples from the patients and controls were analyzed for the factor V Leiden mutation by DNA analysis, using the polymerase chain reaction. There was no significant difference in the prevalence of factor V Leiden between the patients and control subjects. The prevalence of factor V Leiden mutation was 8.1% (3/37) in patients with left atrial thrombus, and 8.8% (6/68) in patients without left atrial thrombus. The prevalence of factor V Leiden was 7.1% (3/42) in control subjects. The prevalance of factor V Leiden was 10% (2/20) in patients with spontaneous echo contrast and 8% (7/85) in patients without spontaneous echo contrast. Multivariate analyses showed that left ventricular ejection fraction was an independent predictor of left atrial thrombus. Factor V Leiden mutation is not a risk factor for left atrial thrombus formation and spontaneous echo contrast in patients with nonrheumatic atrial fibrillation.

Risk of thromboembolism in acute atrial fibrillation or atrial flutter

Atrial fibrillation (AF) is the most common sustained cardiac dysrhythmia, predominating in the elderly, with stroke as a potentially devastating complication. Prevention of the thromboembolic sequelae from AF remains a central focus of practicing clinicians. Although the risk of thromboembolism in chronic AF is well recognized, less is known about the potential risk of systemic embolism in acute AF. In addition, recent data support the notion of a group at considerable risk of embolism from atrial flutter, an arrhythmia typically believed to bestow little increased risk of thromboembolism. The mechanism of thrombus formation, embolization, and resolution in atrial arrhythmias is not well defined, particularly in that of acute AF or atrial flutter. The traditional concept proposes that atrial thrombus forms only after > 2 days of AF and embolizes by being dislodged from increases in shear forces. This widely accepted concept further holds that newly formed atrial thrombus, in the setting of AF, organizes over a span of 14 days. The results of studies based on observations from transesophageal echocardiography examinations have provided provocative insight into the temporal sequence of atrial thrombus formation, embolization, and resolution in AF or atrial flutter and have expanded the traditional concept of thromboembolism in these atrial dysrhythmias. Namely, left atrial thrombus may form before the onset of AF in the face of sinus rhythm. Conversion to sinus rhythm may increase the thrombogenic milieu of the left atrium. Importantly, atrial thrombus may form in the acute phase of AF. Last, thrombi may require > 14 days to become immobile or to resolve. Findings similar to those of acute AF have been reported in patients with atrial flutter and coexisting cardiac pathology. On the basis of these emerging insights fostered by the use of transesophageal echocardiography, it appears appropriate to consider anticoagulation in patients presenting with acute AF or atrial flutter with coexisting cardiac pathology predisposing to left atrial thrombus.

Rhythm management in atrial fibrillation--with a primary emphasis on pharmacological therapy: Part 1

Atrial fibrillation (AF) is the most common, sustained, symptomatic tachyarrhythmia that clinicians are called upon to manage. Management strategies include ventricular rate control coupled with anticoagulation, versus restoration and maintenance of sinus rhythm. Rate control may be achieved pharmacologically, with agents that impair AV nodal conduction directly and/or by increasing parasympathetic/sympathetic balance, or by modifying or ablating the AV nodal region anatomically. Rhythm control may be achieved by electrical or pharmacological conversion followed by maintenance of sinus rhythm by pharmacological (or occasionally ablative) therapies. This article will present current approaches to rate and rhythm control issues in AF. Part 1, the current manuscript, details approaches to rate control and includes a drug selection algorithmic conclusion. It also introduces the subject of the pursuit of sinus rhythm. Parts 2 and 3, to be published in subsequent editions of PACE, will deal with therapeutic measures to restore and maintain sinus rhythm.

Prethrombotic state due to hypercoagulability in patients with permanent transvenous pacemakers

Venous thrombosis is a relatively usual but serious complication of permanent transvenous pacing. However, the pathogenesis has not been defined. To clarify underlying abnormalities in the coagulation-fibrinolysis system in patients with permanent transvenous pacemakers, we measured serum levels of fibrinopeptide A (FPA), thrombin-antithrombin III complexes (TATs), plasmin-alpha 2 plasmin inhibitor complexes (PICs), D-dimer (D-D), beta-thromboglobulin (beta-TG), and platelet factor 4 (PF4) in 53 patients with permanent transvenous pacemakers and 10 control subjects. The patients were divided into two groups, as follows, according to the presence of mural thrombus documented along the pacing lead(s) by digital subtraction angiography and transesophageal echocardiography: Group Th (-), patients without venous route thrombus; and Group Th (+), patients with venous route thrombus. FPA and TAT levels increased significantly even in Group Th (-), and further increased in Group Th (+) compared with control subjects (FPA: 7.5 +/- 4.9, 15.3 +/- 8.8 vs 3.0 +/- 1.4 ng/mL, respectively, P < 0.05; TAT: 2.9 +/- 1.3, 4.8 +/- 2.3 vs 1.7 +/- 0.6 ng/mL, respectively, P < 0.05). There were no differences in levels of D-D, PIG, beta-TG, and PF4 among control subjects, Group Th (-), and Group Th (+). These findings suggest that the hypercoagulable state appears in patients with permanent transvenous pacemakers, even without apparent venous thrombosis. The patients with permanent transvenous pacemakers are thought to be in the prethrombotic state even if they have no venous route thrombosis.

Atrial fibrillation activates platelets and coagulation in a time-dependent manner: a study in patients with paroxysmal atrial fibrillation

OBJECTIVES

To determine whether atrial fibrillation (AF) alone affects the fibrinocoagulation system, we examined the relation between fibrinocoagulation activity and duration of AF in patients with paroxysmal AF (PAF).

BACKGROUND

Patients with chronic AF are at higher risk for stroke and a hypercoagulative state. It is not clear whether this hypercoagulative state is attributable to AF alone or to the underlying disease. There are no reports on the fibrinocoagulation properties in PAF.

METHODS

Fibrinocoagulation variables in 21 patients with PAF were measured during AF and 7 days after recovery of sinus rhythm. There were positive correlations between the duration of AF and beta-thromboglobulin, platelet factor 4, thrombin-antithrombin III complex and fibrinogen. These variables increased significantly 12 h after the occurrence of PAF; thus, patients were classified into two groups according to the duration of PAF: PAF-I group (< 12 h, n = 10), PAF-II group (> or = 12 h, n = 11). Nine age-matched, healthy subjects formed the control group.

RESULTS

Levels of beta-thromboglobulin and platelet factor 4 were significantly higher (p < 0.001) by two-way repeated measures analysis of variance (ANOVA), and thrombin-antithrombin III complex and fibrinogen levels tended to be but were not significantly higher (p = 0.06, ANOVA), in the PAF-II group than in the PAF-I group. There were no significant differences between groups in activated partial thromboplastin time, D-dimer or plasmin inhibitor complex.

CONCLUSIONS

These results indicate that AF itself enhances platelet aggregation and coagulation, which are influenced by the duration of AF. The acceleration of platelet activity and coagulability occurred 12 h after the occurrence of AF.

Risk of thromboembolism in new onset or transient atrial fibrillation

Atrial fibrillation (AF), potentially serious cardiac arrhythmia, occurs in 2% to 4% of persons greater than 60 years of age. The risk of systemic thromboembolism from chronic AF has long been recognized. Little is known about the thromboembolic risk of new onset AF. However, the results of prior studies support a significant risk of thromboembolism because of recent onset or paroxysmal AF. The mechanism of thrombus formation, embolization, and resolution in AF is ill-defined, particularly that of new onset. The traditional concept holds that atrial thrombus forms only after greater than 2 days of AF and embolizes by dislodgement from increases in shear forces. This prevailing concept further proposes that newly formed atrial thrombus, in the setting of AF, organizes over a span of 14 days. The results of recent transesophageal echocardiographic studies have given insight into the temporal sequence of atrial thrombus formation, embolization, and resolution in AF and have expanded the traditional concept of thromboembolism in AF. Namely, left atrial thrombus may form before the onset of AF in the face of sinus rhythm. Conversion to sinus rhythm may increase the thrombogenic millieu of the left atrium. Importantly, atrial thrombus may form in the acute phase of AF. Lastly, thrombus may require more than 14 days to become immobile or to resolve. On the basis of these emerging insights by transesophageal echocardiography, it appears appropriate to consider anticoagulation in patients presenting with new onset or acute AF.

The role of risk factors and trigger factors in cerebrovascular events after mitral valve replacement: implications for antithrombotic management

To determine the effect of risk factors and trigger factors on cerebrovascular events, 622 patients who survived mitral valve replacement between December 1979 and December 1992 were analyzed. Ninety-six patients suffered 139 nonhemorrhagic cerebrovascular events. Data were available on 138 events in 95 patients. There were 32 transient ischemic attacks (TIAs), 57 reversible ischemic neurological deficits (RINDs), and 49 strokes. Age, sex, atrial fibrillation, left atrial size, systemic hypertension, and abnormal body mass index did not discriminate between patients who suffered events and those who did not. In contrast, smoking status differed significantly between patients who suffered events and those who did not. Among current or recent ex-smokers, the risk of stroke or RIND was significantly higher than in non-smokers (p < < 0.001). The odds ratio of suffering any type of event in patients who smoked at any time postoperatively versus those who did not smoke was 2.9 (95% confidence interval: 1.8 to 4.6). Of 61 patients contacted directly, 30% recalled an infective episode immediately prior to their event. A diurnal and seasonal influence on events was also detected with peaks in the morning and in the winter months, respectively (both p < 0.001). It is concluded that there is persuasive evidence for the involvement of several nonprosthetic factors in the incidence of cerebrovascular events after mitral valve replacement. This has implications for patient management and for future analysis of prosthetic heart valve series.

Should all patients undergo transesophageal echocardiography before electrical cardioversion of atrial fibrillation?

The management of anticoagulant therapy in patients with atrial fibrillation undergoing electrical cardioversion remains controversial, largely because of inadequate studies demonstrating risk or benefit, a relatively inconvenient anticoagulation management strategy and the increasing use of transesophageal echocardiography. Recent investigations into the potential mechanisms involved in the development of thrombus and systemic embolism in patients undergoing electrical cardioversion of atrial fibrillation may provide insight into underlying predisposing factors, with subsequent modification of management strategies. Conventional wisdom suggests that preexisting thrombus is responsible for thromboembolic events after cardioversion. However, development of a thrombogenic milieu after cardioversion, particularly in the left atrial appendage, may also be an important predisposing factor. To protect against both potential mechanisms of embolization, these data support therapeutic anticoagulation for all patients with atrial fibrillation of > 2 days in duration from the time of, as well as after cardioversion for a total of 4 weeks, undergoing cardioversion, even in the absence of thrombus on echocardiography. Therefore, the role of transesophageal echocardiography in this setting should be to enable early cardioversion if atrial thrombus is excluded and to identify high risk patients with atrial thrombi so as to postpone cardioversion and avoid the risk of embolization. Ultimately, however, a controlled, randomized and prospective clinical trial will be required to compare conventional management with a transesophageal echocardiography-guided strategy.

Predictors of left atrial thrombus in mitral valve disease

OBJECTIVE

To determine the risk factors for left atrial thrombus (LAT) and the prevalence of thrombi in cases of mitral valve disease whose severity was judged to necessitate surgical intervention.

DESIGN

Hospital record review of all operative cases from 1982 to 1985.

SETTING

A community serving a referral population encompassing 1.5 million people. Only two hospitals in the geographic area performed cardiac surgery, and both hospitals' records were reviewed.

PATIENTS

All 372 patients who underwent either mitral valve replacement or open mitral commissurotomy.

MAIN RESULTS

Twenty-six patients (7%) were noted to have LAT at surgery. Five preselected factors were significantly (p less than 0.05) associated with LAT in univariate analysis: female gender, prior history of embolism, prior anticoagulant therapy, mitral stenosis (MS), and atrial fibrillation (AF). In logistic regression analysis, only MS and AF remained as significant independent predictors of LAT. Mitral stenosis patients in sinus rhythm had a relatively low [2.4 +/- 3.3% (observed +/- 95% confidence interval)] likelihood of having an LAT. Likewise, mitral regurgitation patients in sinus rhythm (n = 139) had an extremely low (0.7 +/- 1.4%) prevalence of LAT. In contrast, MS patients in AF (n = 122) had a prevalence of LAT of 18.0 +/- 6.8%.

CONCLUSIONS

These findings indicate that, overall, LAT in mitral valve disease may be less common than previous studies have suggested. In addition, mitral valve disease patients who remain in sinus rhythm appear to have a low risk of harboring an LAT. Conversely, MS patients, especially those in AF, appear to be at high risk of harboring an LAT. These results may be helpful in formulating strategies for the use of prophylactic anticoagulation in categories of patients with clinically severe mitral valve disease, or perhaps in estimating the likelihood of a cardiac source of embolism in mitral valve disease patients with suspected cerebral or peripheral emboli.

Regression of intracardiac thrombus after embolic stroke

Using two-dimensional echocardiography, we studied the pathophysiology of intracardiac thrombus regression accompanied by anticoagulant therapy in 82 consecutive patients with acute cardiogenic cerebral embolism. We noted intracardiac thrombus in 15 patients; nine of the 15 were started on anticoagulant therapy with warfarin potassium to maintain the prothrombin time between 2.5 and 3.5 (international normalized ratio). Serial two-dimensional echocardiograms were obtained for these nine patients before and after anticoagulation, with the plasma levels of fibrinopeptide A, fibrinopeptide B beta 15-42, and D-dimer measured at the same time. In eight of the nine patients the intracardiac thrombi gradually decreased in size while the plasma level of fibrinopeptide A fell to within the normal range and the plasma levels of fibrinopeptide B beta 15-42 and D-dimer remained above the normal ranges. In the other patient the thrombus disappeared, with embolization to the right arm immediately after starting anticoagulant therapy. Mobile or small thrombi regressed earlier than nonmobile or large ones. We conclude that regression of intracardiac thrombi after anticoagulation may be based on the relative predominance of plasma fibrinolytic activity over anticoagulation-inhibited thrombin activity.