Relationship between prothrombin activation fragment F1.2 and international normalized ratio in patients with atrial fibrillation. Stroke Prevention in Atrial Fibrillation Investigators

Risks and benefits of rate control versus maintenance of sinus rhythm

There are 2 fundamental approaches to managing patients with recurrent atrial fibrillation (AF): to restore and maintain sinus rhythm with cardioversion and/or antiarrhythmic drugs, or to control the ventricular rate only. Over the past few years, there have been several important prospective clinical trials comparing rate control with rhythm control in patients with recurrent AF. The Pharmacological Intervention in Atrial Fibrillation (PIAF) trial was the first prospective randomized study to test the hypothesis of equivalency between the 2 management strategies for AF. The trial demonstrated that rate control was not inferior to rhythm control with respect to symptoms, quality of life, or number of hospitalizations in patients with persistent AF. The Strategies of Treatment in Atrial Fibrillation (STAF) trial was a pilot study that enrolled approximately 200 patients with AF who were randomized to either ventricular rate control or cardioversion and maintenance of sinus rhythm. The results showed that over a 1-year period there was little difference in outcome in terms of morbidity or symptoms. In the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) trial, patients with AF and risk factors for stroke were randomized to either rhythm control or rate control, with both groups receiving anticoagulation with warfarin. There was no difference in the composite end point of death, disabling stroke or anoxic encephalopathy, major bleeding, or cardiac arrest between the 2 arms. In addition, no major differences were noted in functional status or quality of life. The Rate Control Versus Electrical Cardioversion (RACE) trial also reached a similar conclusion. Thus, rate control is an acceptable primary strategy for management of patients with recurrent AF.

Radiofrequency Ablation for Atrial Fibrillation

Catheter ablation has emerged as an excellent treatment option for atrial fibrillation. In appropriate patients, particularly those with paroxysmal atrial fibrillation in the absence of structural heart disease, catheter-based pulmonary vein isolation can eliminate or dramatically reduce the arrhythmia burden. However, with currently available tools, the procedure is complex and labor intensive. Simpler ablation procedures may emerge as newer ablation systems are developed.

Advances in hospital medicine: a review of key articles from the literature

Multiple published studies in recent years have provided results and information that hospitalists can apply directly to patient care. This update summarizes some important articles published over the past 18 months. Article summaries are categorized into perioperative care, infectious disease, diagnosis of venous thromboembolism, end of life care, and guidelines for the management of patients with COPD or atrial fibrillation.

Urinary 11-dehydro-thromboxane B(2) and coagulation activation markers measured within 24 h of human acute ischemic stroke

The aim of this study was to determine the extent of change in platelet and coagulation markers in the acute phase of ischemic stroke and to assess the utility of marker measurement in stroke subtype classification. Urinary 11-dehydro-thromboxane B(2) (11-dTXB2), a marker of in vivo platelet activation, and markers of coagulation activation, including prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complex (TAT), and fibrinogen, were measured in 25 patients with ischemic stroke within 24 h of onset of symptoms. Marker levels in patients with ischemic stroke were compared with those in 19 age-matched controls who had not taken aspirin for at least 2 weeks before sampling and 25 healthy controls. Median marker levels were significantly increased in stroke over those in age-matched controls for fibrinogen (344 vs. 289 mg/dl; P=0.030), F1+2 (1.40 vs. 0.80 nmol/l; P=0.003), and TAT (6.65 vs. 2.20 microg/l; P<0.0001). Median marker levels for seven patients with cardioembolic stroke and 18 with non-cardioembolic stroke were not significantly different for any marker test. Eight patients taking aspirin at the time of the stroke had significantly lower 11-dTXB2 values than patients not taking aspirin (964 vs. 4,314 pg/mg of creatinine; P=0.007). Stroke patients not taking aspirin had significantly higher 11-dTXB2 concentration than age-matched controls (4,314 vs. 1,788 pg/mg of creatinine; P=0.006). Coagulation and platelet activation markers are increased in the acute phase of stroke regardless of the clinical mechanism. This finding suggests that the markers may not be useful for predicting clinical subtype of ischemic stroke in the acute phase.

Prevalence and clinical characteristics of patients with atrial fibrillation: analysis of 20,000 cases in Japan

In Japan, data on the epidemiological and clinical features of atrial fibrillation (AF) are rather sparse; even less data are available on the risk of thromboembolism in nonvalvular AF. The present study enrolled 19,825 patients who visited the cardiovascular clinics of the 13 hospitals in Hokkaido, Japan, between March and July 1995. The prevalence of AF, the clinical characteristics of AF patients, and the occurrence of ischemic events were examined during the 2 year follow-up period. The prevalence of AF increased with age, and the overall prevalence was 14%. Antithrombotic therapy was used in 57% of AF patients and the incidence of ischemic events during the follow-up period was 4.6% in all AF patients. Warfarin reduced the risk of ischemic events in both the valvular and nonvalvular AF groups. A history of cerebrovascular accidents, advanced age, and the presence of underlying heart disease were each associated with a significantly increased risk of ischemic events in the nonvalvular AF group. These results show a lower incidence of ischemic events and more frequent use of antiplatelet drugs in the nonvalvular AF group. Further prospective studies are needed to determine the best preventive methods for thromboembolic complications in Japanese patients with nonvalvular AF.

Atrial fibrillation and thromboembolism: a decade of progress in stroke prevention

Atrial fibrillation is associated with a sixfold increased risk for stroke. More than a dozen published randomized trials of anticoagulants or antiplatelet agents for stroke prevention provide solid evidence on which to base antithrombotic prophylaxis. Adjusted-dose warfarin reduces risk for stroke by about 60% compared with placebo, aspirin reduces this risk (primarily for nondisabling stroke) by about 20% compared with placebo, and warfarin reduces it by about 40% compared with aspirin. Warfarin provides maximal protection against stroke at international normalized ratios of 2.0 to 3.0. Risk stratification of patients with atrial fibrillation identifies those who potentially benefit most or least from anticoagulation; this is important because a substantial percentage of patients with atrial fibrillation have relatively low rates of stroke if they are given aspirin. Many elderly patients with recurrent intermittent atrial fibrillation experience high rates of stroke and benefit from anticoagulation. The value of precordial or transesophageal echocardiography in addition to clinical risk stratifiers for stratifying stroke risk is controversial. Altered hemostasis favoring thrombosis may contribute to formation of atrial appendage thrombus, but these conditions remain ill defined. The past decade has brought unprecedented progress toward understanding thromboembolism in patients with atrial fibrillation and has changed the clinical perspective of a prevalent cardiac arrhythmia into an important opportunity for stroke prevention. Making the most of this promise calls for appreciation of the epidemiology of atrial fibrillation and the concept of risk specificity in the face of diverse therapeutic options.

Changes in levels of factor VII and protein S after acute myocardial infarction: effects of low-dose warfarin

Persistent coagulation activity after an acute myocardial infarction may increase the risk of reinfarction. We prospectively investigated the effects on plasma coagulation of a low, fixed dose of warfarin in combination with aspirin after myocardial infarction. We also evaluated the influence of coagulation activity on clinical outcome. Plasma samples from 97 patients, randomised to 1.25 mg of warfarin daily in combination with 75 mg of aspirin or aspirin alone were drawn 4 days, 1 month, and 6 months after myocardial infarction. Patients receiving warfarin had a greater reduction in factor VII coagulation activity (FVII:C) after 6 months: 0.18 vs. 0.06 U/mL,(95% CI, 0.02-0.22), whereas no differences were seen in levels of protein C, protein S, or prothrombin fragment 1+2. In the acute phase, the level of free protein S was lower than after 6 months in both groups: 25.6 vs. 28.8% (95% CI, 4.19--2.35). Cardiovascular mortality, reinfarction, and stroke were evaluated after 4 years (median). In a survival analysis, every 0.1 U/mL increase in the level of FVII:C1 month after myocardial infarction was associated with an 15% increase in risk of cardiovascular events (95% C1, 1.01-1.30). Warfarin at 1.25 mg daily reduces FVII:C but not systemic thrombin generation measured as prothrombin fragment 1 +2. Low levels of the anticoagulant protein S may contribute to a procoagulant state.

Hemostatic effects of 1 mg daily warfarin on post CABG patients. Post CABG Studies Investigators

Although coronary bypass graft surgery has increased the survival and quality of life of many individuals, patients remain at risk of restenosis and thrombotic occlusion of the coronary arteries and bypass grafts. In the screening period for participation in the multicenter Post Coronary Artery Bypass Graft (Post CABG) trial, the effects of 1 mg daily warfarin were evaluated using paired patient samples collected prior to and after at least 21 days of treatment. In stable patients (n = 40; 39 males 1 female; 51-74 years old) who previously had undergone coronary artery revascularization (1-10 years), no alterations in prothrombin time, international normalized ratio (INR), prothrombin fragment 1.2, or the hemostatic risk factors factor VII antigen and coagulant activity, von Willebrand's factor, fibrinogen, tPA, or PAI-1 were associated with the 1 mg daily warfarin treatment. The observations reported here supported the Post CABG Studies Steering Committee decision to treat patients with 1-4 mg warfarin daily adjusted to achieve INRs not to exceed 2. 0 consistent with low-intensity therapy.