Atrial fibrillation as an independent risk factor for stroke: the Framingham Study

Treatment strategies for atrial fibrillation

Atrial fibrillation is the most common arrhythmia observed in clinical practice, occurring in 0.4% of the general population and in up to 4% of people greater than 60 years old. It is often associated with other cardiovascular disorders, such as hypertension, coronary artery disease, or cardiomyopathy. Critical evaluation and management of patients with atrial fibrillation requires knowledge of etiology, prognosis, and treatment options of this arrhythmia. On initial presentation, emergency electrical cardioversion should be performed if the patient is hemodynamically unstable. If the patient is stable, initial rate control is recommended, using atrioventricular nodal blocking agents. Further treatment mainly depends upon the duration of the episode. Patients who are in atrial fibrillation <48 hours can be safely cardioverted. Patients who are in atrial fibrillation for >48 hours are commonly anticoagulated for 3 to 4 weeks before and after cardioversion because of the risk of thromboembolism formation in the left atrial appendage. An alternate strategy, which is especially attractive when immediate cardioversion is desired, is transesophageal echocardiography to exclude left atrial thrombus followed by prompt cardioversion. After cardioversion, sinus rhythm can be maintained with class I and III drugs, such as flecainide and propafenone or amiodarone and sotalol. New treatment options, such as atrial defibrillation, atrioventricular junctional ablation, or modification of atrial pacing to prevent atrial fibrillation, are currently under investigation. Although atrial fibrillation is so common in clinical practice, it still remains difficult to treat. Conversion and maintenance to sinus rhythm with antiarrhythmic drug therapy has not shown any improvement in mortality, and some patients may benefit more from ventricular rate control. This review article discusses different treatment strategies for patients with atrial fibrillation.

Safety of transvenous low energy cardioversion of atrial fibrillation in patients with a history of ventricular tachycardia: effects of rate and repolarization time on proarrhythmic risk

The objective of this study was to assess the safety and efficacy of transvenous low energy cardioversion of atrial fibrillation in patients with ventricular tachycardia and atrial fibrillation and to study the mechanisms of proarrhythmia. Previous studies have demonstrated that cardioversion of atrial fibrillation using low energy, R wave synchronized, direct current shocks applied between catheters in the coronary sinus and right atrium is feasible. However, few data are available regarding the risk of ventricular proarrhythmia posed by internal atrial defibrillation shocks among patients with ventricular arrhythmias or structural heart disease. Atrial defibrillation was performed on 32 patients with monomorphic ventricular tachycardia and left ventricular dysfunction. Shocks were administered during atrial fibrillation (baseline shocks), isoproterenol infusion, ventricular pacing, ventricular tachycardia, and atrial pacing. Baseline shocks were also administered to 29 patients with a history of atrial fibrillation but no ventricular arrhythmias. A total of 932 baseline shocks were administered. No ventricular proarrhythmia was observed after well-synchronized baseline shocks, although rare inductions of ventricular fibrillation occurred after inappropriate T wave sensing. Shocks administered during wide-complex rhythms (ventricular pacing or ventricular tachycardia) frequently induced ventricular arrhythmias, but shocks administered during atrial pacing at identical ventricular rates did not cause proarrhythmia. The risk of ventricular proarrhythmia after well-synchronized atrial defibrillation shocks administered during narrow-complex rhythms is low, even in patients with a history of ventricular tachycardia. The mechanism of proarrhythmia during wide-complex rhythms appears not to be related to ventricular rate per se, but rather to the temporal relationship between shock delivery and the repolarization time of the previous QRS complex.

Anticoagulation for nonvalvular atrial fibrillation: effects of type of practice on physicians' self-reported behavior

BACKGROUND

This study examines whether social and economic factors affect physician practice and attitude with regard to warfarin anticoagulation in patients with nonvalvular atrial fibrillation.

METHODS

We identified physicians in Baltimore City, Baltimore County, and Prince George's County who (1) had written one or more prescriptions for a digitalis compound during the preceding year, and (2) were classified as general practitioners, family practice specialists, internists, or cardiologists. All 358 physicians fulfilling these criteria were surveyed by questionnaire.

RESULTS

The overall response rate was 43%. Physicians who wrote 15% or more of their digitalis prescriptions for Medicaid patients said they used warfarin at significantly lower rates for patients with nonvalvular AF than other (66% versus 79%, P <0.01). The opposite pattern was seen with regard to aspirin. There were no significant differences in practice pattern between physicians located in urban vs. suburban counties.

CONCLUSION

In our sample, self-reported anticoagulant practices for patients with nonvalvular AF were associated with the percentage of digitalis prescriptions written for Medicaid patients. In this metropolitan area, anticoagulant therapy was reportedly prescribed for approximately 75% of patients with nonvalvular atrial fibrillation.

Recognition and Management of Cardiac Arrhythmias: Part I. General Principles and Supraventricular Tachyarrhythmias

Management of cardiac arrhythmias has undergone major changes in the last few years. In the first part of this review, general principles of arrhythmia diagnosis are discussed. New techniques such as event recording and signal-averaged electrocardiography have a significant role in the clinical management of arrhythmias. Many new antiarrhythmic drugs are now available. Suppression of premature ventricular contractions to prevent malignant ventricular arrhythmias has been demonstrated to be an ineffective strategy. Implantable defibrillators and radio frequency ablation have revolutionized the treatment of arrhythmias. Differentiation of various supraventricular tachycardias has become very important since some these arrhythmias may be cured by radiofrequency ablation. Diagnosis and treatment of common supraventricular arrhythmias are discussed.

Thrombosis and Hemostasis in Cardiology: Review of Pathophysiology and Clinical Practice (Part I)

The adverse consequences of thrombosis are per haps nowhere more evident than in clinical cardiology. Throm bosis and hemostasis are primary issues in the management of patients with atrial fibrillation, prosthetic heart valves, severe left ventricular dysfunction, and coronary artery disease. Clini cal trials have defined a crucial role for anticoagulation with warfarin in patients with atrial fibrillation to reduce the inci dence of stroke. Anticoagulation with warfarin and aspirin in combination offers significant protection from systemic emboli in patients with mechanical prosthetic valves, without a sub stantial increased risk of hemorrhage. The risk of systemic emboli may also be reduced by anticoagulation in patients with severe left ventricular dysfunction. Disturbance of the normal balance of hemostasis is a major factor in the pathophysiology of coronary artery disease. Antiplatelet therapy, antithrombin agents, anticoagulants, and fibrinolytic agents have been used to prevent and treat acute coronary thrombosis and to prevent reocclusion following thrombolysis and interventional therapy. Guidelines are presented for antithrombotic therapy in the prac tice of clinical cardiology.

The medical management of atrial fibrillation

Atrial fibrillation is an extremely common arrhythmia that is associated with significant sequelae. Certain aspects of therapy, such as anticoagulation, are studied in well-constructed randomized trials. Other therapy, such as the maintenance of sinus rhythm with antiarrhythmic agents, is supported by limited evidence. This article reviews the epidemiology and medical treatment of this arrhythmia, addressing anticoagulation, ventricular rate control, and restoration and maintenance of sinus rhythm. Randomized trials in progress that attempt to answer important questions in the management of atrial fibrillation are also discussed.

Thrombosis, antithrombotic agents, and the antithrombotic approach in cardiac disease

To develop a rational approach to antithrombotic therapy, in cardiac disease, a sound understanding is required (1) of the hemostatic processes leading to thrombosis, (2) of the various antithrombotic agents, and (3) of the relative risks of thrombosis and thromboembolism in the various cardiac disease entities. With the understanding of pathogenesis and risk of thrombus formation, a rational approach to the use of antiplatelet and anticoagulant agents can be formulated. Those at high risk of thrombus formation should generally receive a high degree of antithrombotics and, depending on the pathophysiology of the thrombus, may benefit from the concomitant use of antiplatelet and anticoagulant agents. Those with a medium risk of thrombus formation may benefit with the use of an antiplatelet agent alone or anticoagulants alone. Patients at low risk of thrombus formation should not receive antithrombotics. Such rational approach to antithrombotic therapy serves as the basis of this article.

Atrial fibrillation in older stroke patients: association with recurrence and mortality after first ischemic stroke

OBJECTIVES

The objective of this study was to determine the association of atrial fibrillation (AF) with stroke recurrence and mortality and with the causes of death in ischemic stroke patients aged 75 years and older.

DESIGN

A population-based study.

SETTING

The cities of Turku and Kuopio in Finland.

PARTICIPANTS

The study cohort consisted of 2635 consecutive patients aged 75 years and older, with a first ischemic stroke, registered in the FINMONICA Stroke Register.

MEASUREMENTS

28-day and 1-year stroke mortality, causes of death, and recurrence of stroke.

RESULTS

There were 767 stroke patients with AF (mean age 82.2) and 1868 patients without AF (mean age 81.4). Mortality was higher in the AF group both 28 days (33.9% vs 28.1%, P = .003) and 1 year after the attack (52.7% vs 43.0%, P < .001). The age- and sex-adjusted relative risk of death at 28 days was 1.25 in the AF group (95% confidence interval (CI) 1.04-1.50, P = .018), and at 1 year it was 1.41 (95% CI 1.18-1.67, P < .001). In a Cox proportional hazards model, 1-year mortality risk comparing the AF-group with non-AF group was 1.24 (95% CI 1.10-1.39, P < .001). The strongest risk factor predicting 1-year mortality was recent myocardial infarction (MI) (RR 1.90, 95% CI 1.49-2.42). Myocardial infarction was more often the underlying cause of death in the AF group during the period of 28 days, but not from 28 days up to 1 year. The 1-year recurrence rate among those alive at day 28 was 11.5% in the AF group and 9.4% in the non-AF group (P = .240).

CONCLUSION

Recent MI and AF are independent negative prognostic factors in older patients with stroke. Although the relative risk estimates attributable to AF are of the same magnitude in older as in middle-aged stroke patients, the much higher prevalence of AF in the older patients emphasizes its absolute impact on the mortality and recurrence after the first ischemic stroke in the age group 75 years and older. The treatment of coexisting cardiac disease also has the potential to prevent deaths and recurrent stroke events in older persons.

Primary stroke prevention in nonvalvular atrial fibrillation: implementing the clinical trial findings

OBJECTIVE

To review the clinical trials evaluating warfarin for primary stroke prophylaxis in nonvalvular atrial fibrillation (NVAF), to discuss the relative benefits and risks of warfarin versus aspirin therapy, and to review the clinical practice guidelines and identify potential barriers to their implementation in clinical practice.

DATA SOURCES

A MEDLINE literature search was performed to identify clinical trials of antithrombotic therapy for NVAF, clinical practice guidelines, studies evaluating physician practices and attitudes, cost-effectiveness studies, and pertinent review articles. Key search terms included atrial fibrillation, stroke, antithrombotic, warfarin, aspirin, and cost-effectiveness.

DATA EXTRACTION

Prospective, randomized clinical trials were selected for analysis. Clinical practice guidelines from recognized panels of experts were reviewed. Comprehensive review articles were selected.

DATA SYNTHESIS

NVAF is a common arrhythmia that is associated with a substantial risk for stroke. Seven prospective, randomized, clinical trials have conclusively demonstrated the efficacy of warfarin for stroke prevention. The greatest benefits are achieved in older patients and those with comorbidities that increase their risk for stroke. The potential benefits of preventing a devastating stroke, however, must be weighed against the potential for bleeding complications. Warfarin has been shown to be cost-effective in high-risk patients, provided the rate of complications is minimized. Nonetheless, many physicians remain hesitant to implement warfarin therapy in older, high-risk patients. The clinical data on aspirin are less consistent than those observed with warfarin. Aspirin appears to be most effective in younger individuals or those considered to be at low risk for stroke.

CONCLUSIONS

In patients with NVAF, the personal, social, and economic consequences of stroke are often devastating. Clinical trials have provided definitive proof that the risks of stroke can be significantly reduced through the use of appropriate antithrombotic therapy. Despite this evidence and the recommendations of a number of clinical practice guidelines, variations in care exist that continue to place patients at risk. Additional outcomes research is needed to evaluate the impact of the clinical trial findings and practice guidelines on clinical practice and to develop methods for overcoming barriers to implementation.

Meeting the challenge of stroke

It is the elderly who carry the burden of stroke. Whilst 130,000 people suffer a stroke in the UK every year, nearly three quarters of these cases occur over the age of 65 and nearly half occur over the age of 75. As the proportion of elderly in the population continues to grow, inevitably this burden will increase. With Scotland probably experiencing the highest stroke incidence in the UK and stroke already accounting for 5.5% of total hospital costs, challenges clearly lie ahead for the health service and Scottish society as a whole. The extent to which we are able to meet this challenge is becoming clearer. Thus far, therapeutic advance has been rather "low-tech", with organisation of services and the appropriate use of existing interventions showing modest and, just occasionally, dramatic benefits. In contrast, the high hopes raised by many "high-tech" solutions have largely been dashed or remain promising but unproven.

Physician attitudes concerning warfarin for stroke prevention in atrial fibrillation: results of a survey of long-term care practitioners

BACKGROUND

The prevalence of atrial fibrillation (AF) increases dramatically with advancing patient age, and, as a result, this condition is common in persons residing in the long-term care setting.

OBJECTIVES

To assess the knowledge and attitudes of physicians regarding the use of warfarin for stroke prevention in patients with atrial fibrillation in long-term care facilities.

METHODS

We surveyed physicians actively providing primary care to older patients in 30 long-term care facilities located in New England, Quebec, and Ontario. Physicians were requested to complete a structured questionnaire about use of warfarin therapy for stroke prevention in patients with AF residing in long-term care facilities. The questionnaire included two clinical scenarios designed to provide substantial contrasts in patient characteristics including underlying comorbidity, functional status, bleeding risk, and stroke risk.

RESULTS

A total of 269 physicians were asked to participate in the survey, and 182 (67.7%) completed the questionnaire between February 1, 1995, and July 31, 1995. Only 47% of respondents indicated that the benefits of warfarin therapy "greatly outweigh the risks" in this setting; the remainder of physicians indicated that benefits only "slightly outweigh the risks" (34%) or that risks "outweigh benefits" (19%). The most frequently cited contraindications to warfarin use were: excessive risk of falls (71%), history of gastrointestinal bleeding (71%), history of other non-central nervous system bleeding (36%), and history of cerebrovascular hemorrhage (25%). Among the 164 physicians who reported using the international normalized ratio to monitor warfarin therapy, 27% indicated a target range with a lower limit less than 2, 71% indicated a target range between 2 and 3, and 2% indicated an upper limit greater than 3. Among respondents who answered questions about the two clinical scenarios, estimates of the risk of a stroke without warfarin therapy and the risk of an intracranial hemorrhage with therapy varied widely.

CONCLUSIONS

Our findings suggest that many uncertainties surround the decision to prescribe warfarin to patients with AF in the long-term care setting, as well as questions about the appropriate intensity of this treatment when it is prescribed. Concerns about the risks of bleeding appear to prevail over stroke prevention when physicians make such prescribing decisions.

Atrial fibrillation and stroke: elucidating a newly discovered risk factor

Atrial fibrillation is the most common sustained arrhythmia reported in the United States; an estimated 1-2 million Americans have chronic nonvalvular atrial fibrillation. This disorder is associated with a substantial risk of stroke. Several recent studies provide evidence that anticoagulation therapy is indicated for stroke prevention in patients with nonvalvular atrial fibrillation after recovery from a minor stroke. Clinical and echocardiographic criteria help to identify those patients who are at especially high risk for thromboembolic stroke and are candidates for carefully controlled anticoagulation. In an effort to reduce the possibility of thromboembolic events following either chemical or electrical cardioversion, the American College of Chest Physicians has recently prepared guidelines for the use of anticoagulation in the conversion of atrial fibrillation. The efficacy of antiarrhythmic drug therapy for cardioversion is often difficult to assess. Furthermore, it is associated with major risks, including heart failure and exacerbation of arrhythmia, and minor risks, including systemic intolerance. A new National Institutes of Health trial, Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM), will clarify the true risks and benefits of antiarrhythmic therapy for conversion of atrial fibrillation to sinus rhythm. Patients who cannot tolerate drug therapy may benefit from interruption of conduction in the bundle of His, followed by implantation of a permanent pacemaker, the use of radiofrequency energy ablation, or the implantation of an atrial defibrillator. Some patients may benefit from surgical procedures, such as left atrial isolation, the corridor operation, and the maze operation.

Eversion versus conventional carotid endarterectomy: a prospective study

OBJECTIVES

To analyse comparatively eversion and conventional CEA for later association with restenosis, perioperative stroke/death and ipsilateral cerebrovascular events (early, late, disabling and non-disabling).

DESIGN

Prospective non-randomised clinical study.

MATERIALS AND METHODS

A total of 469 patients underwent 514 procedures; 274 (53%) eversion CEA and 240 (47%) conventional CEA. Perioperative monitoring was carried out by clinical evaluation under local anaesthesia or by transcranial Doppler under general anaesthesia. Follow-up was carried out by clinical evaluation and Duplex scanning.

RESULTS

Clamping time was significantly shorter in the eversion group (25.5 +/- 7.4 vs. 28.3 +/- 10.1 min; p = 0.0001; CI delta 4.40/1.12). The perioperative disabling stroke/death rate was 0.7% for eversion vs. 1.2% for conventional CEA, p = 0.6; odds ratio (OR), 0.58. There were two early carotid occlusions (within 30 days) in both groups. According to life-table analysis, after 3 years the probability of > 50% carotid restenosis was significantly lower in the eversion group (2.2% vs. 6.9%, p = 0.03; relative risk reduction 67%). There were no significant differences between the two groups relative to new cerebrovascular events (92% in both groups, p = 0.6). Using multivariate analysis (Cox regression), eversion CEA, and to a lesser extent standard CEA with patch, appeared to protect the vessel from restenosis.

CONCLUSIONS

The eversion technique was associated with reduced clamping time and probability of restenosis. However, because of the nature of a non-randomised study, the present analysis should be confirmed by a multicentre randomised trial.

Atrial fibrillation: maintaining stability of sinus rhythm or ventricular rate control? The need for prospective data: the PIAF trial

Atrial fibrillation is one of the most commonly encountered clinical arrhythmias. Different treatment options for this rhythm disorder exist with the electrical and/or pharmacological cardioversion to sinus rhythm with subsequent antiarrhythmic drug therapy to prevent recurrences being one of the primary therapeutic goals. Another alternative, however, is represented by the control of the ventricular rate in patients with persistent atrial fibrillation. The question of which these two strategies should be preferred in the majority of patients with atrial fibrillation has not been studied in a prospective way. Given the background of conflicting data with respect to the prognostic impact of atrial fibrillation and of the increasing evidence concerning the risks of antiarrhythmic drug treatment in atrial fibrillation, a prospective multicenter trial has been initiated to compare these two therapeutic alternatives prospectively. Patients will be randomly assigned to cardioversion with subsequent antiarrhythmic drug therapy to prevent recurrent atrial fibrillation or to a therapy aiming exclusively at control of the ventricular rate during persistent atrial fibrillation. All patients will receive anticoagulation by means of warfarin (target INR 2.5-3.5) to prevent thromboembolic complications. The rationale and the design of the PIAF trial (Pharmacological intervention in Atrial Fibrillation) are discussed below. The pilot phase of this study has begun patient enrollment in the spring of 1995.

Atrial fibrillation: a review of mechanism, etiology, and therapy

The prevalence of elderly individuals in the populations of developed countries is increasing rapidly, and atrial fibrillation (AF) is quite common in these elderly patients: currently, 11% of the U.S. population is between the ages of 65 and 85 years; 70% of people with AF are between the ages of 65 and 85 years. AF causes symptoms secondary to hemodynamic derangements that are the result of increased ventricular response and loss of atrial booster function. AF can lead to reversible impairment of left ventricular function, cardiac chamber dilatation, clinical heart failure, and thromboembolic events. AF requires treatment in order to prevent these potential complications. Type Ia, Ic, and III antiarrhythmics are capable of converting AF to normal sinus rhythm (NSR). Amiodarone has the greatest efficacy and safety for converting AF and maintaining NSR while digoxin and verapamil are ineffective in restoring NSR. Quinidine, flecainide, disopyramide, and sotalol have also been shown to maintain NSR after conversion of AF. Proarrhythmia is a definite concern with the latter four agents. Alternative therapy for AF includes anticoagulation with warfarin or aspirin for the prevention of thromboembolic events, and a variety of agents to control the ventricular response. All medications used to treat AF carry significant risks in the elderly, whether from proarrhythmia, overdosing because of compliance errors, or hemorrhage secondary to anticoagulation. Treatment of AF must be based on a careful risk-benefit evaluation. The physician must know the capability of the particular patient as well as drug mechanisms and effects in the elderly. The decision to convert patients from AF to NSR or to leave the patient in AF and control the ventricular response represents a complex intellectual challenge. Factors favoring one or the other of these two clinical strategies are discussed. Multicenter clinical trials, for example, the Atrial Fibrillation Follow-up Investigation Rhythm Management (AFFIRM) trial, are currently underway to assess various clinical strategies for maintenance of NSR following conversion from AF. Amiodarone is one of the drugs under investigation.

Pharmacologic management of atrial fibrillation

In an era when many electrophysiologic problems are routinely treated with invasive procedures or implantable devices, drugs remain the cornerstones of treatment for atrial fibrillation. Atrial fibrillation may present as an episodic rhythm in patients who are primarily in sinus rhythm or it may be manifested as rhythm disorder that is permanent. Patients who appear to have an episodic rhythm disorder may be found to be in atrial fibrillation permanently when followed for long periods of time, and prognosis in the two forms is similar. It is, therefore, useful to consider them different manifestations in the same spectrum of disease. This review will address pharmacologic approaches designed to: (1) slow ventricular response; (2) restore sinus rhythm; (3) reduce occurrences of atrial fibrillation; and (4) prevent thromboembolic complications. Nonpharmacologic approaches to treating atrial fibrillation will be briefly reviewed.

Low-energy transvenous cardioversion of atrial fibrillation using a single atrial lead system

INTRODUCTION

Clinical studies have shown that electrical conversion of atrial fibrillation (AF) is feasible with transvenous catheter electrodes at low energies. We developed a single atrial lead system that allows atrial pacing, sensing, and defibrillation to improve and facilitate this new therapeutic option.

METHODS AND RESULTS

The lead consists of a tripolar sensing, pacing, and defibrillation system. Two defibrillation coil electrodes are positioned on a stylet-guided lead. A ring electrode located between the two coils serves as the cathode for atrial sensing and pacing. We used this lead to cardiovert patients with acute or chronic AF. The distal coil was positioned in the coronary sinus, and the proximal coil and the ring electrode in the right atrium. R wave synchronized biphasic shocks were delivered between the two coils. Atrial signal detection and pacing were performed using the proximal coil and the ring electrode. Eight patients with acute AF (38 +/- 9 min) and eight patients with chronic AF (6.6 +/- 5 months) were included. The fluoroscopy time for lead placement was 3.5 +/- 4.3 minutes. The atrial defibrillation threshold was 2.0 +/- 1.4 J for patients with acute AF and 9.2 +/- 5.9 J for patients with chronic AF (P < 0.01). The signal amplitude detected was 1.7 +/- 1.1 mV during AF and 4.0 +/- 2.9 mV after restoration of sinus rhythm (P < 0.001). Atrial pacing was feasible at a threshold of 4.4 +/- 3.3 V (0.5-msec pulse width).

CONCLUSIONS

Atrial signal detection, atrial pacing, and low-energy atrial defibrillation using this single atrial lead system is feasible in various clinical settings. This system might lead to a simpler, less invasive approach for internal atrial cardioversion.

Left atrial size is the major predictor of cardiac death and overall clinical outcome in patients with dilated cardiomyopathy: a long-term follow-up study

HYPOTHESIS

This study was undertaken to determine whether echo-derived left atrial dimension and other echocardiographic, clinical, and hemodynamic parameters detected at the time of entry into the study may influence prognosis in patients with dilated cardiomyopathy during a long-term follow-up.

METHODS

This was a prospective cohort analysis of 123 patients with dilated cardiomyopathy. Clinical evaluation, chest x-ray, M-mode and two-dimensional echocardiogram, exercise test, 72-h ambulatory electrocardiogram monitoring, and cardiac catheterization study were performed in all patients. The study was divided into two phases: in the first phase, patients were divided into two groups according to the left atrial size (> or = 45 mm; < 45 mm), with cardiac death as the end point. In the second phase, all patients were further divided into two groups according to their clinical course. A multivariate analysis was performed to determine independent correlated parameters of cardiac mortality and overall clinical outcome.

RESULTS

Cardiac mortality rate was 47.9%: 29% in the group without left atrial dilation and 54.3% in the group with dilated left atrium. Multivariate analysis revealed that left atrium > or = 45 mm, New York Heart Association functional classes III/IV, and the presence of one or more episodes of ventricular tachycardia at Holter monitoring were independent predictors of cardiac mortality, while left atrium > or = 45 mm, left ventricular end-diastolic pressure > 17 mmHg, and exercise tolerance < or = 15 min were independent predictors of poor clinical outcome.

CONCLUSIONS

Our results revealed that left atrial size is the principal independent predictor of prognosis in patients with dilated cardiomyopathy in that patients with left atrial dilation had an increase in mortality and a worse clinical outcome compared with those without left atrial dilation.

Haemostatic and haemodynamic abnormalities associated with left atrial thrombosis in non-rheumatic atrial fibrillation

OBJECTIVE

To evaluate the role of haemostatic and haemodynamic variables in left atrial thrombosis in non-rheumatic atrial fibrillation.

DESIGN

Case-control study.

SUBJECTS

One hundred and nine patients with non-rheumatic atrial fibrillation.

INTERVENTIONS

Peak blood velocity measured at three sites in the left atrium. Venous blood sampled for coagulant proteins and markers of haemostatic activation.

MAIN OUTCOME MEASURES

Presence of left atrial thrombus and spontaneous echo contrast at transoesophageal echocardiography.

RESULTS

Left atrial thrombus was identified in 19 patients (18%), 16 of whom had spontaneous echo contrast. Patients with thrombus had reduced peak left atrial appendage velocity compared with those without (0.17 v 0.26 m/s; P < 0.001), but no significant reductions in peak mid-left atrial or mitral valve outflow velocity. Patients with thrombus had increased plasma markers of platelet activation-beta thromboglobulin (56.8 v 30.4 IU/ml; P < 0.001) and platelet factor 4 (6.1 v 3.5 IU/ml; P < 0.01)-and of thrombogenesis: thrombin-antithrombin complexes (5.59 v 3.06 micrograms/ml; P < 0.001) and D-dimers (479 v 298 ng/ml; P < 0.01). von Willebrand factor was also increased (1.81 v 1.52 IU/ml; P < 0.05). A multiple logistic regression model identified left atrial appendage velocity (P = 0.001), beta thromboglobulin (P = 0.002), and von Willebrand factor (P = 0.04) as the independent associates of left atrial thrombosis, ahead of the presence of spontaneous echo contrast.

CONCLUSIONS

Haemostatic and haemodynamic abnormalities are associated with left atrial thrombus in non-rheumatic atrial fibrillation, and may help stratify thromboembolic risk.

Ejection fraction and risk of thromboembolic events in patients with systolic dysfunction and sinus rhythm: evidence for gender differences in the studies of left ventricular dysfunction trials

OBJECTIVES

The aims of this study were to describe the incidence and spectrum of thromboembolic events experienced by patients with moderate to severe left ventricular systolic dysfunction in normal sinus rhythm and to study the association between ejection fraction and thromboembolic risk.

BACKGROUND

The annual incidence of thromboembolic events in patients with heart failure is estimated to range from 0.9% to 5.5%. Previous studies demonstrating a relation between worsening left ventricular systolic function and thromboembolic risk are difficult to interpret because of the prevalence of atrial fibrillation, an independent risk factor for thromboembolism, in the patients with a lower ejection fraction.

METHODS

This is a retrospective analysis of the Studies of Left Ventricular Dysfunction prevention and treatment trials data base. Patients with atrial fibrillation were excluded, resulting in 6,378 participants in sinus rhythm at the time of randomization. Thromboembolic events include strokes, pulmonary emboli and peripheral emboli. Separate analyses were conducted in each gender because there was evidence of a significant interaction between ejection fraction and gender on the risk of thromboembolic events (p = 0.04).

RESULTS

The overall annual incidence of thromboembolic events was 2.4% in women and 1.8% in men. On univariate analysis, a decline in ejection fraction was [corrected] associated with thromboembolic risk in women (relative risk [RR] per 10% decrease in ejection fraction 1.58, 95% confidence interval [CI] 1.10 to 2.26, p = 0.01), but not in men. On multivariate analysis, a decline in ejection fraction remained independently associated with thromboembolic risk in women (RR per 10% decrease 1.53, 95% CI 1.06 to 2.20, p = 0.02), but no relation was demonstrated in men.

CONCLUSIONS

In patients with left ventricular systolic dysfunction and sinus rhythm, the annual incidence of thromboembolic events is low. Ejection fraction appears to be independently associated with thromboembolic risk in women, but not in men.

Low energy transvenous cardioversion of short duration atrial tachyarrhythmias in humans using a single lead system

The purpose of this study was to investigate the efficacy and safety of atrial cardioversion using an endocardial single lead system presently used for ventricular defibrillation. The study population consisted of 26 recipients of an ICD in combination with a conventional endocardial single lead system with the proximal spring electrode as anode in the SVC and the distal as cathode in the apex of the RV. Atrial tachyarrhythmias were induced by right atrial burst pacing. If the arrhythmia sustained > 1 minute, biphasic shocks synchronized with the R wave were delivered using the implanted device, beginning with an energy of 4 J. If 4 J failed to terminate the arrhythmia, energy was increased stepwise, if the first shock was successful, a step-down testing was performed after reinduction of atrial tachyarrhythmias. The mean atrial defibrillation threshold was 2.3 +/- 1.2 J (range, 0.5-5 J). A total of 154 shocks were delivered and no adverse effects were observed. The mean defibrillation threshold for atrial flutter was somewhat lower than that for AF (1.8 +/- 1 J vs 2.7 +/- 1.4 J, P = 0.08). There was no correlation between the atrial defibrillation threshold and a history of previously occurring atrial tachyarrhythmias, the kind of the underlying heart disease, a prescription of antiarrhythmic drugs, the dimension of the LA, the LVEF, or the ventricular DFT. Internal atrial cardioversion of short duration atrial tachyarrhythmias using a transvenous single lead system designed for ventricular defibrillation is feasible and safe at low energies, and may have important clinical applications.

Cardioversion of atrial fibrillation in the elderly. ALKK-Study Group. Arbeitsgemeinschaft Leitender Kardiologischer Krankenhausaerzte

The purpose of this investigation was to define cardioversion success rates, frequency of complications of cardioversion, and current treatment practices in elderly patients (aged > or = 65 years) with atrial fibrillation (AF). The results were compared with those in younger patients (aged < 65 years). The investigation was a prospective multicenter observational study with 61 participating cardiology clinics. Consecutive patients in whom cardioversion of AF was planned had to be prospectively registered. Of 1,152 patients registered, 570 (49.5%) were < 65 years old (group 1) and 582 (50.5%) were > or = 65 years (group 2). The overall success rate of cardioversion on an intention-to-treat basis was 76.1% in group 1 and 72.7% in group 2 (p = 0.18). In multivariate analysis, left atrial size and New York Heart Association functional class before cardioversion were identified as predictors of success (p < 0.001, respectively; p = 0.025). These clinical factors were not equally distributed between the age groups: Left atrial size was larger in the elderly than in younger patients (44.0 +/- 6.4 mm vs 42.8 +/- 6.4 mm; p = 0.006) and a New York Heart Association functional class > or = II was more prevalent in group 2 than in group 1 (48.6% vs 29.6%; p < 0.001). The overall complication rates were not significantly different between the 2 groups (4.2% in group 1 vs 5.3% in group 2; p = 0.37). The frequency of patients who were adequately anticoagulated for cardioversion was 56.9% in age group 1 and 39.6% in age group 2 (p < 0.001). In chronic AF the same trend for age-dependent underuse of anticoagulation was observed. Age itself was not a predictor of cardioversion success and did not predispose to higher complication rates. Therefore, cardioversion should be considered in older patients with the same criteria and emphasis as in younger patients. Anticoagulation and antithrombotic medication is underused for cardioversion and in treating chronic AF, especially in elderly patients.

Thrombolytic Therapy for Acute Ischemic Stroke: What Cardiac Physicians Need to Know

The current status of thrombolytic therapy for acute ischemic stroke is reviewed in relation to early work and to the use of thrombolytic agents in acute myocardial infarction. The case of a patient treated with recombinant tissue plasminogen activator for acute ischemic stroke is described to illustrate the improvement in outcome that can be achieved with this therapy in selected patients. A number of recommendations are included for cardiologists on the use of plasminogen activator in acute ischemic stroke regarding the timing, dosage, selection, and monitoring of patients.

Antiarrhythmic drug therapy in the treatment of atrial fibrillation

Treatment of atrial fibrillation is often unsatisfactory because no available drug has been shown to be clearly superior for maintaining patients in sinus rhythm, and all agents have significant potential for toxicity. Selection of an antiarrhythmic drug is more likely to be based on the drug's potential for toxicity, rather than its demonstrated superior efficacy in the treatment of atrial fibrillation. Careful assessment of each patient for contraindications to individual agents and the likelihood of treatment success needs to be done before initiating antiarrhythmic therapy.

Therapeutic strategies for atrial fibrillation. The value of decision analysis

In the absence of randomized, controlled trials of low-dose amiodarone in atrial fibrillation or a randomized, controlled trial of ventricular rate control versus antifibrillatory therapy, a Markov decision analysis is useful in comparing different therapeutic strategies for atrial fibrillation. The decision analysis described compared warfarin, quinidine, and low-dose amiodarone in patients with asymptomatic or minimally symptomatic chronic, persistent atrial fibrillation. This model suggests that electrical cardioversion followed by low-dose amiodarone is a relatively safe, effective alternative to long-term warfarin therapy.

Can a physician recognize an older driver with increased crash risk potential?

OBJECTIVE

To identify factors in a medical examination that distinguish convicted older drivers with traffic violations from other drivers.

DESIGN

Matched case-control study.

SETTING

Two countries in Sweden.

SUBJECTS

Thirty-seven drivers older than age 65, whose driving licenses have been temporarily suspended, each matched to one control subject based on age, sex, type of driving license, year of first license, living area, educational level, and annual distance driven.

MEASUREMENTS

Case and control subjects were compared with respect to medical history, medication use, blood tests, drawing and memory tests, Mini-Mental State Examination, medical status findings, visual acuity, and brain imaging procedures.

MAIN RESULTS

The group of drivers with suspended driving licenses did not differ from matched controls with respect to visual acuity or presence of cardiovascular diseases. However, persons with suspended driving licenses were more likely than control subjects to have suspected or mild dementia (P < .010) and to perform less well on two easily administrated screening tests: copying a cube (P < .010) and 5-item recall (P < .010). Case subjects with crashes had significantly more cardiovascular diseases than case subjects with other moving violations (P < .050). These case subjects with crashes also had significantly more cognitive impairments than control subjects without crashes as shown by a higher clinical dementia rating score (CDR) (P < .001), lower score on the Mini-Mental State Examination (MMSE) (P < .050), and lower level of performance in the copying task (cube) (P < .050) and 5-item recall test (P < .010). They also had evidence of greater cognitive impairment than those case subjects with other moving violations.

CONCLUSIONS

Visual acuity and common medical examination did not distinguish convicted older drivers with crashes or other moving violations from controls. There was evidence that even mild cognitive impairment contributed to the risk of losing a driving license because of crashes.

Atrial defibrillation: can modifications in current implantable cardioverter-defibrillators achieve this?

Atrial fibrillation (AF), the most common arrhythmia resulting in hospital admission, is a major health problem. The limited efficacy of antiarrhythmic drugs to control this rhythm disorder and their potential proarrhythmic risk led to the development of new techniques to ameliorate the treatment of AF. Transvenous atrial defibrillation using endocardial electrodes has been shown to be effective at low energy levels. An implantable atrial defibrillator could be a potentially valuable treatment option for patients with paroxysmal AF that is medically refractory. Research is currently under way to investigate several critical issues concerning this new therapeutic concept: long-term efficacy, safety, patient's tolerance, and an acceptable cost/benefit ratio. It is well known that AF often complicates the use of the implantable cardioverter-defibrillator (ICD) for ventricular tachyarrhythmias. Therefore, it would seem desirable to implement the capability for atrial defibrillation into current ICD systems. It has been shown that atrial defibrillation, using endocardial lead configurations specifically designed for ventricular defibrillation, is feasible at energies well within the capabilities of current ICD technology. Further research is needed to evaluate if some enhancement of the lead configuration in combination with possible advanced technology could reduce the atrial defibrillation threshold to a well tolerated level as a prerequisite for automated atrial defibrillation, in ICD recipients with concomitant paroxysmal AF.

An analysis of the lowest effective intensity of prophylactic anticoagulation for patients with nonrheumatic atrial fibrillation

BACKGROUND

To avert major hemorrhage, physicians need to know the lowest intensity of anticoagulation that is effective in preventing stroke in patients with atrial fibrillation. Since the low rate of stroke has made it difficult to perform prospective studies to resolve this issue, we conducted a case-control study.

METHODS

We studied 74 consecutive patients with atrial fibrillation who were admitted to our hospital from 1989 through 1994 after having an ischemic stroke while taking warfarin. For each patient with stroke, three controls with nonrheumatic atrial fibrillation who were treated as outpatients were randomly selected from the 1994 registry of the anticoagulant-therapy unit (222 controls). We used the international normalized ratio (INR) to measure the intensity of anticoagulation. For the patients with stroke, we used INR at admission; for the controls, we selected the INR that was measured closest to the month and day of the matched case patient's hospital admission.

RESULTS

The risk of stroke rose steeply at INRs below 2.0. At an INR of 1.7, the adjusted odds ratio for stroke, as compared with the risk at an INR of 2.0, was 2.0 (95 percent confidence interval, 1.6 to 2.4); at an INR of 1.5, it was 3.3 (95 percent confidence interval, 2.4 to 4.6); and at an INR of 1.3, it was 6.0 (95 percent confidence interval, 3.6 to 9.8). Other independent risk factors were previous stroke (odds ratio, 10.4; 95 percent confidence interval, 4.4 to 24.5), diabetes mellitus (odds ratio, 2.95; 95 percent confidence interval, 1.3 to 6.5), hypertension (odds ratio, 2.5; 95 percent confidence interval, 1.1 to 5.7), and current smoking (odds ratio, 5.7; 95 percent confidence interval, 1.4 to 24.0).

CONCLUSIONS

Among patients with atrial fibrillation, anticoagulant prophylaxis is effective at INRs of 2.0 or greater. Since previous studies have indicated that the risk of hemorrhage rises rapidly at INRs greater than 4.0 to 5.0, tight control of anticoagulant therapy to maintain the INR between 2.0 and 3.0 is a better strategy than targeting lower, less effective levels of anticoagulation.

Atrial fibrillation with left atrial spontaneous contrast detected by transesophageal echocardiography is a potent risk factor for stroke

Nonrheumatic atrial fibrillation (AF) frequently coexists with other risk factors for cerebral ischemia. This study was originally designed to determine which combinations of clinical and echocardiographic abnormalities were most closely associated with the risk of cerebral ischemic events. Patients with cerebral ischemic events (n = 214) and community-based control subjects (n = 201) underwent transesophageal echocardiography and carotid artery imaging. Adjusted odds ratios (ORs) were determined using multiple logistic regression analysis. Independent risk factors for cerebral ischemia included diabetes, carotid stenosis, aortic sclerosis, left ventricular dysfunction, left ventricular hypertrophy, left atrial (LA) spontaneous contrast, and proximal aortic atheroma. Nonrheumatic AF in combination with LA spontaneous contrast and LA enlargement showed a strong association with cerebral ischemic events (OR 33.7 [95% confidence interval 4.53 to 251]). In subjects with sinus rhythm or nonrheumatic AF, LA enlargement was not associated with an increased risk of cerebral ischemic events in the absence of LA spontaneous contrast. However, only 2 patients and 1 control subject had nonrheumatic AF without LA spontaneous contrast or LA enlargement. Therefore, study of a larger number of subjects is required to address the issue of whether nonrheumatic AF itself carries increased risk. The combination of nonrheumatic AF with LA spontaneous contrast is a potent risk factor for cerebral ischemia. Ascertaining the risk factor in nonrheumatic AF requires adequate examination for underlying cardiac, aortic, and carotid vascular disease. Transesophageal echocardiography may contribute to this assessment.

Transesophageal echocardiography-guided approach to cardioversion of atrial fibrillation

In patients with atrial fibrillation, electrical cardioversion is often performed to relieve symptoms, to improve left ventricular function, and to decrease thromboembolic risks. However, cardioversion of atrial tachyarrhythmias is associated with an increased embolic risk, with an event rate of up to 5.6%. The American College of Chest Physicians recommend 3 weeks of systemic anticoagulation before elective cardioversion and 4 weeks of systemic anticoagulation afterwards. Expulsion of preexisting left atrial (LA) thrombi with resumption of sinus rhythm has traditionally been considered the mechanism for this increased embolic risk associated with cardioversion. The advent of transesophageal echocardiography (TEE) has allowed accurate detection of LA thrombus. Moreover, recent studies using TEE have identified a state of atrial "stunning" immediately after cardioversion, which is considered a thrombogenic milieu in which new thrombus formation and increased or de novo appearance of LA spontaneous echocardiographic contrast have been observed. Furthermore, embolic events have been reported after cardioversion despite exclusion of preexisting LA thrombus by TEE. These studies strongly suggest an alternative mechanism for embolism after cardioversion, ie, atrial stunning with worsened atrial appendage function and enhanced thrombogenesis. Recent studies have shown the safety of a TEE-guided anticoagulation approach in which exclusion of preexisting LA thrombus by TEE enables early cardioversion without the need for the standard 3 weeks of systemic anticoagulation. The importance of maintaining therapeutic anticoagulation has been further emphasized. Although preliminary observational studies of TEE-guided cardioversion are encouraging, there has been no prospective, randomized trial comparing the two strategies of anticoagulation management. The Assessement of Cardioversion Utilizing Transesophageal Echocardiography (ACUTE) pilot study randomized 126 patients from 10 sites and showed the feasibility and safety of the larger scale study. A larger multicenter, prospective randomized trial is now underway and is expected to randomize a total of 3,000 patients. The results of the ACUTE study will definitively establish the safest and the most cost-effective way to manage anticoagulation for elective cardioversion.

Stratification of thromboembolic risk of atrial fibrillation by transthoracic echocardiography and transesophageal echocardiography: the relative role of left atrial appendage function, mitral valve disease, and spontaneous echocardiographic contrast

The role of transesophageal echocardiography (TEE) in thromboembolic risk stratification in atrial fibrillation (AF) has not been established. Left atrial appendage contractile dysfunction in patients with AF predisposes to thrombus formation. The extent of blood stasis and propensity for thrombus can be assessed during TEE by measurement of the peak Doppler velocity of blood outflow from the appendage. Spontaneous echocardiographic contrast (SEC) is a swirling pattern of blood echogenicity that may be detected by TEE in the left atrium in patients with AF. The presence of SEC reflects left atrial blood stasis and a prothrombotic state. SEC is associated with an increased risk of systemic thromboembolic events. Parameters derived from TEE may provide additional prognostic data to clinical history and transthoracic echocardiography in thromboembolic risk stratification in AF.

Current recommendations for the anticoagulation of patients with atrial fibrillation

Atrial fibrillation (AF) is the most commonly encountered cardiac rhythm disorder and is strongly associated with stroke. The risk of stroke and the benefit of anticoagulant therapy in patients with AF associated with mitral stenosis has been well accepted. Until recently the risk of stroke and the role of anticoagulant therapy in patients with nonrheumatic AF was unclear. Over the past decade studies have shown an approximate fivefold increase in the risk of stroke in patients with nonrheumatic AF. The results of large clinical trials have shown a benefit of treatment with anticoagulants and, to a lesser extent, aspirin for both the primary and secondary prevention of thromboembolic complications. Other than patients with a low risk of thromboembolic complications (primarily young patients without clinical risk factors), current guidelines recommend anticoagulation of most patients with AF. The studies that form the basis for these recommendations and the currently published guidelines are reviewed.

The utilization of antithrombotic prophylaxis for atrial fibrillation in a geriatric rehabilitation hospital

OBJECTIVE

To determine the utilization of anticoagulant and antithrombotic agents in older patients with atrial fibrillation.

DESIGN

Retrospective chart review.

SETTING

A geriatric rehabilitation hospital.

PATIENTS

Subjects were 102 patients with atrial fibrillation as an intermittent or prevailing cardiac rhythm during a hospital admission in the 1993 fiscal year.

MEASUREMENTS

Age, sex, and mental status of the patients; duration and etiology of atrial fibrillation; presence of contraindications to anticoagulants or antithrombotic agents; and utilization of these agents in this population.

RESULTS

Of 102 older patients with atrial fibrillation at admission, only 51 were taking some form of anticoagulant or antithrombotic therapy proven effective for stroke prophylaxis (19 warfarin and 32 aspirin). Although 67 patients had relative contraindications to anticoagulation with warfarin, only 25 of the 35 with no contraindications were taking warfarin at the time of discharge. In addition, of the 43 patients with contraindications to warfarin but no contraindications to aspirin, only 28 were prescribed antithrombotic therapy.

CONCLUSIONS

Although anticoagulation or antithrombotic therapies for atrial fibrillation appear to be relatively widely used, there are still significant windows of opportunity for the improvement of clinician practice patterns and clinical outcomes in older patients.

Prevalence of atrial fibrillation and association of atrial fibrillation with prior and new thromboembolic stroke in older patients

OBJECTIVE

To correlate atrial fibrillation with the incidence of new thromboembolic (TE) stroke in older patients with and without prior TE stroke.

DESIGN

In a prospective study of 2101 older patients, electrocardiograms showed that atrial fibrillation was present in 283 patients (13%). At 42-month mean follow-up, atrial fibrillation was associated with the incidence of new TE stroke in patients with and without prior TE stroke.

SETTING

A large long-term health care facility where 2101 older patients were studied.

PATIENTS

The 2101 patients included 1451 women and 650 men, mean age 81 +/- 8 years (range 60 to 103).

MEASUREMENTS AND MAIN RESULTS

Atrial fibrillation was present in 283 of 2101 patients (13%). The mean age was 84 +/- 7 years in patients with atrial fibrillation and 81 +/- 8 years in patients with sinus rhythm (P = .0001). The prevalence of atrial fibrillation was 5% in patients aged 60 to 70 years, 14% in patients aged 71 to 80 years, 13% in patients aged 81 to 90 years, and 22% in patients aged 91 to 103 years (P < .0001). Mean follow-up was 31 +/- 18 months in patients with atrial fibrillation and 44 +/- 27 months in patients with sinus rhythm (P = .0001). Previous TE stroke occurred in 123 of 283 patients (43%) with atrial fibrillation and in 431 of 1818 patients (24%) with sinus rhythm (P < .0001). New TE stroke occurred in 131 of 283 patients (46%) with atrial fibrillation and in 303 of 1818 patients (17%) with sinus rhythm (P < .0001). The log-rank test showed that patients with atrial fibrillation had a significantly higher probability of developing new TE stroke than those with sinus rhythm (P < .0001). The multivariate Cox regression model showed that independent risk factors for new TE stroke were male sex (relative risk = 1.3), prior TE stroke (relative risk = 3.1), and atrial fibrillation (relative risk = 3.3).

CONCLUSIONS

Atrial fibrillation, prior TE stroke, and male sex are independent risk factors for the development of new TE stroke in older patients.

Correlation of paroxysmal supraventricular tachycardia, atrial fibrillation, and sinus rhythm with incidences of new thromboembolic stroke in 1476 old-old patients

The relationship between supraventricular tachycardia and the incidence of thromboembolic stroke has not been previously reported. We investigated in a prospective study the incidence of new thromboembolic stroke in 1476 patients, mean age 81 years, with atrial fibrillation, paroxysmal supraventricular tachycardia, or sinus rhythm detected by 24-hour ambulatory electrocardiograms. New thromboembolic stroke developed at 31-month follow-up in 87 of 201 patients (43%) with atrial fibrillation, at 43-month follow-up in 84 of 493 patients (17%) with paroxysmal supraventricular tachycardia, and at 45-month follow-up in 143 of 782 patients (18%) with sinus rhythm (p < 0.0001 comparing atrial fibrillation with paroxysmal supraventricular tachycardia or sinus rhythm). Kaplan-Meier survival curves showed a higher significance of thromboembolic stroke in patients with atrial fibrillation, compared to patients with paroxysmal supraventricular tachycardia or sinus rhythm (log-rank: p < 0.0001). Multivariate Cox regression model showed that independent significant predictors of thromboembolic stroke were: a) atrial fibrillation (relative risk = 3.31); b) prior thromboembolic stroke (relative risk = 2.85); c) sex (relative risk for women = 0.75); and d) age (relative risk = 1.02). These data show that atrial fibrillation is an independent predictor of thromboembolic stroke in elderly patients, and that paroxysmal supraventricular tachycardia is not associated with thromboembolic stroke.