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

Management of atrial fibrillation in adults: prevention of thromboembolism and symptomatic treatment

Because of its prevalence in the population and its associated underlying diseases and morbidity, atrial fibrillation (AF) is an important and costly health problem. Advancing age, diabetes, heart failure, valvular disease, hypertension, and myocardial infarction predict the occurrence of AF within a population. The management of AF is complex and involves prevention of thromboembolic complications and treatment of arrhythmia-related symptoms. Stroke occurs in 4.5% of untreated patients with AF per year. Independent risk factors for stroke in nonrheumatic patients with AF are advanced age; a history of prior embolism, hypertension, or diabetes; and echocardiographic findings of left atrial enlargement and left ventricular dysfunction. Warfarin decreases stroke by two-thirds and death by one-third; aspirin is only about half as effective overall and is insufficient therapy for those with risk factors for stroke. Options for thromboembolic prophylaxis are use of warfarin for all in whom it is safe or, alternatively, warfarin for those with risk factors and aspirin for those without risk factors. One-half of the patients with AF are 75 years of age or older. The uniform applicability and relative safety of warfarin therapy in this age-group are controversial. Specific therapy for the arrhythmia should be dictated by the need to control symptoms. Symptomatic treatments include rate-control medications and strategies designed to terminate and prevent arrhythmia recurrence. Digoxin, beta-adrenergic blockers, verapamil, and diltiazem slow excessive ventricular rates in patients with AF and may favorably manage comorbid conditions. The efficacy of anti-arrhythmic medications is only 40 to 70% per year in preventing recurrences of AF, and these agents, except amiodarone, may increase the risk of sudden death in patients with certain types of organic heart disease and AF. The use of nonpharmacologic symptomatic therapies such as atrioventricular node modification or ablation with a rate-response pacemaker or surgical intervention is increasing.

Appendage obliteration to reduce stroke in cardiac surgical patients with atrial fibrillation

BACKGROUND

Left atrial appendage obliteration was historically ineffective for the prevention of postoperative stroke in patients with rheumatic atrial fibrillation who underwent operative mitral valvotomy. It is, however, a routine part of modern "curative" operations for nonrheumatic atrial fibrillation, such as the maze and corridor procedures.

METHODS

To assess the potential of left atrial appendage obliteration to prevent stroke in nonrheumatic atrial fibrillation patients, we reviewed previous reports that identified the etiology of atrial fibrillation and evaluated the presence and location of left atrial thrombus by transesophageal echocardiography, autopsy, or operation.

RESULTS

Twenty-three separate studies were reviewed, and 446 of 3,504 (13%) rheumatic atrial fibrillation patients, and 222 of 1,288 (17%) nonrheumatic atrial fibrillation patients had a documented left atrial thrombus. Anticoagulation status was variable and not controlled for. Thrombi were localized to, or were present in the left atrial appendage and extended into the left atrial cavity in 254 of 446 (57%) of patients with rheumatic atrial fibrillation. In contrast, 201 of 222 (91%) of nonrheumatic atrial fibrillation-related left atrial thrombi were isolated to, or originated in the left atrial appendage (p < 0.0001).

CONCLUSIONS

These data suggest that left atrial appendage obliteration is a strategy of potential value for stroke prophylaxis in nonrheumatic atrial fibrillation.

Antithrombotic therapy in atrial fibrillation: a review of randomized trials with special reference to the Stroke Prevention in Atrial Fibrillation II (SPAF II) Trial

Nonvalvular atrial fibrillation is common and is associated with a high risk of system embolism. Recently, several large randomized trials have been completed that have established the efficacy of antithrombotic therapy for both primary and secondary prevention of systemic thromboembolism with an acceptable rate of bleeding complications in these patients. This section of clinical trials review summarizes data from all published randomized trials of antithrombotic therapy in atrial fibrillation. The efficacy of aspirin versus warfarin is analyzed. The role of clinical and echo-cardiographic findings to stratify patients is also highlighted. The Stroke Prevention in Atrial Fibrillation II trial is discussed in detail.

Long-term follow-up of patients treated by radiofrequency ablation of the atrioventricular junction

Radiofrequency ablation of the AV conduction tissue (His-bundle ablation) is an accepted treatment for therapy resistant atrial fibrillation/flutter. However, data on the long-term effects of the procedure are limited. We followed 50 patients for a mean of 17 months after AV junction ablation. The indication was treatment resistant atrial fibrillation or flutter. The patients underwent a standardized interview performed by two nurses. Health care was studied via the in-patient register. Subjective improvement was reported by 88% and the number of days in hospital per year was reduced from 17 to 7. The use of antiarrhythmic drugs was reduced by 75%. If the reduction in costs of drugs and days in hospital is compared with the cost of the ablation and the pacemaker implantation, breaking even is achieved after 2.6 years. We could not confirm that patients with paroxysmal atrial fibrillation note less improvement than those with chronic fibrillation.

CONCLUSION

Ablation of the AV junction is a cost effective treatment with good long-term results and relatively few complications.

RECOMMENDATIONS

Chronic atrial fibrillation: If sinus rhythm cannot be established and in cases in which heart rate regulating drugs have been ineffective, ablation of the AV junction with implantation of a VVIR pacemaker is recommended.

PAROXYSMAL ATRIAL FIBRILLATION

If the patient despite treatment with antiarrhythmic drugs continues to have symptomatic episodes of atrial fibrillation, then AV junction ablation with implantation of a permanent pacemaker is recommended. Patients who have self-limiting episodes of atrial fibrillation should be given a DDDR pacemaker with an automatic mode switch. Patients who do not have self-limiting attacks and require DC conversion, should receive a VVIR pacemaker.

Contemporary management of atrial fibrillation

The incidence of atrial fibrillation approximately doubled for every 10-year increment in age in the Framingham Heart Study cohort; thus physicians will be faced with an increasing patient population with atrial fibrillation. Hypertension is observed to be the most common associated risk factor in both sexes. The management of patients with atrial fibrillation is evolving as a result of a number of published studies. Calcium channel blockers and beta-blockers are emerging as the preferred choices for rate control rather than digoxin. Low-dose anticoagulation therapy has shown beneficial effects not only in primary prevention, but also for secondary prevention of thromboembolism. Thus, patients who cannot be successfully cardioverted should be anticoagulated if there are no contraindications (Table 3) and if they do not fall into the low-risk group--defined as patients under the age of 65 without risk factors (hypertension, diabetes, previous stroke). Patients not eligible for anticoagulation should be on aspirin therapy. Patients with lone atrial fibrillation are not at higher risk for thromboembolism than the general population; therefore, they can be managed without anticoagulation or antiplatelet therapy. Antiarrhythmic treatment should be approached cautiously; amiodarone in low doses is the most effective and safe treatment, but this remains controversial.

Implantable atrial defibrillators

Due to the limited efficacy of antiarrhythmic drugs for atrial fibrillation, several nonpharmacologic therapeutic options have evolved. One of these is an implantable atrial defibrillator. Recent studies have shown that internal atrial defibrillation is feasible with relatively low energies. To date, the optimal electrode configuration involves large surface area catheters in the right atrium and coronary sinus. In humans, atrial defibrillation can generally be achieved with < 2 J using this electrode configuration and a biphasic shock waveform. For shocks < 5 J, there is no significant pathological damage to the atria or coronary sinus. Further investigation is needed to guarantee that atrial defibrillation shocks do not provoke ventricular arrhythmias. Preliminary data suggest that atrial defibrillation shocks synchronized to R waves that are not closely coupled are safe. In addition, the shocks are well tolerated if the shock energy is < 1.5 J. With additional studies to confirm the safety of implantable atrial defibrillators, further reduce shock energy, and improve patient tolerance, an implantable atrial defibrillator can become an acceptable therapy for patients with symptomatic, paroxysmal atrial fibrillation.

The role of transesophageal echocardiography in the diagnosis of ischemic stroke in the elderly

Cardioembolic stroke is quite common (15% of all ischemic strokes) not only in younger patients but also in the elderly. Clinical diagnosis is often difficult. Transthoracic echocardiography (TTE) seems to be the most reliable non-invasive method of examination. Because of the close topographical relationship between heart and esophagus, transesophageal echocardiography (TEE) is particularly suitable to evaluate those cardiac structures (left atrium and appendage) where the embolus can most likely be found. Using TTE and TEE, we studied 62 patients older than 65 years of age (mean age 76 +/- 6), having been affected by ischemic stroke. TEE proved to be clearly superior to TTE in the diagnosis of cardioembolic stroke, without any major complication during the execution of this diagnostic method.

An approach to therapy of supraventricular tachyarrhythmias: an algorithm versus individualized therapy

Approaches to the treatment of supraventricular arrhythmias, including atrial fibrillation, atrial flutter, atrial tachycardia, atrioventricular (AV) reentrant tachycardia, and AV nodal reentrant tachycardia, continue to evolve. Within the past two decades, many new and effective treatments have become available. These include several new antiarrhythmic agents, ablative therapies, pacing and surgical modalities, and cardioversion/defibrillation techniques. This paper provides an algorithm for the treatment of these supraventricular arrhythmias which includes therapy for the acute episode as well as the prevention of subsequent episodes of the tachyarrhythmia.

Prognostic implications of left atrial spontaneous echo contrast in nonvalvular atrial fibrillation

OBJECTIVES

This study examined the influence of left atrial spontaneous echo contrast on the subsequent stroke or embolic event rate and on survival in patients with nonvalvular atrial fibrillation.

BACKGROUND

Left atrial spontaneous echo contrast is associated with atrial fibrillation and a history of previous stroke or other embolic events. However, the prognostic implications of spontaneous contrast in patients with nonvalvular atrial fibrillation are unknown.

METHOD

The study group comprised 272 consecutive patients with nonvalvular atrial fibrillation undergoing transesophageal echocardiography. Clinical and echocardiographic data were collected at baseline, and patients were prospectively followed up, and all strokes, other embolic events and deaths were documented. The relation between spontaneous contrast at baseline and subsequent stroke, other embolic events and survival was analyzed.

RESULTS

Left atrial spontaneous echo contrast was detected at baseline in 161 patients (59%). The mean follow-up was 17.5 months. The stroke or other embolic event rate was 12%/year (15 strokes, 3 transient ischemic attacks, 2 peripheral embolisms) in patients with, compared with 3%/year (5 strokes) in patients without, baseline spontaneous contrast (p = 0.002). In 149 patients without previous thromboembolism, the event rate was 9.5%/year in patients with and 2.2%/year in patients without spontaneous contrast (p = 0.003). There were 25 deaths in patients with and 11 deaths in patients without spontaneous contrast. Patients with spontaneous contrast had significantly reduced survival (p = 0.025). On multivariate analysis, spontaneous contrast was the only positive predictor (odds ratio 3.5, p = 0.03) and warfarin therapy on follow-up the only negative predictor (odds ratio 0.23, p = 0.02) of subsequent stroke or other embolic events.

CONCLUSIONS

Transesophageal echocardiography can risk stratify patients with nonvalvular atrial fibrillation by identifying left atrial spontaneous echo contrast. These patients have both a significantly higher risk of developing stroke or other embolic events and a reduced survival, and they may represent a subgroup in whom the risk/benefit ratio of anticoagulation may be most favorable.

Antithrombotic therapy prescribed for patients with non-rheumatic atrial fibrillation

Patients with non-rheumatic atrial fibrillation have a fivefold increased risk of stroke. Warfarin reduces this risk by approximately two thirds, but evidence for benefit from aspirin is less compelling. We assessed whether our current practice reflects the message of the trials. In a retrospective case record study we reviewed notes of 131 patients with atrial fibrillation (AF), mean age 79 (range 53-95) years, admitted to a medical unit (72) or geriatric assessment unit (59). Thirty-two patients had paroxysmal AF. Of 115 patients with nonrheumatic AF, 36 (31%) had one or more recorded contraindication to anti-coagulation. Although 79 patients (69%) had no recorded contraindication to warfarin, only 2 took warfarin and 15 aspirin prior to admission. Ten patients commenced warfarin and 8 aspirin before discharge. Thirty-nine patients (53%) without contraindication, were discharged without antithrombotic therapy. Despite evidence to support anticoagulating patients with non-rheumatic AF, this rarely occurs.

Prevalence of atrial fibrillation in elderly subjects (the Cardiovascular Health Study)

Atrial fibrillation (AF) is a common arrhythmia in elderly persons and a common cause of embolic stroke. Most studies of the prevalence and correlates of AF have used selected, hospital-based populations. The Cardiovascular Health Study is a population-based, longitudinal study of risk factors for coronary artery disease and stroke in 5,201 men and women aged > or = 65 years. AF was diagnosed in 4.8% of women and in 6.2% of men at the baseline examination, and prevalence was strongly associated with advanced age in women. Prevalence of AF was 9.1% in men and women with clinical cardiovascular disease, 4.6% in patients with evidence of subclinical but no clinical cardiovascular disease, and only 1.6% in subjects with neither clinical nor subclinical cardiovascular disease. A history of congestive heart failure, valvular heart disease and stroke, echocardiographic evidence of enlarged left atrial dimension, abnormal mitral or aortic valve function, treated systemic hypertension, and advanced age were independently associated with the prevalence of AF. The low prevalence of AF in the absence of clinical and subclinical cardiovascular disease calls into question the existence and clinical usefulness of the concept of so-called "lone atrial fibrillation" in the elderly.

Carotid plaque, aging, and risk factors. A study of 457 subjects

BACKGROUND AND PURPOSE

The aim of this study was to assess the prevalence of extracranial carotid artery atherosclerosis and its relation to principal cardiovascular risk factors at different ages in a sample of the general population.

METHODS

B-mode ultrasonography was used to investigate the carotid district in 457 subjects (231 men and 226 women; mean age, 55.4 +/- 18.7 years; range, 18 to 97 years) in the metropolitan area. The ultrasonographic findings were then related to risk factors.

RESULTS

Carotid plaques were found in 178 subjects (38.9%). The prevalence of atherosclerosis, number of plaques, and severity of stenosis were observed to increase with age. Age (P < .0001), cigarette smoking (P < .0001), male sex (P < .001), total cholesterol (P < .05), and, inversely, the ratio of high-density lipoprotein cholesterol to total cholesterol (P < .05) were found to be independently associated with carotid atherosclerosis. Stratified analysis by sex and age showed effect modifications by age on cigarette smoking, total cholesterol, and the ratio of high-density lipoprotein cholesterol to total cholesterol. After multivariate analysis including interaction terms, cigarette smoking and cholesterol levels were not longer found to be associated with carotid atherosclerosis in elderly subjects. Age (P < .01), total cholesterol (P < .05), and diabetes (P < .05) were positively related to the severity of vascular narrowing.

CONCLUSIONS

There is a high prevalence of asymptomatic carotid atherosclerosis in the general population, particularly among the very old. The association between risk factors and carotid atherosclerosis is less pronounced in the elderly than in younger subjects.

Glucose intolerance and 22-year stroke incidence. The Honolulu Heart Program

BACKGROUND AND PURPOSE

This study was conducted to determine whether glucose intolerance and diabetes increase the risk of thromboembolic, hemorrhagic, and total stroke independent of other risk factors.

METHODS

Among 7549 Japanese-American men aged 45 to 68 years and free of coronary heart disease and stroke during 1965 to 1968, history of diabetes, diabetic medication, and nonfasting glucose 1 hour after a 50-g load were used to classify subjects into four glucose tolerance categories. Incidence of stroke over 22 years was ascertained using comprehensive hospital-based surveillance. Age- and risk factor-adjusted relative risks of stroke were determined using a Cox proportional hazards model.

RESULTS

A total of 374 thromboembolic, 128 hemorrhagic, and 36 type-unknown strokes occurred. Incidence of thromboembolic but not hemorrhagic stroke increased with worsening glucose tolerance category. Compared with the "low-normal" (glucose < 151 mg/dL) group, subjects in the "high-normal" (151 to 224 mg/dL), "asymptomatic high" (> or = 225 mg/dL), and "known diabetes" groups all had significantly elevated age-adjusted relative risks of thromboembolic stroke. After adjustment for other risk factors, relative risks remained significantly elevated for the asymptomatic high and known diabetes groups (1.43 and 2.45; 95% confidence intervals, 1.00 to 2.04 and 1.73 to 3.47, respectively). Associations were the same in hypertensive and nonhypertensive subjects and similar but slightly stronger in younger (aged 45 to 54 years) than in older (aged 55 to 68 years) men.

CONCLUSIONS

Subjects with diabetes and elevated glucose appear to be at increased risk of thromboembolic but not hemorrhagic stroke. These associations were largely independent of other cardiovascular disease risk factors. Excess risk is apparent in older as well as younger diabetic individuals and in hypertensive and nonhypertensive subjects with diabetes.

Prophylactic neuroprotection for cerebral ischemia

BACKGROUND

Treatments for acute ischemic stroke have evolved as knowledge about the pathophysiology of ischemic brain injury has advanced. Treatment strategies under development are aimed at offering neuroprotection acutely after focal cerebral ischemic injury, but delayed initiation of therapy may reduce efficacy. Pretreatment before ischemia begins could offer distinct advantages in patient groups at high risk for ischemic stroke.

SUMMARY OF REVIEW

If a neuroprotective drug were available orally, safe, and relatively inexpensive, it could be considered for prophylactic use in high-risk populations. Prophylactic neuroprotection would include (1) short-term neuroprotection before and after high-stroke risk procedures, (2) long-term neuroprotection for primary and secondary intervention in populations at high risk for stroke, and (3) concomitant neuroprotection with agents that have multiple treatment effects. Patients undergoing procedures such as cardiac surgery, endarterectomy, or endovascular therapy, which have a risk of cerebral ischemic events during a defined period, might be considered for short-term, periprocedure prophylactic neuroprotection. Several populations at high long-term risk for initial ischemic stroke have been identified and include those with combinations of vascular risk factors, transient ischemic attacks, atrial fibrillation, and asymptomatic carotid stenosis. Such people, as well as those at risk for stroke recurrence after minor strokes, are readily identifiable and perhaps appropriate for long-term prophylactic neuroprotection. Patients with hypertension and cerebrovascular atherosclerosis have a high stroke risk, and therapies directed at these underlying disorders are available that also have concomitant neuroprotective effects. An ideal drug for trials in these patient groups has not yet been developed, and establishing its efficacy may prove to be an arduous and lengthy task.

CONCLUSIONS

The possibility of ameliorating the consequences of an acute ischemic stroke by pretreating high-risk patients with appropriate neuroprotective agents needs to be explored. Several types of high-risk population for prophylactic neuroprotection can be envisioned and then studied in clinical trials.

Echocardiographic predictors of nonrheumatic atrial fibrillation. The Framingham Heart Study

BACKGROUND

Although structural heart disease is often present in patients with nonrheumatic atrial fibrillation, the echocardiographic precursors of atrial fibrillation have not been reported previously. In this elderly, population-based cohort, our objective was to examine prospectively the echocardiographic predictors of nonrheumatic atrial fibrillation.

METHODS AND RESULTS

Subjects in the Framingham Heart Study were routinely evaluated with M-mode echocardiography; 1924 subjects, ranging in age from 59 to 90 years, comprised the population at risk. Cox proportional hazards modeling was used to analyze the association of selected echocardiographic features with atrial fibrillation risk after adjustment for age, sex, hypertension, coronary heart disease, congestive heart failure, diabetes, and valvular heart disease. During a mean follow-up interval of 7.2 years, 154 subjects (8.0%) developed atrial fibrillation. Multivariable stepwise analysis identified left atrial size (hazard ratio [HR] per 5-mm increment, 1.39; 95% confidence interval [CI], 1.14 to 1.68), left ventricular fractional shortening (HR per 5% decrement, 1.34; 95% CI, 1.08 to 1.66), and sum of septal and left ventricular posterior wall thickness (HR per 4-mm increment, 1.28; 95% CI, 1.03 to 1.60) as independent echocardiographic predictors of atrial fibrillation. For each of the echocardiographic predictors, risk increased progressively over successive quartiles. Moreover, risk increased markedly when highest-risk-quartile measurements for these features were present in combination; the cumulative 8-year age-adjusted atrial fibrillation rates were 7.3% and 17.0%, respectively, when one and two or more highest-risk-quartile features were present, compared with 3.7% when none was present.

CONCLUSIONS

In this elderly, population-based sample, left atrial enlargement, increased left ventricular wall thickness, and reduced left ventricular fractional shortening were predictive of risk for nonrheumatic atrial fibrillation. These echocardiographic precursors offer prognostic information beyond that provided by traditional clinical atrial fibrillation risk factors.

Stroke prevention. An opportunity for efficient utilization of health care resources during the coming decade

BACKGROUND

Stroke is unique among neurological diseases, since it has a high prevalence and burden of illness, high economic cost, and is preventable. Epidemiological approaches to stroke prevention include the "high-risk" and "mass" approaches. In this review we discuss these preventive strategies, target host and discretionary risk factors that are amenable to these measures, and discuss potential cost savings.

SUMMARY OF REVIEW

Projected numbers of strokes prevented for specific stroke risk factors were estimated by using the population-attributable risk estimation for hypertension, cigarette smoking, atrial fibrillation, and heavy alcohol consumption. The projected numbers of strokes that could be prevented were substantial and highest for hypertension and cigarette smoking. Projected yearly cost of stroke associated with these two treatable factors was also substantial.

CONCLUSIONS

The prevention of stroke can be accomplished by the high-risk or mass approach or a combination of these approaches. The high-risk approach prevents strokes but is also expensive. The mass approach may be more cost-effective, which could lead to substantial savings, but this needs to be investigated.

Treatment of atrial fibrillation in a district general hospital

OBJECTIVE

To assess current strategies used to investigate and manage acute atrial fibrillation in hospital.

DESIGN

Prospective survey of all acute admissions over 6 months.

SETTING

District general hospital serving a population of 230,000 in north east Glasgow.

SUBJECTS

2686 patients admitted as emergency cases over 6 months.

RESULTS

Of the 2686 patients, 170 (age range 38-95, mean (SD) 73.5 (10.6) years; 70 men (41%) and 100 women (59%)) were admitted with atrial fibrillation. The principal underlying medical conditions were ischaemic heart disease in 79 (46.5%), rheumatic heart disease in 26 (15.3%), and thyroid disease in six (3.5%). Cardiac failure was present on admission in 61 (36%), cerebrovascular events in 23 (14%), and myocardial infarction in 17 (10%). Of those with a history of atrial fibrillation (102 (60%) including 10 with paroxysmal atrial fibrillation) treatment on admission included digoxin in 71 (70%), warfarin in 20 (20%), and aspirin in 17 (17%); the aspirin was predominantly given for concomitant vascular disease. The mean (SD) inpatient stay was 16 days (19.7) (range 1-154) largely due to the patients with stroke. Thyroid function tests were performed in only 63% and echocardiography in 33%. Overall, the rate of introduction of anticoagulation (seven patients) and attempted cardioversion (21 patient: 19 pharmacological and two electrical) was surprisingly low. Only 49 patients (34% of those not on warfarin) had contraindications to anticoagulation: these included peptic ulcer or gastrointestinal bleeding in 18 (12%), dementia in eight (6%), chronic renal failure or dialysis in eight (6%), and alcohol excess in four (3%).

CONCLUSION

Standard investigations were inadequately used in patients with atrial fibrillation and there was a reluctance to perform cardioversion or to start anticoagulant treatment.

Ischemic stroke and atrial fibrillation. A clinical study

In view of the higher prevalence of severe ischemic stroke among patients with atrial fibrillation (AF) and of the recently reported higher frequency of stroke with AF in females, 516 consecutive patients with ischemic stroke, of whom 93 had AF, were retrospectively evaluated. The main anamnestic, clinical and laboratory features of the AF and non-AF groups were statistically compared and the features of the AF group were statistically evaluated according to gender and age. Our results confirm the greater severity of stroke in AF patients than in non-AF patients and the higher frequency of stroke with AF in female patients. Moreover, a significantly higher frequency of stroke with AF was found in the male 60-69 and the female 80-89 age groups than in the other age groups. Relevant risk factors in females aged 80-89 were hypertension and left ventricular hypertrophy (LVH), while diabetes, alcohol, smoking and LVH prevailed among 60-69 year old males.

Effect of low-intensity warfarin anticoagulation on level of activity of the hemostatic system in patients with atrial fibrillation. BAATAF Investigators

BACKGROUND AND PURPOSE

The Boston Area Anticoagulation Trial for Atrial Fibrillation (BAATAF) demonstrated that low-intensity warfarin anticoagulation can, with safety, sharply reduce the rate of stroke in patients with nonvalvular atrial fibrillation. The beneficial effect of warfarin was presumably related to a decrease in clot formation in the cardiac atria and subsequent embolization.

METHODS

To assess the effect of warfarin therapy on in vivo clotting in patients in the BAATAF, we measured the plasma level of prothrombin activation fragment F1+2. One sample was obtained from 125 patients from the BAATAF; 62 were taking warfarin and 63 were not taking warfarin (control group).

RESULTS

The warfarin group had a 71% lower mean F1+2 level than the control group (mean F1+2 of 1.57 nmol/L in the control group compared with a mean of 0.46 nmol/L in the warfarin group; P < .001). F1+2 levels were higher in older subjects but were consistently lower in the warfarin group at all ages. Fifty-two percent of patients in the control group were taking chronic aspirin therapy at the time their F1+2 level was measured. Control patients taking aspirin had F1+2 levels very similar to control patients not taking aspirin (mean of 1.52 nmol/L for control patients on aspirin compared with 1.64 nmol/L for control patients off aspirin; P > .1).

CONCLUSIONS

We conclude that prothrombin activation was significantly suppressed in vivo by warfarin but not aspirin among patients in the BAATAF. These findings correlate with the marked reduction in ischemic stroke noted among patients in the warfarin treatment group observed in the BAATAF.

Trends in stroke risk factors in the United States

Favorable trends in risk factors have contributed to the decline in stroke mortality. Risk factors for stroke include older age, male sex, black race, low socioeconomic status, heart disease, hypertension, diabetes mellitus, certain medications, cigarette smoking, alcohol, and diet. Improvements in economic and living conditions may have contributed to the decline in stroke mortality. However, increasing longevity, growth in population size, and increased survival with coronary heart and other cardiovascular diseases are likely to increase the numbers of strokes in the future. Effective treatment of hypertension is credited with accelerating the decline in stroke death rates since the 1970s. Reductions in cigarette smoking since the 1960s and in alcohol consumption in the 1980s may have contributed to the more recent decline in stroke mortality, especially among men. Dietary changes possibly related to improvements in stroke rates include lower saturated fat and salt intake. Primary prevention through reductions in highly prevalent risk factors is an important strategy for continuing the decline in stroke mortality.

Chronic atrial fibrillation and stroke in paced patients with sick sinus syndrome. Relevance of clinical characteristics and pacing modalities

BACKGROUND

The goal of the report was to study the long-term incidence and the independent predictors for chronic atrial fibrillation and stroke in 507 paced patients with sick sinus syndrome, adjusting for differences in baseline clinical variables with multivariate analysis.

METHODS AND RESULTS

From 1980 to 1989, we implanted 376 dual-chamber, 19 atrial, and 112 ventricular pacemakers to treat patients with sick sinus syndrome. After a maximum follow-up of 134 months (mean: 59 +/- 38 months for chronic atrial fibrillation, 65 +/- 37 months for stroke), actuarial incidence of chronic atrial fibrillation was 7% at 1 year, 16% at 5 years, and 28% at 10 years. Independent predictors for this event, from Cox's proportional hazards model, were history of paroxysmal atrial fibrillation (P < .001; hazard ratio [HR] = 16.84), use of antiarrhythmic drugs before pacemaker implant (P < .001; HR = 2.25), ventricular pacing mode (P = .003; HR = 1.98), age (P = .005; HR = 1.03), and valvular heart disease (P = .008; HR = 2.05). For patients with preimplant history of paroxysmal atrial fibrillation, independent predictors were prolonged episodes of paroxysmal atrial fibrillation (P < .001; HR = 2.56), long history of paroxysmal atrial fibrillation (P = .004; HR = 2.05), ventricular pacing mode (P = .025; HR = 1.69), use of antiarrhythmic drugs before pacemaker implant (P = .024; HR = 1.71), and age (P = .04; HR = 1.02). Actuarial incidence of stroke was 3% at 1 year, 5% at 5 years, and 13% at 10 years. Independent predictors for stroke were history of cerebrovascular disease (P < .001; HR = 5.22), ventricular pacing mode (P = .008; HR = 2.61), and history of paroxysmal atrial fibrillation (P = .037; HR = 2.81).

CONCLUSIONS

Development of chronic atrial fibrillation and stroke in paced patients with sick sinus syndrome are strongly determined by clinical variables and secondarily by the pacing modality. Ventricular pacing mode predicts chronic atrial fibrillation in patients with preimplant paroxysmal atrial fibrillation but not in those without it.

Transient ischemic attacks in younger and older patients. A comparative study of 798 patients in South Africa

BACKGROUND AND PURPOSE

The literature concerning transient ischemic attacks in young adults compared with strokes in young adults is scanty. This study evaluates the profile of transient ischemic attacks in young patients (aged 45 years or younger) compared with older patients (aged older than 45 years).

METHODS

Between 1981 and 1991, 75 young patients (aged 45 years or younger) and 723 older patients (aged older than 45 years) were diagnosed as having a transient ischemic attack and included in the study. History of presenting transient ischemic attack, risk factors, clinical features, investigations, and etiology were compared on the basis of the above age groups.

RESULTS

In younger patients the presenting transient ischemic attack occurred less frequently in the vertebrobasilar territory (9% versus 21%, P = .03). Risk factor analysis revealed significant differences between the groups, with hypertension, previous smoking history, ischemic heart disease, and peripheral vascular disease being more common in the older group. Migraine and valvular heart disease were more common in the younger group. Approximately 60% of the patients in each group had multiple etiologies. The most common etiology was atheromatous cerebrovascular disease in both groups (74% versus 37% [P < .0001] in the older and younger groups, respectively). Other significant etiologic differences included fibromuscular dysplasia, mitral valve prolapse, and use of oral contraceptives occurring more frequently in the younger group, and ischemic heart disease occurring more frequently in the older group.

CONCLUSIONS

This study reveals the clinical and etiologic differences between younger and older patients with transient ischemic attack. The importance of multiple etiologies in both groups of patients has diagnostic and management implications.

Why is the outcome of transient ischaemic attacks different in different groups of patients?

The outcomes of each of three large cohorts of patients with transient ischaemic attacks, which were studied in the same country at much the same time with the same methods, were compared and found to be quite different from each other. The differences in outcome were related not only to different strategies of treatment but also to differences in the prevalence and level of important prognostic factors (for example, case mix) and other factors such a the time delay from transient ischaemic attack to entry into the study and the play of chance. The implications for purchasers of health care are that they cannot rely solely on non-randomised comparisons of outcome of patients treated in competing units as a measure of the quality of care (which has only rather modest effects) without accounting for other factors that may influence outcome such as the nature of the illness, the case mix, observer bias, and the play of chance.