Atrial fibrillation and stroke: new ideas, persisting dilemmas

Risk factors for systemic embolism in patients with paroxysmal atrial fibrillation

The purpose of this study was to define the risk factors for systemic embolism in patients with recently diagnosed paroxysmal atrial fibrillation. We therefore studied 63 consecutive patients with symptomatic nonvalvular paroxysmal atrial fibrillation and performed a clinical and noninvasive cardiac, peripheral vascular, and neurologic evaluation that included two-dimensional echocardiography, 24-hour Holter monitoring, and computed tomographic brain scan. Patients with predisposing clinical conditions for systemic embolism (valvular heart or coronary artery disease) or paroxysmal atrial fibrillation (sick sinus disease, preexcitation, or thyroid dysfunction) were excluded. At entry 34 patients had idiopathic paroxysmal atrial fibrillation and 29 had hypertension. Fourteen patients had a recent systemic embolic complication: nine had a recent occlusive nonlacunar cerebrovascular accident, two had transient ischemic attacks, and three had peripheral systemic emboli that required surgery. In addition, five patients had evidence of old cerebrovascular accident on the computed tomographic scan (group 1). Forty-four patients had no systemic embolism (group 2). Results of univariate analysis showed that patients in group 1 were older (72 +/- 9 vs 63 +/- 13 years, p less than 0.05), had a higher incidence of hypertension (70% vs 35%, p less than 0.01), and had an increased left atrial diameter (4.1 +/- 0.7 vs 3.6 +/- 0.5 cm, p less than 0.05). Multiple stepwise logistic regression analysis showed that a history of hypertension and left atrial enlargement on two-dimensional echocardiography were significant independent risk factors for systemic embolism in patients with symptomatic nonvalvular paroxysmal atrial fibrillation.

Deleterious effects of long-term single-chamber ventricular pacing in patients with sick sinus syndrome: the hidden benefits of dual-chamber pacing

Nine hundred fifty patients who received three modes of primary pacemaker systems (581 dual-chamber universal [DDD], 84 atrioventricular-sequential ventricular-inhibited [DVI] and 285 ventricular-inhibited [VVI]) over 12 years were studied retrospectively to determine the effect of pacing mode on patient longevity and the subsequent development of chronic atrial fibrillation or flutter. All patients were followed up continuously for 7 to 8 years. Patients were classified according to indication for permanent pacing (sick sinus syndrome or other indication), age at pacemaker implantation (less than or equal to 70 or greater than 70 years) and history of atrial tachyarrhythmia. Fourteen percent of patients developed atrial fibrillation at some time during the study period. Of those, 4% had a DDD pacemaker, 8% had a DVI pacemaker and 19% had a VVI pacemaker. At 7 years, atrial fibrillation was significantly more frequent in the VVI group than in the DDD and DVI groups. In patients with sick sinus syndrome, the incidence rate was even higher in the VVI group but approximately the same in the DDD and DVI groups. Patients in the VVI and DVI groups who had had previous atrial tachyarrhythmia had a significantly higher incidence of atrial fibrillation at 7 years than did those in the DDD group. During the entire period there were 130 deaths in the study group, including 22% of patients with a DDD pacemaker, 38% of those with a DVI pacemaker and 50% of those with a VVI pacemaker. Patient survival at 7 years was lower in the VVI group than in the DDD or DVI groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of prophylactic anticoagulation for direct current cardioversion in patients with atrial fibrillation or atrial flutter

The need for prophylactic anticoagulation to prevent embolism before direct current cardioversion is performed for atrial fibrillation or atrial flutter is controversial. To examine this issue further, a retrospective review was undertaken to assess the incidence of embolic complications after cardioversion. The review involved 454 elective direct current cardioversions performed for atrial fibrillation or atrial flutter over a 7 year period. The incidence rate of embolic complications was 1.32% (six patients); the complications ranged from minor visual disturbances to a fatal cerebrovascular event. All six patients had atrial fibrillation, and none had been on anticoagulant therapy (p = 0.026). The duration of atrial fibrillation was less than 1 week in five of the six patients who had embolic complications. Baseline characteristics of patients with a postcardioversion embolic event are compared with those of patients who did not have an embolic event. There was no difference in the prevalence of hypertension, diabetes mellitus or prior stroke between the two groups, and there was no difference in the number of patients who were postoperative or had poor left ventricular function. Left atrial size was similar between the two groups. No patient in the embolic group had valvular disease. No patient with atrial flutter had an embolic event regardless of anticoagulant status; therefore, anticoagulation is not recommended for patients with atrial flutter undergoing cardioversion. Prophylactic anticoagulation is pivotal in patients undergoing elective direct current cardioversion for atrial fibrillation, even those with atrial fibrillation of less than 1 week's duration.

Therapy in cerebrovascular disease: current status and future directions

OBJECTIVE

To assess the current status and future directions of therapy in cerebrovascular disease.

DATA SOURCES

English language literature search using MEDLINE, Index Medicus, reviews, texts and relevant papers.

STUDY SELECTION

Information has been drawn from approximately 200 articles.

DATA EXTRACTION AND SYNTHESIS

Those articles with most relevance to current practice and future directions in the therapy of cerebrovascular disease have been cited.

CONCLUSIONS

Much progress has been made over the last 30 years in the therapy of primary and secondary prevention of cerebrovascular disease. The introduction of antihypertensive agents has been largely responsible for the decline in mortality from stroke and, in some areas, the incidence. Anticoagulants such as warfarin protect against ischaemic stroke in patients with mitral or aortic valve disease and/or atrial fibrillation. Antiplatelet agents are clearly effective in the secondary prevention of ischaemic stroke after transient ischaemic attacks; the risk of stroke or death is reduced, on average, by 22%. In patients with subarachnoid haemorrhage, ischaemic complications caused by vasospasm are reduced by calcium channel blockers. A new wave of therapies is now on the horizon to minimise tissue damage in the early stages of ischaemic stroke ("tissue rescue") with the introduction of thrombolytic agents, calcium channel blockers, NMDA antagonists and haemodilution techniques and many of these are currently being subjected to clinical trial. If they prove to be effective, our current management of acute ischaemic stroke may alter dramatically.

Stroke prevention in nonvalvular atrial fibrillation: a review of prospective randomized trials

Patients with atrial fibrillation are at risk for cerebral embolism; however, the roles of chronic anticoagulation or antiplatelet therapy for stroke prevention in patients with nonvalvular atrial fibrillation have been controversial. Recently, the results of three large prospective randomized trials that examined the risks and benefits of warfarin or aspirin for stroke prophylaxis in patients with nonvalvular atrial fibrillation were reported. All three studies revealed a reduction in the stroke rate for patients treated with warfarin and a small incidence of major bleeding. One of the studies also reported a reduced stroke rate in aspirin-treated patients. The reduction of thromboembolic events associated with chronic warfarin therapy appears to outweigh the risks of significant bleeding for most patients with nonvalvular atrial fibrillation. Aspirin may offer an alternative for subgroups of patients who are at low risk for stroke or those who are not good candidates for anticoagulation.

Perioperative stroke. Part II: Cardiac surgery and cardiogenic embolic stroke

The major mechanism of stroke in cardiac surgery is embolization. The risk is higher in intracardiac than in extracardiac surgery. The incidence of stoke associated with CABG is about 5%. The cerebral protective properties of isoflurane and thiopentone, acid-base management, and monitoring of cerebral perfusion during cardiopulmonary bypass are discussed. Prophylactic carotid endarterectomy for patients with asymptomatic carotid disease before cardiac surgery is not necessary. Symptomatic carotid disease increases the risk of stroke, and the management of patients who have both symptomatic coronary and carotid artery diseases is discussed. Cardiogenic embolism is probably responsible for many perioperative strokes. Patients with atrial fibrillation, valvular disease, and prosthetic heart valves are at high risk of cardiogenic embolism. Strokes associated with cardioversion, pacemaker insertion, coronary arteriography and angioplasty are explored.

Lone atrial fibrillation and stroke

We studied 21 consecutive patients from the Lausanne Stroke Registry, who had first-ever ischemic stroke and lone atrial fibrillation, with a standard protocol of investigations including brain CT, and non-invasive cardiac and arterial tests. Rarity of associated risk factors and extracranial; arterial disease, presence of distal intracerebral occlusions on early angiography, and topography of cerebral infarct suggested that cardioembolism was the cause of stroke, though echocardiographic evidence for an atrial thrombus was uncommon. There was no recurrence during a post-stroke 14-day phase, during which anticoagulant and antiaggregant therapies were systematically avoided. Though low, the main risk of stroke recurrence was 0.99 per 100 patient-years during a mean follow-up period of 4.8 years, including a mean duration of anticoagulant therapy of 2.3 years in 18 patients. On the other hand, no death, severe cardiac events, or disabling anticoagulation-related hemorrhages occurred.

How often is non-valvular atrial fibrillation the cause of brain infarction?

To calculate how often non-valvular atrial fibrillation should be considered as the cause of ischaemic stroke rather than an incidental finding as in primary cerebral haemorrhage, the frequency of non-valvular atrial fibrillation in 75 consecutive patients with primary intracerebral haemorrhage was compared with that in 63 patients with cortical infarcts and 44 patients with lacunar infarcts who were taken at random from 1487 consecutive patients with cerebral infarcts admitted during the same period. The frequency of non-valvular atrial fibrillation in lacunar infarcts did not differ from that in primary intracerebral haemorrhage (odds ratio: 1.28; 95% confidence interval: 0.32-5.1) (P = 1.0), whereas it was significantly higher in cortical infarcts (odds ratio: 5.57; 95% confidence interval 2.00-15.4) (P = 0.0001). Our findings suggest that non-valvular atrial fibrillation in lacunar infarcts, as in primary intracerebral haemorrhage, is unlikely to be the cause of this type of stroke, whereas perhaps 30% of all cortical infarcts are not caused by non-valvular atrial fibrillation when present. These data are important for the planning and explanatory evaluation of trials on the preventive effect of anticoagulants in stroke patients with non-valvular atrial fibrillation.

Risk factors and causes of stroke in young women in Israel

OBJECTIVE

to identify risk factors and likely causes for stroke in young women, as a basis for designing a strategy for stroke incidence reduction.

DESIGN

retrospective chart review for comparisons between the sexes.

SETTING

general and rehabilitation hospitals.

PATIENTS

all 263 patients aged 17-45 years with stroke over a 15-year period.

EXCLUSIONS

patients seen at 14 general hospitals who were not referred to the Loewenstein.

ASSESSMENTS

data on sociodemographic, anamnestic, and clinical aspects.

RESULTS

stroke under the age of 30 years was more frequent in women, and in them the risk factors differed from those in an older population. The most frequent cause of stroke in the younger women was embolism, in the majority on the basis of a rheumatic valvular defect, whereas in young men the usual cause was atherosclerosis.

CONCLUSIONS

opportunities for preventive initiatives have not always been grasped, and more attention should be directed to such possibilities.

Preliminary report of the Stroke Prevention in Atrial Fibrillation Study

Atrial fibrillation, even in the absence of rheumatic valvular disease, predisposes patients to embolic complications, but the role of antithrombotic therapy in the prevention of such complications has not been fully clarified. We therefore performed a randomized, placebo-controlled trial to evaluate warfarin and aspirin individually as prophylaxis against ischemic stroke and systemic embolism (the primary events) in such patients. Patients eligible to receive warfarin (group 1) were assigned to warfarin (open label), aspirin (325 mg per day), or placebo (aspirin and placebo were given in a doubleblind fashion). Those who were not eligible for warfarin (group 2) received either aspirin or placebo in a double-blind fashion. The placebo arm of group 1 was recently terminated, when evidence emerged that each active agent was superior to placebo. In this paper we report preliminary data on active therapy (with either warfarin or aspirin) as compared with placebo in group 1, and on aspirin as compared with placebo in groups 1 and 2 combined. By November 1989, 1244 patients had been followed for a mean of 1.13 years. The event rates were 1.6 percent per year in the 393 patients who made up the two active treatment arms (warfarin and aspirin) of group 1, and 8.3 percent per year in the 195 patients who made up the placebo arm (P less than 0.00005) (risk reduction, 81 percent; 95 percent confidence interval, 56 to 91). In all 517 patients given aspirin, the rate of primary events (3.2 percent per year) was lower than that in the 528 patients given placebo (6.3 percent per year; P = 0.014) (risk reduction, 49 percent; 95 percent confidence interval, 15 to 69). However, we were unable to show a benefit of aspirin in patients over 75 years of age. These preliminary data indicate that antithrombotic therapy with warfarin or aspirin is effective in the short term in reducing the risk of stroke and systemic embolism in patients with atrial fibrillation due to causes other than rheumatic valvular disease. The relative benefits of aspirin and warfarin remain unclear, and the trial is continuing in order to address this issue.

Cerebral computed tomography in paroxysmal atrial fibrillation

Atrial fibrillation (AF) is associated with an increased risk of stroke. In patients with chronic AF, without clinically known cerebrovascular disease, computed tomography (CT) has revealed a high frequency of abnormal low-density areas suggesting old asymptomatic infarcts. To investigate the frequency of such lesions in paroxysmal AF, 30 patients with paroxysmal AF and 30 controls matched in sinus rhythm, without history of cerebrovascular disease, were CT scanned. Four patients with paroxysmal AF (13%) and 3 controls (10%) had abnormal CT scans with areas of low density with sharp demarcation from surrounding tissue. The abnormal areas probably reflected small, clinically silent infarcts. There were no differences between paroxysmal AF and controls in number and size of abnormal areas with apparent tissue loss. In contrast to chronic AF, the risk of such lesions in paroxysmal AF does not seem to be increased compared with matched sinus rhythm controls. This is in agreement with the clinical experience of a low risk of stroke in paroxysmal AF.