Elsevier

Neurologic Clinics

Volume 26, Issue 4, November 2008, Pages 1129-1160
Neurologic Clinics

Stroke Prevention in Atrial Fibrillation and Other Major Cardiac Sources of Embolism

https://doi.org/10.1016/j.ncl.2008.07.001Get rights and content

The frequency of cardioembolic stroke is expected to rise as the general population ages. Much of the increase may be attributed to atrial fibrillation, the most common cause of cardioembolic stroke and one that plays a substantial role in aging adults. Other sources of cardioembolic stroke may include ventricular thrombus from myocardial infarction, heart failure, structural heart defects such as patent foramen ovale (PFO), atrial septal aneurysm, proximal aortic atheroma, valvular heart disease, and endocarditis. Diagnostic studies, such as neuroimaging, ECG, and echocardiography, are helpful in uncovering cardioembolic sources of stroke. Medical therapy is predicated on the underlying mechanism. For example, warfarin may be indicated in certain patients who have atrial fibrillation, atrial, or ventricular thrombi, and PFO with atrial septal aneurysm and cryptogenic stroke in select young patients to prevent stroke. Newer diagnostic technologies, including multidetector CT and cardiac MRI, may be useful to diagnose cardiac causes of stroke when transesophageal echocardiography is indeterminate or cryptogenic stroke is present.

Section snippets

Cardiac embolism and stroke

Cardioembolic stroke accounts for 20% of all ischemic strokes [1], and its frequency has increased over time, likely reflecting improvement in cardiac imaging [2]. Cardioembolic stroke can be caused by different cardiac disorders, but occurs most commonly from atrial fibrillation in adults (50%) (Fig. 1) [2], [3], [4]. Other important causes include ventricular thrombus (20%), structural heart defects or tumors (15%) and valvular heart disease (15%) (Table 1) [4], [5], [6], [7]. Although the

Diagnostic approach to cardioembolic stroke

A systematic approach is fundamental to diagnose patients who have experienced cardioembolic stroke. For example, the clinical history may provide clues to a cardioembolic source. Patients may have a history of palpitations (eg, mitral valve disease, atrial fibrillation), episodic or sustained tachycardia (eg, arrhythmia or atrial fibrillation with rapid ventricular response), angina or dyspnea (eg, myocardial infarction or heart failure), or stroke symptoms after valsalva (eg, cough, sneeze,

Stroke prevention in atrial fibrillation

Systemic embolization is a potential complication of any form of atrial fibrillation, and it can occur in patients with acute atrial fibrillation lasting as little as 72 hours [12]. The forms of atrial fibrillation proposed by the American College of Cardiology/AHA/ European Society of Cardiology are as follows [32], [33]:

  • • Paroxysmal: self-terminating atrial fibrillation, in which episodes generally last less than 7 days and usually less than 24 hours; it may be recurrent

  • • Persistent: fails to

Antithrombotic strategies

Before the late 1980s, antithrombotic therapy for stroke prevention in atrial fibrillation was limited to those who had rheumatic heart disease or prosthetic heart valves [37]. Between 1989 and 2007, 29 randomized trials were published, evaluating the efficacy and safety of antithrombotic agents for stroke prevention in atrial fibrillation [47]. These studies included 28,044 patients.

Patent foramen ovale

Patent foramen ovale (PFO) is a flap-like defect in the interatrial septum (Fig. 5) and a common finding (25%) in the general population. In utero, PFO allows oxygenated blood from the mother to bypass the lungs and go directly into fetal systemic circulation (by way of the right to left atria pathway). At birth, the lungs expand from breathing air, which fills the lungs with deoxygenated blood that enters the right atrium, the right ventricle, and the lung capillary beds. Blood is oxygenated

Medical therapy

Studies investigating medical therapy for PFO are largely retrospective and do not show any advantage of warfarin over aspirin (see Table 3). Most of these studies, however, have been limited by insufficient power to compare aspirin with warfarin, nonrandomized treatment allocation or nonmasked treatment, or allocation, crossover, or unblinded ascertainment of end points [6].

In the PFO in Cryptogenic Stroke Study (PICCS), patients were randomized to warfarin (international normalized ratio

Surgical and endovascular closure for patent foramen ovale

Recent methods to repair PFO using endovascular means have been developed within the past decade (Fig. 6) [67] and allow this anatomic defect to be treated less invasively [6], [67]. Given the association of PFO in cryptogenic stroke, repair of the defect is a logical target for subsequent stroke prevention. However, no randomized trial has been completed, despite five ongoing studies recruiting patients for PFO closure in cryptogenic stroke (www.clinicaltrials.gov identifiers, NCT00557479,

Aortic arch disease

An overlooked but a potentially serious source of embolic stroke is the aortic arch, especially when proximal aortic atheromatous disease is present [72]. Aortic embolic events may be misclassified as cryptogenic unless adequate transesophageal echocardiography of the aorta is performed. Aortic embolic disease manifests in different forms, including mobile and ulcerated plaques, aortic dissection, and aneurysms (Fig. 7). Patients who have ascending aorta or proximal arch plaques of 4 mm

Myocardial infarction, left ventricular dysfunction, and heart failure

Myocardial infarction, its associated ventricular wall immobility, and subsequent dilated cardiomyopathy may lead to left ventricular thrombus formation and cardioembolic stroke [76], [77], [78], [79], [80], [81]. Cardioembolic strokes may occur within 1 day of myocardial infarction, and approximately half occur within the first week, although stroke risk remains high up to 3 months and then decreases gradually [76], [77], [78], [79], [80], [81]. Anterior wall myocardial infarction carries a

Reduced left ventricular ejection fraction

Among patients older than 55 years, 3.9% have heart failure [83]. When heart failure occurs, stroke risk increases almost threefold by 5 years [84]. The Survival and Ventricular Enlargement (SAVE) trial [85] showed every decrease of five percentage points in left ventricular ejection fraction (LVEF) was accompanied by an 18% increase in stroke risk. More than 50 years ago, experts discovered that warfarin reduced the risk for pulmonary embolism, which was a major cause of death in patients who

Dilated cardiomyopathy

Dilated cardiomyopathy is associated with various different etiologies (ischemic and nonischemic, infectious and infiltrative). The Study of Left Ventricular Dysfunction (SOLVD) [92] clarified the relation between embolic stroke risk and worsening ventricular function. Increased stroke risk was seen only in women (2.4 events per 100 patient-years compared with 1.8 events per 100 patient-years in men). In this study, warfarin and aspirin were associated with a lower rate of death or

Aortic Stenosis

Clinically symptomatic cerebral embolic events are uncommon in calcific aortic valve disease (Fig. 8) [100], [101], [102], [103], [104] unless concomitant atrial fibrillation, reduced LVEF, or mitral valve disease is present. Calcific emboli to the retina (ie, asymptomatic emboli) or after valvuloplasty are reported [102], [105]. Antiplatelet therapy may be initiated in patients who have TIA and bicuspid calcific aortic stenosis, but anticoagulation is generally not recommended unless atrial

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    Dr. Freeman acknowledges research funding provided in part by the Robert H. and Clarice Smith/M.L. Simpson Foundation Trust. Dr. Aguilar chairs the Event Adjudication Committee for the NINDS-sponsored SPS3 trial.

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