What are the cardioembolic sources?

Cardioembolic Sources

Cardioembolic sources of stroke are primarily divided into high-risk and medium-risk categories, with atrial fibrillation being the single most important source, followed by recent myocardial infarction, mechanical prosthetic valves, dilated cardiomyopathy, and rheumatic mitral stenosis. 1

High-Risk Cardioembolic Sources

The following cardiac conditions carry the highest risk for cerebral embolism and generally warrant anticoagulation:

Atrial Conditions

• Atrial fibrillation (both rheumatic and non-rheumatic) represents the most common high-risk source, with 10-20% of patients experiencing systemic embolism 2, 3
• Left atrial appendage thrombus, which is the most frequent site of thrombus formation in atrial fibrillation 1
• Atrial septal aneurysm when associated with other risk features 1

Ventricular Sources

• Recent myocardial infarction (particularly within the first few weeks), affecting 5-12% of patients with clinically apparent systemic embolism 1, 2
• Left ventricular thrombus secondary to myocardial infarction or heart failure 1
• Dilated cardiomyopathy with reduced ejection fraction (stroke risk increases 18% for every 5% decline in ejection fraction below 35%) 1, 3
• Dyskinetic ventricular wall segments identifiable on transthoracic echocardiography 1

Valvular Sources

• Mechanical prosthetic heart valves, which are inherently thrombogenic 1
• Rheumatic mitral stenosis (virtually all rheumatic hearts producing emboli have mitral stenosis, though not all are in atrial fibrillation) 2, 3
• Infective endocarditis affecting native or prosthetic valves 1, 4

Other High-Risk Sources

• Intracardiac tumors (such as atrial myxoma) 1, 4

Medium-Risk Cardioembolic Sources

These sources have more modest or undefined risks, with antiplatelet therapy generally favored over anticoagulation:

Structural Abnormalities

• Patent foramen ovale (PFO), particularly when associated with atrial septal aneurysm or large right-to-left shunt 1
• Atrial septal defect 1
• Mitral valve prolapse with complications (gross mitral regurgitation, atrial fibrillation, or infective endocarditis—uncomplicated mitral valve prolapse alone is NOT considered embolic) 4

Aortic Sources

• Aortic arch atherosclerosis with complex plaques, best identified by transesophageal echocardiography 1, 5
• Atheromatous disease of the proximal aorta 1

Diagnostic Approach

Initial Cardiac Evaluation

• Transthoracic echocardiography is the first-line test, excellent for identifying ventricular sources like dyskinetic wall segments and ventricular thrombi 1
• Electrocardiogram to detect atrial fibrillation or evidence of prior myocardial infarction 1

Advanced Cardiac Imaging

• Transesophageal echocardiography is superior for detecting atrial and aortic sources, including left atrial appendage thrombi, patent foramen ovale, atrial septal defects, and aortic arch atherosclerosis 1
• Cardiac CT or cardiac MRI may be reasonable in patients with embolic stroke of undetermined source when transesophageal echocardiography findings are inconclusive 1

Rhythm Monitoring

• Long-term cardiac monitoring with mobile cardiac outpatient telemetry or implantable loop recorder is reasonable in cryptogenic stroke patients to detect paroxysmal atrial fibrillation 1, 3

Clinical Features Suggestive of Cardioembolic Stroke

Certain presentations increase the likelihood of cardiac embolism:

• Sudden onset to maximal deficit without stuttering progression 3
• Decreased level of consciousness at onset 3
• Wernicke's or global aphasia without hemiparesis 3
• Valsalva maneuver at stroke onset 3
• Co-occurrence of cerebral and systemic emboli 3

Important caveat: Lacunar clinical presentations and especially multiple lacunar infarcts make cardioembolic origin unlikely 3

Paradoxical Embolism

A special category involves paradoxical embolism through patent foramen ovale, where venous thrombi cross to the arterial circulation:

• Occurs when elevated right-sided cardiac pressures (such as from pulmonary embolism) keep the PFO open large enough to accommodate thrombus passage 1
• Accounts for 5-10% of all paradoxical embolisms, with noncerebral sites including coronary arteries, renal arteries, and limb arteries 1
• Transcranial Doppler with embolus detection might be reasonable to screen for right-to-left shunt when PFO closure is contemplated 1