cardioembolic stroke

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Cardioembolic Stroke

One-third of strokes represent intracerebral or subarachnoid hemorrhage while two-thirds represent cerebral ischaemia (1)

Ischaemic stroke can result from a variety of causes such as atherosclerosis of the cerebral circulation, occlusion of cerebral small vessels, and cardiac embolism (1)

  • one-third of ischaemic strokes are of unclear cause, it is increasingly accepted that many of these cryptogenic strokes arise from a distant embolism rather than in-situ cerebrovascular disease, leading to the recent formulation of "embolic stroke of undetermined source" (ESUS) as a distinct target for investigation
  • ESUS working group investigators further proposed that the minimal stroke work-up should include brain neuroimaging with CT or MRI, 12-lead ECG, transthoracic echocardiography (TTE), 24 h Holter-ECG and imaging of both extracranial and intracranial vessels with any available imaging modality (DSA, MRA, CTA, or US)

Risk Factors for Cardioembolic Stroke

Atrial Fibrillation

  • AF is associated with a 3-5 fold increased risk of stroke
  • AF prevalence increases sharply from 0.1% among adults <55 years of age to almost 10% among those >80 years of age (4)

Systolic Heart Failure

  • regional stasis, a hypercoagulable state, and likely undiagnosed AF appear to predispose heart failure patients to cardiac thrombus (5)
    • these patients face at least a 3-fold higher risk of stroke than the general population (5)

Recent Myocardial Infarction

  • a long-established risk factor for ischaemic stroke - association appears causal because thrombi are often seen overlying areas of ventricular dyskinesis which may predispose to a thrombogenic stroke

Patent Foramen Ovale

  • affects approximately 25% of the general population
    • may serve as a passageway for paradoxical embolism from the venous to arterial circulation

Aortic Arch Atheroma

  • approximately 45% of individuals >= 45 years of age harbor atherosclerotic plaque in their aorta
    • been associated with stroke risk (7)
      • particulaly linked with stroke risk are large, ulcerated, non-calcified, or mobile atheromas (occur in approximately 8% of the population)

Prosthetic Heart Valves

  • meta-analysis of studies published between 1985 and 1992 found that patients with a mechanical valve faced a 4.0% annual risk of stroke, which decreased with the use of oral anticoagulation to 0.8% for aortic valves and 1.3% for mitral valve (8)

Other possible causes of thromboembolic stroke include:

  • infective endocarditis, dilated cardiomyopathy, papillary fibroelastoma, myxoma, and mitral calcification

Clinical Presentation

  • classically the presentaton is with the sudden onset of neurological deficits that are maximal at onset - this compares to strokes due to small-vessel occlusion (also known as lacunar strokes) or large-artery atherosclerosis may have a more stuttering course
    • cardiac embolism may lodge in distal arteries supplying the cerebral cortex while small-vessel occlusion affects subcortical tissue
      • cardioembolic stroke can be differentiated from lacunar stroke by cortical signs such as aphasia or visual field deficits
    • note though that clinical characteristics alone cannot reliably classify the underlying cause of ischaemic stroke

Investigation:

  • neuroimaging
    • majority of cardioembolic strokes involve lesions in a cortical territory
      • about half of cardioembolic strokes involve multiple cerebral arterial territories (i.e., both internal cerebral arteries or one internal cerebral artery as well as the basilar artery)
        • this distinguishes cardiac embolism from artery-to-artery embolism due to large-artery atherosclerosis in the cerebral circulation
        • in cardioembolic stroke vascular imaging of the intracranial circulation in the acute phase, such as with computed tomographic or magnetic resonance angiography, often reveals an abrupt vessel cut-off without significant atherosclerotic narrowing of the upstream vessel
  • ESUS working group investigators further proposed that the minimal stroke work-up should include brain neuroimaging with CT or MRI, 12-lead ECG, transthoracic echocardiography (TTE), 24 h Holter-ECG and imaging of both extracranial and intracranial vessels with any available imaging modality (DSA, MRA, CTA, or US) (3)
  • possible aetiologies of ESUS:
    • evidence has indicated that ESUS may often stem from subclinical atrial fibrillation (AF) which can be diagnosed with prolonged heart-rhythm monitoring (5)
    • emerging evidence indicates that a thrombogenic atrial substrate can lead to atrial thromboembolism even in the absence of AF
      • such an atrial cardiopathy may explain many cases of ESUS, and oral anticoagulant drugs may prove to reduce stroke risk from atrial cardiopathy given its parallels to AF
      • improved imaging of ventricular thrombus plus the availability of NOAC drugs may lead to better prevention of stroke from acute myocardial infarction and heart failure

Reference:

  • Krishnamurthi RV et al. Global Burden of Diseases IRFS and Group GBDSE. Global and regional burden of first-ever ischaemic and haemorrhagic stroke during 1990-2010: findings from the Global Burden of Disease Study 2010. Lancet Glob Health. 2013; 1:e259-281.
  • Adams HP Jr et al Classification of subtype of acute ischaemic stroke. Definitions for use in a multicenter clinical trial. TOAST. Trial of Org 10172 in Acute Stroke Treatment. Stroke. 1993; 24:35-41.
  • Hart RG et al. Embolic strokes of undetermined source: the case for a new clinical construct. Lancet Neurol. 2014 Apr; 13(4):429-38
  • Wolf PA, Abbott RD and Kannel WB. Atrial fibrillation as an independent risk factor for stroke: the Framingham Study. Stroke 1991; 22: 983-988
  • Lovett JK, Coull AJ and Rothwell PM. Early risk of recurrence by subtype of ischemic stroke in population-based incidence studies. Neurology 2004; 62: 569-573
  • Kronzon I, Tunick PA. Aortic Atherosclerotic Disease and Stroke. Circulation. 2006; 114:63-75.
  • Cannegieter SC, Rosendaal FR, Briet E. Thromboembolic and bleeding complications in patients with mechanical heart valve prostheses. Circulation. 1994; 89:635-641
  • Ringelstein EB et al. Computed tomographic patterns of proven embolic brain infarctions. Ann Neurol. 1989; 26:759-765

Last edited 11/2019

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