| Abstract: | Stroke is caused by intracerebral or subarachnoid hemorrhage in about 15% of clinical presentations and the remaining 85% result from ischemia. About 15% of ischemic strokes are caused by emboli arising from the heart. In younger patients (18 to 50 years) with ischemic strokes or transient ischemic attacks (TIA), the incidence of cardiac embolism is increased to 23 to 36%. Diagnosis: a) Symptoms: Individual neurologic symptoms of stroke do not provide sensitive or specific indications of the underlying mechanism. In 25 to 82% of patients with possible embolic stroke, there is an acute onset with initially maximal manifestation of neurologic deficits as well an initial loss of consciousness in 20%. Antecedent TIAs occur in 11 to 30% but are more frequently associated with arteriosclerotic vascular disease. Stroke due to cardiac embolism mostly involves the cortex of both hemispheres and causes its symptoms through occlusion of isolated arterial branches. Cerebral infarctions with isolated Wernicke aphasia, global aphasia without hemiparesis and isolated syndromes of the posterior cerebral artery are frequently due to cardiac embolism. The strokes in 16 to 22% of those caused by cardiac embolism are found in subcortical regions. Amaurosis fugax is most frequently due to high-grade stenosis of the internal carotid artery. In association with cardiac embolism, secondary hemorrhage into the infarcted zone can frequently be seen on CT scans. b) Diagnostic procedures: In the case of cardiac embolism, the computer tomography (CT) usually shows infarction in or near the cortex in the region of the middle or posterior cerebral artery. About 10 to 20% of strokes due to cardiac embolism show secondary hemorrhage after the event, more frequently in association with large infarcts and in patients on anticoagulant treatment. Angiography can provide indirect evidence of embolic origin by showing occlusion of an intracerebral artery in the absence of arteriosclerotic changes. Traditional echocardiography may detect a possible source of embolism in 10% of all patients with ischemic stroke, only in 1.5%, however, in patients with no clinical signs of heart disease. Transesophageal echocardiography has a higher sensitivity for detection of sources of cardiac embolism. The use of magnetic resonance tomography and ultrafast CT will assume greater importance in the future. Holter monitoring of the ECG in patients with acute ischemic stroke or TIAs detects arrhythmias possibly responsible for emboli in about 2%. High-risk patients: The most common cause of cardiac embolism is atrial fibrillation (45%), followed by ischemic heart disease (15%) and in 10% each, aneurysm, rheumatic heart disease, prosthetic valve replacement and other cardiac diseases.(ABSTRACT TRUNCATED AT 400 WORDS) |
