Most strokes are thought to be related to atherosclerosis of the large cerebral arteries or small vessel disease related to systemic hypertension. In approximately 30 percent of patients who have had a stroke, a potential cardioembolic source can be identified. High-risk cardiac groups include patients with rheumatic mitral stenosis, atrial fibrillation, acute anterior myocardial infarction, global cardiomyopathy and prosthetic valves. Additional cardiac abnormalities associated with stroke that are identified primarily by echocardiography include patent foramen ovale and atrial septal defect, atrial septal aneurysm, mitral valve prolapse, aortic atherosclerosis and mobile atheroma, left atrial spontaneous echo contrast, and mitral valve strands. O'Brien and associates developed a risk classification system based on the presence or absence of abnormalities found on transesophageal echocardiography to stratify risk in stroke patients without a cardiac source of embolism on clinical examination.
Forty stroke patients without any of the commonly accepted risk factors for cardiac source of stroke were included in the study. Demographic data and medical history were obtained, and a directed physical examination was performed at the time patients underwent transesophageal echocardiography. Patients were considered to be at high risk if any cardiac risk factors were identified on echocardiography. Patients were followed for an average of 14 months to check on treatment and the occurrence of other cardiovascular events.
The presence or absence of abnormalities on transesophageal echocardiography was a predictor of cardiovascular survival (cardiac and stroke) in the study participants. Patients identified as being low risk by echocardiography had a higher rate of survival (92 percent) compared with high-risk patients (78 percent) during the study period.
The data also suggest an association between individual echocardiographic findings, such as left ventricular hypertrophy and the presence of aortic atherosclerotic plaque with recurrent cerebral infarction. Left atrial enlargement and intraatrial spontaneous contrast were associated with stroke death. Typically, the highest yield of transesophageal echocardiography in the setting of stroke is in patients younger than 45 years. Despite a mean age of 67 years, 60 percent of the patients in the present study had a potential cardiac etiology for the stroke.
This study also provides evidence that transesophageal echocardiography may be useful even in patients with a conventionally accepted stroke mechanism to identify an additional cardiac risk factor. For example, the finding of mobile aortic debris in a patient with carotid disease who is also a suboptimal surgical candidate may lead to medical management.
The authors conclude that the results of the study support the hypothesis that a subgroup of patients with aortic atherosclerosis and spontaneous echo contrast is at high risk for stroke or cardiac death. In addition, left atrial enlargement and left ventricular hypertrophy represent risk factors for death and recurrent fatal and nonfatal stroke, respectively. Transesophageal echocardiography also appears to be useful in stroke patients with a low clinical suspicion of a cardiac source of embolism, both for the diagnosis of a potential stroke cause and for prognosis after stroke.