What are the roles of transthoracic and transoesophageal echocardiography in patients with a TIA or stroke?

Approximately 80% of strokes are ischaemic in origin, of which 20–40% have a cardiac basis. TIAs have a cardiac cause in ~15% of cases. Common cardiac abnormalities associated with neurological events include atrial fibrillation, mitral valve disease, left atrial enlargement, left ventricular dilatation, prosthetic valve abnormalities and endocarditis. Clinical examination and simple tests (CXR and ECG) should indicate cardiac abnormality in these situations. The aim of echocardiography is to confirm the presence of important predisposing cardiac abnormalities and in younger patients, typically <50 years, to look for rare cardiac causes that might not be detected by other means. This latter group includes atrial septal aneurysm and patent foramen ovale (PFO) which, although somewhat controversial, are associated with an increased risk of stroke in patients without other detectable abnormalities.

Consequently, echocardiography is particularly useful in patients at both ends of the age scale. Older patients are more likely to have cardiac abnormalities that could give rise to stroke/TIA and young patients frequently have apparently normal hearts, but echocardiography (especially transoesophageal) may indicate the presence of an atrial septal aneurysm or PFO. The pick-up rate of transthoracic echocardiography is extremely low in patients with a normal clinical examination, CXR and ECG, making it a poor screening test. Conversely, the yield in patients with clinical abnormalities or an abnormal ECG/CXR is high and may give useful information for risk stratification beyond simply confirming a clinical diagnosis, for example left atrial size and the presence of spontaneous contrast.

Transoesophageal echocardiography should be reserved for “younger” patients (empirically <50 years) with unexplained stroke/TIA, for patients in whom the transthoracic study is unclear, and for older patients with repeated unexplained stroke/TIA. Transoesophageal echocardiography is particularly useful for looking at the left atrium, atrial septum, left atrial appendage, mitral valve and thoracic aorta, abnormalities of which may give rise to stroke/TIA. There is a tendency to over-report more subtle abnormalities (e.g. slight mitral valve prolapse) that may not be clinically relevant.