Right-to-left shunts may be not uncommon cause of TIA in Japan.

BACKGROUND AND PURPOSE Although 30% to 60% of transient ischemic attacks (TIAs) have embolic sources, the etiology of the remaining TIAs is unknown. Right-to-left shunt (RLS) is one of the most important etiologies of cryptogenic stroke. The aim of this study was to determine whether RLS is related to transient ischemic attack (TIA) of unknown etiology. METHODS We performed transesophageal echocardiography (TEE) and/or transcranial Doppler (TCD) studies for consecutive TIA patients in order to detect RLS from April 2004 to December 2006. TIA patients were divided into three groups, as follows: 1) Cardioembolic TIA, with a patent cardioembolic source, 2) thrombotic TIA, with an atherothrombotic and/or lacunar mechanism, and 3) undetermined TIA, without identified cause of TIA. We compared the characteristics and presence of RLS among these three groups. RESULTS We enrolled 124 TIA patients (age: 67+/-13 years old, 80 men). There were 13 patients with Cardioembolic TIA, 25 with Thrombotic TIA, and 86 with Undetermined TIA. TEE and/or TCD were able to detect RLS in 61 of the 124 (49%) patients. RLS was frequent in patients with Undetermined TIA compared with those in the other TIA groups (60% in the Undetermined TIA group, 28% in the Thrombotic TIA group, and 15% in the Cardioembolic TIA group; p<0.001). Smoking and previous history of TIA were frequent in the Thrombotic TIA group (p=0.030 and p=0.016, respectively). CONCLUSION RLS may play an important role in the etiology of TIA of undetermined cause.