title: Right-to-left shunts may be not uncommon cause of TIA in Japan.
abstract: OBJECTIVE
  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).
  
  
  CONCLUSIONS
  RLS may play an important role in the etiology of TIA of undetermined cause.
authors.affiliation: Department of Stroke Medicine, Kawasaki Medical School, 577 Matsushima, Kurashiki City, Okayama 701-0192, Japan. ytate@nagasaki-u.ac.jp
authors.forename: Yohei
authors.initials: Y
authors.lastname: Tateishi
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Iguchi
authors.forename: Kazumi
authors.initials: K
authors.lastname: Kimura
authors.forename: Kazuto
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Kensaku
authors.initials: K
authors.lastname: Shibazaki
authors.forename: Katsumi
authors.initials: K
authors.lastname: Eguchi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003920:Diabetes Mellitus / Q000208:ethnology; D005260:Female; D006343:Heart Septal Defects / Q000150:complications* / Q000208:ethnology*; D006801:Humans; D006973:Hypertension / Q000208:ethnology; D020766:Intracranial Embolism / Q000208:ethnology / Q000209:etiology; D002546:Ischemic Attack, Transient / Q000208:ethnology* / Q000209:etiology*; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence