Detection of right-to-left shunts: comparison between the International Consensus and Spencer Logarithmic Scale criteria.
BACKGROUND
International Consensus Criteria (ICC) consider right-to-left shunt (RLS) present when Transcranial Doppler (TCD) detects even one microbubble (microB). Spencer Logarithmic Scale (SLS) offers more grades of RLS with detection of >30 microB corresponding to a large shunt. We compared the yield of ICC and SLS in detection and quantification of a large RLS.


METHODS
We prospectively evaluated paradoxical embolism in consecutive patients with ischemic strokes or transient ischemic attack (TIA) using injections of 9 cc saline agitated with 1 cc of air. Results were classified according to ICC [negative (no microB), grade I (1-20 microB), grade II (>20 microB or "shower" appearance of microB), and grade III ("curtain" appearance of microB)] and SLS criteria [negative (no microB), grade I (1-10 microB), grade II (11-30 microB), grade III (31100 microB), grade IV (101300 microB), grade V (>300 microB)]. The RLS size was defined as large (>4 mm) using diameter measurement of the septal defects on transesophageal echocardiography (TEE).


RESULTS
TCD comparison to TEE showed 24 true positive, 48 true negative, 4 false positive, and 2 false negative cases (sensitivity 92.3%, specificity 92.3%, positive predictive value (PPV) 85.7%, negative predictive value (NPV) 96%, and accuracy 92.3%) for any RLS presence. Both ICC and SLS were 100% sensitive for detection of large RLS. ICC and SLS criteria yielded a false positive rate of 24.4% and 7.7%, respectively when compared to TEE.


CONCLUSIONS
Although both grading scales provide agreement as to any shunt presence, using the Spencer Scale grade III or higher can decrease by one-half the number of false positive TCD diagnoses to predict large RLS on TEE.
Lao
Annabelle Y
AY
Neurosonology and Stroke Research Program, Barrow Neurological Institute, Phoenix, AZ 85013, USA. aylmd@yahoo.com
Sharma
Vijay K
VK
Tsivgoulis
Georgios
G
Frey
James L
JL
Malkoff
Marc D
MD
Navarro
Jose C
JC
Alexandrov
Andrei V
AV
D000328:Adult; D000368:Aged; D002544:Cerebral Infarction / Q000145:classification / Q000000981:diagnostic imaging*; D032921:Consensus; D003287:Contrast Media; D017548:Echocardiography, Transesophageal; D019320:Embolism, Paradoxical / Q000145:classification / Q000000981:diagnostic imaging*; D005260:Female; D054092:Foramen Ovale, Patent / Q000145:classification / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D002546:Ischemic Attack, Transient / Q000145:classification / Q000000981:diagnostic imaging*; D008297:Male; D045423:Microbubbles; D008875:Middle Aged; D012372:ROC Curve; D012680:Sensitivity and Specificity; D012965:Sodium Chloride; D017585:Ultrasonography, Doppler, Transcranial / Q000145:classification
D003287:Contrast Media; D012965:Sodium Chloride