Detection of right-to-left shunts may be associated with body size

The aim of this study was to investigate whether physiological factors, including body mass index (BMI), are associated with detection of right-to-left shunt (RLS) by contrast transcranial Doppler ultrasonography (c-TCD).

After prospective c-TCD for stroke patients, we compared clinical backgrounds between patients with positive and negative results for RLS. After counting microembolic signals (MES), RLS were functionally graded as follows (grade 0 = 0 MES, grade I = 1-10 MES, grade II = 11-30 MES, grade III = 31-100 MES if countable, grade IV = over 100 MES or uncountable like a shower.

Subjects comprised 584 patients (203 men, 381 women) with a mean age of 67.9 +/- 11.1 years. RLS was detected in 134 of 584 patients (23%). In univariate analysis, mean BMI was 22.1 in patients with RLS and 23.3 in those without RLS (P= .004). Mean BMI in concordance with RLS grade gradually decreased (grade 0; 22.7, grade I; 20.8, grade II; 20.1, grade III; 19.6, P= .001). After performing the Valsalva maneuver, mean BMI in concordance with RLS grade linearly increased (grade I; 20.6, grade II; 23.2, grade III; 24.8, grade IV; 25.8, P < .001).

Although smaller body size may be associated with detection of RLS, a patient with significant RLS (grade III or IV) had larger body.