BACKGROUND AND PURPOSE
Comparison was performed between unilateral and bilateral power M-mode transcranial Doppler to detect right-to-left circulatory shunt (RLS).
Recorded Doppler data from 87 patients with confirmed RLS referred for transcatheter closure of patent foramen ovale were reanalyzed for embolic tracks (ET) counted from left and right temporal bone windows during bubble study. Unilateral counts were obtained by multiplying each side by 2; bilateral counts were obtained by summing left and right ET. Both unilateral and bilateral ET were converted to a 6-point logarithmic grade. Sex and age group subanalyses were performed.
At rest, significantly more ET were detected with bilateral versus unilateral detection (P= .01), but not following Valsalva (P= .13). Unilateral and bilateral detection were equally able to detect large RLS (grades IV or V) following Valsalva (P= 1.00). For the group aged ≥55 years, the right-hand side yielded greater ET than the left-hand side (mean difference 9%± 37; 95% confidence interval −3 to 21%) at rest (P= .01), but not following Valsalva (mean difference 1%± 25; 95% confidence interval −7 to 9%, P= .10).
Unilateral detection of ET by power M-mode transcranial Doppler is equivalent to bilateral detection to assess RLS.