Angle-independent, real-time estimates of
cardiac blood flow have been obtained with the vector velocity method
Transverse Oscillation (TO) implemented on a conventional ultrasound (US)
scanner. During cardiac surgery, epicardiac examination of the ascending aorta using TO was performed
on six patients; (i) three patients with
healthy aortic valve and (ii) three
patients with aortic valve stenosis. The systolic flow in (i) had a central jet flanked
by retrograde peripheral flow. In (ii)
the systolic flow was more chaotic and aliased.
The two groups had similar secondary flow with a mean
rotation of 4.7 Hz, and similar flow patterns during diastole with stable
vortices in the aortic sinuses and complex flow patterns around the valves. For
comparison, simultaneous measurements were obtained with spectral Doppler (SD) and
thermodilution technique (TD). The mean difference in peak systolic velocity
compared to SD in (i) was 22% and in
(ii) 53%. The mean difference in
volume flow compared to TD in (i) was
30% and in (ii) 32%. The vector
concentration was obtained from TO estimates of the systolic flow as a measure of
flow complexity, where 0 is chaotic flow and 1 is perfectly laminar flow. A
mean vector concentration in (i) was
0.87 and in (ii) 0.41.
This is the first study where blood flow around
healthy and diseased aortic valves intraoperatively has been examined with
vector flow imaging using US. The preliminary results show that TO potential can
become a valuable tool in imaging of the heart.
