Direction-changes and asymmetries of flow through the heart
Philip J Kilner, Guang-Zhong Yang, A John Wilkes, Raad H Mohiaddin, David N
Firmin, Magdi H Yacoub.
Corresponding Email Addresses
Philip Kilner: p.kilner@rbh.nthames.nhs.uk
Guang-Zhong Yang: gzy@doc.ic.ac.uk, http://vip.doc.ic.ac.uk
Supplementary information
Movie files:
Movie 1 Flow in the right atrium (corresponds to figure 1a-b).
Movie 2 Flow in the left atrium (corresponds to figure 1c-d).
Movie 3 Flow in the left ventricle (corresponds to figure 1e-f).
Movie 4 Flow in rocked asymmetric and symmetric open cavity models.
Movie 5 Flow in asymmetric and symmetric models after cessation of rocking.
Contents of supplementary text below:
Table 1: Subjects studied
Table 2: Planes studied by velocity mapping
Alignment of planes in table 2
Magnetic resonance velocity mapping
Consistency of large scale flow topology between subjects
Table 1: Subjects studied
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
m/f
m
m
f
m
f
m
m
m
f
m
m
m
m
f
m
m
m
m
f
f
m
m
age
34 (Figure 1 illustrates studies in this subject)
46
32
34
29
31
35
36
26
34
49
56
51
26
31
39
37
38
42
32
35
26
Table 2: Planes studied by velocity mapping
1 Coronal, 5 contiguous slices, all four chambers
2 Sagittal, 5 contiguous slices, right atrium
3 Sagittal, single slice, mid right atrium
4 Transaxial, mid right atrium
5 Oblique coronal, right atrium-ventricle
6 Coronal, single slice, mid left atrium
7 Oblique sagittal, aortic arch plane
8 Left ventricle – vertical long axis
9 Left ventricle – horizontal long axis
10 Left ventricle – oblique long-axis
11 Left ventricle – short axis, below mitral valve
Subject Nos.
(n=2) 1,2
(n=1) 1
(n=6) 1,2,3,5,16,22
(n=2) 1,9
(n=3) 1,2,7
(n=4) 1,2,10,20
(n=10) 1,3,4,7,16,17,18,19,20,21
(n=8) 3,4,6,8,11,12,13,14
(n=9) 2,3,4,6,8,11,12,13,14
(n=7) 1,2,3,6,9,10,15
(n=9) 1,2,3,4,6,8,9,12,13
Alignment of planes in table 2
Planes 1 and 2 refer to acquisition of 5 contiguous slices, in coronal and sagittal
orientations, respectively, each slice being 10mm thick, to record velocities in voxels
distributed though the volume of a slab 5cm in total thickness.
Plane 3 was sagittal, aligned from transaxial pilot images to pass through the right atrial
cavity and its inlets from superior and inferior caval veins (as in figure 1a-b).
Plane 4 was transaxial, passing through right atrium, tricuspid valve and mitral valve.
Plane 5 was oblique coronal, aligned from transaxial pilots to pass through the right
atrium, tricuspid valve and right ventricle.
Plane 6 was coronal, aligned from transaxial pilots to pass through the left atrial cavity
and its inlets from the superior pulmonary veins. Flow from inferior pulmonary veins
reached this plane from inlets slightly posterior to it (as in figure 1c-d).
Plane 7 was an oblique sagittal plane aligned by location of 3 points in the lumen of the
aortic arch - one placed at the top, one anteriorly and one posteriorly, the last two points
being at right pulmonary artery level. The plane cut through the left atrial cavity, throughplane components of velocity showing directions of flow in upper and lower parts of the
cavity.
Plane 8 was aligned, from transaxial pilot images, with the long-axis of the left ventricle,
passing through mitral valve and ventricular apex.
Plane 9 was aligned, orthogonal to plane 8, with the long-axis of the left ventricle,
passing through mitral valve and ventricular apex.
Plane 10 was aligned, from coronal pilot images, with the long-axis of the left ventricle.
The plane passed through the mitral valve, ventricular apex and aortic valve (as in figure
1e-f).
Plane 11 was aligned, orthogonal to long-axis images, to transect the left ventricle in its
short axis one third of the distance from mitral valve to apex.
Magnetic resonance velocity mapping
Phase difference velocity mapping was performed using a 0.5 Tesla Picker magnet with
modified gradient coils and a surface receiver coil and previously validated phase
velocity mapping software 2,3. A 1.5 Tesla Picker Edge MRI system with commercially
available phase velocity mapping software was used for studies of planes 1 and 6 in
subject 2, and planes 10 and 11 in subject 9. In each plane, components of velocity in x, y
and z directions were mapped using reference and velocity encoded gradient echo
sequences with echo times of 14ms in the 0.5T magnet, or 4.4ms in the 1.5T magnet.
Slice thickness was 8-10mm, field of view 40cm, with 2 averages of 128 phase encoding
steps. On the 0.5T system, reference and x, y and z velocity data were acquired in
successive heart beats, interleaved over a period of 15-20 minutes for all 3 velocity
components in a single plane, depending on heart rate. The 1.5 Tesla system allowed
sequential acquisition of reference and velocity data within 20ms of each other in each
heart beat12. This allowed velocity map acquisitions (x and y, or z components) in 3-4
minutes per plane. Velocity maps were generated by subtraction of reference from
velocity encoded phase images. Each directional velocity map consisted of sixteen or
more cine frames gated from the R-wave of the ECG, distributed through systole and
most of diastole, successive frames being at 40-60ms intervals, depending on heart rate.
Large-scale intra-cavity flow features were visualised as vector maps4 or instantaneous
streamline maps5 for visualisation of in-plane components of velocity, and as grey-scale
maps of velocity for visualisation of through-plane components of velocity2,4.
(reference numbers apply to references at the end of the paper)
Consistency of large scale flow topology between subjects
Right atrium
The dominant flow feature was clockwise rotation of blood, as viewed from the subject’s
right side, with a stream from the inferior caval vein arching up, anteriorly and down the
front of the chamber. This large-scale movement was identified in all six subjects studied
in plane 3 (observing in-plane components of velocity). Through-plane velocity maps in
both subjects studied in plane 4 confirmed upward flow in the posterior half of the right
atrium, and downward flow in the anterior half of the cavity.
Left atrium
The dominant flow feature was asymmetric filling of the cavity, with velocities directed
predominantly to the right in the upper half of the cavity and predominantly to the left in
the lower half of the cavity. Apart from local variations between subjects, this was
broadly consistent between subjects, identifiable in all four subjects studied in plane 6
(observing in-plane components of velocity), and all ten subjects studied in plane 7
(observing through-plane components of velocity).
Left ventricle
The dominant secondary flow feature was transient, asymmetric recirculation of flow
under the free edge of the anterior mitral leaflet, transiently redirecting part of the
inflowing blood towards the outflow tract. This was a consistent finding, identifiable in
all 25 studies (planes 9, 10 and 11) of the left ventricle in a total of 13 subjects. Transient
recirculation was also observed beneath the region of the posterior mitral valve leaflet
(see supplementary figure 11, below) in 8 out of 9 of the studies in plane 9, in 7 out of 9
of the studies in plane 10, and in all 9 studies in plane 11, observing through-plane
components of velocity. Observation of components of velocity directed through the
short axis plane (plane 11) suggests that secondary flow during left ventricular filling
may have the character of an asymmetric annular vortex, its lateral and posterior
development limited by papillary muscles and postero-lateral free wall, so that
recirculation dominates in the sector towards the outflow tract.
Right ventricle
The dominant secondary flow feature was redirection or recirculation of inflow from the
superior part of the tricuspid valve towards the pulmonary outflow tract. This was
identifiable in all 3 in plane 5, and in 5 of the 9 short-axis cuts located through the left
ventricle (plane 11) which also passed through inflow and outflow regions of the right
ventricle. Studies in planes 4 and 11 showed evidence, variable between subjects, of
transient recirculation of inflowing blood distal to the anterior, inferior and posterior
borders of the tricuspid valve.